The manipulation of seasonality of reproduction in sheep
The phenomenon of seasonability of reproduction restricts the ewe to only one lambing around the same time every year, which in turn prevents an even supply of lamb meat to the market. The long term objective of the current study was to develop two systems of early and summer lambing using alternative techniques for the manipulation of sheep production in an attempt to produce high quality lamb throughout the year. In recent years, major advances in our knowledge of seasonality of reproduction have been the recognition of the integral role of the pineal gland and its indoleamine melatonin in the timing of reproductive activity and the use of the pattern of reproductive behaviour in sheep in the manipulation of reproductive processes. Therefore, the current study aimed at examining the use of melatonin and/or the 'ram effect' in early and summer lambing systems in order to report on their effectiveness in advancing the breeding season and/or enhancing fecundity. Also, the concern over the seasonal variation in libido and semen quality in the ram made it necessary to examine ways of eliminating the seasonal depression in the mating performance and capcity of the ram. Experiments 1, 2 and 3 examined the effectiveness of the intraruminal device of melatonin administration and/or the 'ram effect' in advancing the breeding season of the ewes. Also the effects of duration and methods of 'teasing' were assessed.