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Journal of Animal Science, Vol 71, Issue 10 2594-2600, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Norgestomet implants synchronize estrus and enhance fertility in beef heifers subsequent to a timed artificial insemination

R. J. Favero, D. B. Faulkner and D. J. Kesler
Department of Animal Sciences, University of Illinois, Urbana 61801.

Three trials involving 128 heifers were conducted to determine whether norgestomet implants administered during the mid- and late luteal phases after breeding could be used to synchronize a second estrus in nonpregnant, inseminated heifers without adversely affecting pregnancy in pregnant heifers. All heifers were initially synchronized with Syncro-Mate B and artificially inseminated 47 h after implant removal. On d 9 (Trial 1) or d 12 (Trial 2) after the timed AI, the heifers were randomly assigned to treated or control groups. Treated heifers received two silicone implants containing 10.0 mg of norgestomet each (Trial 1) or one silicone implant containing 3.6 mg of norgestomet (Trial 2). Silicone implants were removed on d 21 after the initial AI. In Trial 1, the calving rate to the initial AI of the control heifers was 35 vs 55% for the norgestomet-implanted heifers (P > .05). In Trial 2 the calving rate to the initial AI of the control heifers was 9 vs 45% in the treated heifers (P < .01). At the return estrus 52% of the control heifers returned to estrus within a 3-d period, whereas 93% of the norgestomet-treated heifers returned to estrus within a 3-d period (P < .01). Norgestomet treatment had no effect on serum progesterone concentrations of the pregnant heifers on d 21 after the initial AI. In Trial 3, both control and treated heifers were administered silicone implants containing 3.6 mg of norgestomet on d 12; additionally, the treated heifers received an injection containing 3.0 mg of norgestomet and 5.0 mg of estradiol valerate. Norgestomet implants were removed on d 21.(ABSTRACT TRUNCATED AT 250 WORDS)


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J. S. Stevenson, S. K. Johnson, M. A. Medina-Britos, A. M. Richardson-Adams, and G. C. Lamb
Resynchronization of estrus in cattle of unknown pregnancy status using estrogen, progesterone, or both
J Anim Sci, July 1, 2003; 81(7): 1681 - 1692.
[Abstract] [Full Text] [PDF]


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Copyright © 1993 by the American Society of Animal Science.