Subject: PGF and CL
Joy:
We shared your concern that exogenous administration of PGF may
induce a subfunctional CL. Our concern was the result of a paper
published by Hardin and Randel (Theriogenology 17:669) in which they
showed that PGF induces a CL that produces less progesterone [less
plasma concentrations of progesterone] over the first half of the
estrous cycle than a naturally induced CL in Brahman cattle. The
PGF tested was Cloprostenol as recommended at the 500 ug dose.
Alarmed over this observation we tested PGF in our Brahman heifers
and found that PGF induces a CL that is indistinguishable from a
naturally induced CL. The major difference between their study and
ours is we tested Lutalyse and they tested Cloprostenol. Both trials
evaluated plasma progesterone after PGF.
In our study, within the same heifer the plasma progesterone
curve for the naturally induced CL was not different from the
subsequent Lutalyse [recommended dose of 25 mg] induced CL plasma
progesterone curve. When these data were analyzed comparing a
contemporary group of non Lutalyse treated heifers, again there were no
differences in the first 11 day plasma progesterone curves. Since
there was no evidence for Lutalyse inducing a subfunctional CL,
measured via plasma progesterone, we did not pursue a histological
evaluation of the CL.
Could it be that at the manufacturer's recommended dose there is a
difference in these two products? I am not aware of that study
having been conducted nor am I aware of confirmation of the Hardin
report for Cloprostenol induction of a subfunctional CL.
Next!
michael j fields
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Dr. Michael J. Fields
Professor of Physiology
Animal Science Department Homepage: http://gnv.ifas.ufl.edu/~irbweb/
459 Shealy Drive E-mail : fields@animal.ufl.edu
University of Florida Phone : (352)392-9566
Gainesville, Fl 32611-0910 FAX : (352)846-1073
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