There are as many theories on how and when to deworm your horse as there are products to do it with. The worry has always been the possibility of overmedicating your horse, resulting in eventual resistance to dewormers, or not to deworm at all.
The best first step in your horse's deworming schedule is to see if your horse has worms. You can do this by having your horse's manure evaluated by your vet and getting a fecal egg count. This will tell your vet how prone your horse is to worms allowing your vet to better classify what dewormer products are best and when to administer them to your horse. Rotational deworming is the use of different classification of products and is the most common type of deworming schedule.
Once you have the proper medicine and schedule set up, make sure you give your horse the correct amount based on his weight. And double check that your horse is actually taking in all the dewormer you give him. It's easy to think you got it all in, then have your horse drop his head and it all slide out.
While deworming your horse appropriately is important, so is managing the area where you horse picks up these worms, i.e.the pasture. Worm eggs are passed from the horse into the pasture through their manure. Larvae hatch in the field and are picked up by grazing horses. And this begins the cycle again.
Ways to reduce this risk include picking up manure in paddocks, putting hay/grain in feeders instead of the ground, keeping manure away from water sources, reducing the number of horses grazing in each pasture, rotating and resting pastures every few weeks to interrupt worm life cycles, and drag or harrow pastures in hot, dry weather to break up manure piles; killing eggs and larvae. Some of our barn accessories may be able to help you easily reduce these risks- Check them out!
Using this plan can help protect your horses from parasites now by cutting back on overuse of medications and underuse of pasture management.