Effects of Transvaginal Ovarian Biopsy on Health and Fertility in Mares

This is an historical perspective study from two years of data to determine the effects on health and fertility of a transvaginal ovarian biopsy (TVOB) procedure in mares. In 2012, there were 19 mares included in the study: four healthy non -TVOB mares, 11 healthy TVOB mares, and four mares with ovarian abnormalities. In 2013, there were 19 mares included in the study: four healthy non - TVOB mares, 14 healthy TVOB mares, and one mare with an ovarian abnormality. Four mares (one non - TVOB, two TVOB mares and one mare with an ovarian abnormality) were utilized in both years. Mares were classified into groups: Group 1 - non - TVOB (control n = 8 cycles); Group 2 - healthy mares one TVOB per cycle (n = 36 cycles); Group 3 - healthy mares two TVOB per cycle (n=42 cycles); Group 4 - healthy mares three TVOB per cycle (n = 5); Group 5 - mares with ovarian abnormalities (n = 5). Fertility was assessed as pregnancy rates in cycles in which mares were artificially inseminated with cooled semen from one fertile Quarter Horse stallion. Pregnancy rates were calculated for: non - TVOB Group 1 mares, the remainder of the mare cycles were further subdivided into TVOB mares that had pregnancy data before and after sampling. Pregnancy rate in mare cycles where the ovulation was from a previously biopsied ovary was 77%. Health effects were assessed with daily rectal temperatures, general demeanor and appetite for 72 hours after the procedure. There were no significant effects of TVOB on health or fertility. Histologic sections of ovaries removed from a normal mare were examined. There were no significant gross lesions. Histologic examination of the ovaries showed no fibrotic changes or architectural remodeling. Transvaginal ovarian biopsy of Group 5 mares resulted in a diagnosis of normal versus neoplastic ovarian tissue in 4/5 attempts (one sample was non-diagnostic). The TVOB may be applied to aid in the diagnosis of mares with ovarian abnormalities, and no adverse effects are to be anticipated.  […]