Buck Effect in Goat Reproduction: A Review

Goats are seasonal breeders in the temperate regions. Therefore, female goats do not ovulate or express oestrous cycles during the non-breeding season. ‘Buck effect’ has been well studied in goats, where the introduction of adult intact males helps in the resumption or advancement of ovulation in anestrous females, thereby complementing reproduction during non-breeding seasons. The exogenous hormones or extended photoperiod treatments induce sexual activity in males during the non-breeding season. In the buck effect, exposure to sexually active males is believed to deliver various cues (physical, visual, chemical, and tactile) that induce sexual activity in females. The involvement of chemical cues was considered a potential chemical signal related to the buck effect; therefore, various scent sources of males have been tested to identify those chemosignals. Positively, buck effect pheromone (4-ethyloctanol) was identified in the scent glands of sexually intact males. This pheromone effectively induced Multiple Unit Activity (MUA) volleys in female goats and activated the GnRH pulse generator. Simultaneously, variable factors of the buck effect (time and duration of buck exposure, gonadal and developmental statuses of males and females, male-to-female ratio, prior sexual experience, etc.) have been analysed, and studies are ongoing. Altogether, progressive research on the buck effect and chemical communication in goats has yielded significant deliverables for use in goat production systems and applied research. This review narrates goat reproduction, with a special focus on the buck effect, pheromones, and behaviour. Major Findings: The buck effect is a feasible, cheap, and non-invasive approach for managing goat reproduction. Buck effect is mostly mediated by androgen-driven mechanisms rather than female reliance on male physical cues alone. Testosterone, in particular, play a pivotal role in modifying the sebaceous glands structurally and functionally, thereby enhancing pheromonal signaling that might contribute in part, to the buck effect.