Melatonin advances and condenses the onset of seasonal breeding in greek dairy ewes

Abstract

The indigenous sheep breeds in Greece have a relatively short anoestrus. Some ewes begin to cycle before June but there is considerable variation, both between the within breeds, which may be associated with genotype or with environmental factors. Mating in spring or early summer, with or without synchronisation, is a common practice in order to take advantage of the climatic conditions and of the traditional marketing period for suckled lambs. In many cases the ewes are still being milked daily and are in low body condition. Conception rate is often low and the lambing period - in flocks of around 100 ewes - may extend over several months. Melatonin is known to advance the onset of oestrus in autumn breeding ewes but treatments initiated before June have given equivocal results.

Controlling reproduction in sheep

“…In a further 10 flocks (five flocks Mule-type ewes and five flocks Suffolk-cross ewes) mating started approximately 20 to 30 days after ram introduction in both the treated and control ewes (see Figure 2b). The reduction in the mean interval was largely attributable to a condensation in the length of the mating period due to fewer late mated ewes, a finding consistent with that of Kouimtzis, Belibasaki and Doney (1989) using Regulin® implants in Greek dairy ewes and of Poulton, Brown, Thomas, Kelly, Symons and Arendt (1988) using the intra-ruminal glass bolus of melatonin in Mule ewes. The reduction in the mean interval was largely attributable to a condensation in the length of the mating period due to fewer late mated ewes, a finding consistent with that of Kouimtzis, Belibasaki and Doney (1989) using Regulin® implants in Greek dairy ewes and of Poulton, Brown, Thomas, Kelly, Symons and Arendt (1988) using the intra-ruminal glass bolus of melatonin in Mule ewes.…”

Emploi des implants de mélatonine et des traitements photopériodiques pour maîtriser la reproduction saisonnière chez les ovins et les caprins

“…De plus, la fertilitŽ et le pourcentage de brebis mettant bas des jumeaux sont supŽrieurŝ ceux du tŽmoin. Au total, 15 ˆ 20 agneaux (selon les races) pour 100 brebis traitŽes sont produits en plus par le lot traitŽ (Dunstan et al 1987 (Kouimtzis et al 1989).…”

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

“…The indigenous sheep breeds in Greece have a longer breeding period than most northern European breeds and many individuals show an onset of the breeding season well before the longest day (Vosniakou, Doney and Tsakalof, 1989). Administration of melatonin, either by daily oral doses or as a slow release, subcutaneous implant indicated that the breeding season in these sheep could be advanced by treatment started in April (Kouimtzis, Belibasaki and Doney, 1989). Further studies by Kouimtzis, Laliotis, Lymberopoulos and Vosniakou (1990) have suggested that a successful lambing in October and November can be achieved by the administration of melatonin implants in March, when the day length is still relatively short.…”