Updated August 3, 2023:
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An 8-week feeding trial was successfully conducted using California yellowtail that were feed three different soybean meals (SBMs) at high combined inclusion levels of over 30% for a total of five treatment combinations and a fishmeal control. Yellowtail grew to a maximum average of 141g or 755% weight gain. Survival was high among all treatments (>96%) and food conversion rates were low (1.11-1.16). There were no statistical differences among treatments for any performance measurement. The proximate composition and mineral analysis for the fish at the end of the trial showed no differences between the diets. We also did not see any significant differences in gene expression of intestinal tissue at the end of the trial among five genes evaluated. Qualitative analysis of the intestinal tissues via histology yielded no significant differences across the dietary treatments.
This study showed that fish performance was not impacted by different SBMs or different inclusion rates used in this study. In fact, performance from those diets was similar to the FM control, which bodes well for future commercial application. Further refinements will need to be made to include more SBM in the diets. Our study suggested that it is possible that larger fish could have performed well on diets with no fish meal – diets that smaller fish rejected. Larger fish would be the target for growout trials where most of the feed biomass is consumed, so this area should be explored in future research.