research & training
research & training
Itʼs WAR out there!
Photo by Braam Collins.
DUE TO LARGE-SCALE KUDU MORTALITIES DURING THE DROUGHT OF 2002, KUDU
POPULATIONS DECREASED CRITICALLY IN DIFFERENT NATURE AREAS AND GAME RANCHES
IN NORTHERN SOUTH AFRICA. MASS MORTALITY AMONG KUDUS OCCURS FREQUENTLY, AND
FROM 1981-1986 KUDU MORTALITIES WERE REPORTED FROM NUMEROUS RANCHES
IN THE DRY WINTER MONTHS BETWEEN JULY AND SEPTEMBER (VAN HOVEN 1991).
THE LION (PANTHERA LEO).
CREMASTOGASTER NIGRICEPS. SOURCE: http://antsofafrica.org – SCAN THE QR
CODE OR VISIT www.youtube.com/watch?v=MDECjR3VY3o TO VIEW HOW ANTS
FIGHT OFF ELEPHANTS TO SAVE TREES. ANTS ARE ENLISTED TO SAVE WHISTLING
THORN ACACIA TREES FROM HUNGRY ELEPHANTS. BUT WOULD THE ACACIA TREES
BE BETTER OFF WITHOUT THE THREAT OF ELEPHANTS? FIND OUT HOW THE ANTS,
ACACIAS, AND ELEPHANTS ALL PLAY THEIR PART IN MAINTAINING A HEALTHY BALANCE.
VIDEO BY ANIMAL WIRE.
Photo by Enciktat.
Image by Roger Culos.
VACHELLIA DREPANOLOBIUM (SYN. ACACIA DREPANOLOBIUM), COMMONLY KNOWN AS
WHISTLING THORN (FAMILY FABACEAE), IS A SWOLLEN-THORN VACHELLIA NATIVE TO EAST
AFRICA. LIKE OTHER VACHELLIAS, WHISTLING THORNS HAVE LEAVES THAT CONTAIN TANNINS,
WHICH ARE THOUGHT TO SERVE AS A DETERRENT TO HERBIVORY. LIKE ALL VACHELLIAS,
THEY ARE DEFENDED BY SPINES. IN ADDITION, WHISTLING THORN VACHELLIAS ARE
MYRMECOPHYTES THAT HAVE FORMED A MUTUALISTIC RELATIONSHIP WITH SOME SPECIES
OF ANTS. IN EXCHANGE FOR SHELTER IN THE BULBOUS THORNS (DOMATIA) AND NECTAR
SECRETIONS, THESE ANTS APPEAR TO DEFEND THE TREE AGAINST HERBIVORES, SUCH AS
ELEPHANTS, KUDU AND GIRAFFES. IMAGE BY ROGER CULOS.
THE GREATER KUDU
(TRAGELAPHUS
STREPSICEROS).
L
ife is a non-stop battle
on all fronts. The
tranquillity of the bush
belies the wars that
are being waged there. The most
obvious, dramatic war is the one
between predator and prey; lion or
leopard against antelope, where
being stealthy, alert and swift is
a necessity. But there is also a
silent, unseen war between plants
and animals.
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Over the millennia, plants have
devised ways to avoid being
eaten. Some ways are obvious
– trees can grow too tall to be
eaten and some have long,
sharp thorns. Some plants have
an arrangement with other
organisms, such as aggressive
Crematogaster ants that help to
protect precious food-producing
leaves. They do this by providing
the ant with sweet nectar to eat
and swollen thorns as brood sites.
In return, the ants attack, bite and
sting any unsuspecting elephant,
antelope or giraffe that seeks to
browse the succulent, nutritious
leaves.
These are generally energyexpensive methods of protection.
More efficient and subtle are
inducible defences, such as the
chemicals produced by plants that
deter antelope and even insects
from browsing leaves and other
parts of plants. These chemicals,
collective
known
as
Plant
Secondary Metabolites (PSMs),
include tannins and terpenes.
During the mid-1980s, a study
was done on kudu by Professor
Wouter van Hoven when 3 000
had died. A subsequent postmortem revealed full rumens, yet
the animals had died of starvation.
How was this possible?
