Effect of feeding low-protein, l-lysine and dl-methionine-supplemented diets on the growth performance and carcass characteristics of broilers

Abstract EN

Two hundred day-old unsexed broiler (Cobb 500) chicks were randomly distributed to four groups.

The first (control) group was fed on starter (22 % CP, 3100 Kcal / kg ME, 1.10 % Lysine, and 0.48 % Methionine) and finisher (20 % CP, 3200 Kcal / Kg ME, 0.90 % Lysine, and 0.35 % Methionine) diets.

The other three groups were fed on three starter and finisher is caloric isonitrogenou diets with 2 % lower protein content than the diets of control group with addition of graded levels of L-lysine HCl and DL-methionine to give 120 %, 140 %, and160 % of the NRC (2000), At the end of starting period, the increased Lysine and Methionine content of the low-protein starter's rations didn't affect body weight and gain but increased the feed consumption and decreased the feed conversion ratio of the birds.

At the end of finishing period, body weight, body gain, feed intake, and breast meat yield increased significantly with the increasing of synthetic amino acids in the diets, while the best feed conversion ratio was obtained with 120 % amino acids level.

Plasma uric acid level increased with feeding broiler on low protein diets and with increasing of synthetic amino acids supplementation to the diets.

Plasma Creatinine increased in the birds fed on low-protein diet supplemented with the highest synthetic amino acids level (160 %).

Plasma Calcium wasn't affected by the treatment while phosphorus increased in the birds fed on low-protein, DL-Methionine and L-lysine supplemented diets compared with the control group, which might be as indicator for enhanced growth of these groups.

It could be concluded that the minimum levels of protein (20 % and 18 % for starting and finishing periods, respectively) in the broiler's diets supplemented with 120% of NRC requirements for Lysine and Methionine requirements ensure an optimum body weights, body gains, and feed conversion ratios with reduced plasma level of Uric acid but were inadequate to produce the highest breast meat yield.