In this study, 360 male broilers, out of which 240 of a fast-growing strain (Cobb500), and 120 of a slow-growing strain (Label Rouge), were used to evaluate the effect of dietary fiber on digesta transit time and digestive metabolism during the period of 1 to 42 days of age. A completely randomized experimental design with a 3x2 factorial arrangement was applied, consisting of three groups of birds (slow-growing -SG; fast-growing fed ad libitum -FGAL; and fast-growing pair-fed with SG broilers -FGPF) and two iso-protein diets (a 3100 kcal ME/kg low-fiber diet -LFD-and a 2800 kcal ME/ kg high-fiber diet -HFD-with 14% wheat bran and 4% oat hulls). HFD-fed birds presented lower ME retention (p < 0.001) and lower dry matter metabolizability (DMM) (p < 0.001), which is possibly related to the shorter digesta transit time observed in these birds (p < 0.001). DMM was reduced with age, whereas metabolizable energy remained almost constant (p < 0.001) independently of strain. This may be related to the increase in feed intake as birds age. The slowgrowing strain did not present better utilization of the high-fiber diet as compared to the fast-growing strain in none of the analyzed ages, even though showing a significant better use of fiber and dietary energy from 31 days of age.

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The objectives of the present study were to determine the parameters of Gompertz equations and to determine curves and growth rate, feed intake and body component deposition, as well as allometric coefficients of body water, protein, and fat relative to live weight of male and female broilers of intermediate performance (C44) and high performance (Cobb-500) genetic strains. In total, 384 one-d-old chicks were distributed into four treatments: male Cobb 500, male C44, female Cobb 500, and female C44, with six replicates of 16 birds, according to a completely randomized experimental design. Average body weight, weight gain, and feed intake were weekly determined, and six birds, representing the average weight of each treatment, were sacrificed to determine body composition. Growth curves were built applying Gompertz function, with excellent fit, and growth, feed intake, and tissue deposition rates were obtained by its derivatives. Superior growth rate was obtained for Cobb 500 male broilers. This genetic strain has higher feed intake capacity, which is achieved earlier than in the C44 strain. Protein and fat deposition maturity was reached earlier in males than in females in Cobb 500. The allometric coefficients showed earlier maturity for body water in C44 and females. In terms of body protein, male Cobb 500 broilers reached maturity earlier than females and C44. Body fat deposition maturity was reached earlier in Cobb 500 than in C44. The Gompertz equations obtained in the present study efficiently described body growth, feed intake, and deposition of body components, with a coefficient of determination higher than 0.99.

The present study aimed to evaluate the chemical composition of carbohydrates and nitrogenous fractions of late-crop corn silages with different specific masses (SM; 90, 134, 172, and 214 kg dry matter m -3 ). The silage was held in 20-L mini-silos, and the experimental design was completely randomized, with four replications (mini-silos) per treatment. In the present study, differences in the compression (i.e., SM) of corn silages caused changes in the contents of soluble sugar and nitrogenous constituents; however, SM alone did not explain the entire preservation of the ensiled material. ResumoObjetivou-se avaliar alterações bromatológicas sobre as frações glicídicas e nitrogenadas de silagens de milho "safrinha" com diferentes massas específicas (ME) no momento da ensilagem (90, 134, 172 e 214 Kg de MS.m -3 ). A ensilagem foi realizada em minissilos com capacidade de 20 L. O delineamento experimental foi inteiramente casualizado com quatro repetições (minissilos) por tratamento. O fracionamento foi realizado segundo The Cornell Net Carbohydrate and Protein System (CNCPSv5.0). A ME afetou linearmente os teores de extrato etéreo Ŷ = 1,718 + 0,0041*ME (P = 0,009; R 2 = 39,2), açúcares solúveis Ŷ = 0,9502 -0,003445*ME (P < 0,001; R 2 = 59,9) e fibra solúvel Ŷ = -0,4731 + 0,01158*ME (P = 0,025; R 2 = 31,2). Nos carboidratos, a fração B1 apresentou comportamento linear ascendente Ŷ = 14,88 + 0,2566*ME (P = 0,043; R 2 = 38,4) com o aumento da ME, enquanto as demais frações não foram influenciadas. Nos constituintes nitrogenados houve variação no nitrogênio total Ŷ = 2,003 -0,01065*ME + 0,000036*ME 2 (P = 0,041; R 2 = 38,8), no nitrogênio não proteico Ŷ = 1,436 -0,01103*ME + 0,000036*ME 2 (P = 0,060; R 2 = 35,1), no nitrogênio solúvel Ŷ = 1,715 -0,01450*ME + 0,00005*ME 2 (P = 0,024; R 2 = 43,8) e no nitrogênio insolúvel em detergente neutro Ŷ = 0,4979 -0,001057*ME (P < 0,001; R 2 = 70,6), cujos resultados também contribuíram para as diferenças nas frações A Ŷ = 66,47 -0,5291*ME + 0,00174*ME 2 (P = 0,095; R 2 =30,4), B2 Ŷ = 6,78 + 0,05857*ME (P = 0,076; R 2 =20,8) e B3 Ŷ = 19,03 -0,05565*ME (P = 0,018; R 2 = 34,1) do modelo de Cornell. A ME de compactação, de forma isolada, não serve para explicar, na totalidade, a preservação do material ensilado. Diferentes ME causam alterações no teor de açúcares solúveis das silagens de milho e nos constituintes nitrogenados.