Reproductive performance of ewes grazing red clover (Grasslands Pawera) or white clover—grass pasture at mating

One hundred 3½ to 4½‐year‐old Romney ewes grazed a pure sward of ‘Grasslands Pawera’ red clover from 8 days before to 17 days after the beginning of mating; a similar group of ewes (Controls) grazed white clover‐grass pastures. The formononetin content of the leaf material (dry matter basis) of Pawera at the start and end of grazing was 1.2% and 0.8% respectively. Compared with controls, fewer of the ewes grazing Pawera were mated during the first cycle (80% v . 100%). Over three cycles of mating, 66% of ewes that grazed Pawera returned to service at least once compared with 22% of Control ewes. Mean ovulation rates on day 18 of mating were lower for ewes grazing Pawera than Control ewes (0.79 v . 1.55 ovulations/ewe examined). Of the ewes grazing Pawera 24 were anovular. Lambing performances reflected mating records, with 25% of Pawera ewes lambing to the first cycle of mating (lambs born/ewe lambing (LB/EL) = 1.00); in comparison, 75% of Control ewes lambed to the first cycle of mating (LB/EL = 1.52). These results are consistent with other published work on the effect on ewes of exposure to large amounts of exogenous oestrogens at mating.