This experiment was conducted to examine the effects of dietary L-arginine (Arg) supplementation on growth performance, intestinal morphology, serum biochemical and hematological parameters in meat-type quails. A total of one hundred and sixty 7-d-old male quail chicks were weighed and allocated to four treatment groups of four replicates, with 10 chicks/replicate. Four groups of quail chicks were fed basal diet containing 12.44 g lysine (Lys)/kg of diet (control), basal diet supplemented with

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... .4, 1.21 and 1.84 g Arg/kg of diet (for Arg to Lys ratios of 100, 103, 109 and 114) for 28 days. The birds were fed diets from 7 to 38 d of age. Final body weight and feed:gain tended to improve by increasing Arg:Lys ratio to 109. Relative weight of spleen and bursa were significantly (p<0.05) increased by the addition of 0.4 g Arg/kg of diet. Morphometric parameters of jejunum were not affected by the dietary treatments. The uric acid, and triglyceride concentration of the serum significantly (p<0.05) decreased by increasing the Arg:Lys ratio to 114. Serum HDL-cholesterol concentration were significantly (p<0.05) increased by increasing the Arg:Lys ratio to 114. Monocytes were decreased by increasing the Arg:Lys ratio to 114. In conclusion, our results indicated that Arg supplementation in the quail diets did not appear to have any significant positive effects on performance criteria and although increasing Arg:Lys ratio to 114 could improve serum biochemical parameters.