اثر سطوح مختلف پروتئین و نوع فرمولاسیون جیره بر اساس اسید آمینه کل و قابل هضم بردفع نیتروژن جوجه‎های گوشتی

An experiment was conducted in a 3×3 factorial arrangement (three different dietary protein level: Cobb recommendation, 10 and 20 percents lower than that and three feed formulations: a diet composed of corn and soybean as a control diet, a diet in which wheat, barley and some agricultural by-products were substituted partially instead of corn and soybean of first diet in which its total sulfur amino acids, lysine and threonine was equal to total of these amino acids as per first diet and the third diet was similar to the second one but its digestible sulfur amino acids, lysine and threonine was equal to these digestible amino acids in the first diet) with 4 replicates in a completely randomized design in order to investigate effects of feed type and dietary levels of crude protein on nitrogen excretion of broilers. Effect of feed type on nitrogen intake, retention and excretion of broilers was significant. As corn soybean based diet showed the highest intake, retention and ammonia nitrogen excretion and the lowest nitrogen excretion within the broiler litter (p<0.05). Conversely, feed containing wheat, barley and agricultural by-products formulated based on digestible amino acids, caused the lowest level of nitrogen intake, retention and ammonia nitrogen. Feed formulation based on digestible amino acids somewhat improved the situation of intake, retention and litter excretion of nitrogen by broilers. Decrease in dietary protein content caused a significant decrease in intake, retention and excretion of nitrogen in absolute form (p<0.05) however resulted in a higher percentage of nitrogen retention within each experimental unit.