Oestrus, ovarian activity and embryo survival in ewes grazing high and
low oestrogenic red clover
M. Anwar, R.G. Keogh, M.F. McDonald
Department of Animal Science, Massey University, Palmerston North,
New Zealand SO: Proceedings of the New Zealand Society of Animal
Production. 1993, 53: 303-306
In two trials, ewes (n=16 per group) that were potential recipients for
embryo transfer grazed on a high oestrogenic red clover (Pawera), a newly
developed low oestrogenic red clover (G27) and Ryegrass-White clover
(Control) pastures. The ewes grazed the respective pastures during 12 days
of intravaginal sponge insertion, and for a further 23 days after induced
oestrus. The mean (± sd) interval from sponge removal to oestrus was shorter
(P<0.05) in control (42.0 ± 12.1 H) than Pawera (58.5 ± 16.0 h) and G27
(52.6 ± 13.0 h) groups in trial 1 and comparable intervals in trial 2 were 42.3
± 6.3 h, 46.3 ± 4.5 h and 51.3 ± 17.0 h respectively. In both the trials,
number of ovular ewes and ovulation rate were lower (P<0.05) in Pawera
ewes. The mean (± sd) ovulation rate in Pawera, G27 and control ewes in
trial 1 was 0.63 ± 0.62, 1.63 ± 0.71 and 1.93 ± 1.00; it was 0.31 ± 0.71, 1.17
± 0.93 and 1.53 ± 0.52 for the three groups in trial 2. Following the transfer
into suitable recipients of two embryos per ewe post mortem examination at
35 days showed an implantation rate of 50%, 90% and 85% in Pawera, G27
and control groups in trial 1 and 50%, 50% and 69% in trial 2. It was
concluded that G27, a low oestrogenic red clover is safer than Pawera red
clover in terms of oestrous activity and ovulation rate when grazed around
mating.
Keywords: NZSAPAB;
Formononetin; phytoestrogen; red clover; ewe; embryo transfer;
reproductive performance.
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Last Updated 25-01-1997
