Effect of repeated cycles of melatonin and long light on milk production in the goat

Exposure to long day photoperiod is known to stimulate milk secretion in dairy cattle, but the mechanism has not been determined. Melatonin (MEL), which is produced by the pineal gland, is stimulated during darkness and has been known to mimic the short day signal when administered during long day exposure. Preliminary evidence has suggested that long term MEL treatment sensitizes lactating goats to subsequent long light exposure (Knight, 1993). The present study was undertaken to test if repeated short cycles of MEL would prime goats to subsequent long light effect on milk yield.