Socio-sexual signalling and gonadal function: opportunities for reproductive management in domestic ruminants.

The aims of this review are to summarize the common biological basis of the responses to social stimulus in domestic ruminants and to consider the research still required in order to put this knowledge to practical use on the farm. The mechanisms involved in the stimulation of sheep and goat females, including both the expected ovarian and behavioural responses, are described. In most breeds, the male effect may be used effectively to induce ovulation during seasonal anoestrus. Although good responses have been obtained in most sheep trials, in some experiments using more seasonal breeds of sheep, poor responses were observed. In goats, it seems that this can be partially overcome if teaser bucks are adequately stimulated (by light treatment and melatonin administration). The strategic use of these stimuli to induce fertile ovulations during the postpartum period is also discussed. In cattle, less is known about the physiological mechanisms by which cows respond to stimulation from the bull. Most trials have focused in trying to advance postpartum rebreeding, with very diverse outcomes. The wide variety of interacting factors and the paucity of data make it difficult to draw conclusions regarding the use of social stimuli in postpartum management. The challenge for researchers is to develop social management techniques that will induce oestrus and ovulation whenever farmers require them. Although more research is necessary to improve efficacy in some sheep breeds and in postpartum animals, social stimulation emerges as an inexpensive and hormone-free strategy that may be useful for farmers.