Nitrogen Retention in Broiler Chickens Effects ofDietary Crude Protein and Lysine Levels on Performance and pparent

An experiment was conducted to evaluate the effects of dietary crude protein (CP) and lysine levels on performance and nitrogen excretion in broiler chickens. Four hundred twenty 7-day old chickens from Ross 308 strain were randomly allotted to 6 dietary treatments with 5 replicates of 14 chicks each (7 male and 7 female chicks). The CP levels were 17, 18, and 20 percent and lysine levels were 1.3 and 1.1 percent of experimental diets. Data were analyzed in a completely randomized design as a 2×3 factorial arrangement. Experimental diets were offered ad libitum during starter (7-21 d) and grower (21-42 d) periods. At the age of 42 to 45 days, 2 birds placed in battery cages and their Excreta was totally collected to determine apparent nitrogen retention. Results of the present study showed that the CP levels had a significant effect on feed intake, weight gain, and nitrogen excretion. Among carcass parts only wings weight was affected significantly by the CP levels. The CP levels of 20 and 17 percent resulted highest and lowest nitrogen excretion, respectively. Interaction between CP and lysine had a significant effect on feed intake and N excretion. Chicks fed diets containing 20% CP and 1.1 % lysine showed significantly more feed intake as compared to other groups. The 17% CP and 1.3% lysine diets resulted lowest and highest nitrogen excretion, respectively. In general, best performance results was observed by experimental diets containing 20 % CP and 1.1% lysine but this diet resulted most N excretion among the experimental diets.