I’ve come to the conclusion that the first thing we all need to do when it comes to our horse deworming schedule decisions is “chill.”
Like you, I’ve read many conflicting horse deworming schedule reports. And it seems that for every horse deworming program based on a rotational drug wormer schedule, there’s another one saying only use ivermectin, or yet another one that claims the best worming schedule for horses is a “target program,” which means you should deworm only for the parasites your horse has.
If you go target, you must take a sample of the horse’s manure to the vet to have it analyzed or do it yourself—do you have a microscope in your barn?—and then choose the drug that matches the eggs seen in the sample. If you have the time, money and desire to do this, go for it. I don’t.
But I’m not all-ivermectin either, as some folks say, as I’m reading some reports about resistance there, too (of course it is! The drug has been in use a long time, meaning that a couple of super worms learn to avoid it, then produced more super worms and super-worm grandworms). So I’m going to rotate drugs, but I won’t use a horse deworming schedule based solely on the calendar either, one that says to deworm the horses every 60 or 90 days with a different drug. That’s because each individual drug has a slightly different “repeat” range for a horse deworming program, so you need to mark your calendar by that.
To learn more about deworming, download our FREE guide—Deworming Your Horse: How to find the best deworming schedule for you and your horse.
Ivermectin’s recommended repeat schedule is 6 to 8 weeks; moxidectin is 12 weeks. Most others are every 4 weeks. So, if you’re doing horse deworming every 60 days, and you’re using a lot of the 4-week drugs, your horse theoretically has a gap in his worming schedule, but I don’t over react about it. I think you should also need to factor in the season (low in winter; high in spring) and your own farm management (low 2 horses on 10 acres; high 5 horses on 1 acre).
My equine worming schedule rotates in at least one of the more-expensive broad-specrum horse deworming powerhouses—the ones that get bots and most everything else—and that means either ivermectin or moxidectin. Plus, at least twice a year, that paste dewormer tube should include praziquantel for tapeworms.
When it comes to deworming horses, my advice is to sit back and take a deep breath. If your horses are healthy and between the ages of 2 and 15, they are fairly well equipped to battle small parasite loads. They just need a little well-planned help.
Editor-in-Chief, Horse Journal