I know this other horse does not get properly dewormed due to the fact they have said they had never dewormed him because they couldn't get it in his mouth. They put it in food and hoped he would eat it.
My horse is dropping weight when she already needs to gain. Her and her paddock mate get roughly 50 lbs of hay per day each. So she is not lacking in the food department. Her belly is still kind of big despite regular heavy exercise. She is also on the every 2 month deworming schedule for our barn.