Crocodile
Farming
Research, Development and
On-farm Monitoring
1995 to 1998
A report for the Rural Industries Research
and Development Corporation
by Rob Mayer,
Queensland Department of Primary Industries
October 1998
RIRDC Publication No 98/109
RIRDC Project No. DAQ-188A
© 1998 Rural Industries Research and Development Corporation.
All rights reserved.
ISBN 0 642 57849 4
ISSN 1440-6845
"Crocodile Farming : Research, Development and On-farm Monitoring. 1995-1998”
Publication no. 98/109
Project no. DAQ-188A
The views expressed and the conclusions reached in this publication are those of the author and not
necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person
who relies in whole or in part on the contents of this report.
This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the
Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the
Communications Manager on phone 02 6272 3186.
Researcher Contact Details
Mr Rob Mayer
Queensland Dept of Primary Industries
P.O. Box 1085
Townsville Q 4810
Phone: 07 47222614
Fax:
07 47782970
Email: [email protected]
RIRDC Contact Details
Rural Industries Research and Development Corporation
Level 1, AMA House
42 Macquarie Street
BARTON ACT 2600
PO Box 4776
KINGSTON ACT 2604
Phone:
Fax:
Email:
Website:
02 6272 4539
02 6272 5877
[email protected]
http://www.rirdc.gov.au
Published in October 1998
Printed on environmentally friendly paper by the DPIE Copy Centre
ii
FOREWORD
The crocodile farming industry in Australia is very unstructured and farmers tend to operate
independently. This is not surprising given the way that a lot of the farms began – people
with a fascination with this large reptile and often starting out buying a few adult rogue
animals caught in the wild. Very little has been published about the requirements for
commercial farming of the Australian saltwater crocodile – most of the literature has been on
the American alligator, which is a much more docile animal and has a much less discerning
palate. Hence, the farms in Australia have developed a wide variety of farming techniques,
based mainly on anecdotal or overseas information.
In 1995 RIRDC convened a workshop in Darwin of government, university and private
company researchers to meet with crocodile farmers, product manufacturers, buyers and
exporting agencies to identify research, development and extension strategies for the
Australian industry. ‘Production’, encompassing management and nutrition was identified as
the top research priority.
This report covers the production research carried out by the Queensland Department of
Primary Industries in Townsville and its extension and networking with industry and other
research agencies. It follows on from earlier benchmark work done in RIRDC Project DAQ132A. The main focus of the current project was on:
•
•
•
researching optimal environmental, management and nutritional issues related to
growing juvenile crocodiles to one year of age
setting up and working with an R&D advisory group consisting of farmers and fellow
researchers
extending results quickly via seminars, research publications and producing an
Australian industry newsletter.
This research is part of RIRDC’s New Animal Products R&D Program, which is aimed at
accelerating the development of viable new animal industries in Australia.
Peter Core
Managing Director
Rural Industries Research and Development Corporation
iii
Acknowledgments
This report has been compiled from many sources of information published on the crocodile
R&D activities over the period of the project, including:•
•
•
•
Crocodile Research Bulletin Vol.2 June 1997
Crocodile Capers Newsletter, Issues 1-5
DPI Research Updates (Nov. 1997, August 1998)
Reports on seminars, meetings.
Authors of some of these articles have been S. Peucker (who is also editor of Crocodile
Capers), B. Davis and A. Thomas. I would like to acknowledge their contributions to this
report.
The project has received strong support from the Queensland Crocodile industry, and thanks
must go to K. Cook and A. Darbonne (Cairns Crocodile Farm), A. Neilan (Edward River
Crocodile Farm). P. Freeman and G. McClure (Hartley’s Creek Crocodile Farm, M. and M.
Tabone (Johnstone River Crocodile Farm), and J. Lever (Koorana Crocodile Farm) for
providing hatchling animals each year for research and for their valuable contributions to the
Industry Advisory Group. R. Flemming (Billabong Sanctuary) has provided newly laid
crocodile eggs for research on incubation. These contributions have been essential to the
project.
B Davis is thanked for reviewing several drafts of this document.
As project leader I would like to thank RIRDC Research Manager, Dr. Peter McInnes, for his
encouragement and support and the time he has devoted to reading draft copies of the many
reports that have been produced from this project.
The often hard, unglamorous and mostly unheralded work done by other members of the DPI
team – R. Jack, R. Bloomfield, H. Stephenson, L. Morrissy, S. Johnson and S. Blyth – is
gratefully acknowledged. This report reflects a team effort and this has been central to our
progress.
Finally, M. Read, Department of Environment (Queensland), is thanked for his interested and
keen support for the project.
iv
Contents
Foreword ...........................................................................................................
iii
Acknowledgements ............................................................................................
iv
Executive Summary
vii
1.
........................................................................................
INTRODUCTION
1.1 Crocodile Farming in Australia............................................................................
1.2 Industry Research Needs...................................................………………………
1
1
2.
OBJECTIVES...................................................…………………………………….
3
3.
METHODOLOGY
3.1 Research Animals and Eggs……………………………………………………
3.2 Research Facilities…………………………………...........................................
3.3 Experimental Procedures ………………………………………………………
3.4 Research Program 1995-98…………………………………………………….
5
7
7
8
ENVIRONMENT RESEARCH
4.1 Light………………………………………….....................................................
4.2 Rearing Density……………………………………............................................
4.3 Hide-boards and Water Temperature …………………………………………..
4.4 Water Volume ………………………………………………………………….
9
16
26
27
NUTRITION RESEARCH
5.1 On-farm Evaluation of Pellet Prototypes……….................................................
5.2 Acceptability Trials…………………………………………………..................
5.3 Hatchling Response to Pellets ………………………………………………….
5.4 Pellet/Mash and Water Temperature Trials …………………………………….
5.5 Feed Additives ………………………………………………………………….
5.6 Growth Response Trials ………………………………………………………..
5.7 Recent Developments …………………………………………………………..
5.8 Runts ……………………………………………………………………………
31
32
35
37
41
44
46
46
EGG RESEARCH
6.1 Incubation Study………...............................................…………………………
6.2 Egg Fungal Levels…………………………………………………................…
6.3 Incubation Techniques………………………………………………………….
6.4 Embryonic Mortality……………………………………………………………
51
51
61
61
4.
5.
6.
v
7.
8.
9.
10
ON-FARM STUDIES
7.1 CROCTEL……….………...............................................……..………………….
7.2 Breeder Infertility Investigations…………………………………................…….
63
75
EXTENSION TO INDUSTRY
8.1 Queensland Crocodile Industry Advisory Group.................................................
8.2 Industry Seminars…..………………………………………………..................
8.3 Conferences…………………….……………………………………………….
8.4 Publications ……………………………………………………………………
8.5 General…………………………………….…………………………………….
8.6 Industry Adoption of Research………………………………………………….
77
80
80
81
81
82
NETWORKING
9.1 Northern Territory Organisations……………….................................................
9.2 University of Queensland (Brisbane)………………………………..................
9.3 James Cook University (Townsville)..………………………………………….
9.4 Department of Environment (Queensland).…………………………………….
9.5 Primary Tasks Pty Ltd………………………………………………………….
9.6 US Alligator Organisations……………………………………………………..
9.7 Tourist Parks, Wildlife Sanctuaries and Zoos………………………………….
85
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87
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88
88
89
CONCLUSIONS AND RECOMMENDATIONS
10.1 Research Advances for Juvenile Crocodiles.….................................................
10.2 Priorities for Future Research and Development…………………..................
10.3 Cooperative Activities……………...………………………………………….
91
91
92
vi
Executive Summary
In long established Australian intensive livestock industries (pigs, poultry) research has shown
the economic benefits of providing controlled-environment rearing sheds and least-cost pelleted
food diets. The result has been wide-spread adoption of standard farming practices by
producers in these industries. Also, these industries have set up and strongly supported effective
industry associations, contribute funds to continued R&D and organise regular national and state
workshops and conferences. In contrast, the crocodile farming industry in Australia is a
relatively new industry, research on farming methods for the saltwater crocodile has been very
limited and farmers use a wide variety of farming practices (shed and pen design, rearing
environments) and rely on whatever fresh meat they can buy cheaply to feed their crocodiles.
This is akin to the old practice of feeding swill to pigs. Using fresh meat also requires expensive
transport and storage costs (freezers, electricity). Farmers have developed very independent
attitudes and many incorporate a tourist component to their operations. Odd attempts have been
made to set up state/territory organisations but these have not proved successful. Consequently
no direct funds have been contributed towards crocodile R&D for the industry, although farmers
have contributed ‘in kind’ by providing animals and eggs for research. The industry in
Australia has been able to sustain inefficient production methods in the past, because of the
premium price commanded by the saltwater crocodile skin. However the major international
markets are being flooded with alligator and Caiman skins which are dragging prices down
world-wide. Thus, the industry is rapidly approaching the stage where profit margins are
disappearing. In a buyers’ market more skins are being downgraded to second or third grade,
and these are not economical to produce.
A meeting of Australian crocodile farmers, researchers, manufacturers and local buyers was
convened by RIRDC in Darwin (1995) to discuss R&D needs and to set priorities. This meeting
identified ‘production’ as top priority. Under tightened health regulations, farmers will be
prohibited from using certain traditional cheap sources of crocodile feed (road kills, offal). This
has given added urgency to the development of a pelletised diet. Diets developed for the
American alligator have proved unsuitable for the crocodile, and researchers in other countries
have been trying for years to develop a pellet for related crocodile species (eg the Nile
crocodile) without success.
In the forerunner crocodile cooperative project (DAQ-132A) between RIRDC and the
Queensland Department of Primary Industries (DPI) a specially designed research facility for
juvenile crocodiles (hatching to one year of age) was built at the Oonoonba Veterinary
Laboratory site in Townsville. The research experiments in this report have been conducted in
this facility. The major research aims of the project were to identify optimal rearing
environments and management practices for rearing a crocodile to one year of age, and to
develop a dry food pellet for these sized animals. In the former, experiments showed that
animals grew significantly faster and had superior food-to-weight conversion efficiencies when
•
•
•
•
animals were reared under darkened conditions
hide-boards were provided inside the rearing tanks
water temperature was raised from 32o to 34oC for the earlier months
animal density per tank was at low/medium levels
vii
•
water volume in the tanks was increased (except for ‘medium/large’ graded sizes of
animals nearing one year old).
Farmers in Queensland have begun to implement some of these practices on their farms and
have reported similar success.
In the area of nutrition, six consecutive prototype pellets were intially distributed to farmers to
test on juvenile animals. Animal reaction was observed and noted each time a new pellet was
introduced. Observations followed a set pattern for each farm and feedback from producers was
used to improve subsequent prototypes. At the same time it was decided to devote research
resources at Oonoonba to test six different food flavours and two different food colourings.
Some flavours seemed to stimulate appetite, but the initial pellets were not accepted by the
animals as a sole diet. The breakthrough came when the basic, bland, dry mash ingredient was
mixed with water and put through a standard mincing machine to produce a very moist pellet.
Using a gradual ‘weaning’ process, animals were able to be successfully weaned from fresh
mince to a diet of these pellets, which the animals continued to accept as a sole diet. The basic
mash had not been developed specifically for crocodiles and growth rates of animals fed the
pellets for a period of eight weeks were significantly lower than rates of similar animals
continued on the mince diet. Consequently a meeting of expert animals nutritionists from
around Australia was convened in Townsville (early 1998) to formulate dietary requirements for
young crocodiles. This was followed by a small sample of nutritionally improved pellets which
were manufactured in South Australia and tested on animals in Townsville. These pellets were
accepted by the crocodiles without the need for weaning because of improved palatability
achieved through better diet formulation and pellet manufacturing techniques. DPI is in the
process of acquiring feed milling and pellet manufacturing equipment to continue this important
research work.
DPI has purchased nine small research incubators for crocodile eggs and has been carrying out
research on eggs produced from a nearby wildlife sanctuary. Studies have been made on
bacterial and fungal organisms on the surface of eggs, in nesting material and inside of eggs
which have not banded. This has shown the presence of potentially destructive organisms (such
as fusarium). Research was carried out to evaluate the benefits of washing nesting material and
mucus from the eggs, using either clean water or a disinfectant. Results showed no difference in
embryonic mortality or subsequent hatching rates.
Another main aim of the project was to develop and promote a standard on-farm recording
system for commercial farms and to centrally process such data to provide industry averages.
Two modules of this package, called CROCTEL, have been developed and are being used by
most of the farms in Queensland. Several years of information have been entered into the
program and some central processing of results has begun. This has been useful in identifying a
state-wide problem in declining fertility among captive breeder on farms. Consequently, DPI is
currently working on a collaborative project with the University of Queensland on the problem.
DPI has arranged for the manufacture of 10,000 sachets of special vitamin/mineral supplement
and has set up on-farm research experiments on five Queensland farms to evaluate the effect of
increasing the nutritive value of diets fed to breeder animals.
The Queensland Crocodile Industry Group, consisting of farmers and researchers, was formed
in early 1997 to meet biannually to review crocodile R&D and other general industry issues, and
to act as an advisory group to DPI to prioritise research needs. Subsequent meetings of this
viii
group have been very successful and have ensured that this R&D program has been directed to
industry needs.
Publication of research results and exchange of general industry information (from conferences
etc) has been a high priority in this project. Detailed scientific reporting constitutes the biennial
Crocodile Research Bulletin produced by DPI, and Volume 2 was published in June 1997. To
keep industry and fellow researchers up to date with research findings, regular interim Research
Updates were released in November 1997 and August 1998. A newsletter for the Australian
crocodile farming industry, called Crocodile Capers, was created as a joint DPI/NT Dept of
Primary Industry and Fisheries initiative and five editions have been published.
Apart from one regional meeting of the Crocodile Specialist Group (CSG) in 1993 and segments
in two Intensive Tropical Animal Production seminars (1989 and 1991) there have been no
conferences relating to commercial crocodile farming held in Australia. Hence it is important to
have representation at the biennial meeting of the CSG and also the Australian Society of
Animal Production. DPI has sent representatives to these meetings to
•
•
•
present reports of research on crocodile farming aspects
keep up to date with research on crocodile species and issues common with other
industries (eg aquaculture with pellet development and water recycling)
report back to industry relevant issues, and hold discussions on these topics at
industry seminars.
RIRDC provided funds for the DPI project leader and a representative of the Australian farming
industry to undertake a trip to Florida and Louisiana (Project DAQ-220A) to study the various
types of controlled-environment sheds used for rearing larger sized alligators, and discuss
research needs with US farmers and researchers. The main objective was to identify aspects
crucial to the establishment of a second research facility at Oonoonba in which research could
be carried out on environmental, management and nutrition aspects for rearing crocodiles from
one year of age to harvest size. This has resulted in such a building being constructed and is
currently being used in a new cooperative project (DAQ-247A) on these larger sized animals,
and will complement the results presented in this report.
Thus the important project outcomes which are impacting on the Australian Crocodile Industry
are:
•
•
•
improved nutrition and management for juvenile crocodiles to one year of age
initiation of an on-farm performance recording scheme
strong, effective technical and industry communication linkages within Australia and
with overseas interests.
ix
1.
Introduction
1.1
Crocodile Farming in Australia
In the pig and poultry industries where animals are predominantly reared in
environmentally controlled sheds, research has identified optimal rearing conditions and
these have been adopted across both industries. This has also occurred in the American
alligator farming industry. In all of these industries, special feed pellets have been
developed and are used extensively. In the Australian crocodile farming industry
individual farmers use different rearing strategies, especially for their intensively housed
juvenile crocodiles (hatching to 1 or 2 years old), and use a wide variety of fresh meat
based feeds, supplemented with a variety of vitamin and mineral additives.
The Australian saltwater crocodile produces the best quality skin in the world, and
farmers are keen to exploit this advantage by adopting improved farming practices to
accelerate animal growth rates and reduce the incidence of damage to skins caused by
animals injuring each other.
Crocodile research in Australia, until 1994, had largely been confined to physiology and
to the study of animals in the wild. A few studies had been conducted on commercial
farms. However few facilities had been dedicated to the study of farming aspects of
crocodiles before the establishment of the Department of Primary Industries’
(Queensland) (DPI) facilities at the Oonoonba Veterinary Laboratory (OVL) in
Townsville in 1993.
The commercial crocodile industry in Australia to date has largely progressed on
anecdotal beliefs rather than demonstrated scientific evidence. Farmers are quickly
coming to the realisation that with feed prices continuing to increase and skin prices
falling (due to large numbers of poorer quality alligator and caiman skins coming onto
the market) the Australian industry needs research support.
1.2
Industry Research Needs
A meeting of Australian crocodile farmers, researchers, manufacturers and buyers was
held in Darwin (1995) to discuss Research and Development (R&D) needs and to set
priorities. This meeting identified Production (management, nutrition, skin quality,
breeding, disease) as top priority. Under tightened health regulations, it is anticipated
that crocodile farmers will be prohibited from using certain traditional cheaper
sources of crocodile feed (road kills, offal). This has given added urgency to the
development of a pelletised diet. By targeting research into rearing practices from
hatching to harvest size, DPI’s proposed research program will address these priority
industry issues. Past environmental and nutritional research in Australia has been
done using limited facilities or on commercial farms. Generally results were
inconclusive because of insufficient replication or control over extraneous factors
such as temperature. By contrast, research into rearing practices for juvenile
crocodiles at Oonoonba has produced a series of definite results. (See results
published in the final report for the preceding RIRDC project DAQ-132A.)
1
Consider the much larger North American alligator farming industry. Alligator skins
fetch much lower prices than the ‘classic’ Australian saltwater crocodile skin, and
increased competition from large enterprises in South America has driven prices
down over the years. The US industry has maintained viability by cutting production
costs and increasing rate of throughput (lower profit margin per skin, but producing
more skins). They have achieved this mainly by being able to use special heated
structures and balanced pelleted diets to turn-off an animal at 18-24 months of age.
Currently, Australian farms produce slaughter sized animals at between 3 and 5 years
of age. Unfortunately alligators and crocodiles are biologically quite different so it is
not simply a matter of Australian farmers adopting technology used in rearing
alligators to improve productivity. Research needs to de done specifically on the
crocodile, mainly on nutrition, environmental rearing conditions and management
practices.
Researchers at the Veterinary Research Laboratory in Harare, Zimbabwe, have been
researching the development of a pelleted feed for their closely related Nile crocodile
(Crocodylus niloticus) since 1987 and still have not been able to produce a pellet
which their animals will eat as a sole diet. The only partial success they had was
when they soaked pellets in fresh animal blood. The major focus of this RIRDC
project over the three years has been on nutrition, and on developing a pelleted feed.
The Australian industry is rapidly approaching the stage where profit margins are
disappearing (increasing costs, falling prices, buyers downgrading skin grades).
Either it will decide to act more cooperatively and support R&D, in terms of dollars
and providing more input into planning and evaluating research, or its members will
continue to act more like independent mavericks and rely on their own intuition and
individual marketing with virtually no product promotion.
2
2. Objectives
A. To maximise growth rates and reduce the incidence of runt animals, diseased
animals and animal mortality on Australian crocodile farms by identifying
optimal environmental conditions, diets and management strategies for rearing
animals and managing eggs prior to and during incubation.
B. To oversee the development and evaluation of a pellet feed for young crocodiles
thereby ensuring balanced nutrition and also eliminating the large costs to
industry of labour and storage of frozen fresh meat.