On being grazed, many plants,
such as the hook thorn, Acacia
caffra, raise their tannin levels in
the leaves by up to 94% in only
15 minutes. This tannin level
increases to a remarkable 282%
after an hour. The browsing
animal then moves on to the
next tree as the leaves with high
levels of tannins and terpenes on
that tree become unpalatable. Even
more astonishingly, the damaged
leaves on the browsed tree will
release ethylene that permeates
the air and which disperses
down wind. The warned plants up
to 50m downwind of the browsed
or damaged tree detect the
ethylene in the air and their tannin
levels also increase within five to
10 minutes.
Tannins make the leaves bitter
and unpalatable. The tannin also
complicates the digestion of the
leaf material to such an extent
that it has a negative influence on
the fermentation in the rumen and
the animals starve, even though
they have ingested sufficient
foliage. To counter this, the kudu
browse very little on a single plant
and tend to move on before the
tannin level increases too much.
Finally, browsers that have coevolved over centuries with
trees and shrubs have learnt to
move upwind when grazing, thus
feeding on trees that have not
been ‘warned’.
Moving and browsing upwind is
today often prevented by fences
we use to keep animals confined
to certain areas. We as humans
have therefore removed the
animal’s natural defence against
tannins. So during winter months
when plant material has lower
quality and digestibility, we need
to help these animals.
Tannins are produced by plants
and found in the cell walls of
leaves, flowers, bark and seeds.
There are two broad groups of
tannins:
CONDENSED TANNINS
Condensed tannins make the
leaves astringent and unpalatable,
leading to a reduced intake of plant
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219
Vet on Call
Vet on Call
by Dr Peter Oberem
research & training
research & training
Vet on Call
Vet on Call
Photo by Jez Bennett
THE COMPOSITION OF THE PLANT SPECIES EATEN BY THE GREATER KUDU DETERMINES THE DIET QUALITY, WHICH IMPACTS ON KUDU CONDITION
AND MORTALITY LEVELS. MALES WEIGH 190-270KG (420-600POUNDS), WITH A MAXIMUM OF 315KG (694 POUNDS), AND STAND UP TO 160CM
(63INCHES) TALL AT THE SHOULDER. FEMALES WEIGH 120-210KG (260-460 POUNDS) AND STAND AS LITTLE AS 100CM (39 INCHES) TALL AT THE SHOULDER.
material, which protects the plants
from herbivores. At the normal pH
of the rumen, condensed tannins
have a high affinity for proteins, to
which they bind. They also bind
to carbohydrates of the plant cell
wall and to some minerals.
They
therefore
lower
the
bioavailability of the nutrients
in the gastrointestinal tract and
inhibit absorption. This leads to
a reduction of feed intake, lower
nutrient absorption and a loss
of body condition, even if there
appears to be sufficient browse
available.
It must be remembered that
the effects of tannins are dosedependent.
At low doses, condensed
tannins (CT) may improve the
digestive utilisation of protein,
mainly due to a reduction in protein
degradation in the rumen by the
microbes, resulting in a subsequent
increase of beneficial amino
acids available for digestion and
absorption in the small intestine.
Protein gets deaminated, that is,
broken down, into polypeptides
and amino acids in the abomasum;
these polypeptides and amino
acids get digested and absorbed
in the small intestine (this is the
true protein source of the animal).
At higher levels, the effects
become detrimental to the animal.
At >5% tannin content, the
browse is rejected as food.
AERIAL VIEW OF A HERD OF GIRAFFE (GIRAFFA CAMELOPARDALIS) IN NATURAL HABITAT, SOUTH AFRICA.
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Photo by EcoPrint.
Photo by WOLF AVNI.
THE GIRAFFE IS THE TALLEST LIVING TERRESTRIAL
ANIMAL AND THE LARGEST RUMINANT.
HYDROLYSABLE TANNINS
Hydrolysable tannins inhibit the
secretion of detoxifying enzymes
by the liver, resulting in the animal
being unable to deal with toxins
taken in with the feed.
TERPENES
Terpenes are another group of
plant chemicals that become
problematic, especially during
droughts, winter and early spring.
Terpenes are unpalatable and
they inhibit the production of the
proteolytic digestive enzymes in
the small intestine. They also
inhibit the micro-organisms in the
rumen, which digest the ingested
plant material. This exacerbates the
lack of nutrients and causes further
loss of condition in the animal.
