untitled

produced with 673 kcal of heat, the carbon dioxide in expired air can be used to

calculate the rate of energy used for maintenance. Measurements can be obtained

either in chambers or from gas masks, and the animal must be in its thermoneutral

zone (not shivering, panting, or sweating), resting, and not digesting food. Such

conditions give the basal metabolic rate.

Basal metabolic rates (BMR) of different eutherian mammalian groups, such as those

in Fig. 4.7, when plotted against log of body weight, fall on a line whose slope is

approximately 0.75. Thus Kleiber (1947) produced the general equation:

BMR = 70 W0.75

FOOD AND NUTRITION 47

Fig. 4.6Flow chart of
energy through the
body.

5.0

2.0

1.0

0.5

0

2 20 200 2000

Body weight (g)

Basal metabolic rate (cm

3 O

/g/h) 2

Fig. 4.7Relationship of
basal metabolic rate and
body weight in different
groups of small
mammals. (After
Clutton-Brock and
Harvey 1983, which is
after Mace 1979.)