C. To implement a standard on-farm recording system for Australian farms, and
process the data centrally to provide economic and scientific analysis for the
industry overall.
D. To establish a national extension / development strategy which ensures annual
seminars in both north Queensland (Qld) and the Northern Territory (NT) where
information can be exchanged between researchers, farmers, sanctuary staff,
marketing agents and feed/vitamin manufacturers. To establish a communication
network which builds confidence between people and also allows for the
electronic and written transfer of information.
3
3.
Methodology
3.1
Research Animals and Eggs
Hatchling animals are provided annually by Qld farmers for the subsequent year’s
series of experiments. They are chosen from clutches with large numbers of animals
(to minimise clutch to clutch differences) which hatch over a short period of time (to
avoid age differences). Eggs have been provided from the nearby Billabong
Sanctuary.
‘1995 Cohort’
This cohort consisted of 291 hatchlings from seven clutches (36 to 45 animals per
clutch) which hatched between May 4-15 in 1995 at the Edward River Crocodile
Farm on western Cape York Peninsular. Farm staff had kept each of these clutches in
a separate area and then boxed them up in open weave plastic crates. The animals
were flown to Cairns then driven to Townsville on the same afternoon. On arrival
each clutch was bulk weighed, dipped in an antiseptic / fungicide solution and then
placed in a separate rearing tank.
The animals in the seven tanks were reared under ‘standard’ rearing conditions (air
and water temperatures set at 32oC, diurnal lighting, constant radio noise) for a period
of three weeks to let the animals acclimatise to their new surroundings.
Double tagging was carried out on 14 August 1995 during the animals’ first
individual measuring. With the approval of Edward River management nine of the
smallest animals were donated to the University of Qld Zoology Dept (Sept. 1995) for
research purposes. At a subsequent measuring in October a photocopy machine was
used to record the belly scale pattern of each animal. The final experiment on this
cohort concluded in late March 1996 and the animals were sent to the Cairns
Crocodile Farm.
‘1996 Cohort’
Two DPI officers went to the Cape York farm in April 1996 (the middle of the
crocodile hatching season) to assist Edward River Farm staff in selecting clutches for
research. Temporary identification numbers were attached to animals by means of
plastic strips around the animals’ back legs, and each individual was weighed.
Unfortunately there were only three clutches which had recently hatched with a total
of only 108 animals. These were supplemented with two clutches from the Cairns
Crocodile Farm which the officers weighed and tagged on their return trip to
Townsville. The following week a further four clutches had hatched at Cairns and
these were also selected to be part of the 1996 cohort. In total there were 251
hatchlings from nine clutches (18-41 per clutch) and average clutch weight ranged
from 50 to 79g per animal.
After two months the plastic leg bands were cut off and metal web tags were put on
each animal’s back two feet. Previous experience has shown that web tags have only
5
a 1-3% ‘shedding’ rate, so by double tagging each animal there have been few
problems with tag loss. The 1996 cohort had a much higher incidence of shedding
and at each measuring missing tags were replaced. At four months of age the
animals’ bellies were photocopied during a full measuring.
‘1997 Cohort’
This consisted of 276 hatchlings from eight clutches - one incubated at OVL from
eggs collected from Billabong Sanctuary, four hatched at Edward River Farm and
three hatched at Cairns Crocodile Farm. Numbers per clutch ranged from 18 to 44
and average clutch weights ranged from 50 to 74g per animal.
‘1998 Cohort’
This comprised 273 hatchlings from 11 nests - one from Johnstone River Farm
(Innisfail), four from Billabong Sanctuary and six from Koorana Crocodile Farm
(Rockhampton). Numbers ranged from 12 to 40 per clutch.
Growth pattern for the 1995-97 cohorts over the sequence of experiments is shown in
the following graph.
Figure 1. Growth Patterns for the Cohorts (1995-97) over the Sequence of
Experiments.
‘Eggs’
These were provided by Billabong Sanctuary just south of Townsville. In 1996 there
were 162 eggs from four nests, but because three of the laying females were young,
67% of the eggs were infertile. Nevertheless the infertile eggs were useful in providing
6
information on fungal levels on the external surface and inside the eggs. This was
followed by 192 eggs (from five nests) in 1997 and a further five nests in 1998 from
which 111 hatchlings were successfully incubated.
3.2
Research Facilities
Details of the research shed for juvenile crocodiles has been presented in the RIRDC
final report DAQ-132A. Essentially it consists of six well insulated rooms each
containing two fibreglass rearing tanks. Temperature in each room is controlled by
individual air-conditioning units (capable of maintaining air temperature within ±2oC of
preset levels). Water temperature in each tank can be set independently, and maintained
within ±10C). Artificial lighting is controlled by dimmers and timers.
The seven research egg incubators have been adapted from poultry incubators, featuring
accurate temperature controls. Alarm systems have been added to the temperature
system, and extra ‘bubblers’ have been placed inside the incubators to raise the
humidity levels to 98%.
3.3
Experimental Procedures
Annual cohorts of animals were provided by industry for this work with
approximately 300 newly hatched animals from a number of large nests, each
identified individually by web tags and numbers matched with clutch.
Experiments with discrete-type treatments (eg pelleted diet vs mince) were designed
with replicated pen/tank units so that valid statistical analyses could be carried out on
ensuing data. Experiments involving a single factor with different levels (eg water
temperature) sometimes involved unreplicated pen treatments if the main objective
was to estimate an overall response pattern. In either situation, close attention was
paid to statistical design and setting up of experiments, so that groups of animals
initially assigned to pens were always as uniform as possible. Fellow researchers
have often published non-conclusive research results, with the explanation that
crocodiles exhibit more variation in response to applied treatments than most other
animals, both between and within clutches.
Experience since 1993 suggests that the following are key issues when designing an
experiment on juvenile crocodiles to one year of age:
• allow for a ‘settling-down’ period of two weeks between successive
experiments (when all animals are subjected to the same conditions)
• grade the animals into two size classes
• allocate animals to tank/size groups using the same mix of clutches (as
much as possible, given the actual numbers in each clutch) using an initial
randomisation within these constraints
• fine-tune the allocation (swapping within clutches) so that, for each sizeclass, tanks contain animals with the same average (fasted) liveweight and
also the same range in liveweight
• use a separate ‘give and take’ tank in which to rear runts and any animals
which become sick or diseased.
7
The following guidelines are used in carrying out the experiment:
• fast the animals for at least 48 hours prior to measuring
• catch the animals while they are swimming in the water (they are less
aggressive)
• measure animals only at the start and at the end of an experiment (usually
treatment differences are statistically significant by 8-10 weeks)
• measure food offered and weigh remnants of food uneaten at each feed (this
gives an indication of growth rate in each tank during the experiment)
• feed animals daily from Monday to Friday then let them fast over the
weekend to assist in complete digestion of food in their system
• record belly scale patterns (using a cameras or a portable photocopier)
• record liveweight, total length, snout-vent length and cranial skull length at
each measuring.
3.4
Research Program 1995-98
1995/96
April
May
June
July
August
September
October
November
December
January
February
March
April
May
7 clutches hatch,
arrive at OVL
Pilot light
trial (1)
Pellet acceptance
trial
Pellet nutrition trial
Light trial (2)
Density trial
Animals returned
1996/97
9 clutches hatch,
arrive at OVL
Pellet
mash
trial
Mash acceptance
trial
Mash flavours eval.
Mash
Growth trial
Pellet growth
trial (1)
Pellet growth
trial (2)
Animals returned
8
1997/98
8 clutches hatch,
arrive at OVL
Pellet acceptance
trial
Hide-board trial
Water volume /
area trial (1)
(Air-conditioning
units replaced)
Water volume
trial (2)
4.
Environment Research
4.1
Light
Published Research on Light Effects
It is generally accepted that crocodile species, even from a young age, experience
complex social interactions, with highly developed forms of visual and other sensory
communication. Farming observations on alligators in the USA have demonstrated
that this animal species grows well in dark conditions. Under such conditions
alligators tend to spread out evenly within their rearing pens. Conversely, in fully lit
pens, crocodiles have been observed to crowd together and to favour certain areas
within their confines (Bolton 1989).
A series of three experiments were conducted on a commercial farm in Darwin on C.
porosus (Riese 1995). Two of these trials involved looking at the combined effects of
density (0.1, 0.05m2 per hatchling) and light regimes (12:12 hour diurnal, no lighting).
The first trial involved 230 hatchlings allocated to 15 tanks and was run over a six
week period. Results showed no differences between the two light treatments on
growth rates (average of 0.66 and 0.56g per day for the 12:12 treatment and the dark
treatment at the low density and 0.40 and 0.34g at the high density). This experiment
was repeated in the cooler part of the year using 120 two-month old animals allocated
to eight research pens. Growth was much slower than in the first experiment but
again there was no evidence of light effects (0.34 and 0.27g for 12:12 and dark at low
density, 0.29 and 0.28g at high density). In both of these experiments there was a
tendency for higher growth under the diurnal pattern than under no light. The third
experiment used 80 animals spread across eight pens (at constant density 0.1m2 per
animal) for a 24 day period. It resulted in non-significant results of 0.90g under 12:12
compared with 0.91g under dark conditions. While the water temperatures for the
experiments remained relatively constant (30-33oC) both within the experimental pens
and throughout the farm, air temperatures in the sheds ranged from 20-38oC. Hence
these fluctuations in air temperature both within and between experiments may have
had a larger effect on growth than altering light and made it difficult to accurately
assess the effects of light alone (as stated by the author).
Current Lighting on Australian Farms
Farms in the NT and far north Qld tend to have ‘green-house’ type rearing sheds,
relying on solar heating. Hence the sheds have subdued natural lighting. Farms
which rear juvenile animals in insulated, enclosed buildings generally provide dim
artificial lighting on a diurnal basis. One farm which used to place lids on low rearing
tanks (to keep the animals in darkened conditions) has since discarded the lids since it
was suspected that the small, humid spaces were contributing to increased disease
problems.
Generally the Australian industry has heeded the American experience that alligators
grow better under dark conditions, but their Australian farming operations have
generally made this impractical to implement. There are no scientifically evaluated
9
studies relating to C. porosus under precisely controlled temperature conditions to
determine whether similar benefits of rearing C. porosus under dark conditions would
apply, or to what extent. Results could determine whether modifying farming
practices would be economical.
One important issue associated with rearing hatchling crocodiles in diurnal light is
provision of ‘hides’ for the animals so that during the day they can remain hidden
from view. (This is not an issue for the American alligators since they are generally
reared in darkness.) Thus any research on the effects of light must take into account
any particular types of ‘hide area’ provided.
Pilot Light Study
Opportunity
The 291 hatchlings comprising the 1995 cohort research group arrived at Oonoonba
on 18 May 1995 in seven crates, each crate containing animals from a different clutch.
They were reared under ‘standard’ conditions (32oC water and air, fortified mince
diet, diurnal light) for three weeks to let them recover from the travel from Edward
River (by plane and car) and to get them used to their new surroundings.
At this early age and size it was felt that the animals were too small to tag with
standard metal web tags, so the opportunity was taken to run a ‘pilot’ study on these
animals in their particular tanks while they were growing to a size large enough for
tagging. Normal research techniques require mixing of animals from different
clutches (at least within replicates) to form ‘balanced’ groups of animals on which to
apply a range of different treatments. In the current situation, since the animals were
not marked in any way they could not be ‘mixing’ else clutch identification would be
lost (for future experiments on this cohort). Hence this experiment was very much in
the ‘developmental’ category.
Treatments and Trial Design
Since no previous work had been carried out on the effects of different light levels /
regimes on growth rates of crocodiles in the DPI research complex, and farmers were
using a wide range of different practices in terms of light conditions for their young
animals (some carefully excluding light as is done in the American alligator industry,
some providing direct sunlight into enclosed sheds via skylights, and some relying on
a filtered sunlight through shade-cloth or semi-transparent plastic), it was decided to
compare two extreme light conditions as follows:
LIGHT : the artificial lights in a room were left on 24 hours a day
DARK : conditions in a room were kept completely dark except during the
periods when attendants had to carry out feeding and cleaning operations.
During these periods the lights were set to a very dim level.
Three rooms (numbers 3,4 and 6) were chosen for the ‘light’ treatment and the
remaining three rooms for the ‘dark’ treatment. This allocation was made on the basis
of matched average initial weights (measured on 18/5) of animals in the rooms, as can
be seen from Table 1. The clutches were ‘paired’ on the basis of weight, and each
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0
clutch in the pair was allocated to light/dark at random. The heaviest clutch left over
from this pairing was reared in tank B in room 1 (because there were seven clutches
but only six rooms).
Data and Statistical Analysis
The only data collected when the cohort arrived at Townsville was a bulked clutch
weighing (while the animals were still in their crates) and a count of the numbers in
each crate / clutch to give an average initial liveweight. This varied considerably
between clutches (see Table 1). At the conclusion of the experiment when the
animals were tagged a full set of body measurements were taken. Because of the
large variation in initial liveweight between the clutches, the best assessment of
response to the two light regimes was average percentage weight gain from each tank
/ clutch.
Results
Table 1 shows the average percentage weight gains achieved in each of the research
tanks and the percentage of animals ‘lost’ (either removed as runts or animals dying)
during the two month investigation. Note that:
• The weight change was from 18/5 til 14/8/95, comprising an initial three
week period under diurnal light conditions then nine weeks when the two
light treatments were imposed. Hence the difference in weight gain was an
underestimate of the real differences between the light treatments.
• The percentage was based on the change in average weight of all the initial
animals in a tank to the average weight of those remaining in the tank at
the end of the trial.
Table 1. Results of pilot trial comparing 2 light treatments.
Clutch #
3
7
6
5
4
1
2
Initial allocation
No.
Av.
animals weight (g)
45
68
36
70
45
70
45
73
45
73
30
77
45
93
Light
regime
Dark
Light
Dark
Light
Light
Dark
Dark
Final situation
Room :
% weight
tank
gain
2:B
61
6:A,B
76
5:A,B
75
4:A,B
56
3:A,B
105
1:A
135
1:B
123
% animals
removed
24
33
22
13
11
20
18
There was no obvious relation between % weight gain and % of animals removed
among the three clutches reared under the ‘light’ treatment. Clutch #4 had both the
highest weight gain and the lowest removal rate among the clutches reared under
constant light, indicating that it was a superior clutch. Among the four clutches
reared under dark conditions there was very little difference in removal rates (1824%) but quite a difference in weight gains (61-135%) with the clutches which were
initially heavier than the average (#1,2) giving the most rapid growth rates. These
1
1
results confirm the large response differences between different clutches subjected to
the same treatment, and why it is so important to always try to take this into account
in research design.
From the overall analysis of percentage weight gains (ignoring clutch differences) the
average of all the ‘dark’ data was 98% and the ‘estimated’ corresponding value for
the ‘light’ data (because of the missing value) was 87%. This difference was not
statistically significant (p>.05). In fact, for a difference of this size to be significant
with the degree of variation present in the current data set, there would have had to
have been 40 clutches in 20 blocks (for significance at the 95% probability level).
This again demonstrates why it is so important to use research designs which use the
principle of mixing clutches on the basis of balanced clutch representation.
Light Experiment
The objectives of this experiment were to measure the effects of rearing seven month
old crocodiles for seven weeks under three light regimes:
• ‘dark’ conditions (very dim lighting during daily feeding and cleaning
activities, otherwise complete dark)
• ‘diurnal’ conditions (12 hours light, 12 hours dark)
• ‘light’ conditions (lights kept on continuously).
Experimental Procedures
The animals consisted of the 1995 cohort group. By the age of seven months they
varied in liveweight from 110 to 1100g (excluding 15 smaller runts) so the
experiment was run on two different size classes of animals, termed ‘small/medium’
and ‘medium/large’, with a division point of 385g. There were 19 small/medium
animals per tank (0.21m2 floor area per animal) and 16 medium/large animals per tank
(0.24m2 per animal) and each tank had a hide board suspended at one end. Air and
water temperatures were set at 30 and 32oC respectively for the duration of the
experiment.
Results
After the ‘settling down’ period of six days (when all tanks were maintained under
normal diurnal light) and a further seven weeks when the three light regimes were
imposed a full set of measurements was collected on the animals. Figure1 shows the
change in average fasted liveweight for the two size groups.
1
2
Figure 1. Average fasted liveweights per animal (g) at the start (4/12/95) and end
of the trial (29/1/96). Within each size class columns headed by a similar letter
do not differ significantly (p>.05).
For the medium/large group, the animals reared under dark conditions weighed
significantly more at the end of seven weeks than animals reared under either of the
other light regimes. The same pattern occurred for the small/medium groups but a
higher degree of variability in response from tank to tank (between the two replicates)
meant that the differences were not statistically significant.
Figure 2 shows the corresponding response in total body length.
1
3
Figure 2. Average total body lengths per animal (mm) at the start and end of the
trial. Within each size class columns headed by a similar letter do not differ
significantly (p>.05).
Although the relative differences between the three light treatments were not as
pronounced as for liveweight, the consistency of the results across replicates resulted
in significant differences between the extreme ‘dark’ and ‘light’ treatments for both
size classes.
Table 2 lists the amounts of food eaten (including any ‘waste’ feed flushed out during
cleaning and refilling operations) and comparisons with increase in body weight. All
calculations were made on a tank basis and over the whole eight week period between
when measurings on the animals were done.
Table 2. Amount of food consumed and corresponding weight gain : food eaten
ratios for the groups of animals in the tanks (averaged over both replicates)
Animal size
Light
Food
Food conversion
category
Regime
eaten (kg)
ratio
Small/medium
Dark
18.9 a*
0.28 a
Small/medium
Diurnal
13.4 b
0.28 a
Small/medium
Light
14.3 b
0.27 a
Medium/large
Dark
23.3 c
0.32 b
Medium/large
Diurnal
18.6 d
0.31 b
Medium/large
Light
18.5 d
0.30 b
* Values followed by a common letter do not differ significantly (p>.05).
1
4
In terms of food eaten there were differences between the light regimes (with more
food eaten in the darkened rooms than in the other rooms) and between the animal
size groups, indicating that the density differences of 16 and 19 per tank for the two
groups perhaps should have been made even larger. For food conversion ratios
(weight gained as a proportion of fresh food eaten) the only difference was between
the size classes with the larger animals being more efficient converters of food.
Discussion
C. porosus which had been reared under a diurnal light cycle prior to this experiment
grew faster (in both weight and total body length) when the rooms they were in were
kept as dark as possible for a seven week period. This difference was caused
primarily by an increased consumption of food in the darkened rooms, which may
have been caused by a number of factors (singly or acting in combination):• animals spreading more evenly throughout the tanks in dark conditions
(compared with other rooms where, when the lights are on, animals tend to
crowd together under the hide-boards)
• animals feeling less threatened from external influences when kept in
darkness
• animals feeling less threatened from each other (especially when feed is put
out) when kept in darkness
• animals are less afraid to venture out from under the hide boards to feed in
darkness.
To identify which of these may be the primal cause(s) it would be necessary to
conduct some additional experiments in which hide-areas were extended to cover
whole tanks (which would make the operations of feeding, collection of uneaten food,
and cleaning difficult), and animal movements were regularly monitored (difficult in
darkness or under hide areas).
