How effective are exogenous progestins in mimicking the function of
the corpus luteum of female cattle?
J.E. Kinder, M.S. Roberson, N. Kojima, M.E. Werhman, T. Sanchez,
A.S. Cupp
Department of Animal Science, University of Nebraska, Lincoln,
Nebraska USA 68583-0908
Proceedings of the New Zealand Society of Animal Production. 1993,
53: 287-290
An intensive evaluation of the hormones that are primarily involved in
regulating reproductive function in cows treated with progestins was
undertaken and comparisons were made to cows with a functional corpus
luteum. Cows with a functional corpus luteum were found to have reduced
circulating luteinizing hormone (LH) and oestradiol than cows treated with a
single progesterone releasing intravaginal device (PRID), norgestomet
(progestin used in Syncro-Mate-B synchrony) or melengestrol acetate
(progestin used for oestrous synchrony in the USA). If greater doses of
progesterone than that released from a single PRID are used, concentrations
of LH and oestradiol are like those of control cows in the midliteal phase of
their oestrous cycle. In addition, conception rates are significantly improved
when greater doses of progesterone are used compared to that of cows in
which oestrus is synchronised with a single PRID. We propose that one
reason for reduced conception with oestrous synchrony programmes presently
in use is the failure of the progestins to effectively mimic the function of the
corpus luteum.
Keywords: NZSAPAB;
Progestin; oestrous synchrony; lutenizing hormone; oestradiol; corpus
luteum.
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Last Updated 25-01-1997
