The effects of red clover (Trifolium pratense var. redhead), white clover (Trifolium repens var. S 100) or perennial ryegrass (Lolium perenne var. S 23) on the reproductive performance of sheep

Abstract

SummaryDuring 3 years, three groups of 20 Scottish half-bred ewes were grazed on perennial ryegrass, white clover or red clover. During this period the two legumes were oestrogenic, in terms of teat-length extension of wethers, but the perennial ryegrass was not. The white clover was only markedly oestrogenic when there was a high proportion of diseased leaves. The mean litter size and lambing percentage of the ewes grazed on red clover was significantly reduced. White clover, although it was oestrogenic, had no effect on mean litter size or lambing percentage. The mean litter size of the ewes on the perennial ryegrass was 2·35, 2·30 and 2·24, on the white clover was 2·20, 2·33 and 2·23 and on the red clover was 1middot;60, 1·67 and 1·78 for the three lambings. Lambing percentage of the ewes on the perennial ryegrass was 175, 225 and 218, on the white clover was 210, 222 and 189, and on the red clover was 160, 128 and 118 for the three lambings. The lambing date of the ewes grazing on the red clover was significantly later at the third lambing.

Effects of prolonged exposure of ewes to oestrogenic pasture 1. Permanent flock infertility following long-term grazing of red clover (‘Grasslands Pawera’)-dominant pasture

“…Adams (1979) reported severely depressed incidence of oestrus in clover-affected ewes. In contrast, we found that grazing red clover did not affect the incidence of oestrus over the mating period, a finding supported by Newton & Betts (1973). Barrett et al (1965), using the opposite grazing regime to ours (i.e.…”

“…ewes grazed red clover pasture during pregnancy and lactation), did not record any differences in conception to first service, but did note an increase in barrenness. Newton & Betts (1973) noted significant decreases in litter size in the order of 0.5 lambs per ewe during 3 years of grazing. In our experiment, while litter sizes tended to be higher in C ewes during grazing years, differences were not statistically significant.…”

Fertility of Herbivores Consuming Phytoestrogen-containing Medicago and Trifolium Species

“…Histological examination of the cervix revealed that subclinical infertility was widespread in Western Australian flocks [72]. With isoflavone-containing red clover varieties, ewes exposed long-term had a high incidence of abnormalities of the external genitalia, decreased mating performance and fewer multiple births [73,74].…”

Formononetin content of ‘Grasslands Pawera’ red clover and its oestrogenic activity to sheep

“…When grazed at or about mating, conception rates and ovulation rates (or lambs born per ewe lambing) are decreased (Morley et al 1964;Newton & Betts 1973;Lightfoot & Wroth 1974). Permanent and progressive infertility occurs when formononetin-rich pastures are grazed for prolonged periods at any time of the year (Barrett et al 1965;Davenport 1967;Davies & Maller 1970).…”