The metabolic rate of the new‐born pig in relation to environmental temperature and to age

Abstract

There is very little information available on the metabolic rate of the newborn pig in relation to its environment. Knowledge of this sort would be of considerable interest, as experience shows that the new-born pig is highly susceptible to chilling, which leads to coma and death, and because the animal has very little hair and subcutaneous fat and may therefore be expected to have a correspondingly low insulation against heat loss. The question arises as to the animal's response to cooling of the environment: whether the newborn pig is poikilothermous like the new-born rat (Fairfield, 1948) and mouse (Fitzgerald, 1953), or whether it responds in a manner typical of the adult homoeotherm, that is by increasing its heat production when the environmental temperature falls below the critical temperature for the animal. The results presented here show that the new-born pig is not poikilothermous and that over the environmental temperature range 4-38°C it exhibits a vigorous metabolic response to cooling of the environment. Further, the critical temperature is not definite, but may be in the region of 34-35°C.Some of these results have been the subject of preliminary communications (Mount, 1958a-c). METHODSObservations were made on a total of thirty-six new-born pigs of the Large White breed and eight of the Landrace breed, aged from 1 hr to 7 days and with weights ranging from 0-86 to 2-72 kg. Animals were removed singly from the sow and the rest of the litter in the farrowing pen, and weighed, and the rectal temperature was recorded by a clinical thermometer inserted to a depth of 3-5 cm for 2 min. The pig was then placed, without any other treatment, and without food or water, in the chamber of a closed-circuit metabolism apparatus. The animal was in the dark, and remained quiet for the duration of the experiment; only very rarely was there any agitation.Two chambers were used, both of the design shown diagrammatically in Fig. 1. The outer cover was made of sheet iron in one (volume, 34 1.), copper in the other (volume, 22 1.). Wet-and dry-bulb thermometers and an air stirrer were mounted in the top of the cover, which could be lowered over the housing for the pig, making a gas-tight liquid-paraffin seal in a base tray. The pig rested on 16-gauge galvanized iron wire in the form of a I in. (10 mm) mesh, with a similar

Anemia Blunts the Thermogenic Response to Environmental Cold Stress in Newborn Piglets

“…These similarities include the lack of a thick hair coat, a large surface area to mass ratio, low body fat, and the ability to increase tissue insulation with peripheral vasoconstriction (21,22). These characteristics result in a range of thermoneutral air temperatures which is slightly lower than the human, preterm infant (23,24). Thermal differences with the human infant relate primarily to the nature and magnitude of heat production.…”

“…Thermal differences with the human infant relate primarily to the nature and magnitude of heat production. Piglets have a basal oxygen consumption of 15-20 versus 5-8 ml/kg/min in newborn infants (23,25). Moreover, piglets lack brown adipose tissue, relying on shivering thermogenesis when in a cold environment (3,26).…”

The post‐natal changes in minimal metabolic rate in the pig

“…At birth the animal is exposed to an environment which is T. STUDZINSKI almost always colder than that inside the uterus and an increase in minimal metabolic rate together with behavioural, including postural, adaptation contribute considerably to survival (Mount, 1959(Mount, , 1960. A prominent feature of the metabolic rate in the new-born pig is its dramatic increase on the second day after birth (Mount, 1959) and it is this rise which makes the animals resistant to cooling by the environment.…”

Radiant and convective heat loss from the new‐born pig

“…These temperatures were chosen because they are below the critical temperature (at the lower end of the thermoneutral zone) of 34-350 C for the new-born pig (Mount, 1959), and because they are above the animal's cold limit for metabolic response of about 50 C in still air . After the usual equilibration period of approximately 30-40 min, oxygen consumption rate was determined over a period of a minimum of 30 min, sometimes 45 min; the animal was then removed from the chamber and its rectal temperature measured again.…”