Comparação entre a progesterona injetável e intravaginal na performance reprodutivas em ovelhas

Abstract

Progesterone (P4) is a steroid hormone that has a pivotal control in the regulatory female's reproductive system. Despite the relative knowledge about the use of injectable progesterone in cattle, there is little research on the use of this hormone in sheep production, especially related to their reproductive responses at the beginning of the breeding season. The aim of this work was to compare reproductive performance and serum P4 concentration using injectable or intravaginal P4 in sheep. Two hundred and forty-eight Santa Inês x Dorper ewes with an average reproductive age of 2.5 years, with body weight of 45 kg, body condition score of 2.75, were blocked in the treatments: Control: no administration of P4; CIDR: implant first use intravaginal of 300 mg of P4 for 7 days; 1P4I: application of 15 mg IM injectable P4; 2P4I: application of 30 mg of P4 IM. In the first 12 days, the P4 concentration was sampled each 2 days. Before synchronization (24 h), ewes received 1 mL IM chloropostenol for lysis os CL. Copulation was controlled by males rotating between females lots for 17 days. After the 17 day period, all ewes will remain with the males for another 28 days in the breeding season in a single batch. At the beginning of synchronization, 90% of the ewes were in anestrus, as they had a serum P4 concentration below 1ng/mL. The rate of manifestation of estrus, pregnancy and conception during synchronization were similar in injectable P4 (0.1 and 0.2 mL of P4) and control treatments. However, the P4 implant was able to raise the serum P4 concentration above 1 ng/mL during the 7 days that it was inserted in the ewes. After CIDR removal, there was a large increase in the manifestation of estrus from this treatment, which hastened pregnancy rate in synchronization. It is concluded that treatment with injectable P4 at doses of 15 and 30 mg were not efficient in increasing the reproductive performance of ewes during the breeding season. However, the CIDR treatment was efficient in inducing a large o in the manifestation of estrus after P4 removal in anestrus ewes, causing them to become pregnant earlier during the breeding season.