EFFECT OF DIETARY-PROTEIN CONTENT ON GROWTH AND BODY-COMPOSITION OF FAST AND SLOW FEATHERING BROILER-CHICKENS

1. Broilers were produced from two lines of breeders selected for three generations for fast and slow feather growth. The base population foundation stock originated from a commercial pedigree female line, which carried only the dominant sex-linked late feathering gene K. Three isoenergetic (12.7 MJ AME/kg) starter and grower diets were formulated to contain 280, 240 and 200, and 260, 220 and 180 g/kg protein, respectively, and fed to 156 broilers of each sex to give three starter-grower combinations. 2. Broiler performance in terms of growth, food conversion ratio, carcase meat, fat and protein content was optimised on the 240 to 220 g/kg protein starter-grower series of diets. 3. Birds of the slow line were significantly (P<0.05) heavier at 48 d of age and had the same food intake and food conversion ratio as birds of the fast feathering line. 4. The slow line birds had significantly (P<0.01) shorter feathers and less total plumage weight at 48 d. The slow line birds had significantly (P<0.001) less carcase fat and significantly (P<0.05) more carcase protein than the fast line. The slow line had significantly more carcase meat (P<0.01) within which a greater breast meat yield was evident (P<0.001).