Residual effect of a four weeks grazing of oestrogenic red clover on reproductive performance of ewes in the following six weeks.

M. Anwar, R.G. Keogh, M.F. McDonald

Department of Animal Science, Massey University, Palmerston North, New Zealand

Proceedings of the New Zealand Society of Animal Production 1994, 54: 235-238

The trial was conducted to study if the temporary infertility in ewes induced by oestrogenic clover, would recover accompanied by a concomitant increase in ovulation rate and/or litter size following their removal to a 'safe' pasture. Romney ewes (N - 155) either grazed on Pawera red clover or Ryegrass-white clover (control) pasture for four weeks. Afterwards all ewes grazed ryegrass-white clover pasture and were mated in 3 groups either at the first, third or sixth week post-treatment. Mean ovulation rate was significantly lower (P<0.05) in the Pawera ewes (1.22 ą 0.06) than in the controls (1.49 ą 0.07) on respective treatments after two weeks of grazing. Ovulation rates in ewes after the 1st, 2nd and 3rd mating cycle were 1.60 ą 0.12, 1.41 ą 0.10, 1.27 ą 0.09 (red clover), and 1.64 ą 0.10, 1.67 ą 0.12, 1.30 ą 0.90 (control) respectively. Ovulation rate and litter size were similar for the two treatment groups after joining in week 1, 3 or 6 post-treatment (P>0.05). No increase in ovulation rate/litter size in Pawera group ewes was observed over and above those observed in the control ewes within the six week post-treatment period.

Keywords: NZSAPAB; Ewe; phytoestrogen; formononetin; red clover; reproductive performance; ovulation rate.

Download abstract in text format
Last Updated 25-01-1997