I was worried that once a month was too much, but my sister-in-law and the vet said that I should worm monthly until she's 1 year old. Her babysitter, who's a 30+ year old pony mule gets wormed four times a year. After I saw what came out of my baby I wormed Miss Maude ahead of time with Pyrantel and if she did have worms, I didn't see any. I'll have a fecal done on Monday and I'll ask the vet again about worming less often.
With my dogs I never worm without fecals and my dogs had worms only once in 12 years. Only one of them tested positive, but I wormed all of them just in case.
I am concerned about the toxins in wormers, but I was told that there is no way around it with horses. How do I kill the eggs on the ground?