Selection on a plant-based diet reveals changes in oral tolerance, microbiota and growth in rainbow trout (Oncorhynchus mykiss) when fed a high soy diet

Abstract

A strain of rainbow trout at the Hagerman Fish Culture Experiment Station has undergone a long-term selection program for growth on a plant-based diet (HGM strain). Comparing fish from the F8 generation to a commonly available commercial strain selected for growth (CSS), we sought to investigate potential differences in oral tolerance, intestinal microbiota richness and overall growth when fed a 40% SBM diet. Triplicate tanks (initial mean fish weight 77.9 ± 1.1 g) of each strain were fed diets containing either 0% or 40% SBM over 12 weeks in a factorial design. Fish were weighed every four weeks and subsampled to assess gene expression in the distal intestine. Fish were also sampled at the beginning and end of the study to assess gut histology and characterize intestinal microbiota. At twelve weeks, the HGM strain showed superior growth on both diets (p < .001). Gene expression related to gut health and inflammation show reduced inflammatory response in the HGM fish compared to the CSS strain. Significant effects of strain and diet were also observed on metrics of gut microbiota diversity. Together, these results suggest selection for growth on a plant-based diet also drives selection for increased oral tolerance for dietary soybean meal inclusion.