FOOD-INTAKE ADJUSTMENTS OF CHICKS - SHORT-TERM REACTIONS OF GENETIC STOCKS TO DEFICIENCIES IN LYSINE, METHIONINE OR TRYPTOPHAN

1. Growth, food intake, and food preference were measured in two exper imental lines (White Rocks and White Leghorns) of chickens fed diets v arying in content of lysine, methionine, or tryptophan. Diet A was bal anced in all amino acids, while the remaining 6 diets were moderately (approximately 30%) or slightly (approximately 15%) deficient in eithe r lysine, methionine, or tryptophan relative to NRC recommendations fo r broiler diets. 2. Body weight and food utilisation efficiency of Whi te Leghorns at 10 d of age were not affected by diet, whereas the lowe r concentrations of lysine and methionine depressed these traits in Wh ite Rocks. 3. Tryptophan deficiency reduced food intake of White Legho rns, but not White Rocks. 4. With choice feeding of balanced and defic ient diets from day 10 to 16, preferences between the diets were minim al for White Leghorns, whereas for White Rocks there was an almost imm ediate preference for the balanced diet, followed by lack of preferenc e or preference for the deficient diet. 5. Apparently for some genetic stocks there is rapid adjustment to deficiencies in these amino acids with overconsumption, followed by compensation for preference of the balanced diet. The response, however, will vary depending on the defic ient amino acid.