Estrous Behavior and Pregnancy Rate of Brahman-influenced Beef Cows after Treatment with Progesterone and Prostaglandin F2ct

摘要

Eighty-four multiparous, crossbred cows (1/4 to 3/8 Brahman) were utilized to evaluate the effects of progesterone (P_4) and prostaglandin F_(2alpha) (PGF_(2alpha)) on estrous behavior and pregnancy rate. Cows grazed common bermudagrass throughout thebreeding season. Cows received either a controlled internal drug-releasing (CIDR) insert containing P_4 for 7 d on d 1 of the breeding season or no CIDR (control). On d 7, CIDRs were removed and cows receiving CIDRs were administered PGF_(2alpha) Cowswere exposed to bulls and fitted with a HeatWatch transmitter to record estrous activity during the first 30 d of the breeding season. Thirty-seven percent of cows were anestms at breeding. Duration of estrus (mean = 7.3 +-0.8 h) and quiescence between mounts (mean = 2.3 +- 0.3 h) were similar (P > 0.10) between cows with and without CIDR-PGF_(2alpha) However, cows treated with CIDR-PGF_(2alpha) had an increased (P < 0.05) number of mounts (25.4 +- 2.3) compared with cows without CIDR-PGF_(2alpha) (17.0+- 2.9). Fifty-seven percent of cows administered CIDR-PGF_(2alpha) exhibited estrus within 72 h after CIDR removal. Treatment with CIDR-PGF_(2alpha) tended (P = 0.12) to increase the number of ane-strous cows exhibiting estrus during the first 30 d ofthe breeding season. Pregnancy rate was similar between cows with or without CIDR-PGF_(2alpha). The number of mounts of cows treated with CIDR-PGF_(2alpha) was increased, and the percentage of anestrous cows that initiated estrous cycles during the first 30 d of the breeding season tended to increase when cows were treated with P_4 followed by PGF_(2alpha)