Once a month! Then once around the sixth month mark give a stronger wormer, then the next time worm your horse with your regular wormer. That's what I do and all my horses are heatly! :) P.S. Ask your vet too!

The trouble with wormers these days is that there is so much on the market, ones that kill off different types of worms, for different months, i have all my horses on my yard on a worming programme which i get help and advise from my vet, equest paramox kills absolutly everything and you do not have to worm again untill 12 weeks after, they say around 8 - 12 weeks you should worm.   Again different wormers for different worms, or i have herd of sticking to one brand i.e. equest for the year.  i have never herd that you only worm once a year!!! all i know is that you should double dose or 5 day guard your horse at least once a year for tape worm.  Ask you vet for advice and guidance, or i believe they have an online vet on thrusday on here.  Worming is very important, and this should be done right, i can only tell you what i do for all my horses.  If you are on a large yard or even a little yard with other horses you should be all on a worming programme, cause if only one horse out of the yard is being wormed or if you are all worming at different times and different wormers you are just throwing your money away  as they will counteract each other and not work.  Hope this helps, just seek advice from your vets best of luck