Determination of the protein value of novel poultry meal ingredients for rainbow trout, Oncorhynchus mykiss

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 < 0.0001 explained by the relationships: $\text{Plant}\mathrm{FCR}=0.875-0.0087\text{Inclusion}+0.00062{\text{Inclusion}}^2$ and $\text{Plant intake}=2.02-0.02\text{Inclusion}+0.0014{\text{Inclusion}}^2$, 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.