The metabolic rate of fasting sheep in relation to total and lean body weight, and the estimation of maintenance requirements

Abstract

Calculation of maintenance energy requirements from fasting energy loss is discussed. The fasting energy expenditure and urinary nitrogen loss of six Merino wethers (5–7 years old) were determined at body weights of 60, 50, 40, and 30 kg by means of closed-circuit indirect calorimetry. Body composition was estimated from tritiated water space. Similar measurements were made on 51 other adult sheep of various types and on 12 young animals. Simple correlations between metabolic rate and total or lean body weight of adult sheep are described. There was no evidence of specific effects on these correlations due to age of adults, sex, breed, or body condition. The metabolic rate per unit of lean body weight was the same (c. 27 kcall24 hr/lean kg) for sheep as for man; it was up to twice as great for young animals as for adults. On the average, 24% of the fasting heat production of the sheep was derived from protein oxidation; the proportion tended to increase as the sheep lost condition. Differences between sheep in rate of weight loss during undernutrition could not be accounted for in terms of the measured metabolic rates.