From a farming perspective those farms which rear their young crocodiles in sheds
with artificial lighting should be able to achieve improved growth rates (albeit at an
increased food bill) by keeping conditions in the sheds as dark as possible. This will
also save on electricity costs. The small/medium sized animals kept in darkened
rooms ended up on average 81g (or 18%) heavier than similar animals reared under
the standard diurnal light pattern. For the medium/large groups the difference was
106g per animal (12%). This needs to be offset by the increased food consumption of
291 and 292g per animal for the small/medium and medium/large groups respectively
over the eight weeks between weighings. The fact that the larger animals benefited
more by darkened conditions may suggest that darkness reduces aggressive
interactions between these larger, typically more aggressive animals.
The only difference in food conversion efficiency was between the two size classes,
with the larger groups better converters. This could be due to effects like less wastage
of food in the water rather than any basic biological differences. Larger animals take
bigger mouth-fulls and tend not to waste as much when they return to the water.
Perhaps some of the smallest animals in the small/medium groups were suffering
from runt symptoms and were naturally poor converters because of poor health. In
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5
any case a farmer might elect to maximise his profit by grading his animals and
devoting more attention to the larger animals which have a greater capacity to respond
to conditions like reduced light.
References
Bolton M (1989) The management of crocodiles in captivity. Food Aid Organisation
Conservation Guide. No.22, FAO, Rome.
Riese G (1995) Factors affecting food intake and growth in captive saltwater
crocodiles. MSc Thesis, Department of Zoology, University of Queensland.
4.2
Rearing Density
Background
A series of experiments on saltwater crocodiles (Webb et al. 1992) looked at the
effects of density (7.1 to 17.6 animals / m2) and available space (tank sizes 1.7 m2 and
5.1 m2 area) on growth over the one month period post-hatching. The tanks had 44%
land area, water at 32oC (max depth of 10 cm) and animals were fed on a minced
mixture of pork and chicken heads fortified with a mineral/vitamin supplement.
These experiments resulted in the growth rates given in Table 1.
Table 1. Average % increase in body length of animals reared under different
densities and in different tank sizes (available space)
Experiment
2
1. : tank size 1.7 m
2-4. : tank size 1.7 m2
2-4. : tank size 5.1 m2
7.1
14.5
17.4
18.3
Animal density (no. / m2)
10.6
14.1
17.6
15.5
14.8
12.6
13.9
14.9
14.0
14.1
14.6
14.7
The authors found that in experiment 1 the lowest density treatment tended to produce
the highest increases in total length. In experiments 2-4 there was no significant
effect of density or available space (tank size) on growth rates of animals. However
they warned that since the experiments were carried out in different tanks with slight
variations in thermal characteristics, precise comparisons of density may have been
compromised. They also found ‘dramatic clutch differences’ in growth.
In another series of experiments conducted on a commercial farm in Kenya (Zilber et
al. 1992), hatchling Nile crocodiles (C. niloticus) were reared under a range of
different densities in circular concrete ponds of area 113 m2 (79 m2 under water)
subdivided into eight equal segments (each 14.2 m2). Water temperature varied from
26 to 34oC and air temperatures from 24 to 38oC during the experiments. Animals
were fed a fresh mixture of fish, chicken and red meat, supplemented with vitamins
and minerals. One experiment looked at growth from 2-12 months age under
densities which started at 6, 9, 12, 15 animals / m2 and were reduced by 10% every
two months to reach final levels of 3.9, 5.9, 7.8, and 9.8 animals / m2. The average
growth of animals (in total body length) at each of these density regimes was 34, 31,
1
6
35 and 35 cm respectively, with no evidence that densities had any effect. The same
animals were used in a second experiment with initial densities 7.5, 10, 12.5 and 15
animals / m2 gradually reducing to 4.9, 6.6, 8.2 and 9.8 over the period 12-22 months,
and recorded corresponding growth rates of 31, 29, 29 and 27 cm. Again it could not
be demonstrated that density had affected growth of the animals. The authors
suggested that the use of good management in the trials had enabled the higher
densities to be reared without any fall off in growth. They warned that temperature
had played an important factor in growth during the cold season, especially in the first
experiment, and that there was a wide variation between individual clutches in the
research animals.
An experiment was conducted on hatchlings from the Edward River Farm (Garnett
and Murray 1986) reared in pens 1m x 2m containing a water area of 0.95m x 1m, at
densities of 5, 10 and 20 per pen (ie 2.5, 5, 10 animals / m2 ) though the authors
preferred to relate density to ‘dry land areas’ since ‘that is where the hatchlings form
their highest concentrations’. The experiment ran from hatchling to when the animals
were four months old. Animals were weighed weekly and had measurements on total
length taken once each month. Water supplied to the pens was a constant 30oC during
the trial but air temperature varied from 19 to 36oC. Animals were fed a diet of diced
pork fortified with a vitamin / mineral supplement. The authors found no difference
in growth (weight or length) among the different densities.
An experiment on the effects of density were carried out on juvenile freshwater
crocodiles (C. johnstoni) in a four-chamber controlled environment tank, each
chamber being 4m x 1.8m (Webb et al. 1983). Water temperature and temperature
just above the land area were maintained at 30.4oC (± 1.5) and 30.5oC (± 1.4)
respectively. Animals were fed fish supplemented by vitamins and minerals. The
experiment was run when the animals progressed from three to six months of age and
densities of 4.1, 5.6, 6.8 and 8.1 animals / m2 resulted in average growth rates (in
snout - vent length) of 0.60, 0.56, 0.57 and 0.59 mm per day respectively. The
authors concluded that optimal density was considered to be well exceeded in all pens
and for subsequent experiments using these animals a reduced density of 1.4 animals /
m2 was used.
Experiments were run on C. porosus reared in circular tanks (1m2 area)with water
temperature maintained between 30 and 33oC and air temperature variations of
between 20 and 38oC (Riese 1995). Diet was a mixture of red meat (buffalo, horse,
pig) and chicken heads (70:30) plus minerals, vitamins. In the first experiment
animals were reared at densities 10 and 20 animals / m2 from two days old to six
weeks of age. Average liveweight gain at the low density at 0.62 g/animal/day
(averaged over two light treatments) was significantly higher than 0.37 g/animal/day
recorded at the high density. A second similar experiment was run over a six week
period in the cooler winter months when the animals were two months old and
resulted in reduced growth rates of 0.30 and 0.29 g/animal/day for the two densities,
which was not significantly different. The authors attributed the latter result to the
dominant effect of fluctuating cooler air temperatures.
A trial involving 66 seven-month old alligators (Alligator mississippiensis) of average
weight 727g was run comparing densities of 2.8, 5.6, 8.3 and 11.1 animals / m2 in
1
7
controlled environment chambers of 2.1 m2 and maintained at 28oC (Elsey et al.
1990). After a period of 3.5 months animals recorded average percentage increases in
body weight of 110, 97, 90 and 77% for the above densities respectively. This was a
significant decrease.
A common thread among all the cited published literature on effects of density on
rearing crocodile species is the recognition that temperature plays such a dominant
role in growth response that to carry out experiments without accurately controlling
temperature generally produces inconclusive results. Also, researchers need to be
aware that there are often very large differences in response between different
clutches of animals. This is precisely the reason that we have designed and built our
own special research facility in which we can accurately control (and modify)
environmental conditions such as temperature. It also indicates why we have put a lot
of emphasis and effort in our initial research on the effects of temperature on a range
of different aged animals. Recognition of the importance of clutch to clutch variation
has been a vital element in designing experiments to specific biometrical
requirements. Unfortunately in most of the research referenced the statistical methods
of analysis of the data have used ‘animal to animal’ variation within tanks to test for
treatment differences (applied to whole tanks). This is not appropriate since density
effects are then completely confounded with tank effects and inherent differences
between different groups of research animals.
To be able to estimate true density effects (assuming environmental conditions are
accurately controlled and the same for all tanks) you need either
• replicated tanks of each density
or
sufficient numbers of different densities to generate an overall response pattern.
Objective
The objective of this study was to measure the effects of rearing 8.5 month old C.
porosus for a period of eight weeks at a range of different densities (depending on the
graded size of animal) keeping all other environmental and management factors
constant.
Materials and Methods
On 29/1/96 a full measuring was done on the 1995 cohort of research animals at the
conclusion of the experiment on the effects of light, and all rooms were returned to
the standard diurnal light cycle. There were 210 animals in the tanks in the main
research shed plus 15 animals recovering in the give-and-take tank, and the weights
ranged from 70 to 1710g per animal with an average of 659g. Segregation of
crocodiles by size has been recommended as an important factor in successful pen
rearing (Bolton and Laufa 1982). A new statistical design was formulated which
entailed allocating the 96 heaviest animals (greater than 690g) to six randomly chosen
tanks at densities of 4, 9, 13, 17, 23 and 30 animals per tank, and the next 120
heaviest animals to the remaining six tanks at densities of 5, 10, 15, 20, 30, 40
animals per tank, and the remaining nine smallest animals to the give-and-take tank.
1
8
This number of (unreplicated) densities at each size class was used to provide
sufficient points on which to base an overall response model. As usual the design
allocated animals to tanks on the basis of
• equal proportional representation from the various clutches (as far as
possible)
• approximately equal average initial animal weight per tank (within each of
the two graded size categories).
The tanks are 3m x 1.3m in dimension. The allocation to the experiment was done on
31/1/96 and animals in each tank were reared under constant environmental
conditions of 30oC air and 32oC water. The ‘standard’ diet of minced
beef/kangaroo/chicken heads plus specially formulated mineral/vitamin powder was
fed ad lib to each tank with amounts put out and amounts left uneaten on plates
recorded at each feeding. After a period of eight weeks the experiment was
terminated and a full measuring was done on 26/3/96.
Results
Liveweight response to density for each of the two size groups is shown in Figure 1.
Figure 1. Final average liveweight (g) for the two graded size classes of animals
reared at different densities. The tank response highlighted (#) is regarded as an
‘outlier’ and has not been used in fitting the overall response line for the
medium/large group.
For the small/medium groups of animals there was a significant reduction in final
weight as density increased and this was of an exponential form with rapid decrease
between 5 and 15 animals per tank then flattening out with little difference between
densities of 15 and 40.
1
9
For the medium/large groups there was one tank (density 9) which recorded an
extraordinarily high result completely out of pattern with the other responses.
(Further investigation of this particular response is presented later). If this point is
ignored there is a smooth response pattern which indicated a slightly increasing
curved relationship between final weight and rearing density. This is quite different
to the pattern observed among the smaller animals.
The response in terms of final average body length is presented in Figure 2.
Figure 2. Final average total body length (mm) for the two graded size classes.
The response highlighted (#) has not been used in fitting the response line for the
medium\large group.
The small/medium group responded in a manner similar to that shown for liveweight.
For the medium/large group (having deleted the outlying point) there was more
variation in response pattern than for weight which resulted in no overall pattern
(decrease or increase) with density.
To try to understand the ‘outlying’ response value it was useful to compare the nine
animals in this group with the animals in the medium/large groups at the two nearest
densities (4 and 13). From the experimental design the difference should not have
been caused by either different starting weights or different clutches (roughly the
same proportions from the eight clutches). To see what happened in the ‘magic’ tank
the individual responses (% weight gain vs initial weight) were plotted and compared
with the other groups (see Figure 3).
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0
Figure 3. Individual percentage weight gains of animals in the three tanks
containing medium\large animals at densities 4, 9 and 13 plotted against their
individual weights at the start of the experiment.
This shows that the nine animals each recorded relatively high weight gains and six
had gains of 50% or more. In the tanks with 4 and 13 animals of similar initial weight
only one achieved such a high growth rate. The discussion section will address this
further.
The response of ‘food conversion’ efficiency to different densities is given in Figure
4.
2
1
Figure 4. Food conversion ratios (liveweight as a percentage of food eaten) at
each rearing density. Values estimated at low densities (4,5) are regarded as less
reliable and have been excluded from the range of fitted response line.
Any accurate estimate of food conversion rate needs to be based on 10 or more
animals because of the large variation from animal to animal. Thus the fitted
response in Figure 4 has only been fitted to data in the density range 9-40. There was
no difference in food conversion between the small/medium and the medium/large
groups overall so a single response trend has been fitted. Also the tank with nine
medium/large animals which produced the large gain in weight yielded a food
conversion figure close to the densities around it, so has been used in fitting the
model. The trend was for a significant linear fall in food conversion rate from 26 to
24% as density increased from 9 to 40 animals per tank.
There were no mortalities among the research animals during the experiment. At each
weighing we record any evidence of damage to the skins of each animal. At this
young age injuries are very superficial and heal quickly : but it is interesting to use
these observations as an index of anti-social behaviour in the different groups of
animals in each tank. The incidence of skin damage is presented in Table 2
2
2
Table 2. No. of animals in each density group with evidence of skin damage.
Small / medium groups
Density per tank
No. damaged
5
0
10
0
15
0
20
0
30
1
40
0
Medium / large groups
Density per tank
No. damaged
4
1
9
1
13
1
17
6
23
0
30
5
Clearly most evidence of fighting/biting occurred among the medium/large groups.
An investigation into the relative size of the marked animals in each tank showed no
obvious relation to size ie some were among the smallest in a tank while others were
of medium and large sizes.
It is now appropriate to add the results of this experiment to the results referred to in
the background section, to form some overall consensus. Summaries of the responses
of growth rates to densities are given in Table 3.
Table 3. Growth rate responses to rearing densities from the current experiment
and referenced literature. Other factors relevant to response such as species and
age are also presented.
Reference
Species
Webb et al.
1992
Zilber et al.
1992
Zilber et al.
1992
Garnett and
Murray 1986
Webb et al.
1983
Riese 1995
Riese 1995
Elsey et al.
1990
Current trial
C. porosus
Age of
animals
(months)
0-1
C. niloticus
2-12
C. niloticus
12-22
C. porosus
0-4
6-15 →
4-10
7-15 →
5-10
2.5-10
C. johnstoni
3-6
4-8
C. porosus
C. porosus
Alligator
mississippiensis
C. porosus
0-1.5
2-3.5
7-10.5
10,20
10,20
3-11
8.5-10.5
Current trial
C. porosus
8.5-10.5
1-10
(s/m
group)
1-8 (m/l
group)
Discussion
2
3
Density
(no./m2)
Growth
rates
Response to
density
7-18
12-18%
length
31-35%
length
27-31%
length
not given
nil
.56-.57
mm/day
.62,.37 g/day
.30,.29 g/day
77-110%
weight
36-76%
weight
nil
26-35%
weight
slight
increase
nil
nil
nil
decrease
nil
decrease
decrease
General recommendations for rearing hatchling and juvenile crocodiles have been at
densities not exceeding 11 animals per square metre of pen floor area for hatchlings
and not exceeding 5-6 per m2 for animals up to one year of age (Blake 1994). Various
studies on different crocodilian species have been carried out in the past decade on the
effects of changing rearing densities. Because of the different species, the different
age periods considered, the different levels of densities and other differences between
the studies (water and air temperatures and degree of variation, size of rearing area
‘available space’, different measures of growth response) it is difficult to gain any
overall consistent appreciation of the true effect of density. In fact, most past research
has failed to detect any effect of density on growth rates. (See Table 3.) Hence
discussion will concentrate on the results from the current experiment.
Growth Response
The rapid fall in growth rate (liveweight, length) in the small/medium groups as
density increased from 5 to 15 animals per tank (1.3 to 3.8 animals / m2) suggests that
these sized animals suffer adversely from supposedly increased social interaction as
density increases. This effect diminishes as densities increase beyond 15 animals per
tank. The larger sized animals showed almost no change in growth rates over the
complete range examined 4-30 per tank (1.0 to 7.7 / m2). Fellow researchers (J.
Millan pers. comm.) have postulated that when larger, dominant animals are reared at
low densities in any enclosure they try to ‘claim a section of the area as their own
territory’ and this results in more aggressive behaviour among the whole group as
they defend their areas. However, as density increases animals quickly realise that
there is no way they can try to claim and defend an area when there are so many
equally large animals in the same pen. Thus, the lowest densities will not always
result in the highest growth rates for the whole group. It is possible that a density of
nine per tank for this sized animal in this size and type of tank (giving the ‘outlier’
points in Figures 1,2) is optimal but a more plausible explanation is that this particular
combination of animals just happened to form a more harmonious social group in
which each member was able to get plenty of food (noted by the increased
consumption per animal for this pen) and hence each grew rapidly. Further
experiments would be needed to see which hypothesis was correct.
Food Conversion
The result that there was no overall difference in food conversion efficiency between
the two size groups contradicts results that were observed in previous experiments
where smaller animals were poorer converters of food to liveweight gain. There was
an overall drop in efficiency as density increased in both size groups. There are
various explanations for this:
• animals are more stressed at higher densities
• animals waste proportionately more food in the water at high densities
(rushing to get away from the ‘battle zone’ around the feed trays).
Skin Damage
2
4
More evidence of fighting in the medium/large groups lends weight to the theory that
these animals are more aggressive and perhaps trying to establish territories. Hence,
grading off the smaller animals may be a useful management strategy for farmers in
reducing the overall levels of skin damage.
The response patterns show that smaller animals fare better when reared at very low
densities while larger animals can be reared just as well under higher densities.
Naturally individual farms have different capital cost structures and on-going
operational costs so that the most economic densities to use will depend on a host of
factors:
• animal growth rates, food conversion rates, skin damage, mortality rates at
different densities
• capital costs of tanks, sheds
• operational costs (water, heating, food, labour).
Obviously, operating with large tanks and stocking at high densities will reduce a lot
of these costs but this has to be offset by any reduction in animal performance.
Further experiments are necessary to consider even higher densities for both size
groups of this and other ages, since we do not seem to have reached density levels
where performance starts to really fall off.
References
Blake DK (1974) The rearing of crocodiles for commercial and conservation purposes
in Rhodesia. Rhodesia Sci News. 8 315-24.
Bolton MM and Laufa M (1982) The crocodile project in Papua New Guinea.
Biological Conversation Ed. Duffey. 22 (1982) 169-179.
Elsey RM, Joanen T, McNease L and Lance V (1990) Growth rate and plasma
corticosterone levels in juvenile Alligators maintained at different stocking
densities. Journal of Experimental Zoology. 255 30-36.
Garnett ST and Murray RM (1986) Parameters affecting the growth of the estuarine
crocodile, Crocodylus porosus, in captivity. Aust. J. Zool. 34 211-23.
Riese G (1995) Factors affecting food intake and growth in captive saltwater
crocodiles. MSc Thesis, Department of Zoology, University of Queensland.
Webb GJW, Buckworth R and Manolis SC (1983) Crocodylus johnstoni in a
controlled environment chamber: a raising trial. Aust. Wildl. Res. 10 421-32.
Webb GJW, Manolis SC, Otley B and Heyward A (1992) Crocodile management and
research in the Northern Territory: 1990-92. Proceedings of the 11th Working
Meeting of the IUCN Crocodile Specialist Group. Victoria Falls, Zimbabwe,
August, 1992. 233-275.
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5
Zilber A, Popper DN and Yom-Tov Y (1992) The effect of stocking density, origin of
eggs and water flow on growth, survival and body condition of Nile crocodiles
(Crocodilus niloticus) Herpetological Journal 2 31-34.
4.3
Hide-boards and Water Temperature
Earlier experiments (RIRDC report for DAQ-132A) showed that one and seven
month old crocodiles grew faster under dark conditions. This experiment was set up to
see whether the preferred dark may have been associated with stress, and whether
providing added hide-areas might provide the same benefits. Also, earlier work on
two month old animals had shown improved growth rates when animals were
provided with 34oC water instead of the recommended standard 32oC. Hence water
temperature was included as a second treatment factor to see whether the effect could
be repeated. The animals were all fed the same standard mince diet and air
temperature was set at 32oC in all rooms. Summary results of the experiment are
presented in the following table.
