[Biological value of different proteins used in the early period of postnatal development]

A comparison was made of the efficacy of utilizing proteins that differ both in the amino acid composition and susceptibility to alimentary proteinases. Starting from 15 days of age the rats received formula feeding over a week. The formula feeding included mixtures imitating the composition of the rat's milk and containing the test proteins in an amount of 10%. It was shown that the mixture of casein with milk serum proteins was utilized most effectively. The decrease in the casein content in the diet and replacement of casein by egg albumin, bovine serum albumin or milk serum proteins were found to lead to the lowered efficacy of protein utilization. Energy distribution studies have shown that the decreased efficacy of proteins utilization is accompanied by the increased amount of nitrogen excreted with the urine.