DIETARY ARGININE REQUIREMENT OF FINGERLING COHO SALMON (ONCORHYNCHUS-KISUTCH)

An 8-week experiment was designed to re-evaluate the arginine requirem ent of fingerling coho salmon. Triplicate groups of fish were fed semi purified isonitrogenous (av. protein as g amino acids/100 g dry diet = 45.2) and isolipidic (av. crude Lipid 11.9% dry weight) diets contain ing graded levels of arginine in a 6 x 2 factorial design with six arg inine 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 wa s 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 agains t the actual arginine content of the diets corrected by their apparent digestibility coefficients, a breakpoint was found at an arginine lev el 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 con firm that the arginine requirement of Pacific salmon is the highest am ong the values reported for other salmonid species studied to date. (C ) 1998 Elsevier Science B.V. All rights reserved.