The current trend in aquafeed development is moving away from dependence on traditional protein sources (i.e.: fishmeal) to lower-cost, sustainable alternatives (i.e.: plant protein). However, the incorporation of high levels of plant sourced protein to replace fishmeal in carnivorous salmonids can deleteriously affect the intestine. The intestine is important for the regulation of nutrient absorption and barrier function contributing to overall growth and health in fish, and the paucity of studies in this area encourages the need for further understanding and research.
Here, we report the effects of a plantmeal- vs. fishmeal-based diet on intestinal integrity on two strains of rainbow trout, a commercial strain (CS) and a selected strain reared to grow on an all-plant protein (soy-based) diet (ARS-Sel). A feeding trial of 7 months was conducted to assess overall fish performance. Further electrophysiological characterization was performed using ex vivo intestinal segments (anterior proximal, posterior proximal, mid, and distal intestine) mounted in Ussing chambers to measure transepithelial electrical resistance (TEER) and conductance. TEER and conductance both measure overall intestinal barrier function. For both parameters, significant differences were observed between intestinal segments within strains, as well as differences between strain and diet. Specifically, fishmeal resulted in significant TEER differences between CS and ARS-Sel within anterior proximal (Figure 1) and distal intestine, whereas the plant-based diet resulted in significant effects between strains in the mid intestine. Interestingly, these results illustrate not only differences in regional intestinal permeability within a strain, but there are also major differences from feeding a plantmeal- vs. fishmeal-based diet on intestinal integrity between strains. These results plus histological analyses of distal intestinal segments, as well as expression of genes involved in intestinal permeability (i.e.: claudins) and inflammation will be presented.