| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Journal of Animal Science, Vol 79, Issue 8 2210-2216, Copyright © 2001 by American Society of Animal Science
EVALUATION STUDIES |
S. L. Wood, M. C. Lucy, M. F. Smith and D. J. Patterson
Department of Animal Sciences, University of Missouri, Columbia 65211, USA.
The objective of this experiment was to determine the effect of a GnRH injection within a melengestrol acetate (MGA)-PGF2alpha (PGF) estrus synchronization protocol on follicular dynamics and synchronization of estrus. Pubertal crossbred beef heifers (n = 34) were randomly assigned to one of two treatments. Both treatment groups were fed MGA (0.5 mg x hd(-1) x d(-1)) for 14 d and injected (i.m.) with PGF (25 mg of Lutalyse) 19 d after MGA withdrawal. Melengestrol acetate was delivered in a feed supplement of 1.8 kg x hd(-1) x d(-1). Seventeen heifers received an injection of GnRH (100 microg Cystorelin) 12 d after MGA withdrawal and 7 d before PGF. The control group (n = 17) received only MGA-PGF. Estrus was detected four times/d for 7 d beginning on the day PGF was injected. Transrectal ultrasonography was performed daily on eight heifers from each treatment to monitor ovarian activity and characterize changes in follicular dynamics after MGA withdrawal and until ovulation after PGF. Each of the GnRH-treated heifers either ovulated or had a luteinized dominant follicle following GnRH and subsequently initiated a new follicular wave (8/8, 100%). All GnRH-treated heifers (17/17, 100%) and 94% of controls (16/17) exhibited estrus after PGF. Estrus was exhibited over a 132-h period (12 to 144 h) for control heifers compared with 60 h (48 to 108 h) for GnRH-treated heifers. The peak synchronized period for both treatments was between 48 and 72 h after PGF, during which time 76% (13/17) of the GnRH-treated heifers exhibited estrus compared with 63% (10/16) for controls. Seventy-one percent (12/17) of the GnRH-treated heifers exhibited estrus from 48 to 60 h after PGF, compared with 38% (6/16) for controls (P < 0.05). In summary, injection of GnRH within a 14- to 19-d MGA-PGF protocol increased the synchrony of estrus during the synchronized period and concentrated the period of detected estrus. This protocol may offer potential for the fixed-time insemination of replacement beef heifers.
This article has been cited by other articles:
|
|
 |
|
  N. R. Leitman, D. C. Busch, D. J. Wilson, D. A. Mallory, M. R. Ellersieck, M. F. Smith, and D. J. Patterson Comparison of controlled internal drug release insert-based protocols to synchronize estrus in prepubertal and estrous-cycling beef heifers J Anim Sci, December 1, 2009; 87(12): 3976 - 3982. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. K. Ahola, G. E. Seidel Jr., and J. C. Whittier Use of Gonadotropin-Releasing Hormone at Fixed-Time Artificial Insemination at Eighty or Ninety-Seven Hours Post Prostaglandin F2{alpha} in Beef Cows Administered the Long-Term Melengestrol Acetate Select Synch Professional Animal Scientist, June 1, 2009; 25(3): 256 - 261. [Abstract] [PDF]
|
|
|
|
|
|
D. C. Busch, D. J. Wilson, D. J. Schafer, N. R. Leitman, J. K. Haden, M. R. Ellersieck, M. F. Smith, and D. J. Patterson Comparison of progestin-based estrus synchronization protocols before fixed-time artificial insemination on pregnancy rate in beef heifers J Anim Sci, August 1, 2007; 85(8): 1933 - 1939. [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. F. Bader, F. N. Kojima, D. J. Schafer, J. E. Stegner, M. R. Ellersieck, M. F. Smith, and D. J. Patterson A comparison of progestin-based protocols to synchronize ovulation and facilitate fixed-time artificial insemination in postpartum beef cows J Anim Sci, January 1, 2005; 83(1): 136 - 143. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. K. Johnson and M. L. Day Methods to reduce or eliminate detection of estrus in a melengestrol acetate-PGF2{alpha} protocol for synchronization of estrus in beef heifers J Anim Sci, October 1, 2004; 82(10): 3071 - 3076. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Stegner, F. N. Kojima, J. F. Bader, M. C. Lucy, M. R. Ellersieck, M. F. Smith, and D. J. Patterson Follicular dynamics and steroid profiles in cows during and after treatment with progestin-based protocols for synchronization of estrus J Anim Sci, April 1, 2004; 82(4): 1022 - 1028. [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]
|
|
|
|
|
|
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]
|
|
|
|
|
|
G. A. Perry, M. F. Smith, and D. J. Patterson Evaluation of a fixed-time artificial insemination protocol for postpartum suckled beef cows J Anim Sci, December 1, 2002; 80(12): 3060 - 3064. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
