Originally Posted by riccil0ve
Well I worm every three months. Well... except my filly, the vet said she should be wormed once a month her first year.
Oh, and I don't have a set pattern of brands, I just always get a different wormer than I got the last time.
Then you really need to watch that deworming webinar. You should have at least a set pattern spring and fall---ivermectin/praziquantel or moxidectin/praziquantel. And during the winter months you are in an area where reinfection rates are going to be very low so deworming isn't necessary for adult horses. At temps below 45 degrees, strongyle eggs don't mature into infective larva so can't reinfect your horses.
You are also likely deworming with ineffective drugs for strongyles at fenbendazole has a VERY HIGH incidence of strongyles being resistant to it (more than 90% of areas tested show resistance worldwide) and pyrantel has resistance issues in about 1/2 of the areas tested in studies.
Even veterinary recommendations tend to be way out-of-date these days because vets tend to spend their continuing education time and money on more interesting topics like surgery, endocrine disorders, lameness, etc.