New eco-friendly aquafeed ingredient could protect against viral disease

March 5, 2024

A promising next generation ingredient for aquafeeds is being evaluated at Memorial University’s Department of Ocean Sciences for its potential to impart viral immunity to the farmed fish that consume it.

The exploratory work, co-funded by Genome Atlantic and the Ocean Frontier Institute Seed Fund, involves four Memorial-based scientists, led by marine scientists Dr. Albert Caballero Solares and Dr. Matthew Rise, along with Dr. Chris Parrish, and Dr. Mohamed Elsayed Emam. Also on the team are Dr. Stefanie Colombo, Canada Research Chair in Aquanutrition, Dalhousie University and two epigenetics specialists from the Institut de Ciències del Mar (ICM), Barcelona, Spain.

The ingredient they are exploring is microbial oils and the species being trialed for its immune response is lumpfish. This marine fish species is used by the aquaculture industry as a cleaner fish to reduce sea lice in farmed salmon operations.

The Ocean Sciences Centre is home to North America’s leading cleaner fish R&D facility where lumpfish are raised for scientific and modest commercial purposes. However, Dr. Caballero Solares said the research team is confident the results will be transferrable to farmed salmon. “Yes, we think so. Both are marine carnivore fish, so they share similar requirements,” he said.

“We need to find a balance between what we find interesting from a fish nutrition/immunology point of view and what is relevant to the industry,”

- Dr. Caballero Solares.

Microbial oils are produced by microorganisms, such as microalgae, fungi, and bacteria, which naturally accumulate high levels of lipids. In this instance, the microbial oils come from fungal-like microorganisms processed by a Nova Scotia biotechnology company.

Their product is produced from a non-genetically modified microorganism strain, exceptionally abundant in the omega-3 polyunsaturated fatty acid DHA, which is important for human health and commonly found in salmon and other fatty fish aquafeeds for farmed fish.

“We expect it to have an impact on the immune response of lumpfish that could be leveraged in the design of novel feeds boosting the fish’s resistance to infection. But it’s very new – something that hasn’t been explored yet,” said Dr. Caballero Solares. It is well known that fish immunity can be modulated by diet.

What makes microbial oils of growing interest to aquaculture is their potential to significantly lower the industry’s carbon footprint and reduce the industry’s pressure on fishing and agricultural products, while raising the nutritional value of aquafeeds.

Reliance on fish protein and lipids found in fish meal and fish oil obtained from wild fish have long been an industry concern, due to the pressure they place on already overexploited wild fish stocks. Aquaculture has responded by progressively reducing the amount of fish meal and fish oil in aquafeed, in favour of plant alternatives such as canola.

Microbial oils, because they are sustainable and nutrient rich in omega-3 fatty acids, are now stirring interest as a next level ingredient for aquafeeds. By answering the question about their potential to confer viral immunity, it will help the industry better assess the capabilities of this new ingredient and lay the groundwork for more research.

“We expect it to have an impact on the immune response of lumpfish that could be leveraged in the design of novel feeds boosting the fish’s resistance to infection. But it’s very new – something that hasn’t been explored yet,”

- Dr. Caballero Solares

To assess the immune response, Dr. Caballero Solares said one group of lumpfish will be fed a fish/plant oil-based control diet while the rest will be given a test diet in which the fish/plant oil has been replaced by the microbial oil product.

After eight weeks the fish will be challenged with a viral mimic compound that will prompt the fish to react as if it were a real virus. The lumpfish’s antiviral immune response will then be closely examined.

Dr. Caballero Solares said, “We have used this compound many times in the past with salmon and lumpfish and we know how the fish are likely to respond. The thing we don’t know is how the microbial oil diet will modulate the response in the face of the compound.”

Changes in their lipid composition and genes will be evaluated at Memorial while variance in their DNA methylation will be analyzed at ICM. Methylation involves a reversible chemical modification to DNA that influences how genes are turned on or off in the fish cells. This is a feature of epigenetics, the study of how the interplay between behaviors and environment can change the way genes work.

One of the trickiest aspects is determining the make-up of the test diet. This is where Dr. Colombo’s and Dr. Parrish’s expertise is critically important. “We need to find a balance between what we find interesting from a fish nutrition/immunology point of view and what is relevant to the industry,” said Dr. Caballero Solares.

The project is expected to form the basis for future collaborations and international research as well as new academic-industry partnerships that will attempt to find out how diet-derived fatty acids, DNA methylation and fish immunity are linked. Equally important, the project could help the biotech company that supplied the microbial oil product to develop new formulations of Canadian aquafeeds.

Initial results are expected to be in by the summer, but the project runs to Oct.1.

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