Amino Acid Imbalance and Cholesterol Levels in Chicks

Among the amino acids observed to be essential for optimal growth in chicks, 6 have been tested for their effect on the serum cholesterol levels in diets which were either deficient or more than adequate in one of the amino acids. Under these conditions arginine, lysine and leucine influenced the serum cholesterol level as well as growth. Of the amino acids tested, the toxicity produced by a more-than-adequate amount of phenylalanine caused depression in growth but had no effect on serum cholesterol levels. Lysine and histidine elevated serum cholesterol levels and depressed growth. The toxic effect of lysine could be partly overcome by supplements of a mixture of glycine and arginine or glycine and methionine, but arginine and methionine showed antagonism in their influence on cholesterol level. A mere increase in the dietary nitrogen intake effected by manipulating the amount of a balanced amino acid mixture progressively lowered the serum cholesterol levels. Although not essential for optimal growth, some nonessential amino acids such as serine and aspartic acid in combination, or serine, aspartic acid and alanine decreased serum cholesterol levels in chicks.