An equation describing protein synthesis as a function of energy and p
rotein intake was developed for a simplified model of swine growth. Th
e equation (rectangular hyperbola) contained four fundamental paramete
rs that had physiological and nutritional significance. The four funda
mental parameters were the energy available for protein synthesis, pro
tein available, the minimum energy required to synthesize one kilogram
of protein (7.3 MJ/kg) and the efficiency of protein utilization. In
a series of calibration runs an expression was developed to describe t
he efficiency of protein utilization as a function of body weight, ene
rgy and protein supply, and the maximum possible rate of protein depos
ition. The proposed model provided realistic predictions of protein an
d fat deposition under a wide variety of conditions.