Resumo

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.(AU)

Resumo

Two experiments were carried out to compare two techniques (amino acid supplementation and dilution) for formulating experimental diets for pre-starter (1 to 8 days) and starter (8 to 22 days) broiler chicks and to estimate digestible lysine requirements using the dose-response method. In each experiment, 1,200 male Cobb 500 chickens were randomly distributed according to a 5x2 factorial arrangement (lysine level x formulation technique) with six replicates of 20 birds each. For the supplemented diet, a basal diet was formulated to meet the nutritional requirements, then L-lysine HCl was added to achieve digestible lysine levels of 0.975, 1.082, 1.189, 1.296 and 1.403% in the pre-starter diets and 0.840, 0.932, 1.024, 1.116 and 1.208% in the starter diets. For the diluted diet, a diet high in crude protein (CP) and relatively low in lysine was formulated and to which was added a protein-free diet until lysine levels were similar to those described above for the supplemented diet. The results suggest that the dilution technique favored the performance potential and better met lysine requirements compared with the supplementation technique. Lysine levels required for optimal feed conversion ratio of broilers during the pre-starter and starter phases were estimated at 1.361 and 1.187%, which are equivalent to lysine intake of 0.340 and 0.797 g/day, respectively.(AU)

Resumo

Foi avaliada a eficiência de uma fitase (FT) bacteriana na liberação de fósforo fítico utilizando-se curvas de calibração para características ósseas e de desempenho em frangos de corte. O delineamento experimental foi inteiramente ao acaso, com seis tratamentos e seis repetições até 28 dias de idade. O tratamento-controle foi uma dieta à base de milho e farelo de soja deficiente em fósforo (P). Dois tratamentos corresponderam às dietas basais acrescidas de P suplementar, 0,05 por cento e 0,10 por cento, e os outros à dieta basal com 66, 99 e 131 FTU/kg de ração. A curva padrão é definida pelo efeito da adição de P suplementar consumido sobre características ósseas e de desempenho, e os resultados dos tratamentos com fitase são confrontados com a curva para cálculo de P liberado. A adição de P suplementar influenciou o ganho de peso, o peso vivo e o consumo de ração de forma quadrática, bem como miligramas de cinzas ósseas de forma linear. A curva padrão adotada foi da variável miligramas de cinzas ósseas, pois a resposta linear melhor descreve a curva. As inclusões de 66, 99 e 131 FTU/kg liberaram, respectivamente, 0,048 por cento, 0,049 por cento e 0,062 por cento de P. A fitase bacteriana é eficiente na liberação de fósforo fítico e possui viabilidade econômica.

The objective was to determine the efficiency of a bacterial phytase to release phytate phosphorus using calibration curves for performance and bone characteristics in broiler chickens. A completely randomized design with 6 treatments and 6 replicates was used in an experiment with chickens from 1 to 28 days of age. The control treatment was a diet based on corn and soybean meal deficient in phosphorus. Two treatments consisted of the basal diet supplemented with additional phosphorus (0.05 percent and 0.10 percent), and the other treatments received 66, 99 and 131 FTU/kg of feed. The standard curves represented the effect of the levels of additional P intake on performance and bone variables. Then, the responses of the phytase treatments were compared to the standard curves to calculate the P released. The increasing levels of supplemental P had a quadratic effect on weight gain, live weight and feed intake, and linear effect on mg of bone ash. The standard curve elected was mg of bone ash because linear response better represents the curve. Inclusion of 66, 99 and 131 FTU/kg released 0.048 percent, 0.049 percent and 0.062 percent. The bacterial phytase is efficient in releasing phytate, which may be of economical significance.

Resumo

Two metabolism assays were carried out to determine corn and soybean meal metabolizable energy when enzymes were added. In the first trial, 35 cockerels per studied feedstuff (corn and soybean meal) were distributed in a completely randomized experimental design with four treatments of seven replicates of one bird each. The evaluated treatments were: ingredient (corn and soybean meal) with no enzyme addition, with the addition of an enzyme complex (xylanase, amylase, protease - XAP), xylanase, or phytase. Precise feeding method was used to determine true metabolizable energy corrected for nitrogen balance (TMEn). The use of enzymes did not result in any differences (p>0.05) in soybean meal TMEn, but phytase improved corn TMEn in 2.3% (p=0.004). In the second trial, 280 seven-day-old broiler chicks were distributed in a completely randomized experimental design with seven treatments of five replicates of eight birds each. Treatments consisted of corn with no enzyme addition or with the addition of amylase, xylanase, phytase, XAP complex, XAP+phytase combination, or xylanase/ pectinase/-glucanase complex (XPBG). Corn was supplemented with macro and trace minerals. Total excreta collection was used to determine apparent metabolizable energy corrected for nitrogen balance (AMEn). Differences were observed (p=0.08) in AMEn and dry matter metabolizability coefficient (p=0.03). The combination of the XAP complex with phytase promoted a 2.11% increase in corn AMEn values, and the remaining enzymes allowed increased between 0.86% and 1.66%.

Resumo

Foram conduzidos um ensaio de metabolismo para determinar o valor nutricional do milho termicamente processado (MP) e não-processado (MNP) e outro de desempenho para comparar o uso desses alimentos em dietas pré-iniciais para frangos de corte. Não foram observadas diferenças entre a digestibilidade da matéria seca (MS), do extrato etéreo, da proteína bruta e do amido e valores de energia metabolizável aparente dos tipos de milho avaliados. A energia metabolizável aparente corrigida do MP (3.537kcal/kg de MS) foi maior (P<0,05) que a determinada para o MNP (3.411kcal/kg de MS). No ensaio de desempenho, os tratamentos foram: T1- dieta formulada com MNP; T2 - dieta formulada com MP; e T3 - dieta T1, com substituição isométrica do MNP por MP. Na primeira semana, as aves alimentadas com MP (T2) apresentaram maior consumo (P<0,05) e pior conversão (P<0,05) em relação às alimentadas com MNP (T1). A substituição isométrica do MNP por MP não influenciou no desempenho das aves. No período de 1 a 42 dias, os tratamentos não influenciaram o desempenho dos frangos.