O efeito macho sobre a manifestação de estros em ovelhas Merino e Santa Inês

Abstract

Two experiments were carried out at the farm of University of Western Australia, in Perth, Australia, with the objective of studying the temperament of Merino ewes in response to male effect. In the first one, 30 females were utilized (15 calm and 15 nervous), having as probable parameters of evaluation the changes in the secretion profile of LH. Another group of 30 ewes was also equally distributed according to the temperament (15 calms and 15 nervous) and was studied to evaluate the response to male effect through the analysis of the profile of progesterone production. The results showed that calm ewes exhibited a higher response to male effect (P<0,001) that was demonstrated by a higher average concentration of LH 6 hours before and 6 hours after the ram introduction in the group, as well as higher general average of progesterone concentration (P<0,05) at Day 21 of blood sampling On the second experiment, 402 ewes were submitted to three different treatments, with 134 females per group, being that the first two treatments (G1 and G2) were exposed to teasing for 60 and 15 days, respectively, before the harnessed rams introduction and the G3 was kept without this stimulus until the breeding season. No statistical difference was observed among the treatments (P>0,05) related to weekly estrus distribution identified by the rams (P>0,05) neither in relation to the percentage of pregnancy detected by real time ultrasound (P>0,05). The experiment was done in the experimental farm of Embrapa Tabuleiros Costeiros, in Sergipe State. Santa Inês ewes were utilized from three different categories: post-partum (G1), maiden (G2) and single ewes (G3) which were exposed to male effect through the use of teasers for 45 days. Post-partum females showed a response to male effect similar to that observed in ewes during the season anoestrus, with the concentration of first estrus between Day 17 and 25 after teasers exhibition. On the other hand, maiden and single ewes presented a random estrus distribution concentrated in the first 18 days after the introduction of males. These results confirm the efficiency of male effect on anoestrus females, as well as indicate that animals with a calm temperament presented a higher response to this stimulation.