Ovulation and artificial insemination rates have been observed to decrease in sheep and cows when exposed to dietary phytoestrogens at concentrations greater than 25 mg/kg DM.A grazing trial was undertaken to investigate the effects of coumestrol and other key phytoestrogens on the superovulatory response, embryo numbers and quality in beef cows grazing legume pastures.A 7-week controlled grazing trial was conducted with legume and ryegrass pasture treatments, with cows Vacuum Lid Seal exposed to legumes at two timed treatments, 4 and 7 weeks.Twenty Angus cows were subjected to a conventional estrus synchronization and superovulation protocol.
Embryos were recovered via conventional uterine body flushing 7 days post artificial insemination (AI).Numerous phytoestrogens were identified in both pasture and plasma samples, including coumestrol and formononetin.Concentrations of phytoestrogens in the pasture ranged from 0.001 to 47.
5 mg/kg DM and 0 to 2.6 ng/mL in plasma.Approximately 50% of cows produced viable embryos 7 L-ARGININE 1000MG days post AI.A significant interaction between the effect of treatment groups on the embryo stage was observed (p 25 mg/kg DM of phytoestrogens less than 20 days preceding AI may negatively affect oocyte developmental competence, reduce progesterone production and thus contribute to early embryonic loss.