Re-evaluation of the sulfur amino acid response to various protein levels for live performance and carcass quality in broiler chickens

The aim of this study was to re-evaluate sulfur amino acid response to various protein levels for live performance and carcass quality at ages of 0–18 d, 14–35 d, and 35–49 d. Three flocks of 864, 576, and 720 male Cobb 500 chicks were randomly divided into 6 protein and 4 methionine levels. Four different amounts of synthetic methionine were added to the six protein levels based on corn-soybean diets. At 0–18 d, chicks fed more methionine responded better with improved feed intake, body weight gain, and feed conversion ratio (FCR) in diets lower in protein (< 23.0%) than those of birds given diets with protein levels equal to or above 25.2%. Chickens fed 23.6% protein at 14–35 d or 18.5% protein at 35–49 d had improved FCR. Birds fed 0.18% of synthetic methionine at 14–35d, or 0.10% methionine at 35–49 d had the best FCR. At 49 days, chickens fed 20.3% protein gained more breast meat and had better leg yield than those birds fed diets having less than 15% protein. Broiler chickens responded to increasing amounts of protein, while birds needed more sulfur-amino acid in lower protein diets, especially at young age.