Table 1. Response of 2 size groups (S/M = small/medium, M/L = medium/large)
of two-month old animals to 0, 1 or 2 hideboards per tank in combination with
two water temperatures (32oC, 34oC).
Food consumed
Food conversion
Liveweight gain
(g
ratio
(g/animal/day)
DM/animal/day)
S/M
M/L
S/M
M/L
S/M
M/L
1.5 c*
1.6 bc
0.83 c
1.11 a
1.2 d
1.8 c
Number of
0
2.0 b
2.7 a
0.81 c
0.86 bc
1.6 c
2.3 b
hideboards
1
2.0 b
2.9 a
0.82 c
0.94 b
1.6 c
2.8 a
2
1.7 b
2.4 a
0.70 c
0.87 b
1.2 d
2.0 b
Water
32oC
o
1.9 b
2.5 a
0.94 b
1.07 a
1.8 c
2.6 a
temperature 34 C
* Within each treatment group (hideboard, temperature) values followed by a similar
letter do not differ significantly (p>0.05).
Food intakes for each size class of animal decreased in tanks without hideboards but
there was little difference between one or two hideboards. For both size groups the
34oC water induced a slight increase in food consumption. Hideboards had no
appreciable effect of food conversion efficiency by the S/M animals while among the
M/L animals there were higher, yet more variable results. The higher water
temperature resulted in significantly better food consumption for both size classes.
The combined effects of food eaten and conversion efficiency led to the pattern
observed in liveweight change. The hideboard effect paralleled the response of food
consumed. By increasing food eaten and also efficiency of conversion, 34oC water
produced significantly heavier animals in both size classes (50% for S/M, 30% for
M/L).
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4.4
Water Volume
Trial 1
Part of the reason behind this investigation was the belief by at least one US alligator
research/farming institute that alligators grow better in completely flooded pens.
(Refer to “Study Tour of Alligator Facilities in Florida and Louisiana” May 1996. A
report to RIRDC.) This experiment was set up to compare three different land:water
combinations in the tanks. The ‘standard’ combination for all research to date has
been a 50:50 area ratio of land to water. In this experiment the standard was
compared with a 70:30 and a 20:80 combination. Naturally, by changing the relative
surface area of water, the total volume of water in the tanks also changed. The 30%,
50%, 80% water ‘area’ treatments contained on average 66, 133 and 314 litres of
water respectively in the tanks. Analyses of growth response over the nine week trial
produced results listed in Table 1.
Table 1. Response of two size groups (S/M = small/medium, M/L =
medium/large) of five-month old animals to three different land:water area
ratios in the tanks
Liveweight gain (g/animal/day)
S/M
M/L
4.9 a*
10.7 b
Percentage 30
of
5.3 a
11.0 b
water 50
5.4 a
11.3 b
area 80
* Values followed by a similar letter do not differ significantly (p>0.05)
These results suggest that the 30% water treatment led to lower growth rate in each
size category, but there was quite large variation between the replicate tanks and so
the difference was not statistically significant.
Trial 2
The second water volume trial was carried out on the 1997 research animals from
16/2/98 at 42 weeks of age (average weight 728g) to 19/5/98 at 55 weeks (1019g).
Obviously the volume of water automatically affected water quality (dilution of
animal waste and food scattered in the water). Analysis of variance was carried out
on ‘tank average’ responses.
Treatments for this water volume trial were:•
•
30, 50 or 100% tank floor area under water (volumes 66, 133, 350 litres
respectively)
S/M or M/L size groups
in factorial combination. As this trial was restricted to 10 tanks, the 50% S/M and
M/L treatments were each evaluated in one tank only (the other combinations in two
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tanks each). Rearing densities of 4.9 animals/m2 and 6.4 animals/m2 for the M/L and
S/M size groups were used.
The results of this trial are presented in table 2. When the animals were turned onto
their backs for snout-vent lengths to be measured, a visual inspection was made of the
belly skins and any skins with evidence of marks or scratches were noted.
Table 2. Responses of two size groups (S/M = small/medium, M/L =
medium/large) of ten-month animals to three different land:water ratios in
tanks.
Average weight gain
% of animals with blemishes on
Water level
(g/animal/day)
belly skin
S/M
M/L
S/M
M/L
2.9 a*
6.2 a
17 b
52 a
30%
3.9 a
10.3 a
0c
0c
50%
4.9 a
2.9 a
0c
23 b
100%
* Values followed by a similar letter do not differ significantly (p>0.05).
For the smaller sized animals there was a consistent trend for animals to grow faster
when provided with increased volumes of water in the tanks. This was repeated in the
larger sized animals up to 50% water levels, but the two tanks with 100% water
resulted in very poor growth. The incidence of superficial skin damage recorded
showed significant levels of damage in the shallow water for both size groups, and a
significant amount in the M/L groups in 100% water. This was associated with poor
growth for this latter treatment.
In previous studies carried out using these research tanks, animals of all ages up to
one year of age were observed (by video cameras) to stay more in the heated water
than on the land area or on top of hide-boards. Thus by providing a greater amount of
water (and consequently less land area) the rearing density is effectively reduced.
The diet fed during each trial consisted of minced chicken heads and kangaroo meat,
supplemented with a special vitamin/mineral pre-mix. Animals often dragged pieces
of mince off the feed trays and into the water, so that the water was soon polluted.
This is the reason that the tanks were emptied, hosed out and refilled with warm water
soon after each feeding. Over the weekends when no feeding or cleaning was carried
out, animal waste built up (especially for the ten month old M/L animal groups) and
the water in the 30% tanks became very polluted. The confounding effects of water
volume and water quality were inseparable in these studies and there was no way of
knowing how much each one influenced the lower growth rates recorded in the 30%
tanks.
Patterns in this trial with ten month old animals were more erratic and not helped by
the fact that the trial was restricted to just ten tanks. In particular the M/L animals in
the two tanks with 100% water produced the lowest growth coupled with a significant
amount of skin damage, suggesting that these groups of animals were fighting each
other. Experience in catching animals for measuring has shown that animals are less
aggressive to handlers when the animals are under the water. Hence it was
anticipated that animals would have been less aggressive towards each other in the
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8
100% water tanks. Observations on crocodile behaviour on a commercial farm
(G.McClure, pers. comm.) suggest that dominant animals in a group tend to ‘rule the
water’ forcing less dominant animals to find safe land areas. If there is no land area
provided these latter animals will be forced into closer contact with the bullies. It
might also explain why the 80% treatment in the first experiment did not show the
same negative response.
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5.
Nutrition Research
The crocodile/alligator farming industry world-wide has moved in the direction of
developing and using formulated dry feeds over the last 5-10 years. Use of dry feed
in the American alligator industry has already been well established. Zimbabwean
researchers (F Huchzermeyer personal communications) have developed a feed pellet
for the Nile crocodile and Colombian scientists (Rodriguez et al. 1996) are working
on a vegetable based protein pellet and are evaluating enzymes, growth promotants
(non-antibiotic types) and vitamin E for Caiman crocodiles. Food costs account for
60-80 per cent of the total production costs on Colombian farms.
Other overseas researchers (Morpurgo 1992, Coulson et al. 1995, Rodriguez et al.
1996) reported varying responses to growth rates using dry formulated feed. Coulson
et al. (1995) reported that none of the many dry preparations they trialed could match
the growth rate of animals fed fresh meat, fish or chicken or other fresh products used
as supplements to dry feed. No significant differences in growth were found when 63
three day old Nile crocodiles were fed pellet/ground meat diets of 30:70, 50:50, 70:30
ratios over a seven month period. The authors also reported a significant difference in
the variance between the groups. However the variation in growth rates within the
different groups was smaller as the pellet portion of the diet increased.
Several forms of aquaculture pellets currently available were offered to young
crocodiles but were not eaten. Negotiations were held with Ridley Agriproducts who
have feed mills in Brisbane and Rockhampton.
Pellets diets were expected to offer many advantages including:
• quicker turn-off time for market size crocodiles
• elimination of freezer storage
• provision of a consistent high quality feed which meets the needs of the
animals including the need for vitamins and minerals
• formulated feed that would be stable under tropical farm conditions
• a decrease in nutritionally linked diseases
• reduced labour inputs through ease of handling and feed preparation.
At an industry seminar in November 1995 the idea of developing an odourless mash
that could be added to traditional diets was suggested. This could remove the
problem of acceptability in relation to pellet texture. It was decided that the 1996
hatchlings be tried on mash and pellet diets immediately after hatching.
Diet formulation has been based on the suggested amino acid profile put forward by
Staton and Vernon (1991).
5.1
On-farm Evaluation of Pellet Prototypes
Each crocodile farmer was asked to fill out an evaluation form when trialing
prototype pellets on their farms. Reports on initial prototypes 1-4 have been
presented in RIRDC Report for DAQ-132A. Specific questions were asked relating
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1
to the pellets and method of feeding. The following is a description of the prototype
pellets and a brief summary of the actual assessments.
1996 Prototype 5 and Mash Prototype 1
This pellet was specifically designed for hatchlings. It consisted of high moisture
balls, 5-8 mm in diameter with a soft and rubbery consistency. It was relatively stable
in water and manufactured in two colours (red and brown) with a protein content of
35 per cent and had a relatively strong aroma.
The mash had a very fine texture, was yellow/white in colour with the same protein
content as above but was almost odourless. The basic animal protein ingredients were
fishmeal, bloodmeal and meatmeal, the vegetable protein products were full fat
soybean and wheat and vitamins and minerals were included.
The protein content of the pellets and mash was low (35 per cent). We had hoped to
have a diet based on plant protein to avoid the strong aromas that are given off by
using animal protein products but this did not eventuate due to difficulties with
manufacturing. To increase the plant protein content of the plant based diet at the
time would have significantly increased the cost to the manufacturer. As this was
primarily an acceptability trial, the diet was left at 35 per cent protein.
1996 Mash Prototype 2
This mash was brown in colour, texture as above, 45 per cent protein with a mild
odour.
5.2
Acceptability Trials
Trial 1
This trial ran from 14/8 to 15/9/95, when the two animals grew from 13 to 18 weeks
of age. Animals were tagged and measured on 14, 15th August following the normal
weekend fasting. They were divided into 2 size classes and allocated to a balanced
research design on 16/8. For the remainder of that week the animals were fed the
standard mince ration. The aim of this experiment was to assess the degree of
acceptability of the latest pellet prototype to the animals, evaluated under uniform
controlled conditions. To give the pellets the best chance of success, an attempt was
made to gradually wean animals from their usual diet of minced chicken
heads/kangaroo/beef with vitamin powder onto pellets by slowly substituting pellets
for the mince. The treatments were imposed as follows, with the proportions X:Y
representing the relative composition (on an actual weight basis) of fresh mince :
pellets in the diets:
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2
Week :
Diet A
(control)
Diet B
Diet C
(* 2 days only)
1*
100:0
2
100:0
3
100:0
4
100:0
5
100:0
100:0
100:0
75:25
75:25
50:50
50:50
50:50
0:100
50:50
0:100
During weeks four and five of the trial animals in the tanks fed diet C (100% pellets)
ate virtually nothing, compared with 2 kg of mince (diet A) consumed weekly by the
larger groups in other tanks. This is reflected in associated final liveweights
measured on 15/9 presented in Figure 1. Animals were left in their tanks and all
returned to diet A for a further 24 day period, to see how much the disadvantaged
groups could ‘compensate’ during a recovery period. The graph shows that the
setback experienced by the diet C groups was sufficiently great that they still had
relatively lower weights after the recovery period.
Figure 1. Liveweights of animals fed three diets from 14/8 to 15/9/95 and then
fed the same standard diet until 9/10/95
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3
Pellet Trial II
This trial ran from 9/10 to 20/11/95, when the animals grew from 21 to 27 weeks old.
From the preceding trial, it was noticed that animals were adept in picking out pieces
of mince from the mince / pellet mixes. Some farmers have indicated that when they
actually grind up pellets by putting them through a mincer together with fresh meat,
the pellets become incorporated with the mince and are eaten by their young
crocodiles. Even if pellets can eventually be substituted for part of a fresh meat diet,
the farmers reckon this will be a significant cost saving. Hence, this trial was
designed to
• test whether pellets could be successfully supplemented to a mince diet via
thorough incorporation, and using a more gradual weaning process
• evaluate the nutritional aspects of mince / pellet mixtures (evidenced by
growth rate, and feed conversion ratios).
The procedure used was to put the pellets through the mincer to achieve a ‘mash’
consistency, and then thoroughly mix with the mince so that the pieces of mince were
effectively coated in the drier mash. A design similar to the previous experiment was
used, after the animals had been re-allocated into uniform initial groups. The
treatments were as follows ( proportions X:Y represent relative weights of mince :
pellets)
Week :
1*
2
3
4
5
6
100:0
100:0
100:0
100:0
100:0
100:0
Diet A
(control)
100:0
85:15
70:30
55:45
50:50
60:40#
Diet E
100:0
85:15
70:30
55:45
40:60
50:50#
Diet F
*2 days only
#
Food consumption dropped dramatically during week 5 so the proportions of mince
were increased for the final week
Liveweight changes during this second trial and for a further period of two weeks
(when all animals were fed mince) are shown in figure 2.
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4
Figure 2. Average liveweights of animals fed the three diets from 10/10 to
20/11/95 and then all fed the same mince diet from 20/11 to 4/12/95.
5.3
Hatchling Response to Pellets
The major difficulties in achieving acceptability of a pelletised diet have been in the
areas of odour, texture and preventing the pellets from going mushy. In 1996 a trial
commenced concentrating on three areas: pellet texture, the importance of flavour and
smell and the influence of feed colour.
1996 Hatchlings
An acceptability trial involving 251 saltwater crocodiles, hatched over a nine day
period (9 to 17/4/96) commenced on the 20/4/96. Hatchlings were tagged and
weighed within a few days of hatching. Hatchlings were reared with water
temperature at 32°C and air temperature at 30°C. Three diets were used: pellets,
mash mixed with 28 per cent water and a control mince diet. The mash and water
were mixed together and put through a mincer. This produced a moist textured
“sausage”. None of the hatchlings had been offered any food prior to the
commencement of the trial. Two feed trays per tank were used, one placed in front of
the hideboard and the other placed at varying distances from the first tray. For the
pellet treatment groups, a tray of each colour pellet was offered in each tank. Trays of
the different coloured pellets were placed in reverse positions per tank and varying
distances apart to even out any positional preference. Feed was weighed into and out
of the tanks.
Closed circuit monitors were set up in two of the rooms to monitor the hatchlings’
reaction to the mash and pellet diets. The pellet treatment tank was videoed on a three
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5
hourly tape while the mash treatment was observed for one to two hour periods during
feeding.
On Day 1, within half an hour of the trays being placed into the relevant tanks, some
hatchlings appeared to show interest. Some hatchlings would:
•
•
•
•
crawl over both trays and lay on pellets/mash for periods up to two minutes
approach the trays then back off
cross from one tray to the other
smell the food but not appear to eat any of the pellets or mash.
Pellets and mash were observed in the water at cleaning out. This was thought to
have occurred more from the hatchlings carrying the mash/pellets on their bodies back
into the water after walking through the trays than from taking the food into the water
and wasting some while eating.
Hatchlings in the control groups starting eating from Day 2 of the trial and were
eating well when the trial was terminated after the feeding on 28/4/96. The oldest
hatchlings at this stage were 20 days old and those in tanks fed pellets or mash still
had not apparently eaten any of these diets, relying only on nutrients from the yolk
sac. Hatchlings were not weighed or measured after this short period.
In this trial the pellets and mash were stored under refrigeration which decreased the
aroma of the pellets when they were initially fed out. After four hours in the warm
humid environment of the crocodile facility the smell from the pellets was appreciably
stronger. The manufacturer indicated that the smell associated with the pellets most
likely arose from mould inhibitors and humectants used in the formulation of the
pellets.
Two reasons could be given for the non-acceptance of the trial feed: the nonrecognition of the mash and pellets as a feed source or the strong aroma associated
with the pellets. Colour had no apparent influence on acceptability. It has been
suggested (Manolis et al. 1989) that hatchlings may be genetically programmed to
avoid strong smells and that clutch specific preferences may exist for different diets.
This could account for the non-recognition of the pellets and mash as food sources.
This initial response differs from that in South Africa (F Huchzermeyer personal
communication) where farmers achieved most success in acceptability of pellets when
these were used as the first source of food and even greater success whenever pellets
had some movement associated with them. Research on food preference and
attractability in young Nile crocodiles (Murpurgo et al. 1991) showed that animals
initially preferred live fish over three other diets of dead fish, live chicks or ground
meat. Ground meat was the least preferred The movement of the fish was considered
a part of its attraction. Once the live chicks had been recognised as a feed source they
were preferred to the dead fish. The ground meat was always the least preferred feed.
1997 Hatchlings
Having developed a pellet which juvenile crocodiles could be trained to eat as a sole
diet, it was decided to test whether newly hatched animals would initiate feeding on
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6
such a diet. There were anecdotal claims by people in the industry (both researchers
and farmers) that the best chance of getting crocodiles to eat a pellet was if it was fed
as their first meal. The argument was that once an animal developed a taste for fresh
meat it was going to be very difficult to get it to eat an artifical food pellet.
In this experiment eight clutches of 1997 research animals (newly hatched) were
placed in individual research tanks (since they were considered too small to tag yet).
Two randomly selected clutches were fed the standard meat ration (minced chicken
heads and kangaroo meat supplemented with vitamins and minerals), one clutch with
both meat and pellets on separate trays, and the remaining five clutches were fed
pellets only. Within three days the groups fed mince had initiated feeding and by day
14 average consumption of meat was 4g/animal. Meanwhile, the animals fed pellets
had still not begun to feed by day 19: they would crawl through the pellets and even
‘mouth’ individual pellets but were not seen to swallow any (even though pellets were
small and moist). In the tank with both meat and pellets the pellets were uneaten
while the meat was readily eaten. At this stage it was thought that the animals might
starve to death if the diet was maintained indefinitely, and it was important that the
animals were not set back too much for future experiments. Hence, mince was fed to
all clutches and all of the animal groups previously on pellets began feeding
immediately on the mince. In the subsequent five day period animals in the latter
groups ate 3.6 g/animal/day compared with 5.0 g/animal/day eaten by the groups
which had been on mince throughout.
5.4
Pellet / mash and Water Temperature Trials
A trial commenced on the 29/4/96 with the aim of gradually weaning the hatchlings
onto mince and dry food feed. The hatchlings retained their same basic feed
treatments but the components of the dry food diets changed to 90 per cent mince and
ten per cent mash or pellets. Diet composition gradually changed over a number of
weeks as shown in Table 1. Over a two week period from 13/5/96 two replicates of
each treatment had the water temperature raised from 32°C to 34°C. The air
temperature remained the same at 30°C. This was done to confirm earlier results in
1994 which indicated that young animals housed at the higher temperature produced
more rapid growth rates (in animals fed on a mince diet).
