Effects of a single dose HCG administration on the induction of ovulation, follicular dynamics, uterine changes and pregnancy outcomes in mares during the breeding season

Abstract

In this study, 19 mares brought to the clinic at different times with the complaint of not getting pregnant were followed up. For this purpose, changes in the uterine and ovarian dynamics of mares and behavioral changes in estrus were followed and evaluated. In particular, it was attempted to increase the chance and rate of pregnancy by providing ovulation with ovulation follow-up followed by a single dose of hCG administration (Chorulon, 3.000 IU). All manipulations and applications in the study were carried out between March and July, that is, during the breeding season of the mares. During the study, a B-mode real-time ultrasonography device was used for ovary and uterus examinations of the mares. For the insemination of the mares, fresh semen was obtained from breeding stallions by the artificial vagina method and analyzed fresh semen was used. The intracornual insemination method was used as an artificial insemination method. Pregnancy controls were performed twice on the 15th and 30th days after insemination and the pregnancy status was evaluated according to the criteria of the presence of an embryonic sac in cornu uteri. While the average follicle diameter was around 43.7 millimeter (mm) at the stage when estrus symptoms were at their peak, the diameter of the follicle was 36.2 mm in the USG controls performed at the beginning of estrus. Uterine oedema was measured as 1.78 in the initial phase of estrus, 3.84 in the most intense phase of estrus, and 2.36 during insemination during the same periods. The pregnancy rate was found to be 68% (13/19). As a result, it is recommended to administer gonadotropic hormones such as hCG at an appropriate dose (3000 IU) to mares who have trouble conceiving, especially in cases of delayed ovulation.