Q: I have a 12-year-old gelding on a regular deworming program (I rotate ivermectin, pyrantel pamoate, fenbendazole, and praziquantel/ivermectin) and he’s very healthy*. Is there any problem with exercising him on the same day that I deworm? Should he get some time off after deworming?
If your horse had not been dewormed in a long time, particularly if he were quite young, there would be a slight risk of colic after deworming due to a heavy parasite load being expelled. In that scenario, it might be advisable to give the horse that day off after deworming, or consider a half dose of a fenbendazole product, to avoid killing large numbers of ascarid parasites at once. This half dose would then ideally be followed up within several days with an ivermectin or moxidectin dewormer.
*Editor’s Note: Since this article was originally published, a standard rotation is no longer recommended. Read more about current deworming science here.
Julia H. Wilson, DVM, Diplomate, ACVIM, associate professor & division head, Large Animal Medicine, Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota.