Is milk bad for horses

Before the days of infant formula in the grocery store, a human baby who had lost his/her mother would either be nursed by a wet nurse, or raised on mare's milk.

I have never drank enought to probably properly answer this question, but I have had a taste here and there, and it's been 14 years, and I'm still alive and healthy! We oce had a horse that had so many babies that she constantly lactated, and we used to milk her to feed the babies whose mothers rejected them until we could get Folac (foal formula) from the feed store.