The effect of melatonin on seasonal reproduction of indigenous and crossbred dairy goats in Greece

Abstract

AbstractThe effects of melatonin implants, administered during anoestrus, on the time of onset of oestrus, conception rate and litter size in indigenous (Capra prisca) and crossbred dairy goats were studied on commercial farms in a hill region of northern Greece. In the 1st year, 192 indigenous and 86 crossbred does on one farm (farm 1) were each separated into treated (T) and control (C) groups. The T groups from each breed type were given implants of melatonin on 17 April and 6 May, respectively. Bucks were re-introduced to both T and C groups 5 weeks after implantation. Mean mating dates for indigenous goats were 6 July (s.e. 0·15) (T) v. 13 July (s.e. 0·24) (C). Corresponding dates for crossbreds were 31 July (s.e. 0·61) (T) v. 14 August (s.e. 0·87) (C). Treatment did not significantly affect conception rate. Mean kidding dates (from first service) were 6 December (s.e. 0·18) (T) v. 14 December (s.e. 0·28) (C) for indigenous and 31 December (s.e. 0·64) (T) v. 13 January (s.e. 0·82) (C) for crossbred goats. Litter size was higher in both T groups but the difference was not significant. In the 2nd year the indigenous flock on farm 1 was supplemented by two similar neighbouring farms. Farm 1 had both treated does and control does; farm 2 were all treated and farm 3 were untreated control does. In this year all bucks used on treated does were also implanted. All implants were given on 21 April. Mean mating dates were 21 June (s.e. 0·23) (1/T) v. 9 July (s.e. 0·36) (1/C), and 28 June (s.e. 0·09) (2/T) v. 19 July (s.e. 0·15) (3/C). Conception rate was high in all groups. Corresponding mean kidding dates were 22 November (1/T) v. 11 December (1/C) and 29 November (2/T) v. 22 December (3/C). Litter size was higher (F > 0·05) in T than in C groups.