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Title: Aquacultured rainbow trout (Oncorhynchus mykiss) possess a large core intestinal microbiota that is resistant to variation in diet and rearing density

Author
item WONG, SANDI - University Of North Carolina
item WALDROP, THOMAS - Freshwater Institute
item SUMMERFELT, STEVEN - Freshwater Institute
item DAVIDSON, JOHN - Freshwater Institute
item Barrows, Frederic
item KENNEY, P. BRETT - West Virginia University
item Welch, Timothy - Tim
item Wiens, Gregory - Greg
item SNEKVIK, KEVIN - Washington State University
item RAWLS, JOHN - University Of North Carolina
item GOOD, CHRISTOPHER - Freshwater Institute

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2013
Publication Date: 6/14/2013
Citation: Wong, S., Waldrop, T., Summerfelt, S., Davidson, J., Barrows, F., Kenney, P., Welch, T.J., Wiens, G.D., Snekvik, K., Rawls, J.F., Good, C. 2013. Aquacultured rainbow trout (Oncorhynchus mykiss) possess a large core intestinal microbiota that is resistant to variation in diet and rearing density. Applied and Environmental Microbiology. DOI:10.1128/AEM.00924-13.

Interpretive Summary: Trout are a good source of dietary protein and contain high levels of heart healthy omega-3 fatty acids. However, traditional trout feeds contain fishmeal from wild-caught fish species which are a limited resource. Alternatives to fishmeal need to be found and adopted for the sustainable growth of the aquaculture industry. Significant advances have been made to alternative protein diet formulations in recent years and the growth of fish fed grain-based diets have been reported to be comparable to that of fish fed traditional fishmeal-based diets. Little research, however, has examined the effects of grain-based feeds in combination with alterations in fish rearing density. We compared a traditional diet containing fishmeal to an all-plant-protein diet specifically testing whether differences in rearing density and diet lead to changes in gut microbial flora, rainbow trout health, or fillet yield. At the end of the 10 month feeding study, we found little variation in the gut microbiota, and no difference in intestinal inflammation, or overall survival. Higher final weights were observed in the fishmeal diet groups relative to the grain-based diet groups; however, fish fed grain-based diets were better able to utilize dietary energy for growth. These data suggest that significant changes to rainbow trout diet and rearing density can be achieved without marked alterations in the intestinal microbiota or compromised fish health. These findings support the continued investigation and possible application of an all-plant-protein diet for trout culture.

Technical Abstract: As global aquaculture fish production continues to expand, it is essential that we improve our understanding of how environmental factors interact in fish health and production. Significant advances have been made towards economical alternatives to fishmeal-based diets such as grain-based formulations, and defining the effect of rearing density on fish health and production. Little research, however, has examined the effects of fishmeal- and grain-based diets in combination with alterations in rearing density. Moreover, it is unknown whether interactions between rearing density and diet impact composition of the fish intestinal microbiota, which might in turn impact fish health and production. We fed adult rainbow trout (Oncorhynchus mykiss) fishmeal- or grain-based diets and reared them under high- or low-density conditions for 10 months, and evaluated individual fish growth, production, fin indices, and intestinal microbiota composition using 454 pyrosequencing of 16S rRNA genes. We report that rainbow trout possess a surprisingly large core gut microbiota shared across individuals reared with different diets and densities. Variation in diet and rearing density resulted in only minor changes in gut microbiota composition, despite significant effects of these variables on fish growth, performance, fillet quality and welfare. Significant interactions between diet and rearing density were only observed in evaluations of fin indices and the relative abundance of the bacterial genus Staphylococcus. These results suggest that it may be possible to develop novel aquaculture strategies for rainbow trout without compromising gut microbiota composition.