Should a cattle raiser use a dewormer? There’s no set answer.
“You can’t give a standard recommendation as to how often to treat what stage of animal,” said Dr. Thomas Yazwinski, University of Arkansas Professor of Animal Science, “because that will vary farmer to farmer, location to location, and season to season. There are too many variables; the farmer has to make that decision for himself.”
Yazwinski told Ozarks Farm & Neighbor producers have been dealing for years with the question of what constitutes an economic threshold of treating parasites. He said, “If you wait until you see that there’s a parasitism, then obviously now you have stressed and unhealthy animals, plus you have lost good production out of those animals probably for months prior to the time that you actually visibly notice it. All grazing animals will have parasitism, and each producer has to balance what he feels is the good economic returns as to when he invests in chemical intervention.”
The producer has to decide whether a parasiticide would improve animal performance to the point where it’s worth the cost of the treatment; that goes for both the low end of infestation and the high end, where the treatment may be needed to save the animal but the animal may still underperform for a long time to come. Yazwinski said, “Farmers will go year in and year out for decades, not put a dewormer into their animals and say, ‘Look at all this money I’ve saved; I’m not using a dewormer, and I’m making money every year.’ Great, but there are a lot more people that we can point to who say if you deworm your animals strategically you would get the cost of the anthelmintic, plus two or threefold more than that, due to increased performance of the animal.”
All intestinal parasites reduce the feed efficiency of the animal. In addition to taking away from the nutrition available to the animal, the inflammation caused by the parasites causes fluid and mineral loss through the intestinal track. That would point to even more dramatic performance losses during the winter, when a cow’s feed needs are higher, except worm activity is reduced in the winter compared to the spring or fall, when the parasites are most active on pasture.
Yazminski recommended cattle producers test cattle feces before or on the day of treatment, and then again from the same animals 14 days later, to see if the product is giving good activity.
External parasites can also affect an animal’s winter performance. While fly activity will have diminished, problems with lice could surface, according to University of Missouri Extension southwest region livestock specialist Eldon Cole. “Lice like to set up housekeeping in these long haircoats of cattle during the wintertime,” Cole told OFN, “and if you’re not awfully careful, you can have a pretty full-blown louse population out there on the cattle by the time February and March roll around.” The solution is to bring in the cattle after a hard frost and apply a pour-on or spray that will control lice in the early stages.”
If the infestation is bad enough, it can cause a drop in daily gain. There are two types of lice; the “chewing” louse is just a discomfort for the cattle, but bloodsucking lice can have a bigger impact on profits. If you have parasite problems in your herd, said Cole, “you just need to feed them a little bit more, because when they are sucking blood they are robbing the animal of some of the nutrients that they need for growth and reproduction.”


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