Comparison between different protocols to estrus synchronization and artificial insemination time fixed in Nellore cows in anestrus

Abstract

In this study different methods of estrus synchronization in 139 Nellore cows in November 2006 in Arapoty-PR, was compared.  Four protocols for estrus synchronization was applied. In the first group (G1), was used dispositive vaginal device, impregnated with 360 mg of medroxiprogesterone acetate (MAP) and 2mg of estradiol benzoate (BE). After remotion (day 8), 150 µg of cloprostenol was in the vulva submucosa administered (for all the groups) and 1 mg of estradiol cipionate. In group two (G2) were used as vaginal device impregnated with 360 mg of MAP. After remotion (8th day), 0,75 µg of cloprostenol was injected. In group three (G3), a dispositive intravaginal device re-impregned with 360 mg of MAP was used  and 2mg of BE. After remotion (day 8), the cows received 150 µg of cloprostenol and 1 mg of ecp. In group four (G4), a dispositive intravaginal device re-impregned with 360 mg of MAP was used and after remotion, 0,75 µg of cloprostenol was injected.  For groups G1, G2, G3 the artificial insemination (AI) was performed in a fixed time of 56 hours after the removal of the progestagens. In the group 4, the AI was performed 12 hours after the observation of the estrus. The diagnosis of pregnancy was performed via rectal palpation after two months from the AI. It was concluded that the different protocols used in this research to synchronization of estrus do not influence the rate of pregnancy.