Comparison of Two Timed Artificial Insemination (TAI) Protocols for Management of First Insemination Postpartum

¹ Department of Animal Science, Texas A&M University, College Station, Texas 77843 MJ Schouten Dairy, Hico, Texas, 76457, Dairy Practice, Comanche, Texas 76442 Pharmacia Animal Health, Kalamazoo, Michigan 49002

Two estrus-synchronization programs were compared and factors influencing their success over a year were evaluated. All cows received a setup injection of PGF₂ at 39 ±3 d postpartum. Fourteen days later they received GnRH, followed in 7 d by a second injection of PGF₂. Cows (n=523) assigned to treatment 1 (modified targeted breeding) were inseminated based on visual signs of estrus at 24, 48, or 72 h after the second PGF₂ injection. Any cow not observed in estrus was inseminated at 72 h. Cows (n = 440) assigned to treatment 2 received a second GnRH injection 48 h after the second PGF₂, and all were inseminated 24 h later. Treatment, season of calving, multiple birth, estrual status at insemination, number of occurrences of estrus before second PGF₂, prophylactic use of PGF₂, retained fetal membranes, and occurrence of estrus following the setup PGF₂ influenced success. Conception rate was 31.2% (treatment 1) and 29.1% (treatment 2). A significant interaction occurred between protocol and estrual status at insemination. Cows in estrus at insemination had a 45.8% (treatment 1) or 35.4% (treatment 2) conception rate. The conception rate for cows not expressing estrus at insemination was 19.2% (treatment 1) and 27.7% (treatment 2). Provided good estrous detection exists, modified targeted breeding can be as successful as other timed artificial insemination programs. Nutritional, environmental, and management strategies to reduce postpartum disorders and to minimize the duration of postpartum anestrus are critical if synchronization schemes are used to program first insemination after the voluntary waiting period.

Key Words: estrous synchronization • reproductive management • timed artificial insemination

Submitted on July 11, 2001
Accepted on November 1, 2001

This article has been cited by other articles:

				J. G. Berardinelli, P. S. Joshi, and S. A. Tauck Conception rates to artificial insemination in primiparous, suckled cows exposed to the biostimulatory effect of bulls before and during a gonadotropin-releasing hormone-based estrus synchronization protocol J Anim Sci, March 1, 2007; 85(3): 848 - 852. [Abstract] [Full Text] [PDF]

				J. C. Dalton, R. Manzo, A. Ahmadzadeh, B. Shafii, W. J. Price, and J. M. DeJarnette Short Communication: Conception Rates Following Detection of Estrus and Timed AI in Dairy Cows Synchronized Using GnRH and PGF2{alpha} J Dairy Sci, December 1, 2005; 88(12): 4313 - 4316. [Abstract] [Full Text] [PDF]

				E. R. Jordan Effects of Heat Stress on Reproduction J Dairy Sci, July 1, 2003; 86(13_suppl): E104 - 114. [Abstract] [Full Text] [PDF]