GROWTH PERFORMANCE AND INTESTINAL HEALTH OF TWO DIFFERENT RAINBOW TROUT Oncorhynchus mykiss STRAINS FED A HIGH SOY DIET

In an effort to improve the utilization of soybean meal (SBM) in diets for rainbow trout, fish at the Hagerman Fish Culture Experiment Station (HGM) have been selected for growth on a complete plant-based diet over several generations. Utilizing fish of the F7 generation and a commercial selected strain (CSS), we sought to investigate differences in growth and intestinal health when fed a 40% SBM diet. Triplicate tanks (30 fish, initial weight 77.9 ± 1.1 g) of each strain were fed diets for 12 weeks containing either 0% or 40% SBM in a 2 X 2 factorial design. Five fish from each tank were sampled every four weeks to collect samples of liver and distal intestine for gene expression analysis. At twelve weeks, the HGM strain showed superior growth on both diets (p<0.001) when compared to the commercial strain, with no significant differences in growth within each strain in response to diet (p=0.158; Fig. 1). Analysis of genes related to gut health and inflammation show reduced inflammation in the HGM fish. These results suggest selection for growth on a plant-based diet also drive selection for increased tolerance for dietary soybean meal inclusion.