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Effect of 1 or 2 norgestomet implants inserted from days 15 to 25 after oestrus on follicular development in beef cows

Published online by Cambridge University Press:  05 November 2021

D.A. Adikpe  and
M.J. Bryant
D.A. Adikpe
Affiliation:
Department of Agriculture, The University of Reading, Earley Gate, P. O. Box 236, Reading RG6 6AT, United Kingdom
M.J. Bryant
Affiliation:
Department of Agriculture, The University of Reading, Earley Gate, P. O. Box 236, Reading RG6 6AT, United Kingdom
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Extract

Controlling the timing of ovulation in cows that fail to conceive after insemination would provide a further opportunity for scheduled rebreeding in a group of cows to save time and optimise results. The ear implant Crestar containing the synthetic progestagen norgestomet provides a means of achieving this control (Sinclair et al., 1992; Lowman et al., 1994). Removing the implant on day 25 after oestrus results in less false positive pregnancy diagnoses than removal on day 21 with the implant in place for nine/ten days. However, treatment of beef heifers with a norgestomet implant towards the end of luteal phase to control oestrus and ovulation is associated with development of a persistent ovulatory follicle and reduced pregnancy rate (Mihm et al., 1994). The objective of this study was to determine the effects of treating beef cows with one or two norgestomet implants on the development of the dominant ovulatory follicle of the second follicular wave.

Type
Beef
Information
Proceedings of the British Society of Animal Science , Volume 1996 , March 1996 , pp. 133
Copyright
Copyright © The British Society of Animal Science 1996

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References

Lowman, B.G., Scott, N.A. and Scott, P.R. (1994). An evaluation of some breeding management options in beef herds in the United Kingdom. Veterinary Record 135:9–12.10.1136/vr.135.1.9CrossRefGoogle ScholarPubMed
Mihm, M., Baguisi, A., Boland, M.P. and Roche, J.F (1994). Association between the duration of dominance of the ovulatory follicle and pregnancy rate in beef heifers. Journal of Reproduction and Fertility 102:123–130 10.1530/jrf.0.1020123CrossRefGoogle ScholarPubMed
Sinclair, K.D., Broadbent, P.J., Dolman, D.F. and McNally, J.R. (1992). The effect of a norgestomet ear implant (Crestar) and prostaglandin regime on pregnancy rate and resynchronisation of oestrus in embryo transfer recipients. Proceedings of the 12th International Congress on Animal Reproduction 1:782–784.Google Scholar