According to the Bovans White Leghorn Breeder
Guide (Centurion Poultry, 2012), diets were separated
into 4 phases: (1) 18 to 22, (2) 23 to 32, (3) 33 to 44,
and (4) 45 to 74 wk of age. For each phase, 3 diets were
formulated to have 2 percentage points protein differences
with the amino acid levels decreased or increased
in proportion to CP level (Table 1). Three dietary
treatment groups were established from 3 protein levels
in each phase: 1) high protein diet, 2) medium protein
diet, and low protein diet. Diets were assigned to each
individual cage and each individual hen was the experimental
unit to make 48 replications per treatment.