Dietary arginine requirements of fingerling coho salmon (Oncorhynchus kisutch)

An 8-week experiment was designed to re-evaluate the arginine requirement of fingerling coho salmon. Triplicate groups of fish were fed semipurified isonitrogenous (av. protein as g amino acids/100 g dry diet = 45.2) and isolipidic (av. crude lipid 11.9% dry weight) diets containing graded levels of arginine in a 6 x 2 factorial design with six arginine levels (expected values 3.5, 4.5, 5.5, 6.5, 7.5 and 8.5% of the dietary protein) and two feeding rates (satiation and restricted). The apparent digestibility of arginine in the experimental diets was also evaluated. The growth rates of the fish fed the experimental diets was comparable to that of fish fed a practical control diet, indicating a more than acceptable overall performance of the experimental diets. When broken-line analysis was performed on the weight gain data against the actual arginine content of the diets corrected by their apparent digestibility coefficients, a breakpoint was found at an arginine level of 4.9% of the dietary protein for the satiation-fed groups and of 5.5% for the restricted-fed groups. Results from the present study confirm that the arginine requirement of Pacific salmon is the highest among the values reported for other salmonid species studied to date.