"There is a need to make fish feed more sustainable. One measure could be to turn the salmon, a predatory fish, into a 'vegetarian'," says Norwegian University of Life Sciences researcher, Sabina Leanti La Rosa.
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A team of scientists at the Norwegian University of Life Sciences (NMBU) has created the world’s first comprehensive genetic overview of the gut bacteria in Atlantic salmon.
The groundbreaking research, published in Nature Microbiology on Monday 14 October, offers critical insights into how these microbes help salmon digest nutrients and could pave the way for developing sustainable plant-based feed options for the aquaculture industry.
Led by Associate Professor Sabina Leanti La Rosa, the research explores alternatives to traditional marine ingredients-based salmon feed, aiming to reduce reliance on resources like fish meal and fish oil.
The team studied 211 types of microorganisms from wild and farmed salmon, providing a new understanding of how gut bacteria aid in digestion and nutrient absorption.
“Before introducing plant-based feeds, we need to understand what happens inside the salmon’s gut to optimize the nutritional benefits,” said La Rosa, in a press release.
By employing advanced DNA sequencing and traditional laboratory cultivation techniques, researchers were able to uncover the functions of “good” bacteria in the salmon’s gut, including their role in breaking down plant ingredients and producing beneficial vitamins.
"This is the first overview that has been made of bacterial genetic material from Atlantic salmon. The material is obtained through traditional cultivation methods in the laboratory and advanced DNA sequencing methods using samples from both wild and farmed fish in fresh and salt water," La Rosa explained.
Sabina Leanti La Rosa, associate professor at NMBU - Norway's University of the Environment and Life Sciences.
Salmon are naturally carnivorous, consuming a variety of prey, including insects, insect larvae, small herring, crustaceans, and zooplankton in the wild. However, this research suggests that they could adapt to a vegetarian diet if the right gut bacteria support the digestion of plant-based feeds made from ingredients such as soy, algae, and peas.
“There is a need to make fish feed more sustainable. One approach could be to turn salmon, a carnivorous fish, into a ‘vegetarian',” La Rosa said.
"The demand for food continues to rise as the world's population grows. Salmon farming gives us a great opportunity to provide nutritious, high-protein food for many people. But wild fish stocks alone cannot meet the increasing needs for food production, so sustainable aquaculture is a solution to produce more seafood without overfishing," she added.
Professor Phil Pope, co-author of the study, said the study could pave the way for using plant-based ingredients in aquaculture feed.
"Thanks to this new study, we can now understand how the microbes in the salmon gut work. In this way, we can develop nutritional strategies that adapt the chemical structure of the new feed ingredients we want to add to the salmon diet, to the enzymatic tools that the intestinal microbiota have to break them down," Pope explained.
The team has identified key bacterial strains capable of producing essential nutrients and enhancing the fish’s immune system, thereby making them more resilient to disease.
"By studying the specific microorganisms in the salmon's gastrointestinal tract, we can identify which bacteria contribute to better digestion of plant materials and enhance the fish's immune system, making it more resistant to diseases and infections," said Arturo Vera Ponce de Leon, a researcher at NMBU and the lead author of the study.
"If we understand how the salmon's gut microbiota works, we can design strategies to improve the fish's ability to grow and thrive on new, more sustainable diets. This will help produce larger and healthier fish for human nutrition."
Professor Phil Pope, co-author of the article and one of the project managers for ImprovAFish, of which this research is a part.
The findings have practical implications for the aquaculture industry, which could build on this knowledge to formulate improved salmon feeds and dietary supplements, including prebiotics, tailored to the salmon’s digestive needs, the researchers say.
"This can contribute to improved growth rates, health, and overall fish welfare. It can also improve the nutritional quality of farmed salmon, ensuring that consumers eat fish that is not only healthier but also richer in beneficial nutrients," La Rosa explained.
The research team at NMBU believes that the genetic resource created by the study, named SMGA, will be a valuable tool for future research on salmon gut health and nutrition.
"SMGA is a powerful resource for upcoming studies, where researchers can examine more closely the complex interactions between diet, gut microbiota, and digestion in salmon. We also hope that future studies will expand the overview of the salmon's gut microbiota," La Rosa said.
"This type of study is still at an early stage compared to the more extensive research done on gut microbiota in humans and other production animals. By leveraging insights from other species, this knowledge could lead to innovations in aquaculture and the development of new, more effective feeds for better fish health, sustainability, and nutrition in farming systems," she added.
Partners on the research projected included researchers from NMBU, Nofima, University of Galway, the Swedish University of Agricultural Sciences, and the University of Copenhagen.
The article, Genomic and Functional Characterization of the Atlantic Salmon Gut Microbiome in Relation to Nutrition and Health, is available at Nature Microbiology here.