Non-pheromonal stimulation by the male of LH release in the anoestrous ewe

In the anoestrous ewes, the introduction of rams leads to an increase in the secretion of LH and ovulation. Several studies have led to the hypothesis that a ewe's response to the male is mediated by pheromones, implicating a prevalent role of olfaction. In order to analyse if sensory cues other than smell could influence the ewe's physiological response to the male, an olfactory bulbectomy which destroys both main and accessory systems was performed in seven Ile-de-France ewes with a surgical laser. When presented to intact males, the ewes still reacted to the rams by displaying a LH release similar to the controls (n = 11) whereas no response was obtained after ram's fleece stimulation. This suggests that other sensory cues may replace the pheromone to trigger LH release.