Increase in plasma cortisol concentrations in ewes fed oestrogenic subterranean clover

Pen-feeding oestrogenic clover to ewes increased their plasma cortisol concentration by the third day. This was not due to any change in the variation of cortisol concentration with time of day. Ovulation rate was not affected during the experiment as judged by the levels of plasma progesterone and laparoscopy. The plasma cortisol concentration of ewes also rose within three days of their being placed on oestrogenic clover pasture. During the next 21 days, their mean plasma cortisol was increased by 58 per cent. A previous history of clover disease did not affect this response.