Are fescue pastures good or bad for horses?
The short answer is yes. Good and bad. Fescue is a very successful pasture plant. As most breeders understand, it can mean deadly complications for horses. The long answer is about how to tell if your animals are at risk of a toxin produced by a fungus that grows mutualistically with fescue.
Fescue is an enormously popular pasture grass because of its heartiness in most growing conditions, long growing season and its good stand. For non-horse owners, there is little confirmed risk of toxicity from fescue. For horses not at risk of being pregnant also have little to worry about from the toxicity.
The way that the fungus lives involves production of a harmful substance. The harm is not the the mare herself, but to the way her body communicates with itself and the gestational foal. This substance blocks her bodies ability to produce colostrum along with some other slight birthing abnormalities (thick placenta).
To avoid toxifying the foal, it is recommended that pregnant mares be removed from fescue feeding three months before birthing. My interest in the topic stems from an intervention that we had here locally. A girl was keeping her first bred horse with some cattle on a small ‘hobby farm’. Unbeknownst to them, there was a heavy fescue mix in the grass that the cows and her horse were grazing upon.
I had read bits and pieces about this toxic effect, but had never kept a pregnant mare so cared little about it. Once the neighbor girl caught wind of the possible tragic event looming, she asked for my opinion. I could not opine and did a bunch of homework. It turns out that the toxic affect is not always present and there is a small body of research about why.
Apparently because the toxic fungus is carried on the fescue seeds and stems, so if a horse is in a lush field of fescue eating primarily leaves, she may be safe.
To help out the neighbor we ended up with a mare foaling right in our barn. We allowed her to graze at our house until she and the foal were ready to move. Three summer months is a long time to horse sit especially when new to the large animal birthing process, but we all learned a lot and are much more well rounded horse carers than before. Both mother and baby are fine.
I hope that my research may help you find an alternative situation if your mother mare is at risk of toxic fescue.