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Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F₂^1,2

R. Flores^*, M. L. Looper^,3, D. L. Kreider^*, N. M. Post^*,4 and C. F. Rosenkrans, Jr.^*

^* Department of Animal Science, University of Arkansas, Fayetteville 72701; and and USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927

³ Corresponding author: mlooper{at}spa.ars.usda.gov

Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F₂ (PGF₂) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d –7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF₂; control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF₂ increased (P < 0.05) the number of mounts received (22.5 ± 3.0 vs. 13.7 ± 3.9 for CIDR-PGF₂ vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF₂ (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF₂ than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF₂ decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 ± 1.1 vs. 9.0 ± 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF₂-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF₂ at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.

Key Words: anestrus • beef cow • estrous behavior • progesterone • prostaglandin

This article has been cited by other articles:

				R. Flores, M. L. Looper, R. W. Rorie, M. A. Lamb, S. T. Reiter, D. M. Hallford, D. L. Kreider, and C. F. Rosenkrans Jr. Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows J Anim Sci, May 1, 2007; 85(5): 1318 - 1329. [Abstract] [Full Text] [PDF]