Livestock
Parasite control
Fungus helps clean up wormy paddocks
by
Malcolm Knox,
CSIRO
F
eeding fungus to sheep could provide an
effective alternative to chemical drenches
to control worm parasites, according to
innovative CSIRO research.
Rather than trying to cure round worm
infestations with drugs, the research aims to
develop a method to break the worm life cycle
by preventing livestock ingesting infective
larvae when grazing.
Australian strains of the nematodedestroying fungus, Duddingtonia flagrans,
were first discovered in a survey of sheep
dung during the early 1990s.
When fed to livestock, the fungal spores pass
through the gut of the animal and are excreted
with the worm eggs in the dung. The fungal
spores then germinate and grow networks of
traps which ensnare and kill the worm larvae
soon after they emerge from the eggs.
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Trials using the fungus, fed in grain and
block supplements, have shown a reduction
in worm larvae numbers by up to 90 per cent,
without any harmful effects on soil
microfauna which help break down the dung
in the pasture.
The targeted round worm parasites include
the major worm pathogens of sheep, goats
and cattle (Barber’s Pole worm, black scour
worm and small brown stomach worm) as
well as small stronglyes in horses.
Laboratory and paddock trials
Laboratory and paddock studies have been
carried out to determine the impact of feeding
the fungus as a feed supplement on worm
infections and sheep productivity.
A series of feeding trials was carried out
with young sheep carrying black scour
worm infections. The sheep were maintained
in individual pens and fed fungi treated barley
as part of their daily ration.
The results showed as little as five
grams of grain per sheep per day were
sufficient to virtually eliminate larvae from
faecal cultures. The effect persisted for the
time the fungal grains were fed and for up to
two days afterward.
At Armidale, New South Wales, CSIRO
Livestock Industries also carried out a
paddock trial using 60 4–5-month-old mixed
sex Merino lambs.
The lambs were drenched at weaning
before being placed in six equal groups (based
on liveweight) on pasture which had not been
grazed for 12 weeks. Three groups of lambs
At a glance
• Research indicates feeding
nematode-destroying fungus to
sheep could provide an effective
alternative to drenches to help
control worm parasites.
• When fed to livestock, the fungal
spores pass through the animal’s
gut and are excreted with the worm
eggs in dung. The spores then
germinate and kill the worm larvae.
• Trials using the fungus, fed in grain
and block supplements, have
reduced worm larvae numbers by
up to 90 per cent.
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CSIRO Livestock Industries
Drench resistance is an increasing and costly problem for Australian sheep producers. This article outlines how a
naturally occurring fungus could be used as a biological control tool to reduce the level of worm parasites in
sheep grazing pastures.
Innovative CSIRO research shows feeding fungus
to sheep could provide an alternative method to
significantly reduce worm parasite numbers and
lower chemical drench use.
were fed barley containing the D. flagrans
fungi daily for six months. The barley was
placed in troughs under shelter.
Faecal samples were collected regularly for
nematode egg count estimation along with
bulk (paddock) larval cultures for identification.
Lamb liveweight was also recorded monthly.
Reduced faecal egg counts
The trial showed that feeding young
Merino sheep with the fungi significantly
reduced worm faecal egg counts by up
to 70% which would have a significant
impact on the animal’s overall health (see
Figure 1).
The impact was demonstrated in the
liveweight gains, as the treated lambs each
gained an extra 2.9 kilograms during the
trial (see Figure 2). Analysis of the results
suggested the outcomes could have been even
better if the daily consumption of the fungus
was more consistent.
Future work will look at improved
education of lambs through increased
exposure to supplements before weaning
and by fine-tuning the formulation of the
feed supplements to increase animal
attraction and palatability.
Administration via feed blocks
Fungal grains were incorporated into a
range of feed block formulations to determine
whether this form of administration could
be possible.
Before the start of the fungal block
treatments infected sheep were maintained
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FIGURE 2 Lamb liveweight gain
FIGURE 1 Feeding fungi to sheep reduces worm faecal egg counts
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on a diet of chopped oaten hay and allowed
ad-lib access to a fungi-free urea molasses
block to habituate them to block consumption
before receiving the fungal block.
In all these trials, the fungi survived the
manufacturing process and resulted in
significant reductions in larval numbers.
This was observed even for sheep showing
only modest or irregular block consumption.
The results demonstrate supplementary
feeding or block administration offer
potential feeding options for fungi as a
means of biological control of nematode
parasites.
Environmental impact of fungi
CSIRO researchers also investigated the
possible adverse effects of two Australian
strains of D. flagrans on beneficial soil
organisms in a typical improved pasture.
The presence of fungi in livestock faeces
did not affect the abundance of beneficial
soil nematodes and microarthropods.
There were also no negative effects of
fungal presence on the numbers of other
nematode-trapping fungi.
Over time, there was generally a decline
in the presence of the fungi and the rate
of decline appeared to depend on seasonal
conditions.
Drier conditions appeared to prolong the
presence of the fungi in faecal matter.
Recommendations
In
Australia,
feeding
nutritional
supplements to sheep to enable maximum
productivity is becoming more common,
particularly for young or pregnant animals
at times of nutritional or environmental
stress.
The use of nematophagous fungi for
biological control will target times when
nutritional supplements are likely to be
beneficial since this is often when parasites
are a problem or larvae availability on pasture
is increasing.
Fortunately, when weather conditions are
favourable for the development and survival of
nematode parasites, they are also favourable
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Source: CSIRO Livestock Industries.
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Source: CSIRO Livestock Industries.
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for the germination and colonisation of dung
by nematophagous fungi.
Therefore, as research results suggest,
feeding sheep supplements containing the
fungus at these times could achieve
significant reductions in subsequent larval
numbers and worm infections in sheep.
Concerns have been raised that optimal
reduction in larval development may not
occur unless all animals consume the
required daily dose of spores.
On a flock basis this need not be a
problem provided sufficient animals
consume enough supplement with the
fungus to reduce seasonal peaks in larval
development to manageable levels and not
eliminate them.
With relatively fewer infective larvae in
pasture, productivity losses could be
significantly reduced while sufficient larvae
are present to stimulate immunity to infection.
Future research
A programme of paddock evaluations is
about to be launched involving CSIRO
Livestock Industries, Department of
Agriculture Western Australia, South
Australian Research and Development
Institute, International Animal Health
Products and the Australian Sheep Industry
Co-operative Research Centre.
After completion of these trials over the
next two years it is anticipated a commercial
biological control agent will be available
and strategies for its use in major sheep
producing areas will be finalised. The
fungus-enhanced feed supplement will most
likely be used by farmers in conjunction with
drenches and other parasite management
methods such as strategic grazing.
Acknowledgements: International Animal
Health Products and Australian Sheep
Industry Co-operative Research Centre.
For information contact Malcolm Knox by
email on [email protected], phone
(02) 6776 1440 or fax (02) 6776 1333.
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