Effects of a Gonadotropin Mixture on Reproductive Success in Progesterone- Treated Non-Lactating Anestrous Ewes

Abstract

Using exogenous gonadotropins as part of an estrous induction protocol can have beneficial effects on fertility in ewes bred out-of-season. Few studies have evaluated the efficacy of P.G. 600®, a mixture of gonadotropins with FSH-like and LH-like activity, to increase fertility in anestrous ewes and, in particular, following pre-treatment with progesterone delivered via controlled internal drug releasing (CIDR) devices. The objective of this study was to evaluate the effects of P.G. 600® on reproductive success in progesterone-treated non-lactating anestrous ewes. Ewes, which had been separated from rams for at least one month prior to the beginning of the experiment, received CIDR inserts five days prior to introduction of rams. In the first experiment, ewes were assigned randomly to receive either a 3 mL injection of P.G. 600® [i.m., 240 IU equine chorionic gonadotropin (eCG) and 120 IU human chorionic gonadotropin (hCG)] at CIDR insert removal or no further treatment. In the second experiment, ewes were assigned randomly to receive either a 3 mL injection of P.G. 600® one day prior to insert removal or no further treatment. In experiment 1, incidence of estrus was significantly greater for treated ewes than control ewes, while prolificacy (number of lambs born per ewe lambing) tended to be higher in treated ewes. In experiment 2, treated ewes had significantly higher conception rates and pregnancy rates to first service and tended to have higher overall pregnancy rates than control ewes. A greater percentage of ewes lambed in the treated group than in the control group; however, prolificacy was not different between the groups. In addition, overall lambing rates in ewes treated with P.G. 600® were significantly higher than those of the control group. An injection of 3 mL of P.G. 600® (240 IU eCG and 120 IU hCG) one day prior to CIDR removal significantly increased reproductive success in progesteronetreated non-lactating anestrous ewes. Further, the gonadotropin injection was determined to be economically beneficial.

Hormonal Profiles of Blood Plasma Associated Estrus Synchronization Using Different Concentration of Map and Ecg in Barki Ewes

“…Our findings promote interpretative statement that, the high preovulatory level of circulating estrogen is responsible for induces estrous behavior (Moakhar et al, 2012), and consequently promotes higher levels of estrogen production by the growing follicles, that improve the occurrence of estrus (Dogan and Nur, 2006). So, one would expect estrous responses to be positively correlated with estrogen concentration during the peri-estrus period (Mondal et al, 2006) as a sequel of gonadotropin doses (D'Souza, 2013). Moreover, current observation reinforce the hypothesis of Yildiz et al (2004) they suggests that the prolonged estrus probably results in elevation of circulating estrogen that causes LH peak.…”

“…Similarly, Barrett et al (2004) and Habibizad et al (2015) found that the mean serum estradiol concentrations for the pre-and early post-ovulatory periods were higher in eCG treated ewes compared to the control group. Moreover, the higher doses of gonadotropin (400-600 IU/eCG) would presumably lead to more estrogen production (Moakhar et al, 2012 andD'Souza, 2013) from the largest follicle which is the principal source of estradiol (Munoz-Gutierrez et al, 2002).…”