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LIVESTOCK
Photo: Ben White
PARASITE CONTROL
FREECALL 1800 677 761
Low-chemical parasite control requires
consideration and commitment
Peter James
For QUEENSLAND PRIMARY INDUSTRIES
AND FISHERIES
Parasites: Cattle need to be monitored and moved
between paddocks regularly to minimise internal
parasite loads on pastures and in animals.
At a glance
Reduced chemical use to manage
parasites requires an integrated
management system and
careful planning.
Reducing parasite burdens
through rotational grazing
is a key management tool,
particularly with younger, more
susceptible stock.
Remove highly susceptible
individuals from the herd to reduce
sources of pasture contamination
or direct infestation.
Organic production is strictly
regulated and producers need to
be aware of their control options
and restrictions.
Reducing the use of chemicals to control pests and parasites is about a
well-planned and delivered control programme — not a simple substitution
of artificial chemicals with organic alternatives according to Peter James of
the Queensland Primary Industries and Fisheries (QPI&F).
Whether it’s to gain organic market access
or to reduce resistance, minimise off-target
residues, operator exposure and reduce input
costs, cattle producers across Australia are
looking at ways to optimise and minimise
chemical use on their properties.
Parasite control is a key reason for
chemical use in beef production. And
organic beef markets restrict the use of all
artificial chemicals for all purposes — not
just pest and parasite control.
Key parasites of concern to beef producers
include both external and internal parasites.
The main external parasites are cattle tick
and buffalo flies in northern grazing regions
and lice in southern areas.
Internal parasites encompass mainly
gastrointestinal worms and flukes across all
regions. Internal parasites tend to cause
more problems in higher-rainfall regions or
wetter years across the lower-rainfall
regions.
Worms tend to affect younger stock, with
cattle developing greater immunity to
worms after about 12–18 months of age.
Fluke tends to be a localised problem and
is associated with grazing wet or marshy
areas where the intermediate host snail
is present.
Low-chemical control options
Minimising the use of animal health
chemicals is not as easy as substituting
artificial chemical options with organic or
biological parasiticides.
Effective
low-chemical
control
programmes almost inevitably rely on:
• A well-planned, integrated approach that
incorporates management practices to
94 Farming Ahead August 2009 No. 211 www.farmingahead.com.au
reduce parasite load or livestock exposure
to parasites.
• Sound quarantine procedures to prevent
introduction of parasites
• The selection and breeding of ‘resistant’
stock.
• Where available, the incorporation of
organically-accredited parasiticides or
biopesticides.
Reducing the impact
Cattle mount an immune response to the
presence of parasites and in most cases this
limits the impact they have on the animal.
An animal’s level of nutrition and stress
will influence the efficacy of these immune
responses.
Ensuring stock have
adequate nutrition and a
low-stress environment will
maximise their ability to
resist parasites.
Nutritional supplements and mineral
blocks are often promoted as helping with
parasite control. But with the exception of
copper and Barber’s pole worms, there is
little evidence to indicate that specific
nutrients help stock resist parasites, when
nutrition is otherwise high. If, however,
nutrition is lacking, supplements can help
reduce susceptibility to parasites.
Clean pastures curb parasites
Cattle become infested with worms by
ingesting free-living worm larvae from
contaminated pasture.
LIVESTOCK
PARASITE CONTROL
Organic production
systems and severely
parasitised animals
Photos: Pamela Lawson
Clearly, leaving animals untreated
when they are under stress from parasites
and there is no organically accredited
treatment available, is unacceptable from
a welfare perspective.
Action: The level of dung beetle activity can be assessed visually by noting the amount of soil
disturbance at the edges of dung pads in the days immediately after livestock have grazed a paddock.
These larvae hatch from eggs produced by
adult worms living inside the cattle gut and
eggs are deposited on pasture in cattle faeces.
Set stocking young animals in the same
paddocks contributes to the worm load of
pastures and increases worm challenge
to stock.
A key non-chemical means of managing
worm load in pasture is to minimise the pickup of worms by providing uncontaminated
pastures for young stock.
Producers can spell pasture to allow the
worm larvae to die off before they can infect
young cattle or graze cropping paddocks or
stubbles that have not been recently grazed
by other stock.
Using mature, resistant, cattle to mop up
worm larvae in paddocks after they have
been grazed by young stock also helps clean
a paddock of worm larvae.
