Responses of growing broilers to diets with increased sulfur amino acids to lysine ratios at two dietary protein levels

Abstract

An experiment with 1,440 male Cobb 500 and 1,440 male Ross 308 broilers (14 to 35 d of age) was conducted to investigate the effects of diets having 4 levels of digestible methionine plus cysteine (SAA) on various performance criteria at 2 dietary protein levels (20.5 and 26.0%). Two corn-soybean meal/poultry by-product basal diets were formulated to contain 3,060 kcal/kg MEn and either 20.5 or 26.0% balanced protein, and 1.12 and 1.46% digestible (according to table values) lysine, respectively. Except for SAA, the ratios between essential amino acids were kept identical in both diets according to the ideal protein concept. The ratio between digestible SAA and digestible Lys was 50%. All remaining nutrients met or exceeded NRC (1994) recommendations. Graded levels of SAA were supplemented to obtain digestible SAA to Lys ratios of 62, 69, and 77%, with 77% representing an optimized amino acid balance. Increasing the protein level clearly improved weight gain, feed conversion, breast meat yield, and abdominal fat content. Increasing SAA levels resulted in strong nonlinear or linear dose responses at both protein levels and for both strains. Regression analysis suggested that reducing digestible SAA in a balanced protein (diets with SAA:Lys of 77%) impairs performance, and that optimum SAA:Lys ratio for growing broilers might be higher than 77%, although ANOVA revealed no significant improvement with an SAA:Lys ratio higher than 69%. Responses provide evidence that optimum dietary SAA level depends on dietary protein level and should therefore be related to the protein content.

Effect of protein and methionine levels in a semiorganic diet for dual-purpose type chickens on slaughter performance and nitrogen balance

“…The results of this experiment are generally in agreement with those reported by Carpenter and Muelenaere (1965) and, in part, with the results of Vieira et al (2004) and Quentin et al (2005). For faster growth in chickens, however, a supplement of methionine was effective and amino acid addition also improved FCR and EPI values.…”

“…Addition of synthetic Met enables elimination of excess protein in the diet to cover SAA requirements of fast-and slow-growing broiler chickens (Lewis et al, 1997;Lemme et al, 2005). An optimum level of SAA in feed for chickens may depend on the dietary protein level (Vieira et al, 2004).…”

Respostas de frangos de corte fêmeas de duas linhagens a dietas com diferentes perfis protéicos ideais

“…Todavia, no presente estudo, os benefícios obtidos com a modificação do regime protéico da dieta determinaram respostas similares para as duas genéticas estudadas. VIEIRA et al (2004) e KIDD et al (2005b demonstraram que aves alimentadas com dietas contendo uma alta densidade de aminoácidos apresentaram maior rendimento de carne de peito e menor conversão alimentar e percentual de gordura abdominal quando comparadas com aves que consumiram dietas com uma densidade baixa de aminoácidos. SIBBALD & WOLYNETZ (1986) demonstraram que as exigências de lisina para otimizar o acréscimo de carne de peito em frangos de corte são superiores àquelas para ótimo peso corporal.…”

“…O impacto do custo da proteína na dieta é alto e, portanto, aumentos na sua concentração só são justificáveis quando ganhos no desempenho zootécnico ou no rendimento de carne são viabilizados. Recentemente, tem sido demonstrado que ganhos zootécnicos e de rendimento de carne podem ser obtidos com o aumento da densidade protéica das dietas independentemente da genética utilizada (BARTOV & PLAVNIK, 1998;VIEIRA et al, 2004;KIDD et al, 2005a). Entretanto, existe a possibilidade de que as respostas de cada genética à proteína dietética sejam de magnitudes diferentes, o que indicaria a necessidade de programas protéicos diferenciados para cada uma.…”

Desempenho e peso de frações corporais, na suplementação crescente de lisina, dos 19 aos 40 dias de idade em frangos de corte

“…ACAR et al (1993) verificaram que linhagens de crescimento rápido respondem a diferenças mais sutis de níveis de lisina para desenvolvimento do peito e esse fato se deve à maior capacidade de hiperplasia das células musculares dessas aves. A suplementação (SHUTTE & PACK, 1995) e o balanceamento (LECLERQ, 1998) dos aminoácidos das dietas podem promover aumento no ganho de carcaça, especialmente o peito (POPHAL, 2004) e redução de gordura abdominal (VIEIRA et al, 2004).…”