An experiment was conducted to determine the effects of excess levels of dietary lysine (Lys) and methionine (Met) on some performance traits and economical efficiency of the broiler chicks. 300 one-day-old broiler chicks (Ross 308) were used in a completely randomized design. The birds were allotted to five groups, each of which included four replicates (15 birds per replicate). The groups received the same basal diet supplemented with Lys and Met (as TSAA) in 0, 10, 20, 30 or 40% more than NRC (1994) recommendation. The collected data were analyzed by SPSS software and Duncan’s test was used to compare the means on a value of P< 0.05. The results indicated that the two highest levels of Lys and Met treatments (30 and 40% more than NRC recommendation) led to significant increase in carcass efficiency, breast muscle yield, heart and liver weight and also economical efficiency of carcass yield (P< 0.05), whereas feed conversion ratio (FCR) and abdominal fat pad which were the least in these two treatment groups (P< 0.05). Addition Lys and Met 40% more than NRC tend to significant decrease in body weight gain and economical efficiency of live weight yield but there was no significant effect of the treatments on thigh and leg yield. The finding of this experiment showed that increasing Lys and Met to diets of today’s broiler in excess of NRC recommendations can improve FCR, abdominal fat deposition, carcass efficiency, breast meat yield, and also profitability of production. Results reported here support the hypothesis that it is possible to produce poultry meat with lower fat content and more economical by supplementation excess Lys and Met to broiler foods.
