De worming

What kind of deworming schedule do you have your horses on? Bailee has some bad ones right now (maybe still from the last owner?) so we are giving her the panacur pack! Hopefully that will wipe most of them out!

we switch off between ivermectin and another brand every six weeks

I deworm with Ivermectin in the Fall, and in the Spring give a double dose of Ivermectin Gold. My roan gelding was on a daily deworming powder that went with his feed schedule, but I don't think it was very effective. Our horses are very healthy and look wonderful, so what we're doing seems to be working well.

How wormy is your horse? If lots, I would think that Panacur would work just fine.