Seasonal anoestrus in the ewe results from enhanced oestrogen negative feedback.

This study addressed whether NO acts within the vmPOA to inhibit LH during seasonal anoestrus.

It is concluded that long post-partum anoestrus leads to prolonged calving intervals and poor reproductive performance.

Oestradiol was slightly less effective in eliciting oestrous behaviour in anoestrus and during the transition to the breeding season than at other times.

In the first experiment, LH pulse frequency was measured on days 0, 1, 7 and 14 of treatment during seasonal anoestrus.

Taken together, the results of Experiments 1-3 suggested that NO inhibition may be stronger during the middle than at the end of seasonal anoestrus.