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Table 1. Mash and pellet diets for acceptability and weaning trial
Period
20 - 28/4/96
29 - 31/5/96
3 - 14/6/96
17 - 28/6/96
1 - 5/7/96
8 - 12/7/96
15 - 19/7/96
22 - 26/7/96
29 - 2/8/96
5 - 9/8/96
12 - 16/8/96
% Mince
0
80
70
60
50
40
100
30 or 75
0 or 60
0 or 50
0
% Mash or Pellets
100
20
30
40
50
60
0
70 or 25
100 or 40
100 or 50
100
When the mash component reached 30 per cent, it became difficult to achieve
complete mixing by hand, so the mash and meat were roughly mixed together and
then put through a mincer. This made it almost impossible for the hatchlings to pick
out the meat pieces. The “sausage” produced from this mix had a good texture.
In the period between the measuring on 5/6 and on 15/7/96, 27 animals in “poor”
condition needed to be removed from the main trial and given special care in the runt
tanks. Of these, 18 were in the “control, 32°C” tanks. In the analysis of
measurements taken on 15/7/96 the data from the “removed” animals were included
(even though they were in a different area). However, for subsequent measurements
taken on 19/8/96, data from the two “control, 32°C” tanks were disregarded. In the
week of 22/7/96 it was noticed that the pellets had spoiled. Given the high moisture
content and the age of the pellets, (14 weeks) this was not unexpected. Fungal
contaminant Penicillium sp was isolated from a sample taken of the pellets.
Penicillium sp is an opportunistic contaminant of feed and had grown to the stage
where it was visible on the pellets. Some species of this fungi family can be toxic.
As the toxicity of the Penicillium sp could not be determined immediately the pellet
treatment was discontinued.
On 19/8/96 all crocodiles were weighed and measured. Water temperatures in the
34°C tanks were returned to 32°C. It is interesting to note that it took only three
weeks to switch the pellet treatment groups over to 100 per cent mash (22/7-12/8/96).
In hindsight it was believed that the weaning onto mash could have been achieved
over a much shorter period of time.
Figure 1 shows the average liveweights at three measuring times (at hatching, 7.5
weeks old, 13 weeks old). Figure 2 shows the average total length at ages 7.5 and 13
weeks.
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8
Figure 1. Liveweight response to three diets and two water temperatures
Bodyweights at 5/6/96 and 15/7/96 tended to reflect a temperature effect rather than
any consistent differences between diets. Statistical analysis of the June weights
showed no significant difference between the three feed types but a trend for
hatchlings to grow faster at 34°C than 32°C (significant at 10 per cent probability
level). Average bodyweight at 32°C was 82 g compared with 90 g average
bodyweight at 34°C. By the 15/7/96 there was a significant advantage at 34°C
(p<0.05) with animals reared at 34°C having an average weight of 170 g compared
with an average of 151 g for animals at 32°C.
Figure 2. Total length response to three diets and two water temperatures
3
9
There was little difference in 5/6/96 body length due to diet or to temperature (345
mm at 32°C, 351 mm at 34°C). However the average total body length at 15/7/96 of
404 mm at 32°C was significantly lower than the average length of 421 mm at 34°C
(p<0.05).
The following table shows the increase in weight and length in the period from
15/7/96 and 19/8/96. During this period the crocodiles on the mash/mince diets had
been gradually weaned to 100 per cent mash diet since the pellets had spoiled on the
22/7/96, mash was substituted for pellets in the appropriate diets. (Note that results
from the “control, 32°C” treatment have been deleted due to the large number of runts
which had to be removed prior to 15/7/96).
Table 2. Changes in liveweight and total body length from 15/7 to 19/8/96 due to
three diets and two water temperatures
Treatment
% increase in
% increase in
liveweight
total length
-*
-*
Control (mince)
32°C
21a
96a†
34°C
78b
21a
Mash/mince(#)
32°C
66b
19a
34°C
41c
15b
Mash/mince
32°C
39c
15b
34°C
* There were too many animals removed from this treatment to make any meaningful
calculations.
# These treatments followed on from pellet diets.
† Values in a column followed by a similar letter do not differ significantly (p>0.05).
Conclusions
This initial nutrition research concentrated on achieving acceptability of a pelletised
diet. Different shaped and textured pellets were trialed with moderate success.
Acceptability at a ratio of 50 per cent meat/50 per cent pellets was achieved with most
of the pellets. Acceptability of a straight pellet diet proved difficult. Any increase on
this ratio inevitably led to the animals eating the meat and rejecting the pellets. This
suggested that the meat content at a ratio of 50:50 was enough to camouflage the
odour/taste/texture of the pellets. At levels above this rate, pellets significantly
affected the odour and texture of the feed presented.
Most of the diets trialed were low in protein content but the work was primarily
concentrating on acceptability and not growth rates. Nutritional profiles can be
manipulated to meet the animals’ needs once acceptability has been achieved .
4
0
5.5
Feed Additives
Two short observational trials were conducted to examine whether flavour additives
might increase acceptability of dry formulated diet for crocodiles. Poultry digest and
a number of food flavourings were mixed with the mash. The poultry digest trial had
a twelve day duration from 26/8 to 6/9/96 while the flavour additives trial had a
fifteen day duration from 23/9 to 7/10/96.
Poultry Digest Trial
Animals were allocated on the basis of clutch and bodyweight to form similar groups
of animals in each tank. The treatments were:
• poultry digest sprayed on to the mash (PDS)
• poultry digest incorporated (PDI) mixed by hand with the mash and then put
through the mincer
• control diet consisting of 70 per cent kangaroo/30 per cent chicken heads plus
vitamin/mineral mix (two per cent by weight).
The PDS and PDI treatments were fed on separate trays in the same tank, while the
control was fed on two trays per tank. Poultry digest is a heat-treated mix of chicken
stomachs and their digestive enzymes. Its strong aroma necessitated dilution with
water at the above mentioned rates.
Poultry digest was used at strengths of 35 per cent (week 1) and 20 per cent (week 2)
for the spray treatment (PDS) and 35 per cent for the incorporated treatment (PDI). A
third tray of plain mash was added to each of the PDS/PDI tanks for the final four
days of the trial.
Results
There was little difference in the average weekly consumption of PDS and PDI
treatments per tank (204 g, 298 g respectively). However total feed consumption by
the groups fed the PDS/PDI/Plain mash averaging 574 g per tank per week was
considerably less than the corresponding control diet figure of 1778 g. Total
consumption over the length of the trial for the three treatments was: PDS 3.26 kg,
PDI 4.77 kg (plain mash 1.15 kg) and Control 14.2 kg.
The following table lists the weekly and total consumption figures.
4
1
Table 1. Weekly and total amounts of PDS, PDI, plain mash and control
(mince) consumed.
Room
Tank
Feed
Treatment
Weekly
Total
Total
Consumption
Consumption
Consumption
(g)
per diet (g)
per tank (g)
A
PDS
302/318,269*
889
1
A
PDI
414/267
681
1570
1
B
PDS
234/142,108*
484
1
B
PDI
317/195
512
996
1
A
CONTROL
1350/1562
2912
2912
2
B
CONTROL
1631/1989
3620
3620
2
A
PDS
83/41,69*
193
3
A
PDI
313/210
523
716
3
B
PDS
374/197,164*
735
3
B
PDI
261/206
467
1202
3
A
CONTROL
1855/2121
3976
3976
4
B
CONTROL
1664/2056
3720
3720
4
A
PDS
206/228,58*
492
5
A
PDI
326/234
560
1052
5
B
PDS
157/82,91*
330
5
B
PDI
353/360
713
1043
5
A
PDS
221/91,176*
488
6
A
PDI
342/267
609
1097
6
B
PDS
354/231,224*
809
6
B
PDI
429/273
702
1511
6
PDS = Poultry Digest Sprayed, PDI= Poultry Digest Incorporated in mash
* Indicates amounts of plain mash consumed in the second week of the trial (4 days).
Poultry digest has previously been used in dog food trials and has been shown to
increase rates of consumption (A Stallman personal communication). In the current
evaluation for young crocodiles, the poultry digest did not appear to have any effect
on consumption. Total consumption for PDS/PDI/plain mash dropped in the second
week by four per cent while the control group increased consumption by 19 per cent.
At the end of the poultry digest trial it was considered unnecessary to weigh and
measure the animals due to the short period involved in the digest trial and the low
consumption rates achieved. The strong aroma of the poultry digest would appear to
contribute to the low amounts eaten.
Some indirect comparisons could be made of the effect of the PDS and PDI
treatments by looking at a previous trial using 100 per cent mash diet, with similar
stocking densities. The average consumption was 9 g/animal/day compared with the
6 g/animal/day from this trial.
The poultry digest mixed at the strengths of 35 and 20 per cent had no effect on
increasing the acceptability of the mash diet.
4
2
Food Flavourings Trial
This trial continued on from the poultry digest trial, without any weighing or
reallocation of animals being carried out. Each room was randomly allotted a food
flavour. Seven food flavourings (Saroline Flavouring Premixes) were trialed at a rate
of two per cent by weight added to the mash. An unflavoured mash was used as a
control. The food flavouring premixes were powders containing a natural blend of
oils, natural extractives and other food ingredients. Flavours used were fish, bacon,
chicken, ham, beef, onion or garlic.
The main trial consisted of the first five flavours plus a control (plain mash) each fed
to the two tanks in one of the rooms in the main research facility. Each room was fed
the same additive to avoid having more than one odour per room. The non-animal
based additives (onion and garlic) and a control were trialed in the runt tank.
Of the food flavourings used, the beef treatment recorded the greatest consumption
over the trial period (see Table 2). Apart from bacon, all the flavours outdid the plain
mash control diet. The garlic and onion flavours were stopped after poor
consumption in the first few days of the trial.
When the flavours were mixed with the mash, the smell of the particular flavour was
evident. However, once water was added to form the moist pelleted food, the natural
smell of the mash tended to mask the aroma of the flavourings.
Average total consumption of all flavoured diets was 3.46 g which was higher than
the plain mash at 2.71 kg. The average daily consumption for the PDS and PDI in the
previous trial were 6 g/crocodile/day while the food flavourings averaged 11
g/crocodile/day.
Table 2. Weekly and total feed consumption of mash with various food flavourings
Room
Tank
Flavour
Weekly
Total
Total
Consumption(g) Consumption
Consumption
*
(kg) per tank (kg) per flavour
A
Fish
899/898/391
2.18
1
B
Fish
489/632/211
1.33
3.51
1
A
Nil
407/502/186
1.10
2
B
Nil
541/804/265
1.61
2.71
2
A
Bacon
303/390/142
0.83
3
B
Bacon
556/750/246
1.55
2.38
3
A
Chicken
824/759/253
1.84
4
B
Chicken
601/650/242
1.49
3.33
4
A
Ham
959/1432/332
2.72
5
B
Ham
401/463/206
1.07
3.79
5
A
Beef
643/928/215
1.79
6
B
Beef
1150/1022/349
2.52
4.31
6
* The third figure indicates amount consumed for Day 1 of Week 3.
As expected, neither of the two vegetable based flavours (onion, garlic) enhanced the
mash diets. The garlic flavoured mash was not eaten at all, while 80 g of the onion
4
3
flavoured mash was consumed over the same period. Both treatments were stopped at
the end of the week and animals placed onto the normal mince diet. Beef flavouring
would appear a logical choice of flavour additive to use in crocodile feed. Based on
this short trial work, beef flavouring has been used in subsequent pellet trial work
with some success.
Conclusion
It remains to be seen if the inclusion of a food flavour at higher rates than the two per
cent tested might significantly increase consumption of a dry diet formulation. Three
flavour enchancers of fish, poultry and blood which are used in aquaculture feed
formulations were mixed with alligator dry feed formulation in trial work on the
American alligator (Coulson et al. 1995) and failed. This was not unexpected as the
researchers suspected that what works for one animal species would not necessarily
work for another.
5.6
Growth Response Trials
Four experiments were carried out to evaluate the comparative nutritive value of the
pellets and mash diets. The research was carried out using two sequential year-groups
of animals which hatched in April 1996 and 1997 and details of each experiment are
presented in the following table.
Table 1. Details of experiments conducted at the DPI crocodile research facility
in Townsville since October 1996.
Period
10/10 - 9/12/96
Age of
animals
(weeks)
26 - 34
10/12/96 30/1/97
31/1 - 21/4/97
34 - 42
42 - 54
7/5 - 26/5/97
1-4
Experiment
A. ‘Pelleted mash’ nutrition
(diets of meat, meat+mash, ‘pelletised’ mash)
B. Commercial pellet nutrition
(diets of meat, meat+pellets, pellets)
C. Commercial pellet nutrition
(diets of meat, pellets)
D. Hatchling pellet acceptance
(diets of meat, pellets)
After years of on-farm evaluations of early pellet prototypes DPI has developed a
moist pellet which young crocodiles will eat as a sole diet. These trials were the first
steps in confirming pellet acceptability and evaluating the relative nutritional value of
the basic mash ingredient and a pellet subsequently produced by a commercial feed
milling company (Ridley Agriproducts). The mash and pellets used in the
experiments contained levels of vitamins and minerals equivalent to the levels fed as
additive pre-mix powder to the standard minced diet of chicken heads and kangaroo
meat. However, the protein content of the mash and pellet diets was only 45%, 35%
respectively, compared with 50% for chicken heads and 83% for kangaroo meat (all
on a dry weight basis). There were big differences in the moisture content of the
various diets used in the experiments : meat (73%), pellets (34%), mash (13%),
4
4
meat+pellets (53%), meat+mash (43%). Hence, to provide a fair comparison between
diets, it was necessary to convert all diets to the same ‘dry matter’ basis. Table 2
contains summary information of the results of the three experiments.
Table 2. Response of 2 size groups of juvenile crocodiles (S/M = small/medium,
M/L = medium/large) fed different diets. Food conversion ratios are expressed
as increase in animal liveweight divided by estimated amounts of dry matter
food eaten.
Exp.
A
B
C
Diet
Meat
Meat+mash
Mash pellets
Meat
Meat+pellets
Pellets
Meat
Pellets
Food consumed
(g/animal/day)
S/M
M/L
5.2 d*
8.8 c
7.3 cd 11.9 b
7.7 c
17.0 a
5.8 c
9.7 bc
10.3 bc 16.2 ab
9.3 c
17.8 a
10.3 c
12.8 bc
16.8 b
31.5 a
Food conversion
ratio
S/M
M/L
0.87 bc 1.00 a
0.75 c
0.93 ab
0.26 d
0.33 d
0.99 a
0.93 a
0.55 b
0.60 b
0.21 d
0.35 c
0.62 a
0.63 a
0.08 b
0.16 b
Liveweight gain
(g/animal/day)
S/M
M/L
4.5 d
8.8 b
5.5 cd 11.0 a
2.0 e
5.6 c
5.7 ab
9.0 a
5.6 ab
9.8 a
2.0 b
6.4 a
6.3 a
8.3 a
1.3 b
5.0 ab
* Within experiments values followed by a similar letter do not differ significantly
(p>0.05).
In all three experiments animals in both size classes were eating more dry matter
(DM) in the pelleted diets than in the meat diet. There was generally only a small
difference in DM intake between the pellet diets and mixtures of pellets or mash with
meat. However there were large differences in the animals’ ability to convert DM
eaten into subsequent liveweight growth. Whereas the meat diets produced 87-100%
return rates for animals over the age period 26-42 weeks (experiments A, B) and 6263% over 42-54 weeks (experiment C), the pellet diets returned only 21-35% and 816% over the corresponding periods. This clearly demonstrates that the nutritive
value of the pellets and mash was only about one-quarter of that of the mince fortified
with pre-mix. However, the primary focus over the past three years has been to work
with the milling company to produce a product which the animals will eat, and we
have not worried too much about optimal content.
The end result was that animals fed on sole pellet diets grew slower than animals fed
on a meat or a meat+pellet diet, and in proportional terms this was greater for the S/M
sized animals. These results clearly illustrate the exciting opportunities that now exist
in pellet development. We have been able to get our animals to ingest around twice
as much DM food via a pelleted medium as they were eating on an ad-lib mince diet,
so it is now a matter of increasing the nutritive levels while at the same time keeping
costs to a minimum.
4
5
5.7 Recent Developments
Further pellet development has been on hold since June 1997 while cooperating food
manufacturer Ridley Agriproducts re-tooled its Narangba factory. A special
workshop was convened in Townsville on 21,22/1/98 and respected national animal
nutrition experts were sponsored to attend. Representatives of the Qld crocodile
farming industry were also sponsored to attend. The objectives of the workshop were
to:•
•
formulate least cost diets suitable for hatchlings, grower and breeder
crocodiles
formulate vitamin and mineral pre-mixes to meet the requirements for
hatchling, grower and breeder crocodiles.
Subsequently B. Davis and R. Jack have travelled to South Australia to find out more
about pellet manufacturing equipment and processes. A new pellet prototype (based
on pellets used in the tuna aquaculture industry) was trialed for ‘acceptability’ over a
two week period on the 1997 research animals during the water level experiment.
(Because pellets were offered as replacement diet in all tanks, the existing experiment
was not compromised). Results showed that the pellets were accepted by the 13
month old animals as a sole diet with no wean-on period required.
DPI is in the process of securing milling equipment so that pellets can be made on
site. This will be followed up with on-farm milling demonstrations and further
research on diet formulations to determine optimal content (cost and growth rates).
5.8
Runts
During the time when most of the year’s cohort are being used in the research
complex for a planned experiment, the ‘left-over’ smallest animals are kept in a room
in a separate shed. Most of these animals would be called ‘runts’, but, under various
‘extra care’ strategies, some of these actually begin to grow rapidly, and become large
and healthy enough to be used for the next main research experiment. Naturally, the
actual process of ‘grading off’ these smallest animals so they are no longer competing
with their much larger relatives is in itself likely to be a remedying effect. However
we have found that most runt animals do not respond, and remain in the runt tank or
waste away and die.
This article describes several strategies used on the 1995 and 1996 cohort runts.
Whether any of these strategies would ever be a commercial proposition is yet to be
evaluated and will need further pilot work.
The ‘give and take’ tank consisted of a tilted Reln tank which was been divided into
three compartments. Each compartment had a water heater and hide-board.
4
6
Vitamin Injection Trial (Dec.95 - Jan.96)
In December 1995 there were 16 small animals ‘left over’ from an allocation of the
1995 cohort to an experiment on the effects of light in the main complex. All animals
had just been measured and were 29 weeks old. These left-overs were divided into
two balanced groups of eight animals (on the basis of clutch and liveweight) and one
group were injected with a single dose of the multivitamin Multi® . All animals were
then allocated randomly to the three compartments and reared under standard
conditions (fortified minced meat diet, water and air temperatures set at 32oC) for a
period of eight weeks, after which they were subjected to a full measuring.
Table 1 contains the research information resulting from this pilot study. These
animals were very small for seven month animals and would be regarded by industry
as abject failures. With a wide variation in liveweights at the start of this exercise (50
- 100g) it was decided that a percentage increase in liveweight over the eight weeks
was a better overall index of response than absolute weight gain. Any animal which
doubled in liveweight over the period was regarded as a ‘success’ in terms of being on
the road to possible recovery and potential usefulness.
Table 1. Results of trial comparing injected and control animals.
