Infertility in the horse associated with chromosomal abnormalities.

Reproductive failure was studied in 12 phenotypically normal mares (9 Arabian, 3 Quarter horses, 1 Appaloosa and 1 pony). Karyotyping was performed using lymphocytes isolated from peripheral blood by density gradient procedures, followed by standard culture methods for karyotyping. Nine mares had karyotypes of 63,XO; 1 had 63,XO/64,XX; 1 had 63,XO/64,XY and 1 had 64,XY. All mares had small, firm ovaries that when removed and examined from 4 mares, lacked germ cells and consisted of undifferentiated ovarian stroma.