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

Self Cite

Romney ewes grazed pasture initially containing 0 (C), 30 (M), or 60% (P) Pawera red clover for c. 6 months per year (spring-autumn) during the first 4 (P) or 5 (M) years of a 6-year study. When not grazing red clover, all animals grazed C-type pastures. In Years 3-6, ewes were scored on a subjective 0-3 scale for vaginal abnormalities. More of the animals grazing M pasture scored 1 or higher each year compared to the ewes on C pasture (P < 0.001). Similarly, more of the ewes grazing P herbage were scored 2 or higher than either of the other two groups (P < 0.001). A greater proportion of the ewes on the P sward were mated more than once at each joining, compared with the other two groups (P < 0.01 in Year 3; P < 0.001 in all other years) and consequently there were differences in the mean number of times each ewe was mated. Long-term grazing of oestrogenic red clover results in both a high incidence of abnormalities of the external genitalia and decreased mating performance in ewes. However, these effects appear to be independent of each other. A93026

Section: Discussionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Effects of prolonged exposure of ewes to oestrogenic pasture 2. Occurrence of abnormalities of the external genitalia and altered mating performance

Shackell

Wylie

Kelly

1993

Self Cite

“…'Grasslands Pawera' red clover, a variety bred in New Zealand, contains high amounts of formononetin and is oestrogenic to sheep throughout the year (Kelly et al 1979).…”

Section: Introductionmentioning

confidence: 99%

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

Shackell

Kelly

Johnstone

1993

Self Cite

Romney ewes grazed red clover (P) or mixed red clover/ryegrass (M) pastures for about 6 months/year until mating in Year 4 (P) or 5 (M) of a 6-year study. A further group grazed ryegrass/ white clover (C) pasture continuously throughout the study. At other times all animals grazed ryegrass/white clover pasture as one mob. Ewes grazing P pasture were consistently 3-6 kg heavier than ewes that grazed C pasture. Despite similar proportions of ewes being marked by the ram, and similar ovulation rates, during the first cycle of mating each year, ewes grazing P pastures consistently showed increased returns to service (+30%), increased barrenness (+30%), and fewer lambs born per ewe joined (-0.5) than ewes grazing C pasture. Differences persisted after ewes were removed from treatment pastures, indicating that infertility was likely to be permanent.

“…However, the release of the new cultivar 'Grasslands Pawera' red clover (Anderson 1973) caused some concern, as this cultivar was more productive and persistent than earlier red clovers, had relatively high levels of leaf formononetin, and showed oestrogenic activity to sheep (Kelly et al 1979). Accordingly, it was decided to breed a low-formononetin version of Pawera.…”

Section: A96074mentioning

confidence: 99%

Stupefying and lethal effects of alpha chloralose in chickens

Wilkins

1997

'Grasslands G27' red clover was bred from the tetraploid cultivar 'Grasslands Pawera', with selection aimed at reducing the concentration of the isoflavone, formononetin. Selection proceeded for seven generations and resulted in the formononetin level being less than half of that in Pawera under sward conditions. This reduction increases ewe ovulation, conception, and lambing rates by a significant amount.Other characteristics of G27, probably a consequence of reduced formononetin level, are increased palatability and reduced disease tolerance. Since both of these characters would tend to reduce sward persistence, G27 was selected also for increased shoot density and prostrateness to help counteract these weaknesses.