This study was conducted to relate the performance of broiler chickens fed diets containing growth-promoting antibiotics to changes in the intestinal microbiota. The technique of denaturing gradient gel electrophoresis (DGGE) of amplicons of the region V3 of 16S rDNA was used to characterize the microbiota. Two experiments were conducted, one with broilers raised in battery cages and the other with broilers raised in floor pens. Antibiotics improved the performance of the chickens raised in floor pens only. Avilamycin, bacitracin methylene disalicylate, and enramycin induced changes in the composition of the intestinal bacterial community of the birds in both experiments. The number of bacterial genotypes found in the intestinal tract of chickens was not reduced by the antibiotics supplemented in either environment. However, the changes in the composition of the intestinal bacterial community induced by antibiotics may be related to improvement in growth performance. This was indicated by the suppression of 6 amplicons and the presence of 4 amplicons exclusive to the treatment that had the best performance in the floor pen experiment.

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 models.

RESUMO -Objetivou-se, nesta pesquisa, estudar o efeito dos níveis de energia metabolizável (EM) da dieta sobre o desempenho e o metabolismo energético de frangos de corte machos na fase de crescimento (22 a 43 dias de idade) em condições de temperatura ambiente. Foram utilizadas 288 aves distribuídas aleatoriamente por três níveis de energia da dieta (3.050, 3.200 e 3.350 kcal/kg) e três níveis de alimentação (ad libitum, 75 e 50% do ad libitum), com quatro repetições de oito aves, para determinação das exigências de mantença e das eficiências energéticas. Foi utilizado o método do abate comparativo, sendo que 12 aves foram abatidas no início do ensaio experimental, para determinação da composição corporal inicial, e 144 aves foram usadas para determinação da energia metabolizável das dietas experimentais. Os níveis de energia influenciaram na ingestão de energia metabolizável (IEM) e, conseqüentemente, a retenção de energia na carcaça (ER) e a produção de calor (PC). As exigências de energia metabolizável de mantença (EMm) determinadas foram 131,12; 140,96 e 131,78 kcal/kg 0,75 /dia para os níveis de energia alto, médio e baixo, respectivamente. O nível de energia mais alto (3.350 kcal/kg) na dieta dos frangos de corte proporcionou melhores resultados de desempenho, enquanto o médio (3.200 kcal/kg), melhor equilíbrio na eficiência de utilização de energia para deposição de proteína e gordura, conseqüentemente, melhor qualidade da carcaça, em decorrência da menor deposição de gordura.Palavras-chave: eficiências de utilização da energia, exigência de energia para mantença, metabolismo energético, níveis de energia na dieta Effect of Dietary Metabolizable Energy on Energy Metabolism and Performance in Broiler ChickensABSTRACT -The objective of this work was to study the effect of dietary ME levels on the performance and the energy metabolism of male broilers on growing phase, from 22 to 43 days old. Two hundred and eighty-eight broilers were ramdomly assigned to three energy levels (3,050; 3,200 and 3,350 kcal/kg) and three feeding levels (ad libitum, 75% and 50% ad libitum), with four replicates of eight birds, to determine the energy maintenance requirements and the energy efficiency utilization. The method used was the comparative slaughter. Twelve birds were sacrificed in the beginning of trial to determine the initial body composition and 144 birds were used to determine the AMEn of diets according to ME levels and feeding levels. The dietary ME levels affected the ME intake and consequently in retained body energy (RE) and heat production (HP). The maintenance metabolizable energy requirements were: 131, 141 and 132 kcal/kg of W 0.75 / day for 3,350; 3,200 and 3,050 ME/kg, respectively. The highest ME level promoted better performance of the birds, however, the medium ME level provide better values of efficiency for protein deposition and for fat deposition, consequently, lower body fat composition, showing better carcass quality. IntroduçãoAtualmente, pesquisas nas aréas de genética, nutrição e manejo busc...

