Examination of CORN‐fermented protein and high protein distillers dried grains to replace fish meal and poultry meal in juvenile rainbow trout diets

Abstract The ability of high‐value plant protein concentrates to replace fish meal and other expensive animal proteins in diets for rainbow trout depends on their available nutrient composition, cost and consistency. The aim of this study was to assess the effects of two novel corn protein products (ANDVantage™ 40Y and ANDVantage™ 50Y, The Andersons, Inc.) on the growth performance of juvenile rainbow trout. Two parallel replacement series were applied with test products included at 0%, 7.5%, 15%, 22.5%, and 30% diet dry weight replacing dietary fish meal and poultry meal on a digestible protein (DP) basis. All diets were formulated to 42% DP and 18% crude lipid, supplemented with Lys, Met, and Thr to targets of 3.8%, 1.3%, and 2.1%, respectively, and manufactured by cooking extrusion. Diets were randomly assigned to triplicate tanks of rainbow trout ( Oncorhynchus mykiss , Troutlodge Inc., Sumner, WA) with a mean initial weight of 38 ± 0.7 g (mean ± SD). Fish were cultured in poly tanks (320 L) at n = 20 fish per tank in a recirculating system with a flow rate of 4–6 L min −1 , temperature at 15°C, and a 13:11 light:dark cycle, and fed twice daily to apparent satiation 6 days per week for 12 weeks. Including ANDVantage products at levels above 22.5% decreased growth (gram gain per fish, p < 0.0001). A significant interaction was observed for feed conversion ratio (FCR; p < 0.0001) wherein fish fed ANDVantage™ 40Y had significantly higher FCR than fish fed ANDVantage™ 50Y when fed levels above 22.5%. Optimized inclusion levels, determined by regression analysis for combined data or for each ingredient when interactive effects occurred, indicate that maximum inclusion levels for ANDVantage™ 40Y and ANDVantage™ 50Y in rainbow trout diets range from 13.5% to 21.5% depending on the performance variable assessed.