Field Studies of Advancing the Breeding Season in Farmed Red Deer Using Melatonin Implants: Two Dosage Regimes and the Influence of the Stag

Abstract

Two experiments were conducted on red deer (Cervus elaphus) farms to further investigate melatonin implants for advancing the onset of the breeding season. A three-treatment regime of 2 x 18mg melatonin implants (Regulin) at a 45-day interval was compared with a three-treatment regime using 2 x 18mg melatonin implants at 30-day intervals commencing 8 December. Hinds were joined on 1 to 6 March with melatonin-treated stags.Ultrasound fetal age predictions were undertaken on a sample of each group on each property 25 May to 8 June. The advancement of median-predicted calving dates averaged 12 days for the three-treatment hinds and 15 days for the hinds receiving two treatments when compared with untreated control hinds. A second experiment was conducted to determine whether advancement of estrus in mixed-age hinds could be achieved by exposure to stags with advanced rutting behavior following melatonin treatments. Stags were treated with melatonin commencing 8 December and joined with hinds 1 to 6 March. The median predicted calving dates of hinds exposed to treated stags were 8 to 10 days earlier than those mated to untreated control stags. Prior exposure to vasectomized treated stags resulted in no further advancement of calving. these studies showed that a two-treatment melatonin implant regime resulted in the same advancement of calving as the previously reported three-treatment regime and that stags induced to rut early resulted in advancement of estrus in hinds.