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Abstract
1. One experiment was conducted with medium weight laying hens to determine their threonine requirement between 28–38 weeks.
2. Two threonine‐limiting diets of identical protein quality (summit‐dilution) were used and, by dilution, ten protein contents were produced supplying 2.7 to 5.4 g total threonine/kg diet. The diet with the lowest protein was also supplemented with synthetic L‐threonine. Each diet was fed to 5 groups of 24 laying hens.
3. The daily threonine requirement of the individual laying hens was estimated by direct methods to be 8.7 mg/g egg output plus 43.49 mg/kg body weight for this experiment. Calculated optimum intakes of threonine for various ratios of costs of input to value of output are tabulated. For example, for a flock of medium weight laying hens producing an average of 50 g daily egg mass, the optimum threonine intake (mg/hen d) varied between 700 and 710 for cost ratios (k‐values) varying between 0.002 and 0.001.