Deficient amino acids in protein of dehulled soybean meal for young turkeys

Two 12-day experiments were conducted with Large White turkeys to determine which amino acids are deficient in a diet containing dehulled soybean meal as the sole source of protein. A 22% protein basal diet composed of 43.3% glucose monohydrate, 45.4% dehulled soybean meal, .5% DL-methionine, 6% stabilized fat, and added minerals and vitamins served as the negative control. Two positive control diets were formed by substituting either 16.5% dehulled soybean meal or a mixture containing amounts of essential amino acids equivalent to those in the added dehulled soybean meal in place of an equal amount of glucose monohydrate in the basal diet. Nine additional diets were formed by removing one or more amino acids from the mixture. Each of the 12 diets in a block design was fed to two pens of males and two pens of females with 8 birds per pen from 7 to 19 days of age in each experiment. Average body weight gain of poults fed the 22% protein diet with added amino acids approached that of poults fed the 30% protein diet (288 vs. 300 g, respectively). Removal of the amino acid mixture from the 22% protein diet depressed body weight gain by 19.0%. Depressions of 19, 16, 11, 7, and 6% in body weight gains resulted from the removal of valine, threonine, lysine, phenylalanine (or tyrosine or glycine), and isoleucine, respectively. A decrease of 5% was required for significance (P less than or equal to .05). When evaluated by this deletion technique, effects of valine and threonine deficiency were more pronounced than effects of lysine deficiency in dehulled soybean meal for young turkeys.