Amino Acid Retention and Balance in the Young Rat Fed Varying Levels of Lactalbumin

Abstract

The effect of the level of dietary protein intake upon amino acid balance and retention efficiency was determined over the range of 3.6 to 25.0% dietary protein using high purity lactalbumin as the protein source. A total of 12 diets was prepared and fed to groups consisting of six weanling rats each for a period of 3 weeks. Carcass retention efficiency of essential amino acids was found generally to be inversely proportional to the dietary adequacy of each amino acid although some exceptions were noted. Amino acid retention efficiency and protein efficiency ratio (PER) declined sharply below 6% dietary protein despite the achievement of weight gain. This decline was accompanied by a reduction in apparent synthesis of nonessential amino acids and an alteration in the composition of the carcass gain.