Clutch *
1
2
2
7
3
4
4
4
4
4
5
5
5
6
6
6
Initial
liveweight
(g)
100
100
90
90
90
100
60
60
110
110
60
80
60
70
110
50
Final
liveweight
(g)
260
220
220
220
140
320
70
180
240
250
(died)
150
210
90
230
70
Injected
Yes
No
Yes
No
Yes
No
Yes
No
No
Yes
No
Yes
Yes
No
No
Yes
% weight
increase
‘Success’
160
120
144
144
56
220
17
200
118
127
(died)
87
250
29
109
40
Yes
Yes
Yes
Yes
No
Yes
No
Yes
Yes
Yes
No
No
Yes
No
Yes
No
Thus, four of the eight animals which were injected (50%) were judged as ‘successes’
compared with six out of the eight which were not injected (75%). Because of the
small numbers of animals in this study, this difference is not statistically significant
(p>.05). The trend was opposite that observed in an earlier pilot trial on runts of the
1993 cohort (results described in Bulletin No.1). Accurate evaluation of treatment
effects may be clouded by ‘clutch’ differences - unfortunately there are insufficient
4
7
numbers of animals in the different clutches to regard clutch as a factor in the data
analysis.
The fact that there was only the one mortality over the observed two month period
indicates that runts surviving to seven months have the ability to struggle on when
separated and reared with similar sized animals.
Feeding Trial (June-July 1996)
The 33 smallest animals in the 1996 cohort in June 1996 (seven weeks old) were split
into three groups on the basis of balanced liveweight and each group placed in one of
the compartments in the runt tank. Each group was reared for a period of six weeks
under the same environmental conditions (as described in the previous section), but
subjected to different feeding strategies:
(A) individual animals force-fed (standard mince diet) twice weekly for the
first two weeks
(B) animals offered standard mince over which small live worms were placed
(C) animals offered standard mince plus Snappy Tom® tinned cat food. (This
particular pet food was the only one to show any promise in an earlier
pilot trial which looked at a wide range of dry and wet pet foods.)
As for the preceding experiment an animal was given a ‘success’ rating if it achieved
a certain percentage weight increase. Because the animals were very young (seven
weeks old) and the period was only for six weeks, this level was set at 50%. The final
results are presented in the following table.
Table 2 (i). Percentages of ‘successes’, percentage mortalities and final average
liveweights (of survivors) for the three feed treatment groups.
Feed Treatment
A
B
C
Percentage
of successes
0
45
55
Percentage
mortality
36
18
18
Av. final weight
(g) and range
66 (50-70)
67 (50-90)
68 (40-90)
These results suggest that force feeding very young hatchlings is an ineffective
strategy (high mortality rate and no ‘successes’), and may have been worse than doing
nothing at all - although there was no such true ‘control’ in this experiment.
Naturally, frequent catching of animals and the process involved in force feeding
would be expected to generate extra stress for these animals. The other two strategies
may offer hope although again there was no control for comparison.
It is always interesting to look at results in terms of clutch effects. This was done in
the following table for those clutches with sufficient numbers of runts represented in
the pilot study.
Table 2 (ii). Clutch effects in terms of percentages of ‘successes’ and mortalities
and initial / final average liveweights for the runts in this study.
4
8
Clutch
no.
No.
animals
6
7
8
9
5
6
6
5
Av. initial
weight
(range)
42 (40-50)
47 (40-50)
48 (40-55)
58 (55-60)
Percentage
mortality
29
45
0
17
Av. weight of
survivors (range)
61
68
67
60
(40-90)
(50-85)
(60-75)
(50-70)
Percentage
successes
28
27
17
0
These results suggest that there are real differences between clutches, both in
mortality rates and also in the overall level of ‘successes’, even though the sample
sizes are small so no proper statistical analysis is meaningful. Interestingly, clutch #9
had the largest sized animals at the start of the investigation but none of these animals
‘kicked on’ and the average final weight (of survivors) was lowest of all the clutches.
References
Coulson RA, Coulson TD and Herbert JD (1995) Metabolic rate, nutrition, and
growth of the alligator. Department of Biochemistry and Molecular Biology,
Louisiana State University Medical Center. Louisiana USA.
Manolis SC, Webb GJW, Barker SG and Lippai C (1989) Nutrition of crocodiles.
Proceedings of the Intensive Tropical Animal Production Seminar, Townsville,
Queensland Australia 1-21.
Morpurgo B, Gvaryahu G and Robinzon B (1991) Food preference, fish attractability
and behaviour manifested toward new feed in young Nile Crocodiles, Crocodylus
niloticus. Physiology & Behaviour 50:1-4.
Morpurgo B (1992) Growth rates and food conversion efficiency in Nile crocodile
hatchlings fed on pelletised food. Proceeding of the 11th Working Meeting of the
IUCN Crocodile Specialist Group, Victoria Falls, Zimbabwe, August 1992.
Rodriguez MA, Clavijo LA, López O, De Geradrino A, Ceballos C, Arboleda JJ,
Silva AE and Guerrero PH (1996) Avances en la Nutrición de Caiman crocodilus.
Proceedings of the 13th Working Meeting of the Crocodile Specialist Group, Sante
Fe, Argentina, May 1996. 347-354.
Staton MA and Vernon BP (1991) Formulated Crocodile Feeds. Proceedings of the
Intensive Tropical Animal Production Seminar Townsville, Queensland Australia.
239-248.
4
9
6.
Egg Research
6.1
Incubation Study
This preliminary trial was conducted to test the suitability of chicken incubators for
the hatching of crocodile eggs, and to investigate diseases associated with incubation.
A number of smaller incubators allow for more experimental freedom than one large
incubator (e.g. for research involving temperature or disease, where there cannot be
different situations in the one unit).
One hundred and sixty-two eggs from four nests (with 31, 50, 47 and 34 eggs) were
received within three days of lay from Billabong Sanctuary (just south of Townsville).
Each clutch of eggs was placed in an individual incubator which had three shelves,
each holding one steel, open-weave, lidded tray lined with approx. 30 mm of
vermiculite. Two trays of water with air stones attached to individual pumps were
used to raise humidity levels in each incubator.
During the trial 16, 50, 13 and 30 eggs from the respective clutches were discarded as
infertile (little or no signs of the ‘banding’ that occurs in developing fertile, viable
crocodile eggs); 22 were dead at hatching from bacterial contamination (21 from one
nest where a number of the eggs were cracked after the young mother had trodden on
the nest); one was mummified; one was dehydrated; and 29 healthy crocodiles were
hatched. The high percentage (67%) of infertile eggs is not indicative of commercial
breeding operations in Australia and in this case is probably due to immature females
- only one nest produced a reasonable proportion of fertile eggs (34 out of 47).
The trial showed that the temperature range was well controlled (with a fan
distributing heat from the heat bulb evenly) but that the humidity was in the range 9398%. This resulted in excess water loss from the eggs and a large number of eggs
developed air sacs larger than normal. Addition of extra air stones and a more
effective door seal will be required to lift levels to the desired 99% value.
Gaseous exchange (O2 / CO2) needs to be enhanced by reducing the number of eggs
per incubator to 30 or fewer. There was reasonable bacterial and fungal
contamination (mainly Pseudomonas spp., Enterobacter spp., Citrobacter spp. and
Alcaligenes spp., plus Fusarium solani, Aspergillius spp. and Penicillium spp.).
Five eggs in the one clutch yielded Salmonelas arizonae (subsp. 36 ser. 61:r:z 53).
Washing the eggs in Arocide, or a similar type compound, before incubation could be
one experiment worth trying before fungal contamination / infection trials begin.
6.2
Egg Fungal Levels
During the past few years, all crocodile eggs that have been submitted to OVL have
been examined for bacterial and fungal contamination of both the internal contents as
well as the external shell. The number of eggs submitted has not been large but a
similar pattern of contamination has been observed from farm to farm.
5
1
The following is a short note to indicate the types of bacteria and fungi present in
crocodile eggs sent in from four different farms in northern Qld.
All the eggs examined in this survey were a mixture of those that were clearly
infertile (no banding) and those that showed, by candling, that a band had originated
but had not progressed.
Eggs were handled as little as possible and, in the laboratory, gloves were worn to
limit any contamination whilst processing. Processing was performed in a biological
safety cabinet. Each egg was placed in a sterile bag with 10 ml of buffered peptone
water and massaged gently to wash off organisms that were not irreversibly attached
to the egg shell. This liquid was then used to inoculate an appropriate set of bacterial
and fungal media. The washed egg was removed from the bag and aseptically cleaned
by dipping and washing in amyl alcohol before being allowed to dry. Sterile scissors
and forceps were used to crack and cut open the egg so that the contents could be
collected and tested for internal microbial contamination.
Samples were examined for the presence of Salmonella spp. and other enteric
organisms, for soil and water bacteria such as Pseudomonas spp., Aeromonas spp.,
etc., and for the presence of fungi. Blood agar, MacConkey agar, LMG (lysinemannitol-glycerol) agar, bismuth sulphite agar, Rappaport-Vassiliadis broth,
Sabourad agar and Mycological agar were used. The bacterial plates were read after
24-48 hours at 37oC and any suspect colonies replated for further study and
identification. The fungal plates were incubated at 28oC for 7-14 days. Cultures were
examined and identified by morphological characteristics. Where nesting material
was available, these too were sampled and examined.
The following tables give an indication of the microorganisms found in and around
crocodile eggs. Table 1 shows the results for bacteria isolated from outside and inside
the submitted eggs from four different farms while Table 2 shows the results of
bacterial isolations from nesting material from three of the four farms. Tables 3 and 4
show results for fungi isolated from eggs and nesting material respectively.
5
2
Table 1. Bacteria isolated from the inside and outside of crocodile eggs collected from four farms in northern Queensland. These
either infertile or were cases of non-progression of banding
Bacterium
Achromobacter spp.
Acinetobacter spp.
Aeromonas hydrophila
Aeromonas caviae/sobriae
Alcaligenes spp.
Bacillus spp.
Citrobacter spp.
Enterobacter aerogenes/agglomerans
Enterobacter cloacae
Escherichia coli
Klebsiella oxytoca/ pneumoniae
Proteus spp.
Pseudomonas aeruginosa
Pseudomonas fluorescens
Pseudomonas putida
Pseudomonas stutzeri
Salmonella spp.
Serratia liquifaciens/marcescens
Farm 1
Inside
(21)*
1
1
0
0
0
11
3
4
0
0
0
4
0
1
2
1
1
0
Outside
(13)
0
1
0
0
3
10
2
0
0
0
0
0
0
0
0
3
1
2
Farm 2
Inside
(7)
0
0
0
1
1
1
2
0
0
0
0
0
1
0
0
0
0
0
Outside
(4)
0
0
0
0
1
4
0
0
1
1
0
0
1
1
0
2
0
0
* These are the total numbers of samples tested
5
3
Farm 3
Inside
(5)
0
0
0
0
1
0
0
0
4
0
0
0
0
0
0
3
0
0
Outside
(5)
0
0
0
0
1
0
1
1
4
0
0
0
1
1
0
4
0
0
Farm 4
Inside
(51)
0
1
4
4
1
2
6
0
11
0
0
0
7
3
3
9
4
0
Outside
(32)
0
2
6
1
5
24
5
4
13
0
4
0
4
9
4
6
4
0
eggs were
All Farms
Inside
Outside
(84)
(54)
1
0
2
3
4
6
5
1
3
10
14
38
11
8
4
5
15
18
0
1
0
4
4
0
8
6
4
11
5
4
13
15
5
5
0
2
Table 2. Bacteria isolated from nesting material received from three farms
Bacterium
Acinetobacter spp.
Aeromonas spp.
Bacillus spp.
Citrobacter spp.
Enterobacter spp.
Klebsiella spp.
Pseudomonas aeruginosa
Pseudomonas fluorescens
Pseudomonas putida
Pseudomonas stutzeri
Pseudomonas spp. (others)
Salmonella spp.
Nesting Material
Farm 1 (6)
1
2
6
1
4
1
4
3
2
4
0
0
Nesting Material
Farm 2 (2)
0
0
0
0
0
0
2
0
0
0
2
0
5
5
Nesting Material
Farm 4 (1)
0
0
0
0
0
0
1
1
0
1
0
1
Total
(9)
1
2
6
1
4
1
7
4
2
5
2
1
Table 3. Fungi isolated from the inside and outside of crocodile eggs collected from four farms in northern Queensland
Fungus
Acremonium spp.
Alternaria spp.
Aspergillus flavus
Aspergillus fumigatus
Aspergillus glaucus
Aspergillus niger
Aspergillus terreus
Aspergillus spp.(others)
Cladosporium spp.
Cunninghamella spp.
Curvularia spp.
Fusarium spp.
Mucor spp.
Nigrospora spp.
Paecilomyces lilacinus
Paecilomyces spp.
Penicillium spp.
Rhizopus spp.
Scedosporium spp.
Scopulariopsis spp.
Syncephalastrum spp.
Farm 1
Inside
(13)
0
0
0
0
0
0
0
0
0
0
0
9
0
0
1
0
0
0
0
0
0
Outside
(13)
3
0
4
4
0
1
0
0
1
0
0
12
0
0
1
0
4
0
0
0
0
Farm 2
Inside
(4)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Outside
(4)
0
0
0
0
0
0
0
4
0
0
1
1
0
0
0
0
2
0
0
0
1
5
7
Farm 3
Inside
(5)
0
0
0
0
0
0
0
0
0
0
0
4
0
0
0
0
0
0
0
0
0
Outside
(5)
0
0
0
0
0
2
0
0
0
0
0
4
0
0
0
0
3
0
0
0
1
Farm 4
Inside
(41)
0
0
0
1
0
0
0
0
0
0
0
31
0
0
0
1
0
0
1
1
0
Outside
(32)
0
1
26
9
9
25
4
3
3
0
3
6
0
2
0
4
20
14
1
5
3
All Farms
Inside
Outside
(63)
(54)
0
3
0
1
0
30
1
13
0
9
0
28
0
4
0
7
0
4
0
0
0
4
44
23
0
0
0
2
1
1
1
4
0
29
0
14
1
1
1
5
0
5
Table 4. Fungi isolated from nesting material collected from three farms
Fungus
Aspergillus flavus
Aspergillus fumigatus
Aspergillus niger
Aspergillus terreus
Aspergillus spp. (others)
Cladosporium spp.
Cunninghamella spp.
Fusarium spp.
Malbranchea spp.
Paecilomyces lilacinus
Paecilomyces spp.
Penicillium spp.
Rhizopus spp.
Scopulariopsis spp.
Stemphyliopsis spp.
Trichoderma spp.
Veronaea botryosa
Verticillium spp.
Nesting Material
Farm 1 (6)
0
1
2
0
1
2
0
6
1
6
0
5
1
1
1
6
1
1
Nesting Material
Farm 2 (2)
0
0
1
0
0
0
2
0
0
0
0
2
1
0
0
0
0
0
5
9
Nesting Material
Farm 4(1)
1
0
1
0
0
0
0
1
0
0
1
1
1
0
0
0
0
0
Total
(9)
1
1
4
0
1
2
2
7
1
6
1
8
3
1
1
6
1
1
The results were not unexpected from eggs laid into a nest made of local herbage, soil and
water especially if the eggs were not washed before transfer to the incubators. The presence
of faecal contamination was also expected.
The most common bacterial isolates from the outsides of the eggs were environmental
organisms such as Bacillus spp., Alcaligenes spp. and Pseudomonas spp., especially P.
aeruginosa, P. fluorescens and P. stutzeri. The major faecal contaminants included
Enterobacter cloacae, Citrobacter spp. and Salmonella spp.
From the egg contents, a similar picture appeared with Bacillus spp., Citrobacter spp.,
Enterobacter spp., Pseudomonas spp. and Salmonella spp. being consistently isolated.
With the isolations from the egg contents, it is possible that there may have been
contamination from the external shell even with the precautions taken, however, a number
of the ‘dead’ eggs (initial banding seen) were of a custard-like consistency inside.
The nesting material showed presence of the same bacteria.
Where fungi were found on and in the eggs and in the nesting material, a number of
ubiquitous fungi were isolated. It appeared, however, that only one of the genera had the
ability to easily penetrate the shell and that was Fusarium spp., which has recently been
incriminated in embryonic deaths of crocodiles in one farm in central Qld. Other fungi
commonly isolated from the outside of eggs and from the nesting material included
Aspergillus spp., especially A. flavus and A. niger, Penicillium spp. and Rhizopus spp.
As more eggs are submitted for culture, it will be interesting to keep building up the picture
of the normal flora as well as determining causes for embryonic death.
6.3
Incubation Techniques
Five clutches of eggs were provided by Billabong Sanctuary in 1998 for research into
incubation techniques, using the seven small research incubators in the incubation room.
These related to bedding material on incubation trays and washing/disinfecting eggs. The
experiment consisted of six factorial treatment combinations (± washing eggs in water,
nesting material/vermiculite/nothing as bedding material for the eggs in the incubator trays).
Results showed that there were very little differences between any of the treatments, though
there were large differences between the clutches. Washing eggs or bedding them on
different media offered on advantage as long as temperature and humidity are optimal – a
‘good’ clutch will produce healthy hatchlings. One hundred and eleven animals
subsequently hatched from these eggs.
6.4
Embryonic Mortality
Samples of infertile and early embryonic death eggs were sent from farms to OVL for tests.
One species of bacteria (Enterobacter spp) and two species of fungi (Fusarium,
Paecilomyces) were commonly found in association with dead embryos. From other
literature the Fusarium organism is reported to be present in 20-30% of soils in Qld, and
depends on soil type - sand is a poor carrier. Dead hatchlings were also sent for postmortems.
61
7.
On-farm Studies
7.1
CROCTEL
Background
The impetus for developing a standard, computerised on-farm data recording scheme came
from a number of different areas. In Australia, crocodile farms are required by legislation
(since crocodiles of both native species are ‘protected’ animals) to compile and submit
regular statistical information on the numbers of eggs and animals of different
ages/categories that they have on their farms. At earlier information seminars farmers
suggested that it would be useful if a computer program could be accessed (specifically
developed or modified from existing programs) which would enable them to automatically
‘spit-out’ information required by authorities in a form suitable to them. Such an organised
system with its requirement for regular, accurate input of basic farm data would lead to
more accurate figures than currently being assessed for audit purposes.
Government and industry administrators (in areas of animal production, marketing, trade,
conservation, research) need up-to-date and accurate information about the crocodile
industry both within states and for all of Australia. This has been very difficult to achieve
in the past because of the different recording schemes used by individual farms (both in
types/extent of records logged and ways in which it has been stored and used), the different
types of information required by the government agencies in different states, and the
different levels of direct government input into collecting and collating such data. (In the
NT government officers go onto farms at regular intervals to carry out audits of animal
numbers.) A standardised system owned and used by all farmers is the only way of
generating accurate industry statistics.
An assessment (based on confidentiality of information) of production figures from
individual farms and across farms will be invaluable to researchers in identifying problem
areas and whether these are localised or widespread throughout the industry. Researchers
can then target specific research experiments towards solving problems and offer
recommendations to industry. Standard-format production figures will also be valuable for
farmers who can compare their particular figures with industry ‘averages’.
Part of the current RIRDC funded project for DPI is dedicated to developing, evaluating
and promoting such a standardised recording scheme, which has been given the name
CROCTEL. It has been derived from a similar system which has proved very useful for the
pig industry in Qld (called SOWTEL). Both systems have been written by Rod Bloomfield
based at Kairi Research Station on the Atherton Tableland.
Primary Tasks Pty Ltd, a Victorian consulting company, expressed a keen interest in having
such a system developed for the crocodile industry. It was looking at the possibility of
extending a similar scheme to other emerging animal industries (eg emus) in a separate
RIRDC project.
