Some Qualitative Amino Acid Needs of Adult Swine for Maintenance

Abstract

A purified diet containing crystalline L-amino acids at a level to simulate the essential amino acid composition of a 3% crude protein, corn-soybean meal mixture was used to qualitatively evaluate some amino acid requirements for maintenance of the nongravid, postestrual gilt. No external symptoms of amino acid deficiency were noticed as a result of complete omission from the diet of those amino acids found to be required for maintenance. Diet consumption although controlled and not ad libitum was excellent regardless of the pattern of amino acids imposed. Neither protein-depleted nor protein-nondepleted gilts required arginine or histidine for maintenance. Hemoglobin was not significantly reduced by omission of either of these 2 amino acids from the diet. With a leucine-void diet, nitrogen balance exceeded 1 g/day, indicating that leucine, too, was nonessential for maintenance. In order of decreasing effect, a dietary void of threonine, isoleucine, lysine or phenylalanine reduced nitrogen balance. Nitrogen utilization was extremely poor with diets containing a void of either threonine or isoleucine. Regardless of whether dispensable or indispensable for maintenance, an amino acid omitted from the otherwise complete diet caused a lowered plasma level of this amino acid.