What causes a mare to not produce colostrum?

Many different things can cause a mare to not produce colostrum. The most common reasons are illness, hormonal imbalance, and fescue toxicity. Fescue toxicity is the most common and the most preventable reason for lack of colostrum in the mare. Removing a pregnant mare from infected fescue grass is vital to preventing this problem.

Fescue grass also causes problems in joints, and possibly even an abort for a mare. I would make sure that she has plenty of clean water (no mud, algae, etc. in it) and get a few bales of premium hay for the lady. If you suspect fescue toxicity, do not waste time but I would call a vet to check her over well also.