Moxidectin, for example, is restricted against use in foals younger than 4 months. Products that are labeled as safe for use on foals without age restrictions can help protect foals during this critical early period. And remember to check which parasites are controlled by your dewormer. That means establishing a program and sticking to it. Package instructions will specify how often you will need to deworm your horse for maximum effectiveness.
Most deworming products call for reapplication every six to eight weeks.
Some products may claim a longer duration, but take a close look - you may find that their extended killing power applies to only one or two parasite types. Your horse is exposed regularly to other parasites in addition to small strongyles and should be dewormed more often to control the broadest spectrum of parasites. Deworming formulations vary, so read those label directions carefully to make sure you're giving the proper dose for your horse's weight.