Originally Posted by kitten_Val
Fecal egg count test. Positive -> talk to the vet. Negative -> deworm 2-3 times/year, at least once with Zimmectin Gold or Equimax (to take care of tape worms that don't come up in fecal test).
I personally will not use Zimectrin Gold, I had a horse have a horrible reaction to it. I like using Equimax. It actually contains more deworming product too.
My vet says (for low/none shedders) Moxidectin/praziquantel in the spring and Ivermectin/praziquantel in the fall.
Theories on deworming have for sure changed over the last couple of years from what they were before.
If this is a topic you have not discussed with your vet it is worth bringing up. Different parts of the country have different protocols to follow.