Effect of adding the Limiting Amino Acids to Low – Crude Protein Diets on Performance of Broiler Chicks.

This study was conducted to study the effect of decreasing the dietary crude protein level while supplementing the essential amino acids on growth performance, carcass, some blood constitutes of broiler chicks.  An experiment was done using 252 one day-old broiler chicks Arbor-acres, randomly allotted to seven dietary treatment groups; the first group positive control with optimum CP level (PC), the second group negative control (NC) low 3 points than requirements, and groups 3 up 7 were fed the NC diet but supplemented incrementally with the essential amino acids; lysine, lysine+ methionine,  lysine+ methionine+ tryptophan, lysine+ methionine+ tryptophan +threonine and lysine+ methionine+ tryptophan+ threonine+ valine, respectively to cover the dietary requirements for each amino acid during starter, grower and finisher periods. Results show that there were no significant differences between treatments (P=0.242) on starter live weight. For grower period the control group with optimum CP % level, followed by low CP % diet supplemented with all amino acids had significantly the highest live body weight compared with  the low CP group without supplemental amino acids (P= 0.006). The gains in body weight were found to be significant during grower and finisher phases the highest values were observed in the positive control and low CP supplemental with all AA diets. The same two treatments the best FCR for the overall experimental period compared to the other treatments. Carcass traits were not significantly affected by dietry treatments. Plasma total protein (P=0.034), albumin (P=0.002), and triglycerides (P=0.002), were significantly affected by dietary treatments. The lowest feed cost per kg live weight gain of chickens were found in the experimental group (T7) containing all amino acids supplemented to the low CP diets. It could be recommended to decrease the dietary CP level of broiler chicks by 3 points without affecting the growth performance up on supplementing the essential AA.