63
Development
Because of proximity Rod Bloomfield initially worked mostly with Hartley’s Creek
crocodile farm (located north of Cairns in Qld) to develop the first prototype of the
computer model. He and Steve Peucker (DPI) have since regularly visited the other farms
in Qld to get farmers’ suggestions and specific needs of such a system. Rod also took the
opportunity of canvassing ideas/need of a selection on farms in the NT in a once-off visit in
April 1996.
The module of CROCTEL relating to animal numbers / fertility / mortalities has reached an
advanced stage and has been in full evaluation mode at Hartley’s Creek. Peter Mullaney
(Primary Tasks) had been assisting in evaluating the recording sheets, standard definitions,
and how the data could be analysed. He was instrumental in keeping the development team
focussed and on our toes. Peter Mullaney passed away in late 1996 and his expertise and
cheerful enthusiasm will be sorely missed.
The second module, dealing with growth rates and production costs, is still at a relatively
early stage of development. It has proved more difficult to ‘standardise’ these areas to
satisfy the needs of individual farmers.
Prototype
Examples of the current prototypes of recording sheets for the two modules are presented at
the end of this section. Each sheet has the capacity to record a large amount of information,
since different farms tend to prefer different kinds of data. Some particular pieces of
information are critical for the overall system to be of any use, but a lot of the other
information is optional and the CROCTEL system will still be able to generate useful
results without such information.
Uses
Most of the anticipated benefits of having CROCTEL accepted and used by all farms have
been outlined in the ‘background’ section. It is planned that farms will ultimately be
responsible for updating their record data base in CROCTEL and will periodically send
copies (on disk) to either the DPI or NTDPIF so that state and national figures can be
compiled and published. In the meantime, officers from both state government departments
will be assisting in making sure that the relevant farm records are regularly being entered on
the recording sheets and then onto computer.
The issue of confidentiality needs to be carefully addressed. As an example, consider the
single production statistic ‘mortality rate in hatchlings from hatching to three months of
age’. Each farmer participating in the scheme will be sent regular summary reports of state
and national figures of mortality rates (and all other parameters). These reports will include
averages, ranges (ie extreme values) and perhaps whole distributions, but in no generally
released reports will there be any form of individual farm identification, nor will individual
figures be cross-tabulated in any way such that people in the industry could ‘guess’ as to
farm identity (eg listing mortality rates for Australian farms together with total number of
hatchlings from farms).
64
Each particular farm will also already have (if they are fully using CROCTEL on site) or
will be sent, its own corresponding figures, so that these can be compared with the overall
industry figures. For example, a farm might have a mortality rate of 8% for animals in the
first three months, and the national average might be 5%, with a range from 2% to 15%.
Hence, the farmer can assess that his mortality is higher than average (and he might see
what he could do to reduce it to at least the ‘average’ of 5%), but he is not as badly off as
one farm which had the highest rate of 15%.
As production costs (especially food) keep increasing, it is going to be more important for
individual farmers to identify areas of their operation which are producing poor results (in
terms of industry averages). They can then run projections on how much it might cost to
remedy these areas and balance this against anticipated improvements in productivity.
From overall CROCTEL reports, researchers can readily identify areas of production which
have problems and the geographical extent of such problems. Funding bodies will also
finally be able to objectively assess their priorities in supporting requests for R&D funds,
and, in having accurate statistics on the current value of the industry and how it has been
increasing, balance funding for crocodiles against that for other industries.
Recent developments
The 1998 nesting data from all Qld farms participating in the scheme has been entered on
CROCTEL. At a meeting of the industry advisory group in Townsville in April 1998, Rod
Bloomfield demonstrated the package using real data, and discussed issues relative to
developing the modules relating to grower animal production and product sales. He
subsequently visited the Edward River farm to install the package on the farm’s computer
and provide training for local farm staff on how to use the package directly.
CROCTEL was very useful in generating information on hatching rates for the Qld industry
for preparing a report given by Bernie Davis to the international CSG meeting in Singapore
(July 1998).
65
Queensland Department of Primary Industries
Form A :
Nesting Tally Sheet
Breeder identification
Nest
ID
Female
ID
Male
ID
Colony
ID
Company :
Collection
Date
Age
days
Year :
Temperature
(°C)
Nest
Incubator
Eggs in nest
Total
No.
Mean
Size
L | C
Mean
Wt.
gms
Lost
No. Infertile
CROCTEL
Species :
Eggs in incubator
Damaged
:
Fertile
Banded
Sheet No.
Sheets
Incubator
mortalities
Early
Mid
term
of
Hatched
Full Date No. Deforterm
med
Scute
No.
Pen
ID
Queensland Department of Primary Industries
Form B :
Date
Company :
Crocodile Movements
Pen
ID
Hatchlings
No.
Growers
No.
Scute
No.
Length
mm
Year :
Method of movement
Breeders
Wt.
kg.
Sex
M/F
No.
69
Breeder
ID
No.
Processed
No.
Sold
live
No.
Culled
No.
Died
:
CROCTEL
Species :
Transfer
No.
Out
Purchased
Sheet No.
Receiving
Pen ID
Comments
of
Queensland Department of Primary Industries
Form C :
Feed used
Company :
Year :
Species :
:
CROCTEL
Sheet No.
of
% of feed to
Colony/
Pen ID
Date
Feed Type
Cost
$/t
Amount Hatchlings
kg
Growers
Sheets
% of feed to
Breeder
s
Colony/
Pen ID
Date
Feed Type
Cost
$/t
Amount
kg
Hatch
lings
Growers
Breeders
Queensland Department of Primary Industries
Form D :
Crocodile Processing
Crocodiles
Live Animal
Belly
width
mm
Date
No.
Scute
No.
Pen
No.
Length
mm
Wt.
Kg.
Company :
No. in each Skin
Grade
1
2
3
:
Year :
Total Wt. kg.
4
Meat
Byproduct
Value $
Skins
Meat Bypro- Disposed
to.
ducts
CROCTEL
Species :
Sheet No.
of
Skin Grade Price
Price/kg.
1
2
3
4
Meat
Byproduct
7.2
Breeder Infertility Investigations
The Problem
Over the 1996/97 and 1997/98 breeding seasons the hatching rate for the Edward River
Crocodile Farm suddenly declined from previous seasons’ levels. Egg shells seemed to be
thinner than normal and yolks looked anaemic. CROCTEL was used to process similar
hatching information from other Qld farms and showed that the same trend was occurring on
many of these farms as well.
Possible Causes
Genetic researchers at the University of Queensland (UQ) secured a grant under the Strategic
Partnership with Industry – Research and Training Support (SPIRT) scheme, with joint
partners
•
•
•
•
Edward River Crocodile Farm
DPI
Qld Dept of Environment
Crocodile Specialist Group
to investigate the problem at Edward River. The two target areas were genetics and breeder
nutrition. UQ scientists were to take samples from crocodiles in the breeding lagoons and use
DNA techniques to map the breeding patterns. DPI’s role was to design and implement an
experiment at Edward River to test the effects of supplementing diets fed to breeders with
vitamins and minerals. Unfortunately, because of the nature of the breeding lagoons, very few
‘replicates’ of treatment vs control groups was possible.
Links with Current Project
At a RIRDC review of crocodile (and other emerging industries) R&D activities in Australia
(Canberra 1997) the review panel recommended that nutrition should be a high priority
research area for crocodiles and that DPI should coordinate activities in this area and coopt
experts on animal nutrition from both within DPI and from other organisations to work on this
area. Hence, when this breeder nutrition problem was proved to be state-wide, it clearly fell
within the priority objectives of DAQ-188A. Consequently experiments were set up on a
further four farms in Qld, some with many one-on-one breeding pens. An additional
experiment is also in progress in WA.
Potential Benefits
The following table indicates how beneficial a relatively small improvement in hatching rate
will be.
Hatching
rate (%)
No. hatched per Estimated value ($)
40 eggs
of no. hatched
incubated
471
19
665
57
23
805
67
27
945
77
31
1085
87
35
1225
97
39
1365
100
40
1400
1
The current situation at Edward River Farm
Action
UQ researchers have taken blood and skin (scute) samples from hatchlings and the mother
attending that nest, and all large breeding males in the lagoons. Early results suggest that
multiple paternity is occurring and mapping of the breeding systems which occurred in the
1997/98 season is underway.
DPI has worked with Rhône-Poulenc and a packaging company to manufacture 10,000
specially formulated vitamin/mineral sachets, each weighing 35g, and suitable for adding to a
1kg piece of meat for feeding to breeder animals. The formulation was originally published in
ITAPS and confirmed at a specially convened meeting of animal nutrition experts from across
Australia, held in Townsville in January 1998.
R. Mayer visited participating farms to inspect the breeding layouts and, in consultation with
the individual farmers, worked out an optimal research design for each farm, and discussed
the logistics for farmers to follow. Essentially it was necessary to identify ‘equivalent pairs’
of breeding pens and randomly assign one from each pair to be fed the supplement, while the
other was to be fed just the normal farm diet and act as a ‘control’. The first assessable results
will become available in the 1998/99 breeding season.
If the vitamin additives prove successful in arresting the declining fertility rates, a more
efficient type of packaging will be needed to be developed for the industry – the current
prototype is costly to manufacture and presents some problems for farm workers to insert into
meat pieces. A smaller tablet form or a slurry applied via an applicator gun would each seem
to offer benefits.
76
8.
Extension to Industry
8.1
Queensland Crocodile Industry Advisory Group
Meeting 1
At the August 1996 industry seminar (Cairns) DPI suggested to industry to form an
advisory group to oversee crocodile R&D undertaken by DPI and to be available during the
year to discuss research results and assist in interpreting the various results. This was
accepted enthusiastically at the meeting and representatives from the four largest farms in
Qld volunteered to form the group. There was some disappointment that no research
scientists from outside DPI were involved, and subsequent negotiations with the Qld
Department of Environment (DoE) have resulted in crocodile biologist Mark Read joining
the group. This group held its inaugural meeting in Townsville in Feb. 1997. Day 1 was an
industry ‘in-house’ session at which the group discussed overall industry issues and then
more specific R&D activities that it saw as important. The second day was spent with
researchers from DPI, DOE and James Cook University (JCU), during which the following
issues were discussed:
•
•
•
•
organising the 1997 research hatchlings for DPI
update on design of the ‘grower’ research facility for Townsville
recent research results on pellets
related crocodile research projects - DNA work by University of Queensland,
electrical stimulation of meat (DPI), electrical restraint of animals (DPI), skin
disease (JCU), monitoring population levels in the wild and the potential for
‘ranching’ eggs in selected parts of Qld (DoE)
• brief evaluation of two DPI publications (Research Bulletin and newsletter)
• specific areas in which DPI should be assisting the farming industry in Qld providing the services of an engineer to advise farms on shed heating and design,
disseminating information on housing types used in the NT, research results from
other organisations, cost/benefit analyses on production, investigation into the
viability of cracked eggs, effects of osmosis when washing eggs, feeding
regimens, Sparganosis.
Meeting 2
This meeting was held in Cairns in December 1997. Participants included two industry
representatives from Qld, one from the NT and RIRDC manager Dr. P. McInnes. Some of
the major issues debated included the following.
Approval has been given for the Edward River farm to carry out local monitoring surveys of
crocodiles in the wild, with the aim of setting up a trial on ‘ranching’
There seems to be an increasing problem with egg mortality. An hypothesis put forward by
one farmer was that after several consecutive years of below average rainfall, the water in
which breeding animals were kept had increased significantly in salinity and that this might
in turn be transferring into the eggs laid. Other possible causes of low hatching rates were
suggested as ‘nests too hot’ and ‘behavioural problems among groups of breeding females’.
There are many obstacles in establishing a tannery in Australia:
77
• it is regarded as a ‘noxious’ industry, and so must satisfy stringent environment
impact requirements
• most chemicals must be imported
• technical expertise must be imported
• to be viable, it would need at least 20,000 skins each year, and so would need all
existing farms in Australia to supply to it, as well as handling other types of
skins.
Dr. McInnes stated that RIRDC felt strongly that the results from each of its sponsored
projects (irrespective of which research group was involved) must be extended to the whole
Australian industry, and provided financial support in existing programmes for such
interaction to occur.
For CROCTEL to achieve maximum benefit (for farmers, government, researchers) it needs
to be implemented on a national scale. This is one activity which has the potential to
generate more cooperation between the states. It was felt that an overall ‘industry report’
should be prepared from the information that individual farms supplied to the CROCTEL
scheme. Farms should also consider the possibility of interrogating the data compiled from
their own operation (eg comparing responses from different sections), as well as comparing
overall statistics with other farms. These aspects should be discussed with individual
farmers, to identify specific ‘hypotheses’ (or gut feelings of what might be happening!) and
then the farm data should be analysed to test these out.
There was some discussion on runts - possible causes, cures, and whether there was any real
potential for research gains in this area. One farm reckoned it had a low rate of runts and
hatchling mortality (around 3%). Work was referred to from PNG which looked at runts,
and suggested that tests should be centred on the gut (perhaps stomach acids damage the gut
lining when there is no food for long periods of time). Perhaps OVL could do such tests on
its runt animals. It seems very important to get hatchlings eating as quickly as possible most farms use established feeders introduced as ‘trainers’ to newly hatched animals. Other
‘solutions’ tried have been use of antibiotics, adding iron to diets (some success in pigs),
and grading off runts and penning them separately. This last strategy proved worse than
leaving them with their healthier mates! NT veterinarian J. McInerney had carried out
some work on looking at the effects of adding Vitamin B and hormones on ‘curing’ runts,
but with no obvious success.
Rearing density was nominated as one area of interest - there seems to be an optimal density
which suppresses dominance, and this can be at a reasonably high level. Research needs to
quantify response in terms of overall growth rates and to see whether there is any effect on
food conversion efficiency rates.
It was felt that more emphasis should be placed on assessing ‘behavioural’ aspects and
responses of the groups of animals subjected to different treatments in an experiment. This
was especially relevant in research into rearing density, feed space / number of individual
stations, and feed types (eg mince vs pellets).
It has been noticed on farms that animals really start to fight among themselves at around
two years of age. One suggestion for research involved colouring the water (with vegetable
based dye). Any management procedure which results in the animals ‘spreading out’ more
evenly in their rearing pens was thought to have great benefits. On most farms, irrespective
78
of types of pens or water troughs, animals tend to congregate in dense masses, which leads
to high density and a waste of resources.
It was felt that more effort should be made in videoing animal behaviour, and that this
should also be catered for in the new grower shed. The existing cameras and monitors we
have been using for several years are a bit dated and requiring more frequent servicing.
In reviewing the previous industry seminar (held the preceding day) it was felt that there
should have been more prepared written reports for participants to take away for further
consideration and for reference, and the seminar should have been more oriented to actual
‘outcomes’. The main seminar should be kept to one day’s duration, held once per year and
earlier than December (when farmers are busy preparing for nesting). It was suggested that
there should be more emphasis on the final product - perhaps incorporating a trade display.
This was successful at the last ITAP seminar, at which the talk on skins and storage was
especially well received. Other industry groups (eg ostrich) include product displays as part
of their conferences, and few people know what a top quality skin looks like. It would also
be interesting to compare the results of first grade skins tanned in Australia with similar
skins sent overseas for tanning. A scientific experiment could be set up to compare the
output quality of different tanneries by sending them ‘equivalent’ ranges of skins to tan, and
take similar measurements on the finished products. The ‘technical’ parts of the seminar
were still too complicated for most of the audience. People were not very interested in how
the experiments were conducted - they just want a summary of the important results and
how these might impact on their own farming situation.
Meeting 3
This meeting was held at Townsville on 3/4/98 to inspect progress on the grower shed
construction and be shown a CROCTEL demonstration. Other topics were discussed were:
•
•
•
•
•
pellet research
breeder vitamin research
egg research
electrical stunning project
proposed marketing project.
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8.2
Industry Seminars
Industry seminars have been held annually during this three year project. Following is a
brief outline of the seminar held in 1996 as an example. This annual seminar was held in
Cairns over a two day period on the 27 and 28th August and was well attended by the
stakeholders in the industry. Most of the farms had representatives at the seminar and there
were representatives from aquaculture (one of whom has had extensive experience in
crocodile farming in Papua New Guinea), leather manufacturers and Austrade.
Other research organisations represented at the seminar were Primeat (the research arm of
the Queensland Livestock and Meat Authority) now defunct, Primary Tasks and the Wet
Tropics Management Authority. The program coordinator from RIRDC, Dr. Peter
McInnes, participated on Day 1 of the seminar. Representatives from Northern Territory’s
Department of Primary Industry and Fisheries (NTDPIF) and the Western Australian (WA)
industry were sponsored to attend as well.
The agenda for the meeting was:
Day 1
Day 2
8.3
•
•
•
•
Report on the study tour of the USA alligator industry.
Discussion - research for grower crocodiles.
Aspects of design for the new proposed research facility.
Reports on crocodile research in other organisations.
•
•
•
•
•
•
•
Review of Day 1.
Report on CROCTEL.
Industry/research situation statement.
Extension program across states.
Evaluation session of the whole seminar.
Tour of Austpan tanning and processing plant.
Tour of Hartley’s Creek Crocodile Farm.
Conferences
Crocodile Specialist Group (CSG) Meeting
Presenting a paper at the biennial Crocodile Specialist Group (CSG) meeting in Santa Fe,
Argentina (May 1996) afforded R. Mayer a unique opportunity to
• bring DPI’s initial research results and research capabilities to the attention of
overseas researchers
• find out the latest research being done on aspects of crocodile farming
• develop rapport with experienced researchers scattered around the world.
The CSG recognises the importance of scientific networking and sent a letter of
encouragement to the Minister of Primary Industries along these lines. The minister
responded, agreeing that international scientific cooperation was most desirable. In its 1997
international newsletter CSG acknowledged the work that DPI was pursuing in crocodile
R&D and astutely pointed out to its readers that the research bulletin ‘emphasises the
importance of communication within the industry and between different sectors and
80
national and international collaborators’ and that it ‘is a very original and useful vehicle for
getting basic research and technical information quickly to the producer where it can be
applied’.
A report on the meeting was included in the industry newsletter Crocodile Capers (issue
No.2) and a verbal report was given at the annual industry seminar.
Australian Society of Animal Production (ASAP) Conferences
R. Mayer and S. Peucker attended the 21st biennial ASAP conference in Brisbane in July
1996 and presented a poster on crocodile research results for water temperature and rearing
density. The theme for the conference was ‘Animal Industries Responding to Change’.
R. Mayer participated in the 22nd conference in Armidale (20-24 April 1998) at which he
delivered a paper entitled ‘Developing a Pelletised Feed for Farmed Saltwater Crocodiles’.
This paper was well received, and made the ‘daily news’ sheet produced for the conference.
The main theme for this conference was ‘Sustainability and Quality Assurance – Two
Imperatives for Animal Production’. These two issues are also very important for
Australian Crocodile farmers. There were relevant contact sessions on ‘Animal Behaviour
and Management’, ‘Nutrition’, ‘Meat (quality, tenderness, electrical stimulation, chemical
residues)’ with series of papers on each. A report on how issues relate to crocodile farming
is included in Issue No.5 of Crocodile Capers.
8.4
Publications
The main publication for research undertaken by DPI in the crocodile area is our Crocodile
Research Bulletin, of which Volume No.2 was published in June 1997. There were also
two issues of ‘Research Update’ issued in November 1997 and August 1998 to industry and
fellow researchers to keep them up to date with recent findings.
