Digestibility of diets based on corn and soybean meal or soybeans treated by roasting or extrusion, with or without an enzyme supplementation, was measured by "true" (Sibbald) methods, by analysis of excreta, and by analysis of ileal digesta. Only analysis of ileal digesta was able to consistently measure differences between soybean and enzyme treatments in the digestibility of CP, starch, fat, and ME. The amino acid (AA) digestibility of the diets was measured by analysis of the ileal contents. Whereas enzyme supplementation improved overall CP digestibility by 2.9%, this improvement was not equal for all AA. Of the AA most important for broilers fed corn-soybean diets, the digestibilities of Lys, Met, and Arg were not improved or not improved significantly by the enzyme supplementation; however, that of Val was improved by 2.3% and that of Thr was improved by 3.0%. A performance trial demonstrated that enzyme supplementation with equal diet formulation improved BW and the feed conversion ratio by 1.9 and 2.2%, respectively. A second performance trial compared standard diet formulations with formulations using enzyme supplementation and energy levels that were reduced by the amount of improvement provided by the inclusion of enzyme in the first performance trial. No difference was seen between treatments, showing that the improvement of nutrient utilization brought about by enzyme supplementation completely compensated for the reduced energy content. Whereas enzyme supplementation should allow a reduction in CP formulation as well, individual AA were not improved equally by supplementation and should also be balanced.

Two experiments were conducted to develop and evaluate a model to estimate ME requirements and determine Gompertz growth parameters for broilers. The first experiment was conducted to determine maintenance energy requirements and the efficiencies of energy utilization for fat and protein deposition. Maintenance ME (MEm) requirements were estimated to be 157.8, 112.1, and 127.2 kcal of ME/kg(0.75) per day for broilers at 13, 23, and 32 degrees C, respectively. Environmental temperature (T) had a quadratic effect on maintenance requirements (MEm = 307.87 - 15.63T + 0.3105T(2); r2= 0.93). Energy requirements for fat and protein deposition were estimated to be 13.52 and 12.59 kcal of ME/g, respectively. Based on these coefficients, a model was developed to calculate daily ME requirements: ME = BW(0.75) (307.87 - 15.63T + 0.3105 T2) + 13.52 Gf + 12.59 Gp. This model considers live BW, the effects of environmental temperature, and fractional fat (Gf) and protein (Gp) deposition. The second experiment was carried out to estimate the growth parameters of Ross broilers and to collect data to evaluate the ME requirement model proposed. Live BW, empty feather-free carcass, weight of the feathers, and carcass chemical compositions were analyzed until 16 wk of age. Parameters of Gompertz curves for each component were estimated. Males had higher growth potential and higher capacity to deposit nutrients than females, except for fat deposition. Data of BW and body composition collected in this experiment were fitted into the energy model proposed herein and the equations described by Emmans (1989) and Chwalibog (1991). The daily ME requirements estimated by the model determined in this study were closer to the ME intake observed in this trial compared with other modelxs.

A performance trial was conducted with broiler chicks to study the effect of phytase (PHY) supplementation in diets formulated with reduced AME, Ca,

The present study was carried out to compare the growth curve, performance and carcass yield of two broiler strains, Paraíso Pedrês (PP) and ISA Label (ISA), raised in confined or semi-confined systems. It was used a completely randomized design with five replicates, consisting of 20 and 29 birds in semi-confined and confined systems, respectively. Semi-confined birds had free access to pasture at 28 days of age. Performance data were recorded weekly by building growth curves as well as calculating the growth rate. After reaching the recommended body weight (2.5 kg), male birds were slaughtered for physicochemical analysis of carcass, parts and organs. Semi-confined PP and ISA birds showed higher growth potential, higher weight gain, lower feed intake and better feed-to-gain ratio than confined birds. No interactions were observed for carcass yield and meat quality characteristics. Males presented higher yields of feet, drumstick, thigh, drumstick + thigh, and heart, while females presented higher breast and abdominal fat yield. Breast meat from ISA Label birds was more yellowish than from PP, whereas less soft meat was observed in semi-confined birds.

O objetivo nesta pesquisa foi avaliar o potencial de crescimento, desempenho zootécnico e as características de rendimento da carcaça, das partes e dos órgãos e a qualidade da carne de três linhagens de frango de corte: Cobb (CB), Paraíso Pedrês (PP) e ISA Label (IL). O delineamento foi inteiramente casualizado, com cinco repetições de 29 aves por tratamento. Semanalmente, com os dados obtidos para peso corporal médio, foi descrito o crescimento das aves, utilizando-se a equação de Gompertz e, com sua derivada, foi obtida a taxa de crescimento das aves. Três aves de cada repetição foram selecionadas e abatidas para análises do rendimento da carcaça, das partes e dos órgãos. As características físico-químicas da carne foram avaliadas utilizando-se o peito de duas destas aves. As aves CB apresentaram maior potencial de crescimento e, entre as caipiras o maior potencial foi observado para PP. Quanto ao desempenho, observou-se que a linhagem CB apresentou maior ganho de peso e consumo de ração, seguida pelas aves PP e IL. Maiores rendimentos de carcaça, de peito, sobrecoxa, fígado, intestinos e proventrículo foram obtidos com as aves CB em relação às caipiras, que não diferiram entre si. As aves CB apresentaram carne de peito com maior pH e maior capacidade de retenção de água que as de linhagens caipiras, que apresentaram carne de peito menos macia e com maior intensidade da cor vermelha. Maior potencial de crescimento e maiores rendimentos de pés, coxa, coxa+sobrecoxa e de coração foram verificados nos machos, enquanto, nas fêmeas, maiores rendimentos de peito, porcentagem de gordura abdominal, fígado, moela e proventrículo. As aves CB em relação às caipiras possuíram maior potencial de crescimento e maior rendimento de partes nobres, mas as caipiras apresentaram atributos diferenciados que justificam sua criação.