The proportion of seasonal anoestrous ewes that ovulate in response to the introduction of rams has long been thought to be influenced by pheromone production by the rams (Watson and Radford, 1960). More recently the role of the sexual behaviour of the rams as a source of ewe stimulation has been demonstrated (Perkins and Fitzgerald, 1994). The present study investigated the hypothesis that the exposure of rams to ewes in oestrus can enhance rams’ sexual behaviour and consequently improve the efficacy of the ram effect.

Sixteen groups of 16 anoestrous ewes, described as the experimental ewes, were randomly allocated to 4 treatments and 4 periods. Treatments were as follows; ewes introduced to 2 rams (R), ewes introduced to 2 rams and 4 oestrous ewes (RE), ewes introduced to 2 rams recendy exposed to 4 oestrous ewes (ER) and ewes introduced to 2 rams recently exposed to 4 oestrous ewes plus a further 4 oestrous ewes (ERE). Treatments were replicated 4 times (4 periods) with 2-week intervals starting on 4 July. Another group of 16 ewes remained isolated from rams during the course of the experiment (C).