Clinical aspects of ovarian pathology in the mare

Abstract

Equine ovarian abnormalities can be divided for clinical purposes into abnormalities of follicular development, ovulation abnormalities, luteal dysfunction, ovarian tumors, and miscellaneous abnormalities. The objective of this review is to discuss specific causes of ovarian pathologies within these groups, their effect on fertility, diagnostics, and treatment options. It is concluded that ovarian abnormalities is a common cause of subfertility and infertility in the mare. Mares with abnormalities of ovarian follicular development caused by gonadal dysgenesis, advanced age, and equine Cushing's disease are generally more difficult to treat compared to mares with persistent anovulatory follicles, persistent corpus luteum, luteal insufficiency, or ovarian tumors. Recent data on the effect on follicular development following subcutaneous implantation of slow release GnRH agonist deslorelin acetate is discussed. It is concluded that deslorelin acetate can cause temporary down-regulation of FSH secretion with associated prolonged inter-ovulatory intervals. Removal of the implant following ovulation may circumvent this side effect. The use of testosterone and inhibin assays to accurately diagnose mares with granulosa-theca cell tumors (GTCT) is discussed, α-Inhibin, but not dimeric inhibin is elevated in approximately 90% single blood samples from mares with GTCT. Daily fluctuations in serum testosterone, makes a single blood samples analysis of this hormone less predictable for the tumor.