Eco-friendly aquafeed ingredient could protect against viral disease

Researchers will test fungal-based oil in lumpfish diets and its impact on fish’s resistance to infection.

Credits: Genome Atlantic
March 22, 2024

A next-generation ingredient for aquafeeds is being evaluated at Memorial University’s Department of Ocean Sciences for its potential to provide 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 Albert Caballero Solares and Matthew Rise, along with Chris Parrish, and Mohamed Elsayed Emam. Also on the team are Stefanie Colombo, Canada Research Chair in Aquanutrition, Dalhousie University and two epigenetics specialists from the Institut de Ciències del Mar (ICM), Barcelona, Spain.

The ingredients they are exploring are microbial oils and the species being trialed for its immune response is lumpfish.

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

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.

“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 Caballero Solares.

To assess the immune response, 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be fed a fish/plant oil-based control diet while the rest will be given a test diet in which the fish/plant oil has been replaced by the microbial oil product.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, fish will be challenged with a viral mimic compound that will prompt the fish to react as if it were a real virus.

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 Colombo’s and 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 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.