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Control of Ovulation Rate in Beef Cattle.
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2002-06-01
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Morris, D.G., Hynes, A., Kane, M.T., Diskin, M.G., Sreenan, J.M., Control of Ovulation Rate in Beef Cattle, End of Project Reports, Teagasc, 2002.
Abstract
Under intensive production systems, the greatest potential for effecting increases
in production and economic efficiency in the beef cow herd lies in the possibility
of increasing the frequency of twin births. Embryo transfer is technically a
successful method of inducing twin births in cattle. While an embryo transfer
approach is too costly to allow commercial twinning, it has been used to show
that ovulation rate and not uterine capacity is the limiting factor in increasing the
reproductive rate of the cow. While ovulation of one or more viable oocytes is
central to normal reproduction, knowledge of the control of ovulation and of
folliculogenesis on which ovulation depends, is limited. In spite of the fact that
many follicles are subjected to the same endogenous hormonal environment and
theoretically should all be capable of ovulating, only a tiny proportion do. While
gonadotrophic hormones play a central role in ovarian follicle development and
ovulation, their action at the ovarian level seems to be controlled by intra-ovarian
factors. This intra-ovarian control of ovulation is thought to be exerted partly by
the hormone inhibin and partly by other, as yet, unidentified compounds in
follicular fluid. This project focused on identification and isolation of ovarian
compounds involved in the control of ovulation rate, followed by immunisation
against these compounds in order to study the effect on ovulation and the twin
calving rates. The main results are summarised here and detailed results have
been published in the papers listed at the end of this report.