ABSTRACT This study aimed at assessing the effect of pelleted and expanded maize-based feeds prepared with different moisture levels (ML, 0.8 and 1.6%) particle size (PS, 650 and 850µ) of ingredients on metabolizable energy, ileal digestibility of amino acids and broiler performance. A total of 720 one-day-old male broiler chicks of the Cobb strain were used. The experiment was performed over a period of 40d (days) and birds received water and feed ad libitum. From 10 to 13d higher AMEn values were obtained for birds fed expanded feeds with 1.6% ML and 850µ PS. Higher values AMEn were encountered when adding 0.8% ML in pellet feeds with 850µ or 1.6%ML/650µ PS. Expanded and pelleted diets with 1.6% ML (independent of PS, 650 or 850µ) presented higher amino acid digestibility. For diets with 0.8% of ML, better result for the digestibility of amino acids were obtained with PS 650µ for expanded and 850µ for pelleted diets. Higher weight gain was observed in broilers fed diets with 1.6% moisture at 21 and 40d. Feed conversion was improved by adding 1.6% ML only at 21d. Regarding carcass characteristics, expanded diets combined with PS of 650µ led to a higher accumulation of abdominal fat. The birds fed expanded diets at 1.6% moisture had higher breast yields. We concluded that to increase the use of nutrients, EMAn and broiler performance, it is recommended that pelleted diets be prepared with the addition of 1.6% water to the mixer and a particle size of 850µ.

ABSTRACT Two trials were performed to determine apparent metabolizable energy (AME) and AME corrected for zero nitrogen balance (AMEn) values and coefficients of apparent metabolizability of nitrogen (CAMN) and of ether extract (CAMEE) of slow- and fast-growing broilers (Isa label and Cobb, respectively) fed four different diets between 10 to 17 days or 28 to 35 days of age. The method of total excreta collection was applied. The tested feedstuffs were corn, whole corn germ (WCG), sorghum, and soybean meal (SBM). A randomized block experimental design was applied, with two treatments (breeds) and four replicates of ten animals each in the first trial, and four replicates of six animals each in the second trial. No differences in CAMN values were observed between the breeds; however, Isa Label birds presented higher CAMEE for all tested feedstuffs. The AME and AMEn values obtained in Isa Label chickens fed the corn diet were 5.75 and 3.44% higher relative tothe Cobb birds, respectively. Breed did not influence AME and AMEn values of the other tested feedstuffs. Independently of breed, age influenced the AME and AMEn values of WCG, sorghum and SBM, suggesting that birds become utilize feed more efficiently as they age.