On the basis of previously validated biological concepts, a model of postnatal growth in livestock is proposed. It postulates the existence of two leading processes, cell proliferation in growth plates of bones and nuclei multiplication in skeletal muscle tissue, and surmises that the basic kinetic parameters of RNA and protein metabolism in cross-striated muscles remain steady (relatively constant) throughout the period from the early postnatal stage to maturity. The weight of skeletal muscle tissue is predicted on the basis of a dynamic sub-model and the weights of the skeleton, carcass and live body are calculated using regression relationships. When applied to farm animals, the model adequately fit experimental data and predicted that each biological type and separate group of animals (breed, sex, line, etc.) has an optimal zone of growth intensity with the most effective transformation of food into body components. We conclude by sketching directions for future work, and suggesting some possible practical implications.