1. The objective of this study was to determine a metabolisable energy (ME) requirement model for broiler breeder hens. The influence of temperature on ME requirements for maintenance was determined in experiments conducted in three environmental rooms with temperatures kept constant at 13, 21 and 30 degrees C using a comparative slaughter technique. The energy requirements for weight gain were determined based upon body energy content and efficiency of energy utilisation for weight gain. The energy requirements for egg production were determined on the basis of egg energy content and efficiency of energy deposition in the eggs. 2. The following model was developed using these results: ME = kgW0.75(806.53-26.45T + 0.50T2) + 31.90G + 10.04EM, where kgW0.75 is body weight (kg) raised to the power 0.75, T is temperature ( degrees C), G is weight gain (g) and EM is egg mass (g). 3. A feeding trial was conducted using 400 Hubbard Hi-Yield broiler breeder hens and 40 Peterson males from 31 to 46 weeks of age in order to compare use of the model with a recommended feeding programme for this strain of bird. The application of the model in breeder hens provided good productive and reproductive performance and better results in feed and energy conversion than in hens fed according to strain recommendation. In conclusion, the model evaluated predicted an ME intake which matched breeder hens' requirements.

The objective of this study was to evaluate the effect of betaine in methionine-and choline-reduced diets fed to broilers submitted to heat stress. In total, 1,408 male broilers were randomly distributed into eight treatments, according to 2 x 4 (environment x diet) factorial arrangement, with eight replicates of 2 birds each. Birds were reared environmental chambers under controlled temperature (25-26 °C) or cyclic heat-stressing temperature (25-31 °C). The following diets were tested: positive control (PC), formulated to meet broiler nutritional requirements; negative control (NC), with reduced DL-methionine and choline chloride levels; and with two supplementation levels of natural betaine to the negative control diet (NC+NB1 and NC+NB2). Live performance, carcass traits, and intestinal morphometrics were evaluated when broilers were 45 days of age. The results showed that all evaluated parameters were influenced by the interaction between environment and diet, except for breast meat drip loss. The breakdown of the interactions showed that birds fed the PC diet and reared in the controlled environment had greater breast drip loss than those submitted to the cyclic heat-stress environment. Birds submitted to cyclic heat stress and fed the PC diet presented the lowest feed intake. Feed conversion ratio was influenced only by diet. The FCR of broilers fed the NC+NB2 diet was intermediate relative to those fed the PC and NC diets. The addition of betaine in the diet, with 11.18% digestible methionine and 24.73% total choline reductions, did not affect broiler live performance, carcass yield, or intestinal morphometrics.

RESUMO -O objetivo do trabalho foi determinar equações de predição das exigências de proteína bruta (PB) para frangos de corte machos e fêmeas através do método fatorial. Na determinação das exigências de proteína bruta para mantença, foi utilizada a técnica do balanço de nitrogênio. As exigências de proteína bruta para o crescimento foram determinadas em função do conteúdo de nitrogênio na carcaça e a eficiência de utilização do nitrogênio da dieta. A partir dos valores das exigências para mantença e para crescimento foram elaboradas equações de predição para as exigências diárias de PB (g/ ave/ dia) para frangos de corte machos (7 a 21 dias -PB = 1,323xP 0,75 + 0,256xG, 22 a 42 dias -PB = 1,323xP 0,75 + 0,277xG e 43 a 56 dias -PB = 1,323xP 0,75 + 0,283xG) e fêmeas (7 a 21 dias -PB = 1,748xP 0,75 + 0,258xG, 22 a 42 dias -PB = 1,748xP 0,75 + 0,274xG, e 43 a 56 dias -PB = 1,748xP 0,75 + 0,300xG), em que P = peso corporal (kg) e G = ganho de peso diário (g/dia). Recomenda-se a utilização das equações para a determinação das exigências mínimas de nitrogênio ou proteína bruta somente com atenção no atendimento das exigências em aminoácidos.Palavras-chave: equações de predição, exigências de proteína bruta, frangos de corte, ganho de peso, mantença, método fatorial Prediction Equations for Protein Requirements on BroilersABSTRACT -The objective of this study was to determine prediction equations for crude protein (CP) requirements for males and females broilers using the factorial method. In order to determine the crude protein for the maintenance was used the nitrogen balance technique. The crude protein requirements for weight gain were determined based on body nitrogen content and nitrogen utilization efficiency for the diet. Considering the requirements for maintenance and weight gain were elaborated prediction equations for CP requirements (g/bird/day) for males broilers (7 to 21 days -PB = 1.323xW 0.75 + 0.256xG, 22 to 42 days -PB = 1.323xW 0.75 + 0.277xG, and 43 to 56 days -PB = 1.323xW 0.75 + 0.283xG) and females (7 to 21 days -PB = 1.748xW 0.75 + 0.258xG, 22 to 42 days -PB = 1.748xW 0.75 + 0.274xG, and 43 a 56 days -PB = 1.748xW 0.75 + 0.300xG) where W = body weight (kg) and G = daily weight gain (g/day). The prediction equations utilization is recommended to determine the minimal nitrogen or crude protein requirements considering the amino acid requirements. Rev. bras. zootec., 30(5):1521-1530, 2001Introdução Na avicultura as exigências nutricionais são constantemente reavaliadas para permitir a otimização dos nutrientes das dietas, uma vez que a nutrição e alimentação das aves varia muito em função da diminuição nos custos de produção ou pelas constantes variações genéticas em busca de melhores desempenhos e maior competitividade.O fornecimento adequado de proteína para aves em crescimento tem o objetivo de dar condições às aves expressarem o máximo desenvolvimento corporal, com formação de massa muscular e empenamento. Por outro lado, o fornecimento inadequado de proteína provocará redução no crescimento...

