title: The influence of ambient temperature on metabolism and body temperature of newborn and growing reindeer calves (Rangifer tarandus tarandus L.).
abstract: Thermoregulatory capacities of 51 reindeer calves (Rangifer tarandus tarandus L.) aged 1-35 days were studied at -26.5 to +35.0 degrees C ambient temperatures at Kaamanen reindeer research station, Finland (69 degrees 10' N) during calving periods in May 1981 and May-July 1982. The newborn calves aged 1-4 days maintained a high body temperature (Tre) (mean +40.2 degrees C) even at the lowest experimental temperature of -22.5 degrees C by increasing their metabolic rate five-fold above the level at +11.0 degrees C. Heat production of the new-born calves was largely based on the metabolism of brown adipose tissue, stimulated by cold-induced discharge of the sympathetic nervous transmitter, noradrenaline (NA). Sensitivity of the calves to exogenous NA disappeared during the first 3-4 weeks of life. Thermal conductance of the calves was low at low ambient temperatures, but rose strongly as Ta increased above +10 degrees C. The extensive peripheral cooling, especially in the feet, was demonstrated in the calves aged 1-10 days. The lowest foot temperature (+10.5 degrees C) was measured in a 4-day-old calf at -14.5 degrees C. Slight shivering thermogenesis was recorded in the calves aged 1-4 days and occasionally in the older calves at low values of Ta. Shivering appears to be a reserve mechanism against severe cold. At about +20 degrees C and above the calves increased their Tre (approximately 1 degree C), oxygen consumption and heart rate. In the newborn calves oxygen consumption rose four- to five-fold and in 1-month-old calves about two-fold. Fast growing calves (maximum 400 g/day) appear to be more stressed by heat than by cold exposure.
authors.forename: P
authors.initials: P
authors.lastname: Soppela
authors.forename: M
authors.initials: M
authors.lastname: Nieminen
authors.forename: S
authors.initials: S
authors.lastname: Saarela
authors.forename: R
authors.initials: R
authors.lastname: Hissa
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D001831:Body Temperature; D001833:Body Temperature Regulation; D001835:Body Weight; D004734:Energy Metabolism; D005260:Female; D006339:Heart Rate; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D012053:Reindeer / Q000254:growth & development*; D012881:Skin Temperature; D013696:Temperature
chemical_list: D009638:Norepinephrine