Proteomic mechanisms underlying soybean meal-induced enteritis resistance in selected rainbow trout

Authors: BLEDSOE, JACOB - University Of Idaho; REDMAN, NATHAN - University Of Idaho; SIMMONS, DENINA - University Of Ontario; TUDOR, CHASE - University Of Ontario; Welker, Thomas; Romano, Nicholas; Overturf, Kenneth

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2025
Publication Date: 12/8/2025
Citation: Bledsoe, J., Redman, N., Simmons, D., Tudor, C., Welker, T.L., Romano, N.P., Overturf, K.E. Proteomic mechanisms underlying soybean meal-induced enteritis resistance in selected rainbow trout. Journal of the World Aquaculture Society. 56(6): e70068. 2025. https://doi.org/10.1111/jwas.70068.
DOI: https://doi.org/10.1111/jwas.70068

Interpretive Summary: Soybean meal (SBM) is a common alternative to fishmeal in aquaculture diets due to its availability and low cost. However, SBM-induced enteritis in carnivorous fish like rainbow trout limits its use. This is because rainbow trout that eat SBM have strong inflammatory responses in the intestines as an immune response that resembles inflammatory bowel disease, which is not beneficial for trout farming. To address this, a strain of rainbow trout (Sel) has been selectively bred for over two decades for tolerance to high-SBM diets. This study investigates the mechanisms behind the Sel strain’s enhanced growth and resistance to SBME. Both strains of fish were fed a fishmeal diet (good diet) or SBM-diet based diet (that can cause SBME). It was found that the commercial strain experience SBME based on looking microscopically at the intestine under a microscope, but the Sel fish did not experience such severe changes in the intestine. This was likely due to a suppressed immune response, and thus inflammatory responses, to eating SBM. The reduced inflammation in the Sel group contributed to better growth by the intestine being in a better condition to absorb nutrients. This helps pave the way for potentially suppressing inflammatory responses in the intestine of rainbow trout and decrease reliance on fishmeal. Such as decreased reliance on fishmeal will improve aquaculture sustainability and decrease feeding costs to the farmer.

Technical Abstract: Soybean meal (SBM) is a common alternative to fishmeal in aquaculture diets due to its availability and low cost. However, SBM-induced enteritis in carnivorous fish like rainbow trout limits its use. To address this, a strain of rainbow trout (Sel) has been selectively bred for over two decades for tolerance to high-SBM diets. This study investigates the physiological mechanisms behind the Sel strain’s enhanced growth and resistance to SBME using label-free proteomics of plasma and intestinal tissues. A seven-month feeding trial was conducted with the Sel strain and a commercial strain (Com), each fed either a fishmeal-based (FM) or plant-based (PM) diet. Fish were sampled at early (two months) and late (seven months) stages for histology and proteomic analysis. Histology revealed significant enteritis in the Com PM group, characterized by shortened, widened intestinal villi and increased inflammation. In contrast, the Sel strain showed no signs of enteritis on the PM diet, indicating a genetic basis for tolerance. Proteomic analysis identified 3,912 proteins in plasma and 1,008 in the intestine, with distinct tissue-specific profiles. Principal component analysis revealed greater group separation at the late timepoint, especially in the intestine. Differential protein expression showed changes in immune response, inflammation, apoptosis, and nutrient metabolism, with the Com PM group showing the most pronounced alternations. Gene ontology and pathway enrichment analysis highlighted differences in immune regulation and protein turnover. The Sel strain’s ability to moderate inflammatory and apoptotic responses likely contributes to improved nutrient absorption and growth on SBM diets. These findings offer insights into the mechanisms behind SBME resistance in the Sel strain and suggest strategies for improving plant-based diet utilization in aquaculture, potentially reducing reliance on fishmeal and improving industry sustainability.