A total of 180 unsexed broiler chicks (Arbor Acres, 7 days old) were used to assess the effects of different levels of arginine (Arg) supplementation on growth performance, carcass, hematology response and economic efficiency of broiler under heat stress (HS). Broilers were randomly divided into five treatment groups from 7 to 35 days of age. Birds of the first group were served as the positive control group and fed the basal diet without any addition under normal conditions, while the other four groups were exposed to HS and fed a basal diet supplemented with 0, 0.5, 1.0 and 2g Arg/kg diet. Supplementation of different levels of Arg improved BW, BWG and feed conversion ratio (FCR) compared to the negative control group. Chicks receiving Arg under HS had higher red blood cells, heamoglobin and packed cell volume compared to the positive control group. Supplementation of different levels of Arg to the broiler diets under HS significantly improved the relative weights of dressing, liver, spleen, bursa and thymus compared with the relative weight of the negative group and the positive control group. Supplementation with different levels of Arg duet significantly improved and recorded the best economic efficiency, relative economic efficiency, lower meat production cost and net profit margin than the positive and negative control groups.

In conclusion, the present results indicated that under HS, supplementation of dietary Arg to broiler diets could be able to elevate the adverse effect of HS and improve the productive performance, carcass traits, hematology and economic efficiency.