One experiment was run with broiler chickens to evaluate the metabolizable energy (ME), ((apparent (MEA), true (MEV), apparent corrected for nitrogen retention (MEAn) and true corrected for nitrogen retention (MEVn)). The traditional and the forced fed methods were compared in a factorial design 4×8 (methods×feedstuffs) with four replicates. Seven feed ingredients originating from wheat were used in five experiments: wheat grain, wheat germ, white wheat flour, dark wheat flour, wheat bran for human use, wheat bran for animal use and rough wheat bran. The first two methods were the traditional methodology with ad libitum feeding, using birds with different ages, 13 and 39 day-old, respectively. The feedstuffs tested substituted 40% of a reference diet. In methods three and four the birds were fasted 30 hours and forced fed 25g of the feed ingredients (Sibbald, 1976). In all the experiments a treatment was included with fasting birds, to determine metabolic and endogenous losses. In method four caecectomized birds were used. Feeds and excreta were analyzed for dry matter, protein and gross energy for determination of the metabolizable energy values. MEA and MEAn values were smaller when the birds were forced fed. Caecectomized birds showed the highest values of MEV. The feedstuffs MEVn values determined by the traditional method did not show statistical differences among the feeds, however some feed ingredients resulted in different values when compared with those determined with forced fed birds. The MEV/MEA and MEVn/MEAn relationships were narrowed in the methods with ad libitum feed consumption.
bird; apparent metabolizable energy; true metabolizable energy; nitrogen balance
