Partition of energy for growth in the steer

A method was developed to determine the way the growth of active protein depends both on age and plane of nutrition. The method assumes that active protein grows according to the relation 1-exp(t/tau) on any single plane of nutrition. Tau varies hyperbolically with the nutritional status. Parameters for the nutritional dependence are estimated from a plot of the energy available for growth as a function of 1/(tau-tau 0) where tau is the time constant for growth of active protein and tau 0 is the minimum possible time constant. This plot is forced through the origin. Once the complete dependence of tau is known, the energy available for growth can be partitioned between the production of new active protein and the deposition of lipid for any age and any plane of nutrition. The method was successfully applied to Moulton's data for the growth of steers. About 80% of the energy available for growth of active tissue is stored, either as new active protein or as lipid. This total efficiency changes little, either with age or with plane of nutrition, although the ratio between active protein and lipid production changes strikingly. The relation between the available energy and lipid production is probably concave.