Premarin (estrogen for HRT) is made from pregnant mares' urine. Because of the outcry of animal rights people against the fact that the horses were forced to remain constantly in one place as their urine was tapped and because their foals were usually euthanized, this may have changed somewhat. I think there has been a synthetic substitute mentioned, and foals are now rescued and adopted out.
Many mustangs are rounded up in the Southwest desert and, along with unwanted old or feeble tame horses, are slaughtered and the meat sold to Europeans for food. The last slaughterhouse in the U.S. Recently closed, so now horses are transported to Mexico and Canada for slaughter.