Both tannins and terpenes have
the additional negative side effect
of lowering the rumen pH, which
is detrimental to the growth of the
microorganism populations in the
rumen. Furthermore the high levels
GIRAFFE FEEDING ON ACACIA THORN TREES.
of tannins and terpenes in the
browse inhibit digestion resulting
in constipation, rumen (gut) stasis
or slow movement of feed through
the digestive tract, health
constraints, decreased feed
intake and a slow deterioration
in general body condition.
Tannin and terpene-containing
dry plant material is inherently
lower in important nutrients like
digestible protein, energy, essential
minerals and vitamins; the animals
will struggle to maintain a healthy
immune and reproductive system.
So when considering semi-extensive fenced-off areas, where the
available forage (browse) becomes a scarce commodity during
a drought or winter (including the
early spring season), browsing
animals not only have to cope
with food that is poorer in quality
and quantity, they must cope with
food that is more toxic (tannins
and terpenes).
What makes things worse is
the fact that many female animals
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research & training
You ARE
REG. NO. V26352 ACT/WET 36/1947
Get the most out
of winter forage
• Maximiseutilisationofnutrientsfrombrowse
especiallyduringwintermonths.
• Limitsthedigestiveconstraintsfromtannins
andterpenesassociatedwithbrowseby
theadditionofPVPandPEG.
• Containsessentialvitaminswithadded
Biotinsupportedbyorganicmineral
complexes,essentialaminoacids,
magnesiumandmicroelements.
• Supportshoofconditionandhorn
growth,fertility,growthandimmunity.
Manufacturer & Registration Holder:
Camelus Grondstowwe cc. PO Box 468, Oudtshoorn, 6620
Distributed by: Afrivet Business Management (Pty) Ltd, Co. Reg. No. 2000/011263/07
PO Box 2009, Faerie Glen, 0043, Tel: +27 (0)12 817 9060, Web: www.afrivet.co.za
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Helpline: 0860
VEEARTS
/ 0860
833 2787
Vet on Call
what you eat!
from different species are pregnant and thus carrying their young
during this time. These animals
are most likely to be under nutritional stress, which will clearly
limit their immune systemʼs ability
to maintain optimal health and
long-term reproductive efficiency.
So how do we escape the
damaging effects of these
chemicals?
1. Combat tannins and terpenes through nutrition. This
is done by the targeted supplementation of the diet of
these antelope with the following:
a. Polyethylene glycol (PEG): PEG
binds the tannins and terpenes
so strongly that it removes
them from the leaf proteins,
thus making the proteins
available to the microbes in
the antelope’s rumen.
b. Polyvinyl pyrolidone (PVP):
It similarly binds the tannins
and terpenes.
c.Dry browse or graze is
normally associated with low
concentrations of digestible
protein. High-quality essential
amino acids such as lysine and
methionine should be included
in the supplement, supplying
the microorganisms with
rumen-digestible protein so
they can proliferate, allowing
them to assist in fermenting
and digesting the available
forage.
d. Supplementation of important
minerals and vitamins, which
are naturally low during this
time of the year.
Sensible use of such supplements during winter, early
spring and times of drought
will allow the game rancher’s
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Vet on Call
̔ GAMEMIN BROWSE ʼ OFFERS AN ALLIN-ONE WINTER SUPPLEMENT WITH
TANNIN INHIBITORS, MINERALS AND
VITAMINS.
browsing antelope to maintain
their body condition better and
maintain the efficiency of their
immune systems. It will also
achieve
better
reproductive
efficiency. The pitfalls of smaller
fenced-off properties, winter and
drought conditions can therefore
be escaped.
Grazing ruminants, rhino and
zebra will also benefit from these
types of supplements. The PVP,
PEG, amino acids, minerals
and vitamins result in superior
digestion of dry grass, particularly
when limited, and no nutrient
supplementation (feed) exists.
Today there are products on the
market specifically developed to
address this complex of nutritional
needs precipitated by poor feed or
browse, tannins, terpenes and the
stress of winter or drought.
For more information
contact Dr Peter Oberem:
[email protected]
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