Aim: Aim of this study was to determine the effects of organic and inorganic manganese (Mn) at different levels supplemented to diets of the broilers under stocking density stress on performance, carcass and hematological parameters.

Materials and Methods: A total of 1000, day-old broiler chicks were divided into one control group and nine treatment groups, each consisting of 100 chicks. The control group was fed the basal diet only, whereas experimental groups were fed with basal diet supplemented with organic Mn (6.25, 12.5 and 25 mg/kg of Mn-methionine) and inorganic Mn (12.5, 25 and 50 mg/kg Mn-oxide), organic + inorganic Mn (3.125 + 6.25, 6.25 + 12.5 and 12.5 + 25 mg/kg Mnmethionine + Mn-oxide).

Results: The livability increased by the supplementation of both organic and inorganic Mn on days 29 to 49 and 0 to 49 (P<0.001). Live weight gain until 15 days of age increased in the groups receiving 3.125 + 6.25 mg/kg Mn-methionine + Mn-oxide (P<0.05). On day 49, the relative weights of spleen increased in the 12.5 mg/kg Mnmethionine and 6.25 + 12.5 Mn-methionine + Mn-oxide groups compared with the other groups (P<0.05), whereas the abdominal fat quantity in the same days decreased in the 6.25 + 12.5 Mn-methionine + Mn-oxide group compared with the control group (P<0.05). The heterophil/lymphocyte ratio decreased in the in the group receiving Mn-methionine, 25 and 50 mg/kg Mn-oxide and 3.125 + 6.25 mg/kg Mn-methionine + Mn-oxide groups on day 49 (P<0.05).

Conclusions: Supplementation of 12.5 mg/kg organic Mn, or a mixture of organic and inorganic Mn (3.125 + 6.25 mg/kg and 6.25 + 12.5 mg/kg) have positive effects on the performance, livability and stress response of broiler chicken subjected to housing stress.