A study of the metabolism of two breeds of pig: (With some remarks on a third)

Abstract

The metabolism of a Berkshire and a Middle White pig has been investigated by means of the calorimeters at the School of Agriculture, Cambridge. The general routine and technique of the observations have been as heretofore. Measurements of the fasting katabolism of each of the two pigs have been obtained in a series extending from an early age to maturity, and the phenomena in general follow the lines of those originally discovered in the Large White; but the fasting katabolism of the Middle White was below that of the Large White earlier studied. The fall in body temperature and in metabolism during the fasts were found to be correlated, and the possible effect of skin colour in this matter is noted. The effect of environmental temperature is investigated and reasons are given for supposing that the critical temperature of the Middle White pig is very low. It is concluded that the existence of a maximum somewhere in the curve showing fasting katabolism per unit area at different ages is necessitated by the two physiological facts ( a ) that warm blooded animals have to be maintained at a temperature which varies only within very narrow limits, and ( b ) that the processes of growth are accompanied by waste of energy as heat.