Effect of Excess Lysine and Methionine on Immune system and Performance of Broilers

The present work was carried out to investigate the effects of excess dietary Lysine (Lys) and Methionine (Met) on some blood immune parameters and the performance of broiler chicks. Three hundred male Ross 308 broilers were allotted to five groups each of which included four replicates (15 birds per replicate) in a completely randomized design. The treatment 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 blood lymphocytes and decrease in Heterophyls and ratio of Heterophyls to Lymphocytes as a stress index (P<0.01). There was a linear increase in Newcastle antibody parallel with increasing dietary Lys and Met in 42 days of age (P<0.01) but not 21d. Carcass efficiency, breast muscle yield, heart and liver weight were also increased by the two highest levels of Lys and Met (P< 0.05), whereas feed conversion ratio (FCR) was 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 (P<0.05) but there was no significant effect of 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 immune system functions, FCR, abdominal fat deposition, breast meat yield and carcass efficiency. Results reported here support the hypothesis that it is possible to produce more healthy and economic poultry meat by supplementation excess Lys and Met to broiler diets.