Reproductive performance of postpartum ewes treated with insulin or progesterone hormones in association with ram effect

Conceptus loss in Santa Inês ewes carrying twin pregnancies by natural mating or embryo transfer

Commercial application of reproductive biotechnologies such as multiple ovulation and embryo transfer depends on its overall efficiency. Sheep embryo transfer is gradually gaining wider adoption, but pregnancy rates after embryo transfer remain lower than those derived from natural mating for most breeds. The work was aimed to evaluate embryonic and fetal losses in Santa Inês ewes carrying twin pregnancies by natural mating or embryo transfer. Ewes were subjected to synchronized natural mating by ram effect or used as recipients for embryo transfer. Ewes diagnosed as carrying twin pregnancies at day 25 were used in the experiment (n = 42). Conceptus viability was monitored by ultrasonography on days 30, 35, 40, 45, 50, and 55 after conception. Conceptus loss was similar (P > 0.05) within natural mating 11/42 (26.19%) and embryo transfer 14/42 (33.34%). However, overall embryonic loss (80.0%) was greater (P < 0.05) than fetal loss (20.0%), with no difference within groups The results allow the conclusion that conceptus loss after embryo transfer is similar to natural mating and occurs predominantly during the embryonic stages.

Progesterone (P4), luteinizing hormone (LH) levels and ovarian activity in postpartum Santa Inês ewes subject to a male effect

Abstract. This study aimed to establish P4 and luteinizing hormone (LH) levels and ovarian activity as approaches to monitor the cyclicity of ewes under postpartum anestrus after the male effect approach. Santa Inês females (n  =  66) were evenly distributed into experimental groups where they were brought into contact with an intact male during the postpartum period of 35 to 40 days (T1) and 55 and 60 days postpartum (T2). Ewes were isolated from males for 30 days before the onset of the experiment. Estrus events were detected in 93.30 % (T1) and 100 % (T2) of females. Mean P4 concentrations (η g mL−1) before and after mating were 0.53 ± 0.17 and 4.55 ± 0.24 (T1) and 0.73 ± 0.06 and 4.90 ± 0.11 (T2), respectively, and concentrations were found to be lower (P  <  0.05) before contact between genders. Preovulatory peaks of LH (η g mL−1) were evaluated at 42 (T2) and at 80 h (T1) after exposure to males, with mean ovulatory follicles of 7.90 ± 0.31 (T1) and 8.50 ± 0.30 mm (T2) and a mean number of ovulations of 1.50 ± 0.54 (T1) and 1.60 ± 0.51 (T2). Pregnancy rates were 85.70 % (T1) and 93.3 % (T2), with no difference (P  >  0.05) between groups. Results showed that the male effect was effective for inducing and concentrating the occurrence of estrus in postpartum ewes that had lambed within 35 to 60 days previously. Moreover, preovulatory LH peaks occurred within 80 h after physical contact between genders, which led to follicle luteinization and increased P4 concentration, without compromising pregnancy rates. The male effect can be used with postpartum ewes that had lambed within 35 to 40 days previously in order to decrease time between deliveries.