Join Date: Jun 2017
Location: middle of nowhere
Did your vet do a fecal count? If not, and they haven't been dewormed lately, I would deworm. On a small amount of land with limited grazing, it's nearly impossible for horses not to have some parasites.
Have teeth checked and floated.
Increase amount of hay and add in some higher-quality forage-- alfalfa, or a complete senior feed that includes some forage in the amount. The key to getting weight on horses is forage more than concentrated feed.
Consider a vitamin E deficiency. Many horses need supplementation, particularly during winter months, or year-round with out access to lush, thick pasture.
I would start with teeth and dewormer. If either of those are an issue, you can pour as much feed through as you want but it won't make much difference.