Partial Replacement of Fishmeal with Soybean Meal and Soy Protein Concentrate in Diets of Atlantic Cod

Juvenile Atlantic cod Gadus morhua (initial weight = 24.1 +/- 1.4 g [mean +/- SE) were fed diets in which fish meal (FM) was replaced with soy protein concentrate (SPC) and soybean meal (SBM) in isonitrogenous, isocaloric diets for 84 d. A standard marine finfish diet (3 mm, 54% protein, 14% fat) was modified to produce four experimental diets in which 50% of FM was replaced with soy at 0:1, 1:1, or 1:2 ratios of SPC: SBM and 100% FM replacement with a 1:1 ratio of SPC:SBM. No differences in mortality or feed intake were detected among treatments, and fish fed the 50% FM replacement diets, in any combination, grew as well or better than the control for all variables investigated. Cod fed the 100% FM replacement diet exhibited the lowest growth and differed from the control with respect to final body weight, growth, specific growth rate, and thermal-unit growth coefficient. No enteritis was observed in histological sections. These results indicate that 100% fish meal replacement is not recommended, but 50% replacement can be used without significant reductions in growth or condition indices.