Effect of oestradiol implants and protein nutrition on plasma
FSH levels in ovariectomised ewes
J.F. Smith, G.J. Cruickshank, E. Payne, J. Konlechner, J. Parr,
L.T. McGowan and R.R. McLaughlin
MAF Technology, Ruakura Agricultural Centre, Private Bag,
Hamilton
Proceedings of the New Zealand Society of Animal Production.
1990, 50: 145-148
As part of the study into the mechanism by which nutrition
influences ovulation rate two trials have been conducted to examine the
effect of protein intake on the negative feedback of oestradiol-17Beta
(E17Beta) on plasma FSH levels. In Trial 1 three groups of
ovariectomised ewes (n=8) fed on a low protein (LP 11%, 10 MJ ME) diet
were treated with silastic implants of E17Beta. Four days after implant
insertion one group was changed to a high protein (HP 22%) diet while
another was treated orally for 10 days with phenobarbital (1 g/d). The
E17Beta implants were removed 6 days after treatment started. In Trial 2
groups of ewes (n=6) were given either full (HE) or 1/2 size (LE)
implants for 5 days. All ewes were fed on a LP diet but 2 groups were
infused abomasally with 100g/d of protein (HP) commencing 3 days before
implant. FSH levels were monitored 4 x d throughout both trials and
expressed as a percentage of pre-treatment values. In Trial 1 FSH
levels were 33% on day 11 after implant with no treatment difference.
However after implant removal the values for the LP ewes returned to
100% by day 17 while for the HP and phenobarbital group values remained
at 33%. In Trial 2 the levels 4 days after implant insertion were 37%,
and 48% for the HE and LE ewes. Again protein treatment delayed
recovery following implant removal. These results do not support the
hypothesis that the increased ovulation rate following protein
supplementation is due to a reduction in negative steroid feedback on
FSH levels.
Keywords: NZSAPAB;
FSH, protein nutrition, oestradiol, ovariectomised ewes;
phenobarbital; steroid feedback
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Last Updated 25-01-1997
