Abstract

PERALTA-TORRES, JA; AKE-LOPEZ, JR; CENTURION-CASTRO, FG  and  MAGANA-MONFORTE, JG. Comparison of estradiol cypionate vs estradiol benzoate on estrus response and pregnancy rate in synchronisation protocols with CIDR in Bos indicus heifers and cows. Universidad y ciencia [online]. 2010, vol.26, n.2, pp.163-169. ISSN 0186-2979.

The objectives of the study were to compare the effect of estradiol cypionate (CE) vs estradiol benzoate (BE) on the estrus rate, the interval of CIDR removal to estrus (IRC-E) and the pregnancy rate, and to evaluate the change in body condition (CC) on the pregnancy rate in 227 Zebu females (cows and heifers). Each female received one CIDR plus 1 mg BE; three groups were formed after CIDR removal: I) CE, that received 0.5 mg of CE; II) BE, that received 0.5 mg of BE 24 h after CIDR removal; and III) control, that received 1 ml of saline solution. A higher estrus rate was observed in females in CE (72%) and BE (79%) than in the control group (35%; p < 0.05). No significant difference was found among the cows and heifers within each group (p > 0.05). No effects were recorded for the IRC-E or the pregnancy rate among the different groups, nor among the cows and heifers within a group (p > 0.05). The females that gained BC presented a higher pregnancy rate (52%; P < 0.05) than those that maintained (35%) or lost BC (34%). In conclusion, the use of CE and BE in cows and heifers has a similar positive effect on the estrus rate, but not on the pregnancy rate. The increase in body condition in the synchronised females is a significant factor that favours the pregnancy rate.

Keywords : Estradiol benzoate; estradiol cypionate; synchronisation; pregnancy rate; body condition.