Relative deficiencies of amino acids and nitrogen per se in low protein diets for young turkeys

Three experiments were conducted to determine the relative deficiencies of lysine, threonine, valine, and nitrogen per se in a low protein diet composed primarily of corn, soybean meal, and .3% added DL-methionine fed to young turkeys. Diets containing 22, 26, and 30% protein served as controls. A mixture of amino acids (AA) was added to the 22% protein diet. Additional diets were formulated by individually removing lysine, threonine, or valine from the AA mixture and by adding 4% glutamic acid to each to form a 5 X 2 design exclusive of 26 and 30% protein diets. In each experiment, each diet was fed ad libitum to two pens of nine male poults and two pens of nine female poults of a medium body-size variety from 8 to 19 or 20 days of age. Body weight gains and feed consumptions were increased (P less than .001) by supplementing the 22% protein diet with the AA mixture or by increasing the protein level to 26 or 30%. Removal of either lysine, threonine, or valine from the AA mixture produced body weight gains and feed efficiencies smaller (P less than .001) than from the fully supplemented diets but greater (P less than .05) than from the unsupplemented diets. The addition of 4% glutamic acid to the diets failed to improve performance, indicating that nitrogen per se is not the limiting factor for growth. From these results, it is postulated that sulfur AA appear more deficient than either lysine, threonine, or valine in the 22% protein corn-soybean meal diet containing .3% added methionine.