INDUCTION TO POST PUERPERAL ESTRUS BY USE OF DIFFERENT WEANING PROTOCOLS IN CROSSBREED CATTLE

Abstract

This study sought to evaluate alternatives for estrus induction in the post-partum in crossbred cattle, through the use of different management systems, involving the suckling of calves. One hundred twenty cows in anestrus, with body condition score 3.0 (scale of 0 to 5) and between 60 to 90 days post-partum were used. Animals were divided in three groups (G): G1 (controlled suckling) consisting of 71 cows, G2 (early weaning) with 27 animals and G3 (control), 22 cows with no restriction to feed their calves from birth to weaning. The animals were studied during the breeding season 2008/2009 and were bull mated. Thirty seven cows from 120, were weekly examined by transrectal ovarian ultrasonography, to observe ovarian follicular dynamics. The results showed that the incidence of ovarian follicles occurred faster and more intensive in G1 and G2 compared with G3 ; the pregnancy rate after the end of the breeding season, showed that G1 and G2 had a higher pregnancy rate than G3 (p < 0,05). There was no difference in pregnancy rates between G1 e G2.  It was concluded that the systems of controlled suckling and early weaning optimized reproductive performance of animals, leading to the induction of post partum estrus in beef cows by reducing the open period between calving and breeding, and a better pregnancy rate than the control group.