Treatment of Ovarian Inactivity in Mares During the Breeding Season with PMSG/hCG, PMSG or GnRH and the Effect of Treatment on Estradiol and Progesterone Concentrations

Abstract

The objective of the present study was to treat ovarian inactivity in mares during the breeding season by using three protocols. Mares (n = 52) kept under field condition in the Green Mountain area, north of Libya were examined transrectally by ultrasound during the breeding season. They were assigned to have inactive ovaries which was confirmed by measuring serum estradiol and progesterone concentrations. Mares were treated with either PMSG/hCG (n = 32), PMSG alone (n = 10) or GnRH (n = 10). Estrus was detected by stallions and mares in estrus were allowed to be mated two times 2 days apart and examined for pregnancy by ultrasound one month later. The results showed that in the PMSG/hCG group, 19 (59.4%) mares out of 32 exhibited estrus, while 6 (60%) and 5 (50%) mares out of 10 exhibited estrus in PMSG and GnRH groups, respectively. Also the results showed that 16 mares (50.0%) ovulated in PMSG/hCG group compared with 4 mares (40.0%) in GnRH group. However, there was no ovulation in PMSG group. Conception rate was 37.0 and 30.0% in PMSG/hCG and GnRH groups, respectively. Hormonal analysis showed that estradiol and progesterone concentrations were basal at start of treatment. Thereafter, estradiol concentration increased dramatically during estrus in all treated groups. Moreover, progesterone concentration increased 10 days post-mating in PMSG/hCG and GnRH groups while still low in PMSG group. Finally, we conclude that PMSG/hCG and GnRH can be used to treat ovarian inactivity in mares and induce follicular growth and ovulation. On the other hand, we cannot recommend PMSG alone to treat ovarian inactivity in mares.