Articles | Volume 60, issue 2
Original study
02 May 2017
Original study |  | 02 May 2017

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

José Carlos Ferreira-Silva, Tracy Anne Burnett, Paulo Francisco Maciel Póvoas Souto, Paulo Castelo Branco Gouveia Filho, Lucas Carvalho Pereira, Mariana Vieira Araujo, Marcelo Tigre Moura, and Marcos Antonio Lemos Oliveira

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.

Short summary
In face of the ongoing demand to reduce the interval within deliveries to increase sheep reproductive efficiency, the male effect could be used to shorten anestrus postpartum in ewes. The male effect is a simple, effective and low-cost approach to reducing the duration of postpartum anestrus without affecting pregnancy rates. In conclusion the male effect can be used with postpartum ewes that have lambed within 35 to 40 days previously in order to decrease time between deliveries.