A view of recent development on the effect of nutrition on
ovulation rate (the flushing effect) with particular reference to
research at Ruakura
J.F. Smith
MAF Technology, Ruakura Agricultural Centre, Private Bag,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1991, 51: 15-24
The results in this field over the last 10 years at Ruakura and
relevant international data is reviewed. The nutrients involved have
been defined and a likely mechanism of action indicated. Pasture
allowance experiments indicated effects of pasture quality and a series
of pellet feeding trials defined effects of both energy (linear) and
protein (threshold) intakes. The threshold effect of protein was
confirmed by the abomasal infusion of protein. Analyses of changes in
blood concentrations of amino-acids indicated the involvement of the
branched-chain amino-acids (BCAA) and this has been confirmed by an
increased ovulation rate after intravenous infusion of BCAA. It is
concluded that the static and dynamic liveweight and the immediate
nutrient effects are the same response measured at different times. The
rate at which the response develops is dependant on the type of
feedstuff.
Studies into the mechanism of action in both intact and ovariectomised
ewes have ruled out effects on pituitary release of FSH either directly
or via interference with negative feedback influences. This indicates
that the effect is at the ovarian level and is mediated either by direct
action of the BCAA or indirectly via a metabolic hormone.
Keywords: NZSAPAB;
Nutrition; ovulation; branched chain amino acids; ewes; protein;
energy; FSH; negative feedback; insulin
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Last Updated 25-01-1997
