In Holstein calves, noradrenaline (NA) was injected subcutaneously at a dose of 0.1mg/kg at 1,8,18,30 and 45 days of age, and the changes in rectal temperature, packed cell volume (PCV) and plasma free fatty acid (FFA), glucose and lactate levels were measured. NA-injection caused increases in all these measurements. An increase in rectal temperature was highest in 8-days old calves, and an elevation in PCV and FFA level was higher in older calves. At 1-day old, plasma lactate level was higher than thereafter, and NA-induced elevation in glucose level was sustained continuously. NA-induced elevation in plasma glucose level was larger in younger than older calves. There was no significant relationship between changes in rectal temperature and plasma metabolite levels after NA injection.Jpn. J. Zootech. Sci., 52(6): [467][468][469][470][471]1981 Thermoregulation in cold climate is primarily brought about by a reduction of heat loss and an increase of heat production (thermogenesis). The latter, i. e., cold-induced enhancement of metabolism in body tissue is called chemical thermoregulation.During sudden cold exposure, most increase of metabolic activity is brought about by shivering due to rhythmic muscular contraction, and, however, an increased heat production is also observed without shivering (so called nonshivering thermogenesis) in many animals1,2). It has been recognized that this nonshivering thermogenesis is operated in brown adipose tissue predominantly by the calorigenic effect of noradrenaline (NA) which is released from the tissue's sympathetic innervation2,3)However, the relative importance of NA-induced thermogenesis in neonate varies with species3), and the informations on the postnatal transition of metabolic response to NA are limited in calves. In the present experiment, NA was injected subcutaneously to 1-45 days old calves, and the changes in rectal temperature and blood metabolite levels were estimated.
Materials and . MethodsFour newborn male Holstein calves (43-52kg) were used. They were fed 6kg of whole milk twice daily till 45 days of age, except 4kg daily during the first 10 days in 2 calves whose live weight at birth were 43kg, and hay was fed ad libitum.Responses to NA injection were studied at 1(23-27hrs),8,18,30 and 45 days of age. At 1-day of age, the calves had already suckled colostrum from their dams, so