Fertility of Herbivores Consuming Phytoestrogen-containing Medicago and Trifolium Species

Abstract

Despite their unrivalled value in livestock systems, certain temperate, pasture, legume species and varieties may contain phytoestrogens which can lower flock/herd fertility. Such compounds, whose chemical structure and biological activity resembles that of estradiol-17α, include the isoflavones that have caused devastating effects (some of them permanent) on the fertility of many Australian sheep flocks. While the persistence of old 'oestrogenic' ecotypes of subterranean clover (Trifolium subterraneum) in pasture remains a risk, genetic improvement has been most effective in lowering isoflavone production in Trifolium species; infertility due to 'clover disease' has been greatly reduced. Coumestans, which can be produced in Medicago species responding to stress, remain a potential risk in cultivars susceptible to, for example, foliar diseases. In the field, coumestrol is often not detected in healthy vegetative Medicago species. Wide variation in its concentration is influenced by environmental factors and stage of growth. Biotic stress is the most studied environmental factor and, in lucerne/alfalfa (Medicago sativa), it is the major determinant of oestrogenicity. Concentrations up to 90 mg coumestrol/kg (all concentrations expressed as DM) have been recorded for lucerne damaged by aphids and up to 600 mg/kg for lucerne stressed by foliar disease(s). Other significant coumestans, e.g., 4'-methoxy-coumestrol, are usually present at the same time. Concentrations exceeding 2000 mg coumestrol/kg have been recorded in diseased, annual species of Medicago. Oestrogenicity of some Medicago species is also influenced by maturity and senescence. Studies in Israel, North America, Europe, New Zealand and Australia have confirmed that coumestans in lucerne, represent an acute or sub-acute loss of reproductive efficiency in herbivores, e.g., sheep, cattle, and possibly horses. When sufficiently exposed peri-conception, coumestrol, sometimes present in lucerne, be it as pasture, hay, silage, pellets, meal, and sprouts, is associated with what can be an insidious, asymptomatic, infertility syndrome. Most livestock research with oestrogenic lucerne has been conducted with sheep. Ewes may be at risk when the coumestrol concentration in their diet exceeds 25 mg/kg. In studies where lambing was compared for lucerne and a phytoestrogen-free treatment, the mean decrease in lambs born/ewe was 13%; ewes on lucerne, exhibited a lower frequency of multiple births.

Alfalfa Coumestrol Content in Response to Development Stage, Fungi, Aphids, and Cultivar

“…In addition, the focus of these studies was to provide advice for sheep production systems. Further research to determine the response of cattle reproductive performance to coumestrol would be of benefit, both to corroborate with the studies described in Reed (2016), and to provide an indication of the coumestrol level that may be a risk to cattle fertility. Across the experiments in this study a range of alfalfa stand ages were used, however this was often in different months or years and so they cannot be compared.…”

“…Most research has been conducted on the effect of coumestrol on sheep. However, as detailed in a review by Reed (2016), a few studies have also reported impaired fertility in cattle.…”

Variation of Phytoestrogen Content and Major Agronomic Traits in Alfalfa (Medicago sativa L.) Populations

“…A strong association between formononetin intake and equol concentration in plasma was demonstrated, so that cows' milk can be considered as a source of equol in human nutrition [20][21][22][23][24][25]. On the other hand, consumption of forages with high concentrations of formononetin and coumestrol has shown to cause temporary or permanent reproductive problems in some ruminants, mostly in sheep and cattle [26][27][28][29][30].…”

Review on Mineral Malabsorption and Reducing Technologies

“…They also cause haemolysis of red blood cells and are toxic to rats [32]. Saponins from Bulbostermmapaniculatum and Pentapamax leschenaultii have alsobeen demonstrated to have anti-spermal effects on human spermatozoa [33]. They significantly inhibited acrosine activity of human sperms and the spermicidal effect was attributed to strong damage of the spermal plasma membrane [34].…”