AIS stands for Androgen Insensitivity Syndrome - it is a recessive defect which causes females to be sterile.
Mares will look and act like a stallion. Heavily muscled, aggressive to other mares in heat and displaying other typical stallion behaviours. These mares can be helped by gelding them. They look like mares in every way but they also have internal male testicles.
It has been documented in Quarter Horses, Throughbreds and Standardbreds,
If you have an AIS mare or suspect you have one we would be very interested in her pedigree - please consider contacting us.