Determination of the protein value of novel poultry meal ingredients for rainbow trout, <i>Oncorhynchus mykiss</i>

Abstract The aim of this study was to assess the digestible protein value of three novel poultry products (Pea/Lentil‐PM, Hen on Hen‐PM, and soybean meal (SBM)‐PM), then a growth trial with a 2 × 5 design was conducted where SBM‐PM was included at five levels: 0, 5, 10, 15, and 30% in both a fish meal (FM)‐based diet and a plant protein (PP)‐based diet. Thirty rainbow trout (initial size = 10.7 ± 0.15 g; Troutlodge Inc, Sumner, WA) per tank were stocked into a 15°C recirculating system. Fish in triplicate tanks were fed twice daily to apparent satiation for 12 weeks. SBM‐PM had no effect on final weight ( p = 0.3665; FM 233 vs. PP 237) or growth rate ( p = 0.4703; FM 2070% vs. PP 2097%). Significant interactions between dietary protein and SBM‐PM for both intake ( p = 0.0080) and FCR ( p = 0.0081) indicate increased intake of fish fed the plant protein‐based diet without SBM‐PM. Regression modeling of this effect yields a polynomial model with an R‐square of 0.78; p &lt; 0.0001 explained by the relationships: and , respectively. These values suggest that the SBM‐PM can be included up to 30% in rainbow trout feeds to reduce feed costs without negatively impacting performance.