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Quantitative Aspects of Lysine Deficiency and Amino Acid Imbalance¹

Department of Poultry Science, Rutgers — The State University, New Brunswick, New Jersey

A series of studies on amino acid imbalance have been carried out in growing chicks. The following observations were recorded:

1. The chick is as susceptible to an amino acid imbalance as has been reported for the growing rat.

2. An imbalance could be created through the addition of an essential amino acid mixture deficient in one amino acid (lysine) which was also limiting in the dietary protein.

3. It could be shown that the imbalance is due to an altered ratio of the limiting amino acid to the total available protein or essential amino acids.

4. The imbalance, through the addition of an amino acid mixture deficient in the one limiting amino acid, was most pronounced when the level of the limiting amino acid was such that it permitted growth above maintenance but below the optimum growth rate.

5. The imbalance manifested itself in a reduced feed consumption and therefore a reduced consumption of the most limiting amino acid, but there was no evidence that the limiting amino acid was utilized less well than in the case where no imbalance was created.

6. The amino acid composition of nitrogenous mixtures which will produce an imbalance appears to be specific for essential amino acids that are either in themselves or in combination with the dietary protein sufficiently balanced as to permit growth when the single amino acid limitation is overcome. Single amino acid supplements or a mixture of non-essential amino acids produced an imbalance which was not related to the deficiency or limitation of one amino acid, but in the case of the non-essential amino acid mixture it was related apparently to the adequacy of all the essential amino acids in the diet.

Manuscript received 18 January 1960.