Strategies for Conquering Parasites on the Farm
Internal parasites can be a big problem on some farms. The traditional approach to controlling
parasites was to deworm the entire herd at the same time– usually spring and fall. Along with
mass medicating, dewormers were rotated each time to a different class of medication. While
this approach may have worked on some farms, we are now finding that those practices
contribute to parasite resistance. Unfortunately, resistance to dewormers is permanent,
making that medication ineffective on the farm forever.
Managing the parasite load on a farm requires paying attention to the animals AND the
pastures. Pasture contamination with parasite larvae is one of the biggest obstacles to
maintaining healthy animals. Deworming the herd twice yearly does not significantly reduce
overall herd parasite problems. Most adult farm animals have built up a natural immunity to
parasites. They have very low worm burdens. If we continually expose them to dewormers,
resistance will build. Statistically, the majority of worms are found in approximately 20% of the
herd. These are the animals that demonstrate clinical signs of internal parasites – they are the
animals that need to be dewormed. To effectively control parasites you should, specifically
target the animals that require deworming (based on clinical signs), promote careful use of
dewormers, and manage the animal environment. By doing this, you can reduce parasite levels
without developing resistance to dewormers.
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Use the “Five Point Check” system to determine which animals require
deworming
A summary on how to perform the “Five Point Check” can be found on our
website: http://bit.ly/akfarmpest
Young and geriatric animals are most at risk
Submit a fecal sample for analysis. This can be done through your local
veterinary clinic or a regional diagnostic lab. Be sure to request the centrifuge
method of fecal analysis. It is the most accurate method of assessing livestock
feces for parasite eggs.
Submit feces from 10% of herd or from individual animals that are having issues
Match the right dewormer to the specific parasites found on your farm
o Consult with your herd veterinarian
Alaska Agricultural Pest Project
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Divide herd into age groups and dose to the heaviest animal in the group
o Use a weight tape or scale
Choose strategic times to deworm (based on “Five Point Check”)
o After the first hard frost to eliminate larvae that have arrested in tissues
o Late gestation to prevent egg surge around the time of parturition
Clip area on back if using pour-on dewormer. Hair/wool makes it difficult for
the solution to absorb through the skin.
Consult your veterinarian about other deworming methods that may be
appropriate for your farm/animals
o Different dosage for goats, treating on consecutive days, and/or
withholding feed prior to administering oral dewormers (not in late
pregnancy!)
DO NOT use moxidectin (Cydectin) unless you have proven resistance on the
farm. This category of anthelmintic does not currently exhibit resistance, so it
should be used when all other categories of anthelmintics are no longer
effective.
Be mindful of milk and slaughter withdrawal times for all drugs administered!!
Reduce larval numbers on pastures
o This can be accomplished by rotating pastures and mowing tall
vegetation after animals are done grazing. By resting and mowing
pastures, sunlight is allowed to reach the bottom of the plants, thus
killing parasite eggs and larvae by drying them out. Egg and larval burden
decrease, reducing the risk of parasitism when grazed in the future.
Manage stocking rate
o Parasites have fecal-oral transmission – if the animals graze near feces,
the risk of parasites is HIGH! Allowing for adequate grazing space can
lessen the risk.
o If animals numbers can’t be reduced, may have to go to dry lot system
Keep feed and feces separate
o Do not feed on the ground – use feed bunks/racks
o Clean up feed that has fallen out of bunk. Do not allow animals to eat
hay that has been trampled or defecated on.
Work closely with your veterinarian to develop a parasite management routine. Every farm is
different – only you and your veterinarian can develop a plan that makes sense for your farm!
Alaska Agricultural Pest Project