Responses of broilers to amino acid intake.

The main objective of this research was to measure the responses of broilers to methionine + cysteine and to threonine intake, to determine their efficiencies of utilization for growth and their intake for optimum response in the starter, grower and finisher phases. Six dose-response trials were conducted with male and female Cobb broilers in these three phases of growth. Measurements included body weight gain, digestible amino acid intake, feed conversion ratio, the proportion of feathers in the protein deposited and the amino acid and lipid deposition in the body. The efficiency of utilization of the amino acids studied was calculated by linear regression of amino acid deposition and the amino acid intake for each phase. Despite the differences between sexes and phases, the efficiency of utilization remained unchanged, being 0.56 and 0.73 for methionine+cysteine and threonine, respectively. The methionine+cysteine intakes estimated for optimum feed conversion ratio were 231 mg/day and 524 mg/day in the starter and grower phases, respectively, for both males and females, and 923 mg/day and 1053 mg/day for females and males, respectively, in the finisher phase. For threonine these intakes were 184 mg/day, 612 mg/day and 823 mg/day in the three phases, for both males and females.