Animal Science Abstract
Diurnal rhythm of melatonin in young calves and intake of melatonin in milk
M. Valtonen1,A, A.-P. Kangas1, M. Voutilainen1 and L. Eriksson2
AE-mail: Maija.Valtonen@uku.fi
1Institute of Applied Biotechnology, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland2Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, PO Box 57, FIN-00014 Helsinki University, Finland
Abstract
Peripheral concentrations of melatonin in the neonatal mammal are low and the diurnal rhythm is not apparent during the first days or weeks of life. Maternal milk provides a rhythmic although low source of melatonin to the newborn. Diurnal rhythm of serum melatonin was monitored in Friesian calves from birth to 4 weeks of age. Some of the calves under 1 week of age had no clear nocturnal elevation of serum concentrations of melatonin. Thereafter the nocturnal melatonin elevation was apparent in all calves and of the same amplitude as in adult cattle. The effect of oral intake of night-time milk or milk supplemented with low doses of synthetic melatonin was studied during day-time in a group of Ayrshire calves aged 1 to 5 weeks. Two and a half or 3 litres of night-time milk with a mean melatonin concentration of 40 pg/ml, providing 0.1 to 0.12 mg melatonin, did not cause any change in the day-time serum concentrations of melatonin, neither did addition of melatonin in doses up to 10 mg per animal. Only the highest dose of melatonin 200 mg in 2 l of milk (0.1 mg/ml) caused an elevation of day-time serum concentrations of melatonin. These studies show that the pineal gland of a very youg calf is functional and that the concentration of melatonin in blood does not reflect the concentration in milk at the time of feeding. The presence of melatonin in milk suggests, however, its potential significance for the neonate.
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