Reproductive performance of ewes after grazing on G27 red clover,
a low formononetin selection in cultivar Pawera.
M.F. McDonald, M. Anwar, R.G. Keogh
Department of Animal Science, Massey University, Palmerston North,
New Zealand
Proceedings of the New Zealand Society of Animal Production 1994,
54: 231-234
One hundred and fifty ewes grazed either on a high oestrogenic red clover
(Pawera), or a new, low oestrogenic selection of red clover (G27), or control
pastures before mating. The treatment groups (n = 25) and grazing lengths
prior to mating were (1) Pawera, 6 weeks; (2) G27, 6 weeks; (3) G27, 12
weeks; (4) G27/Ryegrass-white clover (rg-wc), 6 weeks/6weeks; (5) Rg-wc
(control 1), 6 weeks, and (6) White clover (control 2), 6 weeks. The ewes were
mated as one group on rg-wc pasture immediately after the grazing treatments.
Formononetin concentration was significantly lower in G27 (0.26%) than in
Pawera red clover (0.55%) (P<0.05). Ovulation rates in ewes after the first
service were similar for all treatment groups (P<0.05). The incidence of return
to service was significantly higher in Pawera ewes (72.7%) than in any of the
other groups (P<0.01). The return rates for the other groups were 33.3%
(G27/6weeks), 25.0% (G27/12 weeks), 4.8% (G27/rg-wc), 9.5% (rg-wc) and
14.3% (white clover). Most ewes which were mated at the next two cycles
became pregnant. It is concluded that the fertility in the ewes grazing G27 red
clover was better than that in ewes grazing Pawera red clover, however there
may have been some impairment in contrast to animals grazing control pasture.
Keywords: NZSAPAB;
Ewe; phytoestrogen; formononetin; red clover; reproductive performance.
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Last Updated 25-01-1997
