We’ve already talked about barber pole worms—one of the biggest health threats to sheep and goats in the United States—and some natural methods for deworming livestock, such as herbal dewormers, pasture plants that help fight worms and copasure boluses. Let’s wrap up this series on internal parasites with some steps you can take to get the most out of chemical dewormers on your farm.
It’s important to realize that worms are becoming resistant to most dewormers on the market. This is especially true of sheep and goat worms, but it’s a problem in other species, like horses, cattle, llamas and alpacas, as well.
Resistance happens because one worm in millions of worms has a genetic characteristic that makes it resistant to a specific dewormer. When you use that dewormer over a period of time, it gradually kills off nonresistant worms until all that remains to breed and create more worms are the ones that dewormer can’t touch. Unfortunately, this isn’t at all uncommon.
The solution isn’t to continually switch dewormers: The experts say that if a dewormer works on your farm, you should use it for at least one year. According to the Southern Consortium for Small Ruminant Parasite Control, resistance happens when people deworm too often and they under-dose dewormer when they do. The trick is to find a dewormer that works and then deworm animals only when they need it, based on fecal exams or FAMACHA testing. It’s also important to give your animals enough dewormer, so you don’t just kill off weaker worms and allow tough, resistant worms survive. If you can’t weigh your animals to figure out the proper dosage requirements, learn how to tape weigh them. It’s easy and it works!
Even if you deworm properly, you can introduce dewormer-resistant worms when you bring new animals to your farm. Isolate newcomers and ask your veterinarian or cooperative-extension agent which dewormers to use before they join the rest of your livestock. A common ploy is to deworm using a full dose of two dewormers from different chemical classes (there are three: benzimadoles, imidazothiazoles and macrocyclic lactones) at the same time, then take a fecal sample to your vet in a week to see if they did the trick.
Don’t use specific dewormers, dosages and means of deworming animals just because a farmer friend said it’s OK. Ask your vet first! Some dewormers cause terrible problems if used at the wrong time, in the wrong dosage or in the wrong way.
Most chemical dewormers are given orally. Paste dewormers for horses are fairly easy to administer, but oral dewormers are often more difficult to give to us smaller animals because our dewormers rarely come in tubes. When deworming a sheep, a llama or a goat like me, use a dose syringe designed for the purpose, and try to deposit the dewormer on the base of the tongue. That way goes to the rumen, where it’s more effective. If you stick dewormer in the front of a ruminant’s mouth, most of it goes to the abomasum instead.
It’s not much fun for us, but if you fast us overnight before deworming, dewormers are more effective. But don’t deprive us of water. We need that!
And always observe drug withdrawal times when using milk or meat from chemically dewormed animals. You’ll find that information on dewormer labels, or your extension agent can fill you in.