Impact of Melatonin on Time of Breeding in Farmed Red Deer

Abstract

Seasonal breeding and late puberty, under the influence of pineal melatonin secretion, limit the productivity of farmed red deer (Cervus elaphus). These studies recorded responses to exogenous melatonin given daily in an afternoon feed. Given for 3 months starting midsummer, melatonin advanced by 5 weeks breeding and conception dates in adult and pubertal hinds. Given for several months starting late winter to cyclic hinds, melatonin induced continued estrous cyclicity, and to anestrous hinds, which had previously been exposed for 1 month to continuous light or for 6 weeks to artificial long days, melatonin advanced by 4 months the onset of the next breeding season. Conceptions were thereby achieved in midsummer. Given for 12 months starting late winter to 8-month-old hinds, melatonin delayed puberty, but if such hinds had previously been exposed to artificially long days for 5 months or to continuous light for 1 month, puberty was advanced by 6 or 2 months, respectively. Calves resulting from out-of-season conceptions and born in winter or spring achieved live-weight targets early in the production year. Strategic melatonin administration, therefore, offers the potential to control puberty, breeding, and calving dates to advantage.