Uso de Benzoato de estradiol no início do protocolo Heatsynch em vacas da raça holandês lactantes.

Abstract

The aim of this study was to evaluate the use of estradiol benzoate inducing and synchronizing the follicular development in Holstein cows during a Heat Synch protocol. Two hundred and thirty primiparous (n= 110) and multiparous (n= 120) Holstein cows were enrolled in a Heat synch program consisting of a CIDR containing 1.9 g of progesterone, either a new one or previously used once (7d use), plus either 25 µg GnRH i.m or 2mg estradiol benzoate (EB) injection on day 0 (82 + 6 DIM) and all cows were given 25 mg PGF2α i.m upon CIDR removal seven days later (day 7) followed by an injection of 1 mg of estradiol cypionate (ECP) i.m at day 8. Used CIDRs had been thoroughly rinsed with a mild disinfectant solution, air-dried, and stored in a dry, enclosed container after first use. Cows were then observed for signs of estrus (twice daily at 7:00 and 18:00) for three days following CIDR removal. Cows observed in estrus were inseminated 12 h later. The fixed factors analyzed were the hormone used to the follicular wave induction at the be ginning of Heat Synch protocol, GnRH (n = 120) and estradiol benzoate (EB) (n = 110), and the CIDR uses (either a new one, second or third use). A single technician was responsible for the estrus detection and insemi nations. Pregnancy status was determined by ultrasonography at 30 to 35 d. Data were analyzed by the LOGISTIC procedure of SAS. Conception rate did not differ (P =0.86) between hormone groups GnRH and EB. In addition there was no difference (P = 0.18) in estrus signs between hormones treatments, as well as between primiparous and multiparous cows (P = 0.23). The CIDR uses did not differ (P = 0.75) in conception rate. Also there was no interaction (P>0.05) between CIDR uses and hormones treatments. In conclusion, EB may be used to induce and synchronize the follicular wave at beginning of Heat Synch protocol in dairy cows, as well as conception rates are not affected by CIDR uses.