SUMMARY
This research was carried out to determine the effects of diets containing different levels of threonine on the performance, carcass characteristics, and serum biochemical parameters of growing Japanese quails. In the study, a total of 240 mixed sex quail chicks at the age of one day were randomly allocated to 6 treatment groups with 4 subgroups. Experimental diets were prepared to contain threonine at 0.84 (without L-threonine addition), 1.02 (control), 1.10, 1.20, 1.30 and 1.40% levels, and quails were fed with these treatment diets for six weeks. The threonine level of the diet did not statistically affect the performance and carcass parameters of quails, but the best feed efficiency was obtained at 1.10% threonine level. While serum cholesterol, total protein, albumin, creatinine, calcium and AST levels were not affected by dietary threonine level, serum glucose, triglyceride, globulin, urea, and phosphorus levels were statistically affected. With 1.30% threonine in the diet, serum glucose and triglyceride levels were minimum, while serum globulin level was maximum. Serum phosphorus level considerably increased at 1.40% threonine level compared to the control group. According to these results, it can be said that the addition of 1.10% threonine to diet would be proper for growing quails.