RESUMO

RESUMO -O trabalho foi realizado com o objetivo de determinar, pelo método fatorial, as exigências de energia metabolizável (EM) de frangos de corte. Foi conduzido um ensaio em câmaras climáticas mantidas às temperaturas de 13, 23 e 32 o C (±2 o C) para se verificar o efeito da temperatura sobre as exigências de energia metabolizável para mantença utilizandose a técnica do abate comparativo. As exigências de energia metabolizável para ganho de peso foram determinadas com base no teor de energia corporal e na eficiência energética de utilização da EM. As exigências de mantença foram de 159,36; 116,17 e 128,66 kcal/kg 0,75 /dia para 13, 23 e 32 o C, respectivamente, verificando-se efeito quadrático da temperatura sobre as exigências de mantença (EMm=300,14 -14,61.T + 0,2876.T 2 , r 2 =0,90). As exigências de EM para ganho de peso corporal foram de 3,72 kcal/g para machos e 3,98 kcal/g para fêmeas de 1 a 21 dias; 4,21 para machos e 3,93 para fêmeas de 22 a 42 dias; e 4,51 para machos e 7,04 para fêmeas de 43 a 56 dias. Considerando-se as exigências determinadas, foram elaborados modelos de predição das exigências diárias de energia para frangos de corte, nos quais foram considerados o peso corporal, a temperatura ambiente (para estimativa das exigências de mantença) e o ganho de peso (para cálculo das exigências de ganho).Com base nas comparações das exigências determinadas pelos modelos e nas recomendações do manual da linhagem, conclui-se que os modelos elaborados predizem as exigências energéticas dos frangos de corte.Palavras-chave: exigências de energia, frangos de corte, método fatorial, temperatura ambiente Metabolizable energy requirements for maintenance and growth of broilersABSTRACT -This work was conducted to determine the energy requirements for broilers using the factorial method.The metabolizable energy (ME) requirements for maintenance (MEm) were determined at 13, 23 and 32 o C (±2 C) by the comparative slaughter technique. ME requirements for weight gain were estimated considering the net efficiency of energy utilization for growth and body energy content. The energy requirements for maintenance were of 159. 36, 116.17, and 128.66 kcal/kg 0.75 /day at 13, 23, and 32 o C, respectively, and quadratic effect of temperature (T) on the maintenance requirement (MEm=300.14 -14.61 T + 0.2876 T 2 , r 2 =0.90) was detected. Metabolizable energy requirements for weight gain for males and females were of 3.72 and 3.98; 4.21 and 3.93; 4.51 and 7.04 kcal/g, for the periods from 1 to 21, 22 to 42 and 43 to 56 days of age, respectively. Considering the requirements, prediction models were designed for ME requirements using adjustments for body weight, daily weight gain and temperature. The models predicted the ME requirements for broilers as redult of from breed manual recommendations and the studied models.Key Words: broilers, energy requirements, factorial method, temperature IntroduçãoAtualmente, as pesquisas, tanto em genética como nutrição e manejo, visam à redução dos custos de produção sem prejudicar ...