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

Authors: Sealey, Wendy; GAYLORD, T. - Us Fish And Wildlife Service

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fish meals are used in fish feeds due to their high protein content and ability to support rapid growth. Poultry meals, created from slaughtered poultry, offer some of the highest protein content among ingredients with potential for replacing fish meal but are expensive. Novel poultry protein blends, devised by combining poultry meal with other low-cost proteins, have been created to address the projected shortage of cost-effective protein sources for fish feeds. However, variation exists in these products affecting their nutritional value for rainbow trout. To investigate the protein value of three novel poultry products, a USDA ARS physiologist at Bozeman Fish Technology Center collaborated with a US Fish and Wildlife Service researcher to assess availability of nutrients for rainbow trout. A novel poultry protein product was then used to replace graded levels of the protein ingredients on an available nutrient basis in both traditional fish meal and modern plant-based rainbow trout feeds, and effects on feed intake, growth, and health were assessed. Results indicate that dietary inclusion of the poultry blend improved intake and feed efficiency of rainbow trout fed a plant-based diet and had no negative effects when included in a traditional fish meal based feed. Protein blends that combine the palatability and digestibility of animal products with the availability and cost effectiveness of plant feedstuffs can create a sustainable dietary protein source for rainbow trout that reduces the feed cost and optimizes the feed nutritional profile.

Technical Abstract: The aim of this study was to assess the protein value of three novel poultry products (Pea/Lentil-PM, Hen on Hen-PM, and Soybean meal (SBM)-PM)). The control and test diets were formulated to contain 37.3 % digestible protein and 20.0 % crude lipid. A growth trial with a 2 x 5 factorial design was conducted where SBM-PM was included, at five levels: 0, 5, 10, 15, and 30% in both a practical-type fish meal-based diet and plant protein-based diet. SBM-PM was exchanged for fish meal and poultry meal, or soy protein concentrate and corn protein concentrate in each series, respectively. Thirty juvenile rainbow trout (initial size=10.7 ±0.15 g; Troutlodge Inc, Sumner, WA) per tank were stocked into a recirculating system consisting of 250-L poly tanks connected to a common bio-filter with spring water inflow of approximately 20% makeup. Water temperature was maintained at 15 °C. Fish in triplicate replicate tanks were fed experimental diets twice daily to apparent satiation for 12 weeks. SBM-PM, inclusion had no significant effect on final fish weight (P=0.3665; FM 233 vs PP 237) or growth rate expressed as a percent increase (P=0.4703; FM 2070% vs PP 2097%). Significant interactions between dietary protein base and SBM-PM inclusion level for both intake (P=0.0080) and FCR (P=0.0081) indicate that the significant protein source effects are driven by increased feed intake of fish fed the plant protein-based diet without SBM-PM inclusion. Regression modeling of this effect for FCR yields a polynomial model with an R square of 0.78; P<0.0001for both FCR and intake explained by the relationships: Plant FCR=0.875-0.0087 Inclusion+0.00062 'Inclusion'^2 and Plant intake=2.02-0.02 Inclusion+0.0014 'Inclusion'^2, respectively. Taken together, 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.