Arginine (Arg) is an essential amino acid for poultry due to their lack of a functional urea cycle, and it plays a critical role in growth, metabolism, and immune function. This study aimed to determine the optimal dietary digestible Arg levels for maximizing growth performance and processing yields, while also assessing its impact on meat quality and immune response in Japanese quails. A total of 600 meat-type Japanese quails were assigned to fve dietary groups with varying digestible Arg concentrations (0.75 %, 1.00 %, 1.25 %, 1.50 %, and 1.75 %), ensuring adequate levels of other amino acids. Arginine requirements were estimated using both linear one-slope broken-line and quadratic broken-line models. The optimal digestible Arg levels for body weight gain, feed effciency, and carcass yield during the frst 21 days were 1.24 % and 1.61 %, 1.49 % and 1.70 %, and 1.20 % and 1.48 %, respectively, based on the linear and quadratic broken-line models. Meat quality parameters showed no signifcant differences; however, malondialdehyde concentrations in the thigh and pectoral muscles were signifcantly lower in Japanese quails fed 1.25 % and 1.50 % Arg diets (P < 0.05), indicating improved oxidative stability. Additionally, birds fed the 1.25 % Arg diet exhibited signifcantly higher IgG and total antibody responses against sheep red blood cells compared to those fed the 1.75 % Arg diet (P < 0.05). In conclusion, the optimal dietary digestible Arg level for Japanese quails during the starter phase is estimated at 1.49 %, based on the linear broken-line model for feed effciency with the highest r² value. Furthermore, a minimum of 1.25 % digestible Arg is required to support favorable oxidative stability and immune function.
