Metabolic Heat Production of Neonatal Calves during Hypothermia and Recovery

Abstract

Metabolic heat production and rectal temperature were measured in 19 newborn calves (41.8 +/- 3.7 kg) during hypothermia and recovery when four different means of assistance were provided. Hypothermia of 30 degrees C rectal temperature was induced by immersion in 18 degrees C water. Calves were rewarmed in a 20 to 25 degree C air environment where thermal assistance was provided by added thermal insulation or by supplemental heat from infrared lamps. Other calves were rewarmed by immersion in warm water (38 degrees C), with or without a 40-ml drench of 20% ethanol in water. Resting (prehypothermia) and cold-induced summit metabolism of the calves was 2.5 +/- .1 and 8.2 +/- .22 W/kg and occurred at rectal temperatures of 39.5 +/- .06 and 36.2 +/- .26 degrees C, respectively. During cooling, metabolic heat production declined at the rate of .65 W/kg per degrees C decline in rectal temperature. The time required to regain euthermia from a rectal temperature of 30 degrees C was longer for calves with added insulation and those exposed to heat lamps than for the calves in the warm water and warm water plus ethanol treatments (90 and 92 vs 59 and 63 +/- 6.4 min, respectively). During recovery, the calves rewarmed with the added insulation and heat lamps produced more heat metabolically than the calves rewarmed in warm water. Total heat production during recovery was 34.1, 31.1, 18.3, 16.9 +/- 1.07 kJ/kg for the calves with added insulation, exposed to the heat lamps, in warm water and in warm water plus an oral drench of ethanol, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoregulatory responses of the newborn pig during experimentally induced hypothermia and rewarming

“…In our conditions, fasted piglets aged 2 h became hypothermic and reached a body temperature of 30 'C in less than 150 min when exposed to an ambient temperature of 14 'C. A similar rate of body cooling was induced by cold exposure in anaesthetized adult rats (Kilgour & Williams, 1996) and by immersion in cold water in newborn calves (Robinson & Young, 1988b). In newborn lambs, less than 2 h were necessary to reduce body temperature to 30 'C during immersion in cold water (Robinson & Young, 1988a).…”

“…Indeed, from our data, one can calculate that heat production fell by 2-50 W between 34.4 and 30°C, corresponding to a Qlo (temperature coefficient) value close to 1.9. Higher thresholds have been found in newborn calves (36.2°C; Robinson & Young, 1988b) and lambs (37.9°C; Robinson & Young, 1988a) during immersion in cold water. However, adult anaesthetized rats were able to maintain a maximal heat production until their body temperature reached 32-31°C (Kilgour & Williams, 1996).…”

“…Surprisingly enough, the relationships between body temperature, heat production and shivering intensity during acute hypothermia have not been extensively studied in this species. Moreover, at this age, hypothermia can be experimentally induced in conscious piglets exposed to a constant cold temperature whereas previous studies on the progressive induction of hypothermia in other species were performed either on anaesthetized animals (Olson, South & Hendrix, 1983; Kilgour & Williams, 1996) or on conscious animals exposed to an increasing cold challenge (Davis & Mayer, 1955;Stott & Slee, 1987;Robinson & Young, 1988b). In both cases, the actual relationship between body temperature, shivering and heat production could be significantly modified.…”

Endocrine And Metabolic Adaptations Of Calves To Extra-Uterine Life

“…Heat production of newborn animals is a consequence of metabolic processes in body tissues, the metabolism of brown adipose tissue, shivering during physical activity and heat increment of feeding [116,117].…”

“…An intake of 2 kg of colostrum is able to meet the energy requirement of a 40 kg new-born calf held at 10 °C for 24h. Early consumption of colostrum is therefore very important for thermoregulation [116,132].…”