Utilization of Malt Protein Flour in Fingerling Rainbow Trout Diets

Abstract

Two feeding experiments were conducted to evaluate malt protein flour (MPF) as an alternative protein source for the diet of rainbow trout Oncorhynchus mykiss fingerlings. MPF is a new protein rich by-product from brewer's spent grain. Experiment 1 was conducted to clarify the suitable substitution level of MPF for white fish meal (WFM) in the diet. The control diet, containing WFM as the sole protein source, and isonitrogenous (40% crude protein) experimental diets, containing MPF substituted for 20 to 80% of WFM protein, were fed to fish with an average initial weight of 10 g for 6 weeks. Weight gain and feed efficiency in fish fed the diet substituting MPF up to the 60% level were not different (p > 0.05) from those in fish fed the control diet. There were no significant differences in protein and energy retention between 0 to 40% substitution level. In Experiment 2, crystalline essential amino acids (EAA) were supplemented in the diets containing MPF to simulate the EAA composition in the control diet. Consequently, no significant differences were detected in protein and energy retention between 0 to 60% substitution level. Thus, these results suggest that MPF is a promising alternative protein source for the diet of fingerling rainbow trout. © 1994, The Japanese Society of Fisheries Science. All rights reserved.