Should I keep her on just hay today and leave out the mare and foal feed?
I think I would for just today. Just give hay today.
If she is losing weight you might want to slowly increase the grain, you are giveing her. And on average, horses need 1/3 of a bale of hay a day. Feed that amount, if you notice a lot of waste you can cut back to save the waste. How many times a day do you feed?
Becky