Comportamiento reproductivo de vacas criollas con amamantamiento restringido y sincronización del estro

reproductive performance of creole cows with restricted suckling and estrus synchronization. the objectives were to study the reproductive performance, initiation of post-partum ovarian activity, response to restricted suckling, estrus synchronization, and conception rate using artificial insemination at a fixed time of creole rodeo cows (c). in chihuahua, méxico, during the summer 2008, twenty-seven cows were used over 95 d, and the beginning of post-partum ovarian activity was detected by ultrasonography. hormone treatment for estrus synchronization was administered to 22 cows (n=11 per group). in treatment1 (t1) the cows (n=11) received a cidr with 1,9 g of progesterone and one im injection with 1 mg of β-estradiol + 50 mg of p4. the cidr was removed after d 7 and an im injection of 30 mg of pgf2α was applie d. after 24 h, 1 mg of β-estradiol was applied, and the cows were inseminated 54 h after removing the cidr. t2 (n=11) was similar, but the im injection contained β-estradiol only. the c showed aggressive behavior (ab) during the restricted suckling. the average days from the beginning of the ovarian activity were 11,66 d and only 11,11% of the cows exhibited estrus during initial ovarian activity. one hundred percent of the animals underwent estrus on d 9 post synchronization, there were not differences (p>0,05) among the levels of progesterone of the t1 (4,94±0,331 ng/ml) vs the t2 (4,87±0,30 ng/ml. there was a t*ds interaction for concentrations of progesterone and e2 (p=0.06). there were no differences (p>0.05) in conception rate (18,8%). adding p4 with a cidr did not increase the levels of progesterone in c.