HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bader, J. F. Articles by Patterson, D. J. Search for Related Content PubMed PubMed Citation Articles by Bader, J. F. Articles by Patterson, D. J.

A comparison of progestin-based protocols to synchronize ovulation and facilitate fixed-time artificial insemination in postpartum beef cows¹

J. F. Bader^*, F. N. Kojima^*, D. J. Schafer^*, J. E. Stegner^*, M. R. Ellersieck, M. F. Smith^* and D. J. Patterson^*,2

^* Department of Animal Science and and Agricultural Experiment Station, University of Missouri, Columbia 65211

² Correspondence—phone: 573-882-7519; fax: 573-884-4798; e-mail: pattersond{at}missouri.edu.

The experimental objective was to compare pregnancy rates after fixed-time AI in postpartum suckled beef cows following administration of two progestin-based protocols to synchronize ovulation. Cows (n = 424) at three locations (n = 208, 122, and 92 per location) were stratified by age, BCS, and days postpartum (DPP) and assigned randomly to one of the two treatment protocols. The MGA Select-treated cows (MGA Select; n = 213) were fed melengestrol acetate (MGA, 0.5 mg•cow^–1•d^–1) for 14 d and carrier for 8 d, and then GnRH (100 µg i.m. Cystorelin; d 26) was injected 12 d after MGA withdrawal, and PG (25 mg i.m. Lutalyse) was administered 7 d after GnRH. Cows assigned to the 7-11 Synch protocol (7-11 Synch; n = 209) were fed carrier for 15 d and MGA for 7 d, and then injected with PG on d 22 (d 7 of MGA), GnRH on d 26, and PG again on d 33. Artificial insemination was performed at fixed times for cows in both treatments at 60 or 72 h after d 33 PG for 7-11 Synch and MGA Select groups, respectively. All cows were injected with GnRH (100 µg of i.m. Cystorelin) at AI. There was no treatment x location interaction for age (P = 0.90), BCS (P = 0.64), or DPP (P = 0.93), and the results were therefore pooled for the respective treatments (age [7-11 Synch, 5.5 ± 0.2; MGA Select, 5.5 ± 0.2], BCS [7-11 Synch, 5.7 ± 0.1; MGA Select, 5.6 ± 0.1], and DPP [7-11 Synch, 41.1 ± 1.1; MGA Select, 42.1 ± 1.1]). Blood samples were collected 8 and 1 d before MGA or carrier to determine pretreatment estrous cyclicity (progesterone 1 ng/mL; 7-11 Synch, 59/209 [28%]; MGA Select, 54/213 [25%]; P = 0.50) and again on d 33 PG to evaluate treatment response as a percentage of cows with progesterone concentrations in serum 1ng/mL (7-11 Synch, 184/209 [88%]; MGA Select, 177/213 [83%]; P = 0.15). Pregnancy rates resulting from fixed-time AI did not differ (P = 0.25) between treatments (7-11 Synch, 128/209 [61%]; MGA Select, 142/213 [67%]), nor did pregnancy rates (P = 0.77) at the end of the breeding season (7-11 Synch, 198/208 [95%]; MGA Select, 204/213 [96%]). These data indicate that pregnancy rates were comparable after fixed-time AI, following administration of the 7-11 Synch and MGA Select protocols. Both protocols provide opportunities for beef producers to use AI and eliminate the need to detect estrus.

Key Words: Beef Cow • Estrus Synchronization • Fixed-Time Artificial Insemination

This article has been cited by other articles:

				D. C. Busch, D. J. Schafer, D. J. Wilson, D. A. Mallory, N. R. Leitman, J. K. Haden, M. R. Ellersieck, M. F. Smith, and D. J. Patterson Timing of artificial insemination in postpartum beef cows following administration of the CO-Synch + controlled internal drug-release protocol J Anim Sci, July 1, 2008; 86(7): 1519 - 1525. [Abstract] [Full Text] [PDF]

				D. J. Schafer, J. F. Bader, J. P. Meyer, J. K. Haden, M. R. Ellersieck, M. C. Lucy, M. F. Smith, and D. J. Patterson Comparison of progestin-based protocols to synchronize estrus and ovulation before fixed-time artificial insemination in postpartum beef cows J Anim Sci, August 1, 2007; 85(8): 1940 - 1945. [Abstract] [Full Text] [PDF]

				G. C. Lamb, J. E. Larson, T. W. Geary, J. S. Stevenson, S. K. Johnson, M. L. Day, R. P. Ansotegui, D. J. Kesler, J. M. DeJarnette, and D. G. Landblom Synchronization of estrus and artificial insemination in replacement beef heifers using gonadotropin-releasing hormone, prostaglandin F2{alpha}, and progesterone J Anim Sci, November 1, 2006; 84(11): 3000 - 3009. [Abstract] [Full Text] [PDF]

				J. E. Larson, G. C. Lamb, J. S. Stevenson, S. K. Johnson, M. L. Day, T. W. Geary, D. J. Kesler, J. M. DeJarnette, F. N. Schrick, A. DiCostanzo, et al. Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2{alpha}, and progesterone J Anim Sci, February 1, 2006; 84(2): 332 - 342. [Abstract] [Full Text] [PDF]