Worm larvae seldom move more than
fifty millimetres up into a pasture, so
reducing stocking rates so animals do not
have to graze close to the ground can reduce
severe worm burdens.
Grazing younger, susceptible stock first
on longer pasture before introducing older,
more resistant stock to graze lower down
and mop up the larvae, can also help reduce
burdens.
Grazing young cattle in with
older stock or other species,
such as sheep, can also
dilute the worm challenge to
the young stock.
The worst management option is to
continually graze young stock in the same
paddock, year after year.
Spelling paddocks also can reduce tick
contamination in northern grazing regions.
Although tick larvae can survive on pasture
for up to seven months, in most areas
spelling for four months will reduce
numbers to low levels and even eight weeks
can substantially reduce tick populations.
The most effective non-chemical control
for fluke is to fence off or avoid grazing
swampy, wet areas where intermediate host
snails live. Some producers have reduced
stock exposure by draining or revegetating
wet areas and providing watering points
away from risky areas.
Seek out susceptible animals
Within a herd it is common to find
individual animals that regularly have high
parasite burdens. These animals continue
to provide a source of pasture contamination
for worms and ticks, or infestation from
other herd animals in the case of buffalo
flies and lice. Where possible cull susceptible
animals.
Some particularly sensitive animals react
strongly to buffalo fly bites and can develop
open lesions, even when fly numbers are
relatively low. Also cull these animals
where possible.
Walk-through buffalo fly traps can be an
effective non-chemical control option
when placed where cattle will walk through
them frequently, for example when
accessing water.
Much of the observed variation in
susceptibility to parasites, both between and
within breeds, has a genetic base. Zebu breed
types, such as Brahman and Santa Gertrudis
and their crosses, are generally more resistant
to external parasites than British breed types,
such as Angus and Hereford. But there is also
variation within a single breed type.
Dung beetle benefits
Active populations of dung beetles rapidly
break down dung pats, reducing buffalo fly
and bush fly breeding habitat, reducing
worm larvae hatching and aiding in worm
control by reducing pasture contamination.
Artificial parasiticides can reduce dung
beetle breeding but low-chemical systems
are unlikely to affect beetle populations
(for more information on the benefits of
dung beetles see Farming Ahead August
2008, No. 199).
Better biosecurity
One of the most common ways to introduce
parasites to a property, particularly lice or
resistant worms and ticks, is to import them
through newly-purchased or agisted stock.
Quarantine new animals from the existing
herd to reduce the risk of infecting stock.
Most organic accreditation systems
provide for the use of non-organic
accredited compounds to treat animals
under stress from parasites without
compromising the overall accreditation
of the property. These provisions usually
include conditions that the treated animals:
• Are removed from organicallyaccredited land.
• Do not come into contact with other
animals in the herd.
• Must not be sold into organic markets.
Check with an accrediting body for
specific guidelines on how to deal with
heavily parasitised animals.
Note that all commercially sold
parasiticides, whether organic, biological
or synthetic chemicals, must be
registered before they can be legally
applied to food animals.
The APVMA considers that a product is
likely to require registration if any claim is
made on a label, advertisement or website
that the product is intended to modify
the health, production, performance or
behaviour of animals.
For full details on what constitutes a
veterinary chemical product contact
the APVMA:
(02) 6210 4700
www.apvma.gov.au/about_us/
contact.shtml
Lice are obligate parasites and spread
almost exclusively by direct contact between
animals. If lice are found in the new herd,
reduce their spread by avoiding contact
between the infested herd and other cattle.
A commercial cattle tick vaccine has been
developed and can be used in low-chemical
systems, although the situation is less clear
for organic producers. The use of vaccines
is restricted and producers are best to seek
clarification on a case-by-case basis.
Research for an improved vaccine option is
currently underway by the Beef CRC.
MORE INFORMATION For organic production,
producers require formal accreditation through
a certifying body. Consult the National
Standard for Organic and Bio-dynamic Produce,
available from www.daff.gov.au/agriculturefood/food/organic-biodynamic.
ACKNOWLEDGMENT This article is courtesy of
the Queensland Primary Industries and
fisheries’ Beeftalk magazine.
CONTACT Peter James, QPI&F
(07) 3362 9409
[email protected]
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