Role of male-female interaction in regulating reproduction in sheep and goats

The induction of synchronous ovulatory activity in anovulatory sheep and go ats after the introduction of males, the 'male effect', has probably been u sed to advantage since these species were domesticated and the underlying p hysiological and behavioural mechanisms have been progressively elucidated over the Fast 50 years. Less well understood is the analogous effect of oes trous females on males. This review examines the nature and importance of t hese male-female interactions in sheep and goats, and describes the most im portant internal and external factors influencing the reproductive outcomes of such interactions. It is proposed that the male and female effects are both components of a self-reinforcing cycle of stimulation that, under idea l conditions, culminates in the synchronous very rapid onset (within days) of fertile reproductive activity. However, precisely because of the speed o f this response, it is suggested that mechanisms have evolved to limit its efficacy, and thus prevent conception at inappropriate times. The complexit y of these factors and the interactions between them are highlighted, and a broad conceptual framework for understanding them is proposed based upon a n appreciation of variation in both the responsiveness of the target animal and the quality of the signal from the signalling animal.