RED DEER — Parasites picked up in pastures can reduce a dairy cow’s milk production and inhibit its ability to fight off disease.
“One of the things we have seen in the last 10 years is that we have really learned how these parasites affect the immune system,” said Donald Bliss, a veterinary parasitologist from Wisconsin.
His company, Mid America Agricultural Research, has researched parasite control in all livestock species.
Internal parasites depress the immune system and reduce milk production and feed intake, which results in poor growth in calves.
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Control strategies differ from farm to farm, he told the Western Dairy Seminar in Red Deer March 12.
Grazing animals are exposed to parasites, while cows living in confined barns on concrete floors have less risk.
Not all animals need deworming, but Bliss recommends keeping animals parasite free for the first 100 days of lactation.
“For $2 or $3 worth of dewormer to get those animals in good shape, (it) doesn’t make much sense to leave those parasites in there,” he said.
The immune system is compromised when worms such as ostertagia enter the digestive system.
The ostertagia completes its life cycle by entering a gastric gland located in the gut. The larvae grow, expand and eventually destroy the gland. This shuts down stomach acid production, and the cow cannot digest fibre properly.
Cows that are trying to fight off the parasites cannot produce enough antibodies and become susceptible to bacteria and viruses.
Bliss suggests deworming in the fall, but cows that are turned out on fresh pasture first thing in the spring will be exposed again.
If the cattle are held back until July, most of the parasites should have died off and the animals can safely graze.
Pastures should also be rotated frequently.
Fecal samples should be collected to identify what is in the manure.
Random samples can be collected in a plastic bag and sent for analysis to identify the parasites and estimate how many are present.
The correct treatment can be used once the parasite eggs have been identified.
Some parasticides are fatal to dung beetles, which remove manure and work as a natural predator for fly and parasite larvae.
“If you kill those dung beetles off, you actually increase your parasite challenge,” he said.