Crocodile Capers, the industry newsletter is edited by S. Peucker, and is a more informal
publication. This is compiled every 6 months and issues have been produced in January
1995, July 1996, February 1997, November 1998 and August 1998.
8.5
General
MEDIA
There have been numerous requests for radio and television interviews and stories for the
local newspaper over the past two years and DPI has always been keen to oblige, using this
as an important extension activity. People are fascinated by crocodiles.
‘Radiant Living’ Television Program
‘Radiant Living’ is a popular north Qld cooking program. In 1996 the program producers
came to Townsville to film a couple of cooking segments at a two day Home and Leisure
Display. S. Peucker gave a short interview on the virtues of crocodile meat, its processing
and handling. He also stressed that it was legal to sell crocodile meat for human
consumption from farmed animals. While the segment attracted plenty of onlookers and
people were keen to taste the meat, the response to the recipes was poor. It seemed to be
81
very much an image problem and also, in part, lack of availability of the product
particularly in the Townsville area.
Children’s Television Programmes
Two children’s educational television programs, ‘Hot Science’ and ‘Totally Wild’,
approached DPI to do segments on our work at OVL and farming/conservation in general.
The programs are a useful tool in educating the young and not so young. (DPI has also
supplied school students with material for projects on crocodiles.)
POTENTIAL INDUSTRY MEMBERS’ INQUIRIES
There have been six genuine inquiries about crocodile farming during the period since June
1995. Interested people were shown DPI’s research facility and given a well balanced view
of the industry. It was also recommended that they talk to existing farmers. A small
booklet was compiled from relevant articles from previous ‘Intensive Tropical Animal
Production Seminars’ and given out. These articles gave people a good basic understanding
of crocodiles and farming requirements.
COMPUTERS
Aussie Croc Net
Aussie Croc Net was created by a DPI colleague, Rod Thompson. Mr Thompson has also
set up a number of Aussie Nets for industries like beef, sheep, horticulture, ostrich and fish.
Aussie Croc Net is a discussion group which can be used to increase communication within
the industry. It can bring together crocodile producers, researchers, consultants, zoos,
wildlife parks and students
8.6
Industry Adoption of Research
A mail survey was sent to all recipients of ‘Crocodile Capers’ newsletter in late 1997
asking, among other things, what research the farmers had adopted. Of the eight replies
from farmers, five said that they had already modified some of their farming practices,
specifically in the areas of:•
•
•
•
increasing water temperature for hatchlings
changing rearing densities
reducing the amount of light in the rearing sheds
changing feeding regimes.
Several farmers stated that they had raised the water temperature for hatchling animals
(from hatching to four months of age) from the previously accepted industry standard of
32oC to 34oC, and one farmer replied that this had “stimulated growth rates in comparison
to last year’s figures” and paralleled the research results that DPI had reported. (A
summary report of the results of the survey was published in Issue No.5 of the newsletter).
A major benefit of this RIRDC project has been that it has provided funds for Qld crocodile
farmers to meet together regularly with researchers from DPI and universities (and also
with sponsored representatives from the farmers in NT and WA) to discuss research and
common industry issues. This had not occurred prior to DPI’s research and extension
82
program with RIRDC. This interaction has fostered open debate and frank exchange of
ideas, and farmers implementing changes to their operations to gain benefits which other
farmers had achieved.
83
9.
Networking
As information from our research experiments started to accumulate it became clear that a
communication network needed to be developed with other organisations involved in
crocodile research, development and extension. This needed to include overseas links
because research relating to farming the Australian saltwater crocodile is a rather narrow
and specialised field with relatively little work having been done.
Fellow research and educational organisations (universities, government departments,
environmental agencies, educational wildlife parks) have their own specific agendas for
crocodile research. These might include, for example, conservation of crocodile species,
aspects of life in the wild, understanding the mechanisms of basic physiology.
Nevertheless there are many issues such as DNA technology, animal nutrition, growth rates,
mortalities, individual identification and safe handling techniques which are common to
programs undertaken by the different organisations. Members of the DPI research team
have maintained an on-going dialogue with many fellow scientists, often on an
opportunistic basis.
9.1 Northern Territory Organisations
1995 Meeting
The NT Department of Primary Industry and Fisheries (DPIF) hosted a meeting convened
by RIRDC coordinator Dr Peter McInnes in July 1995 for crocodile farmers, researchers,
administrators, conservation groups and manufacturers from around Australia to discuss
research priorities for the industry. (A copy of report on this meeting can be obtained on
request from RIRDC or DPI.)
1996 Meeting
A scientific team from DPI (B. Davis, R. Bloomfield and R. Mayer) met with counterparts
in DPIF in Darwin in April 1996 to discuss R&D for the crocodile industry in Australia.
The principal research staff from Wildlife Management International (WMI) also
participated in the R&D discussions. Because of earlier contributions in identifying aspects
for incorporating into CROCTEL and participating in last year’s Cairns information
seminar, Dr. Peter Mullaney (Primary Tasks) was invited to participate in the meetings and
planning sessions.
An important initial step in these negotiations was to formulate a ‘situation statement’ for
the crocodile farming industry in each state, and then for the particular R&D infrastructure\
capability\ interests of the various parties. A copy of this statement is listed on the next
page.
Crocodile Research, Development and Extension Resources – April 1996
Facilities
Staff
Present
Research
Support
Services
Financial
Support
Services :
Regulatory
Animal health
Extension
Policy
Research
Strengths
Weaknesses
General
NT Govt.
(DPIF)
4 hatching tanks
(100/tank)
QLD Govt. (DPI)
Wildlife Management Int.
12 hatching tanks (3050/tank)
6 incubators, prep.
room, hospital room
1.0 FTE
Minimal
Lab – DPI
Biometrician
NT Govt. $60.000
(salaries,
operational)
9 people = 3.7 FTE’s
Juvenile (0-12 months)
Environment,Nutrition
Vet. Lab.
Pig geneticist
QLD Govt. - $300,000
$200,000 (for new
grower shed)
RIRDC - $50,000 pa
15 hatching tanks (60-100/tank), 7
small, 2 large incubators (>10,000
eggs), 1 lab.Prep. room, 20 breeder
pens (20 pairs), 1 lake (subadults),
7 raising pens (<300 animals)
7 professional, 2 technicians
Breeding, selective breeding,
temperature and skin patterns
DPIF
75%
0%
100% private
0%
5%
5% (through JCU)
0%
10%
30% (0.7 FTE)
0%
5%
10%
0%
5%
55%
100%
On-farm
Research – juveniles,
demonstrations
growers
Animal health
Lacks research
Availability of animals
farms
(small genetic pool)
No external
Reliance on external
funding
funds to operate
General lack of positive interaction between govt. departments and state
industries
No national farming associations with state/territory branches
This identified that DPI had 3.7 FTE’s allocated to crocodile R&D, the DPIF had 1.0 FTE,
and WMI with nine employees could only continue to do work in the crocodile area under
fully paid consultancy arrangements. Also the DPIF carried out the regulatory tasks for the
NT industry (counting stock, issuing permits) which in Qld was done by the Dept. of
Environment
It was felt that the newsletter Crocodile Capers was a useful extension medium and should
continue to be a joint government venture. DPIF asked if DPI could undertake printing and
distribution of all future issues. It was emphasised that if the newsletter was to truly reflect
an Australian perspective, then:
•
•
•
•
articles from all states (include WA) need to be elicited
editorial responsibility must be shared alternately between DPI and DPIF
it should include up to date industry figures
it could include the ‘situation statement’ that is being developed.
86
Despite last minute invitations to farmers to participate in the 1996 meeting (issued during
farm visits) none attended, so the review was conducted purely from a government
perspective, and how the needs of the two state industries were perceived. P. Mullaney
suggested that DPI ought to develop a ‘prospectus’ to sell the package. Perhaps it would be
better to start with a simpler form and then once farms are happy to use it and can see how
it can be used, develop more sophistication. Do not try to cater for every conceivable need,
or try to get headings that everyone agrees to before releasing it to farms for initial use.
1998 Meeting
A group of Qld researchers and farmers went to Darwin (8 May) to meet with NT
counterparts to discuss research and extension. This project sponsored M. Read from the
Qld Dept of Environment (to present a report on the joint DPI/UQ research on breeder
infertility and as our expert crocodile biologist in the team) and two members of the Qld
Industry Advisory Group – Alicia Darbonne and John Lever (minutes of the meeting by V.
Simlesa of NTDPIF).
9.2 University of Queensland (Brisbane)
The zoology department under the guidance of departmental head Professor Gordon Grigg
has continued to foster research on various aspects of crocodiles by post-graduate
researchers.
R. Mayer obtained from the university a preview copy of Gregor’s masters thesis on
‘Factors Affecting Food Intake and Growth in Captive Saltwater Crocodiles’ and later meet
with him in Sydney, where he now works, to discuss some of his research findings. His
research was conducted on a commercial crocodile farm in the NT and included measuring
the effects on feed intake and subsequent growth in juvenile crocodiles due to
•
•
•
•
•
different types of shelter (amount, type) constructed over rearing tanks
animal stocking density and light conditions
clutches (‘mixed’ groups vs ‘same clutch’ rearing in tanks)
stress levels as measured by testosterone and corticosterone levels in animals
vitamin B injections.
All of this work is directly relevant to the research objectives of our program and we have
extensively referenced Gregor’s work in presenting our own research findings.
9.3 James Cook University (Townsville)
G. Buenviaje gained a M.Sc. degree in veterinary pathology from JCU and returned to work
in the Philippines as a university lecturer and pathologist. He has since returned to JCU to
pursue PhD studies in skin diseases of crocodiles with associate professor Phil Ladds as
supervisor. His first task has been to conduct a survey of skin diseases on farms and then
isolate the causal organisms. He has identified the cause of ‘brown spot’ skin disease and
will be working with researchers at DPIF in Darwin using their research facilities to identify
transmission processes. DPI has been assisting Dr Buenviaje in providing biometrical
advice for his various experiments, providing ‘runt’ animal specimens for him to work on,
and sponsoring him to attend industry seminars and present his findings to farmers.
9.4 Department of Environment (Queensland)
87
Mark Read undertook a PhD research project at the University of Queensland involving
nutrition. The research was carried out at a crocodile farm in PNG. After returning to
Australia and completing his PhD thesis Mr Read joined Dept of Environment as crocodile
biologist to carry out surveys of population levels of C. johnstoni and C. porosus in North
Qld and assist in the capture/relocate program for problem animals. He has joined the Qld
Crocodile Industry Advisory Group.
9.5 Primary Tasks Pty Ltd
The DPI team had developed a strong cooperative working relationship with this company
through its director Dr Peter Mullaney. Dr Mullaney initiated the partnership in 1995 as part
of a project he was doing for RIRDC on emerging animal industries. He saw that the
CROCTEL package that DPI was developing had a lot of direct relevance to his project,
and was happy to help advance CROCTEL. We were fortunate to have had Dr Mullaney’s
expert input and drive over the years. Dr Mullaney contributed to two industry seminars in
Cairns and also to the meetings in Darwin. Since Dr Mullaney’s death, the director, Mr
Arthur Stubbs, has continued to work with the DPI group on similar areas.
9.6 US Alligator Organisations
Government agency research in the US comes under the umbrella of wildlife conservation
and the ‘sustainable use’ program whereby alligators and eggs can be taken from the wild.
Eggs are incubated under controlled conditions and the resulting hatchlings are sold to
farmers. Research has tended to focus on incubation methods, growth rates and survival
rates in the wild rather than aspects of farm production. Universities have a much wider
charter which includes some practical research with direct application to the farming
industry (eg nutrition).
Florida Game & Freshwater Fish Commission
This group is involved with incubating eggs collected from the wild. Some areas of specific
on-going interest include
• techniques for ‘solidifying’ eggs prior to investigative dissection purposes
• possible ‘imprinting’ for crocodile species
• use of ‘diversionary’ objects (like lengths of black hose) to reduce the incidence
of animals biting each other.
Office of the Crocodile Specialist Group (Florida University)
Office of the Crocodile Specialist Group (CSG) – Florida University maintains a worldwide reference library and its executive officer has a keen personal interest in crocodile
R&D. R. Mayer and Qld crocodile farmer P. Freeman collected several very useful
references while visiting the university of Florida and discussed issues like
• potential uses for DNA technology
• the importance of female hierarchies in breeding colonies (may be just as
important as the well documented male hierarchies)
• possible ways of ‘single rearing’ for crocodile species to eliminate the incidence
of skin damage due to fighting.
88
Professor Cardeilhac has extensive experience in research in the alligator farming industry
and has developed an ‘expert’ reputation among farmers. His main area has been in diet
and nutrition. His experience in working with balanced groups of research animals in an
intensive, controlled environment has meant that he has been confronted with the same sort
of logistical and scientific problems that we have come up against. It was very useful to
compare our experiences and how we dealt with various ‘problems’ in research. He kindly
presented us with a complete folio of reports on all the research that he has done over the
years and we promised to keep him up to date with the results of Qld work.
Louisiana Dept of Wildlife and Fisheries
P. Freeman and R. Mayer were afforded visiting scientist status during their visit to the
Rockefeller Wildlife Refuge (accommodation, meals) and crocodile expert Ruth Elsey
made their stay very enjoyable and rewarding. She took them to look at alligator farms in
the area and thus enabled the DPI to establish a link with the U.S. industry. Ms Elsy is
carrying on the pioneering work of Mr Ted Joanen, who, though now retired, met with them
to discuss crocodilian R&D and his keen perceptions of what drives these magnificent
reptiles. The refuge has insulated research tanks for small animals and also some breeding
pens. Both Ms Elsy and Mr Joanen were very encouraging and supportive of the avenues of
research that DPI was planning to undertake and keen to maintain a regular exchange of
ideas and information.
9.7 Tourist Parks, Wildlife Sanctuaries and Zoos
It is easy for researchers to overlook the importance that these enterprises assume in the
‘educational’ area and there have been suggestions by sectors of the farming industry that
DPI should totally exclude such areas from its crocodile R, D & E program. However live
crocodile displays have an enormous tourist attracting power and parks generally make a
feature of crocodile feeding and guided information tours. They are in a unique position to
influence the opinions of a sizeable proportion of the population. Hence it is important that
the information that they are imparting is scientifically correct and unbiased, and that issues
such as sustainable use and conservation are accurately portrayed. DPI distributes copies of
all its crocodile publications (bulletins, newsletters, travel reports) to the parks and zoos
which are know to maintain crocodiles.
The reptile curators contacted are genuinely interested in learning as much as possible about
crocodiles, provided that such information is soundly based and not just individual pet
theories. Any advances made in the fields of nutrition (eg dry pelleted feed), disease
control, responses to environment, understanding social interactions among animals will be
of direct benefit to the ways in which they maintain their animals.
Individual parks like the Qld Reptile and Fauna Park are actively involved in their own
scientific programs relating to understanding wild populations of native species (numbers,
distribution, whether there are sub-species) and are cooperating on DNA projects.
Special mention should be made to Billabong Sanctuary outside of Townsville and its
manager Mr Bob Flemming. The sanctuary has been set up to concentrate on public
education on Australian wildlife and for the past two seasons it has provided DPI with eight
clutches of eggs to incubate in small research incubators so that the DPI team could gain
89
experience in this area. DPI took the opportunity of testing nesting material for disease
organisms, and autopsied any embryos which died during the incubation process.
While DPI is primarily involved in assisting the primary industry of crocodile farming, it is
a public service organisation and so also has a duty to disseminate correct information to
the general community and an efficient way of doing this is through the excellent public
education program facilities provided at the various wildlife parks.
90
10. Conclusions and Recommendations
10.1
Research Advances for Juvenile Crocodiles
Research on different environmental factors involved in rearing juvenile crocodiles under
the specific conditions of the research facilities has shown that animals grow better when:•
•
•
•
•
water temperature is raised to 34oC
hide-boards are suspended inside rearing tanks
animals are not over-crowded
rearing rooms are kept dark
water volume is increased.
These effects have been scientifically proved in separate experiments on animals at specific
ages, and farmers have begun adopting these practices on a commercial scale and reporting
similar benefits. Juvenile crocodiles appear to go through physiological/behavioural
changes between hatching and one-year of age, and can be expected to respond to the above
factors to different degrees (eg increasing the volume of water for older, larger sized groups
of animals produced reduced growth and more evidence of antagonistic interactions).
Hence research on environmental/management issues needs to be carried out at each
particualr stage of growth to quantify the different responses. Another example of agespecific response is water temperature. Improved growth at 34oC is accentuated in the first
few months when animals are still absorbing nutrients from their egg sacs. A key to
research success may well depend on a deeper understanding of animal behaviour and
using it to commercial advantage.
All of the experiments reported earlier in this report have involved just one or two factors
(with all other factors kept uniform). Further research needs to be done to test whether the
factors are acting additively or interactively. For instance there is no guarantee that
combining the best individual practices will result in the best combination.
Developing a pellet food which juvenile crocodiles will eat as a sole diet has been a major
breakthrough. The prototypes used so far have been targeted towards ‘acceptability’ rather
that animal growth and hence have produced poorer growth responses compared with
standard meat diets. Priority research is needed to improve the nutritive properties of the
prototype pellets, and to carry out controlled experiments to compare growth achieved by
the different diets.
10.2
Priorities for Future Research and Development
For juvenile crocodiles (hatching to one year old) the top research priority is to develop a
pelleted food which will:•
•
•
•
•
be cost effective
be readily available to farmers from feed mills or manufactured on farms
be able to be stored without refrigeration or freezing
produce equal or superior growth in animals (compared with current fresh meat
diets)
incorporate optimal amounts of essential vitamins and minerals (for animals at
different growth stages).
91
For grower size animals (one-year old to harvest size), research priorities are:•
•
identifying rearing practices which reduce the incidence of skin damage (eg
rearing density, amount of water, feeding strategies, incubating for females
offspring only, mixed sexes,grading on size, diet type)
improving growth rates (have animals reach slaughter size at 2-3 years of age
rather than the 3-4 years currently. This has been achieved in the American
alligator industry by using specially formulated pellet diets and controlledenvironment rearing sheds).
For breeding animals priorities are:•
•
•
•
•
10.3
addressing the serious declining fertility rate among captive breeders
optimal pairings of breeders (eg one male with one female or several females)
procedures to reduce the amount of fighting that occurs among breeding animals
researching the nutritional requirements of animals, including vitamins and
minerals
if multiple paternity can be demonstrated, determining its effect on breeding
performance and hatching rate.
Cooperative Activities
On-farm evaluation of ‘breeder nutrition’ has begun, involving five major farms in Qld and
one in WA. The trials have been scientifically designed to complement each other so that
the resulting information generated will have maximum scientific value and a wide sphere
of application. The success of the Qld Industry Advisory Group has helped this degree of
cooperation between DPI and the industry. Specific research facilities are very expensive
to set up and operate, especially involving adult animals. One farm in WA has almost 100
breeding pairs of animals which would be ideal for research. This farm has recently
indicated that it would be interested in cooperative research ventures. It is important that
such cooperative ventures with industry are expanded to produce maximum benefits in
applied R&D.
The recent research planning meeting held in Darwin (May 1998) between the major
research organisations involved in crocodile R&D together with farming representatives
from QLD, NT and WA was a very productive and useful forum for exchanging results of
recent research and planning future research and potentially collaborative activities. It is
essential that such meetings continue to occur and it is appropriate that RIRDC should
undertake the role of convening such meetings at least every two years.
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