Journal of Animal Science, Vol 74, Issue 5 1084-1091, Copyright © 1996 by American Society of Animal Science

JOURNAL ARTICLE

Use of a gonadotropin-releasing hormone agonist or human chorionic gonadotropin for timed insemination in cattle

E. J. Schmitt, T. Diaz, M. Drost and W. W. Thatcher
Department of Dairy, University of Florida, Gainesville 32611-0920, USA.

Three experiments were conducted to evaluate a synchronization protocol with AI at a predetermined time. In Exp. 1, 169 dairy heifers were assigned randomly to two groups: 1) timed AI (TAI), consisting of GnRH agonist injection (d 0, 1700), PGF2 alpha injection (d 7, 1700), GnRH agonist injection (d 8, 1700), and AI (d 9, 0800); and 2) AI at estrus (AIE), consisting of GnRH agonist injection (d 0, 1700), PGF2 alpha injection (d 7, 1700), and AI at detected estrus. Pregnancy rate was 25.8% for TAI (n = 89) compared with 48.7% for AIE (n = 80; P < .001). Experiment 2 was comparable to Exp. 1, but the second GnRH agonist injection in TAI was given 48 h after injection of PGF2 alpha. Heifers in TAI (n = 187) were inseminated at detected estrus if estrus occurred within 39 h after administration of PGF2 alpha (n = 47). Pregnancy rates were 45.5% for TAI and 48.0% for AIE (n = 177). Conception rate was reduced for TAI (45.5 [85/187] < 61.2% [85/139]; P < .005). In Exp. 3, the second injection of GnRH agonist, given at 48 h after injection of PGF2 alpha, was replaced with hCG (3,000 IU, i.m.). No differences in pregnancy rate were detected for TAI (52.9% [54/102]) vs AIE (56.1% [55/98]). Conception rate was reduced for TAI (52.9 [54/102] < 72.3% [55/76]; P < .005). Delaying the second GnRH agonist injection by 24 h improved pregnancy rate, but replacing the second injection of GnRH agonist with an injection of hCG did not prevent a reduction in conception rate.

This article has been cited by other articles:

				D. J. Ambrose, D. G. V. Emmanuel, M. G. Colazo, and J. P. Kastelic Short Communication: Pregnancy Rates to Timed Artificial Insemination in Holstein Heifers Given Prostaglandin F2{alpha} Twenty-Four Hours Before or Concurrent with Removal of an Intravaginal Progesterone-Releasing Insert J Dairy Sci, July 1, 2008; 91(7): 2678 - 2683. [Abstract] [Full Text] [PDF]

				K H Al-Gubory, S Camous, G Germain, P Bolifraud, A Nicole, and I Ceballos-Picot Reconsideration of the proposed luteotropic and luteoprotective actions of ovine placental lactogen in sheep: in vivo and in vitro studies. J. Endocrinol., March 1, 2006; 188(3): 559 - 568. [Abstract] [Full Text] [PDF]

				A. R. Rabiee, I. J. Lean, and M. A. Stevenson Efficacy of Ovsynch Program on Reproductive Performance in Dairy Cattle: A Meta-Analysis J Dairy Sci, August 1, 2005; 88(8): 2754 - 2770. [Abstract] [Full Text] [PDF]

				H. Rivera, H. Lopez, and P. M. Fricke Use of Intravaginal Progesterone-Releasing Inserts in a Synchronization Protocol before Timed AI and for Synchronizing Return to Estrus in Holstein Heifers J Dairy Sci, March 1, 2005; 88(3): 957 - 968. [Abstract] [Full Text] [PDF]

				H. Rivera, H. Lopez, and P. M. Fricke Fertility of Holstein Dairy Heifers after Synchronization of Ovulation and Timed AI or AI after Removed Tail Chalk J Dairy Sci, July 1, 2004; 87(7): 2051 - 2061. [Abstract] [Full Text] [PDF]

				J. M. DeJarnette, R. B. House, W. H. Ayars, R. A. Wallace, and C. E. Marshall Synchronization of estrus in postpartum beef cows and virgin heifers using combinations of melengestrol acetate, GnRH, and PGF2{alpha} J Anim Sci, March 1, 2004; 82(3): 867 - 877. [Abstract] [Full Text] [PDF]

				E. A. Hiers, C. R. Barthle, MK. V. Dahms, G. E. Portillo, G. A. Bridges, D. O. Rae, W. W. Thatcher, and J. V. Yelich Synchronization of Bos indicusxBos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2{alpha} in combination with melengestrol acetate J Anim Sci, April 1, 2003; 81(4): 830 - 835. [Abstract] [Full Text] [PDF]

				D. J. Patterson, F. N. Kojima, and M. F. Smith A review of methods to synchronize estrus in replacement beef heifers and postpartum cows J Anim Sci, February 1, 2003; 81(14_suppl_2): E166 - 177. [Abstract] [Full Text] [PDF]

				R. Sartori, R. Sartor-Bergfelt, S. A. Mertens, J. N. Guenther, J. J. Parrish, and M. C. Wiltbank Fertilization and Early Embryonic Development in Heifers and Lactating Cows in Summer and Lactating and Dry Cows in Winter J Dairy Sci, November 1, 2002; 85(11): 2803 - 2812. [Abstract] [Full Text] [PDF]