The chemical composition and the metabolizable energy values of ten protein feedstuffs fed to broilers at different ages were evaluated. The traditional method of total feces collection was used to determine the values of apparent metabolizable energy (AME) and apparent metabolizable energy corrected by nitrogen (AMEn), in male broilers in the periods from 21 to 30 (first period) and from 41 to 50 (second period) days of age. The experiment was analyzed as a complete randomized design with 10 treatments, six replicates and six (first trial) and four poultry (second trial) per pen. The following feedstuffs were evaluated: cottonseed meal, corn gluten meal, soybean protein concentrate, two meat and bone meals, fish meal, full fat poultry by-product meal, two spray-dried plasma and erythrocytes. The AMEn (kcal/kg) values on as-fed basis in the first and second experimental periods were as follows: cottonseed meal, 1,963 and 2,461; corn gluten meal, 3,608 and 4,013; soybean protein concentrate, 2,043 and 2,155; meat and bone meal 36%, 1,249 and 1,573; meat and bone meal 45%, 1,391 and 1,766; fish meal, 3,055 and 3,077; full fat poultry by-product meal, 2,990 and 3,172; spray-dried plasma 70%, 2,673 and 2,730; spray-dried plasma 78%, 3,027 and 3,704; and erythrocytes, 2,834 and 3,256. All AME and AMEn meal values obtained in the second period were higher than those obtained in the first one.
broilers; chemical composition; metabolizable energy
