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

Authors: BLAUFUSS, PATRICK - University Of Idaho; GAYLORD, GIBSON - Us Fish And Wildlife Service; SEALEY, WENDY - Us Fish And Wildlife Service; Overturf, Kenneth - Ken; POWELL, MADISON - University Of Idaho

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2020
Publication Date: 3/28/2020
Citation: Blaufuss, P., Gaylord, G., Sealey, W., Overturf, K.E., Powell, M. 2020. 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. Aquaculture. 525. https://doi.org/10.1016/j.aquaculture.2020.735287.
DOI: https://doi.org/10.1016/j.aquaculture.2020.735287

Interpretive Summary: Aquaculture is the fastest growing sector of animal agriculture. Fishmeal has been the main protein component for salmonid aquaculture species in the past, but due to its limited availability and rising cost there has been increasing pressure to replace fishmeal with sustainable protein sources, mainly from plants. The use of plant protein to substantially replace fishmeal leads to reduced growth rates, increased feed conversion ratios, and potential reduced health caused by intestinal enteritis. Through genetic selection the ARS has developed a strain of rainbow trout that has improved tolerance to all plant protein formulated feeds, better growth and does not develop intestinal enteritis. In the presented research the ARS strain, when compared to another commercial strain fed either a high plant meal formulated feed or a fishmeal based feed, showed improved growth, reduced inflammatory response, and significant changes in microbial type and abundance in the intestine. This research demonstrates that fish can be selectively improved to utilize plant material as a protein source. The ARS improved strain stays healthy when fed plant-based formulated feeds, is in great demand by trout producers, is a proven model for the study of nutrient utilization in fish, and demonstrates the potential for improvement in other species.

Technical 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 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 for gene expression analyses. Fish were also sampled at the beginning and end of the study for gut histology and intestinal microbiota. At twelve weeks, the HGM strain showed superior growth on both diets. Gene expression related to gut health and inflammation show reduced inflammatory response in the HGM fish compared to the CSS strain. Strain differences were also apparent in microbiota abundance. These results suggest selection for growth on a plant-based diet also drives selection for increased oral tolerance for dietary soybean meal inclusion.