Self-selection among diets differing in methionine content by chickens of different lines

Two trials were conducted to compare the ability of chickens from different genetic lines to select among diets differing in methionine. In Trial 1, chicks from White Plymouth Rock (HW) and White Leghorn (HA) lines were offered a choice of diets containing .85, .58, or .44% methionine from 1 through 7 days of age. In Trial 2, a slow-growing line of White Plymouth Rocks (LW) was used in addition to the same lines used in Trial 1. A choice of the three diets was offered from 1 through 13 and from 20 through 23 days of age. During the period from 14 through 19 days of age, all chicks were fed the .44% methionine diet. In both trials, Line HW chicks first exhibited a dietary preference at 5 days of age. Line HA chicks did not discriminate among diets in either trial when given a choice from 1 day posthatch. They did, however, exhibit a preference starting on Day 20 in Trial 2 (after being fed the deficient diet). No dietary preferences were exhibited by chicks from Line LW. Results of these trials showed that selection among diets varying in methionine content was influenced by genotype, age, nutritional state of the chick, and their interactions.