Preliminary observations on the occurrence of the equine XO syndrome

Abstract

Clinical and cytogenetic observations were made on seven mares which had never bred when sent to stud. In six of these, the chromosome count was 63,XO with one X chromosome missing and, in one case, two cell lines were present with a 63,XO/64,XX chromosome constitution. All mares showed signs of the equine Turner's syndrome and it is suggested that sex chromosome abnormalities may be quite a common cause of sterility in the mare.