Effects of dietary methionine and threonine on growth performance, carcass traits and blood metabolites of broilers in a hot environment

The current study aimed to evaluate the effects of different levels of methionine and threonine in the diet on growth performance, carcass traits, and blood metabolites of broilers in a hot environment. One thousand and two hundred Cobb 500 day-old chicks were randomly selected and divided into the following six dietary groups (8 replicates of 25 birds each): control [diet related to COBB RECOMMENDATION, 2014; methionine + cysteine: 0.92 (starter 0-21 d), 0.79 (finisher 22-35 d); threonine: 0.89 (starter 0-21 d), 0.75 (finisher 22-35 d)], two groups with two levels of methionine [110% (1.01, 0.87) and 120% (1.10, 0.95)], two groups with two levels of threonine [110% (0.89, 0.75) and 120% (0.82, 0.97)], and one group with one level of methionine & threonine [120% (1.10, 0.97; 0.95, 0.82)], according to Cobb recommendation diet. During experiments feeding was done in a two phase schedule (starter 0-21 d; finisher 22-35 d). The experimental diets were formulated with varying levels of methionine (0.92, 1.01 and 1.10) and threonine (0.89 during starter (0-21 d), (0.79, 0.87 and 0.95) finisher (22-35 d). At the end of the experiment (35 days), two birds from each replicate were slaughtered to determine carcass characteristics and blood metabolites. Results showed that at 21 days of age, a diet of 110% methionine and 110% threonine increased (P < 0.05) body weight, weight gain and feed conversion ratio. At the age of 35 days, 110% methionine and 110% threonine treatments showed the highest (P < 0.05) body weight and feed conversion ratio, whereas feed intake was lowest (P < 0.05). The best average daily gain and survivability were related to treatments of 110% methionine and 110% threonine. Breast meat yield was better (P < 0.05) for 110% methionine in the diet than all other dietary treatments. Blood metabolites were similar for all dietary treatments. From the results of the present study, it may be concluded that supplementation of methionine and threonine at 110% of the Cobb recommendation diet can increase growth performance for commercial broilers in hot environments.