Table also shows the ratio of the volume of carbon dioxide evolved to that of the amount of oxygen consumed during oxidation. This is the respiratory' quotient or RQ. It is an important concept in energy metabolism. From the table you can see that RQ is usually between 0.7 and 1.0. However, RQ near 0.7 shows that fat is being metabolised and RQ near 1.0 suggests carbohydrate metabolism. RQ in between 0.7 and 1.0 could indicate either protein or a mixed diet metabolism.
Quite often animals cannot utilise the entire food value because not all the food they consume is fully digested. Also some portion is excreted as urea or ammonia. In general, it has been observed that animals have a higher intake of food than what is indicated by their oxygen consumption data so that their body weight is kept steady'. The oxygen consumption per unit weight/per unit time mm 3O2/g/hr tends to decrease with higher body weight of animals. In other words, small sized animals like mouse, shrew, etc., have a higher metabolic rate than a large sized animal (an elephant) as evidenced by their oxygen consumption. Accordingly smaller animals have a need to feed constantly. This would also mean that an elephant can survive without food for a much longer period of time than a mouse.