The effect of hCG, administered in diestrus, on luteal, ovarian and uterine blood flow, peripheral progesterone levels and pregnancy rates in mares

Abstract

Although advances in the management of brood mares have led to an increase in conception rates, early embryonic loss is still a major concern in equine practice. However, administration of hCG in diestrousmares has been reported to increase pregnancy rates and progesterone production. The aim of this study was to analyze the effects of a postovulatory hCG-treatment on luteal, ovarian and uterine blood flow, peripheral serum progesterone concentrations and pregnancy rates in the mare. Thirty-four mares were inseminated, 17 with cooled and 17 mares with frozen semen, and randomly assigned to three experimental groups after ovulation (D0). Group 1 (n 1⁄4 12) served as untreated control, Group 2 (n1⁄411) received a single intravenous injection of 2500 IU hCG on D5, and Group 3 (n 1⁄4 11) got an analogous hCG-application on D 11 of the cycle. On D0 during the first 12 h post ovulation colour Doppler ultrasonography was performed every 4 h, and afterwards in 12-h-intervals until D3 in all groups. The control group was examined once daily until D13. Mares in the treatment groups were examined once daily until the hCG-administration. Thereafter ultrasonographic examinations were performed every four hours for the first 12 h and in 12-h-intervals for the following three days. The total as well as the perfused luteal area, and the blood flow