Determination of threonine requirement of Arian 386 broiler strain in finisher period (days 22 to 42) by evaluating the responses of performance, immunity and blood parameters

This study was conducted to determine threonine requirement of Arian 386 broiler chickens at finisher period (days 22 to 42), using performance, immunity and blood parameters responses in a completely randomized design with six levels of threonine (0.66, 0.76, 0.86, 0.96, 1.06 and 1.16%), five replicates and 20 birds per each replicate. Requirement was determined by broken line method. Average daily feed intake was not affected by dietary level of threonine during days 22 to 42. Average daily weight gain and feed conversion ratio in broiler chickens fed the level of 0.66% threonine were respectively lower and higher compared to the other groups. The serum concentrations of glucose, cholesterol, triglyceride, calcium, phosphorus, albumin, total protein, LDL and globulin were not affected by different levels of threonine. The serum concentration of uric acid was reduced in birds received 0.96% threonine comparing the other groups and serum HDL level was increased in birds fed with 0.66 and 0.76% threonine. Number of white and red blood cells, percentage of hematocrit, heterophil, lymphocyte, heterophil to lymphocyte ratio, titer of antibody including IgG, IgM and total antibody in response to SRBC injection were not affected by different levels of threonine. Considering serum uric acid and HDL, threonine requirement during finisher period were estimated 1.058 and 0.995%, respectively. Totally, range of 0.9-1.0% can be suggested for threonine requirement of Arian 386 broiler chickens in finisher period (days 22 to 42).