Published online by Cambridge University Press: 27 March 2009
Nutritive values can be resolved into two factors-quantity and quality. The former is represented by the gross energy and the latter by the coefficient of availability (D/T – 0·35), where T is total and D digestible organic matter.
In the natural, vegetable feeding stuffs the gross energy of the total organic matter is practically the same in all cases except those which are peculiarly rich in oil and protein (cakes, etc.). The coefficient may therefore be applied directly to the total organic matter and, subject to a correction in the case of cakes, nutritive values may be expressed in terms of available organic matter (D–0·35T). These terms may be translated into energy values or starch equivalents by simple multiplication.
The method is simple and illuminating. It shows that the nutritive value of the total organic matter depends almost entirely upon its digestibility and, except in the case of cakes, only to a negligible extent upon its chemical composition. Nutritive value is not proportional to digestibility but a linear function of the same, and in substances of low digestibility, slight change in digestibility may cause manifold alteration in nutritive value.