AbstractOne hundred eighty hybrid broiler chicks of the Peterson x Hubbard line, in 18 groups of 10, were used to compare six diets (three replications). The diets consisted mainly of maize, soybean and fish meals, and vegetable oil, and varied in levels of metabolizable energy (kcal/kg) and protein (g/kg) as follows; (A) 3,000/230, (B) 3,200/230, (C) 3,400/245, (D) 3,400/260, (E) 3,600/ 260, and (F) 3,800/260. Mean values per chick at wk 4 for treatments A to F, respectively, were as follows: weight gain, 994; 1,053; 1,105; 1,055; 1,063; and 943 g; and feed conversion, 1.81, 1.71, 1.57, 1.55, 1.48, and 1.48 g/g. Weight (g) and yield (%) of carcass at wk 4, respectively, were 693 (66.7), 740 (67.4), 774 (67.3), 725 (66.0), 740 (67.0), and 653 (66.0). Sample evaluation of these carcasses and of locally produced and imported carcasses showed percentage of breast to be highest in the imports (30.8) and in treatment C (30.6). In the objective criterion of conformation [weight (g)/pectoral músete area (cm2)], carcasses of C (19.8) and E (18.7) were highest. Percentages of water and of protein in the dry matter (DM) were highest in imported carcasses (70 and 52, respectively). In percentage fat in the DM, those of A and C and local commercial carcasses were highest (42), and those of F (32) and the imported (35) were lowest. Diets C and E, which promoted rapid, efficient growth and desirable carcasses, are recommended for use with "Cornish" chicks.
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