Is there a link between declining marine osmolytes in feed and rising winter wounds and ulcers in salmon?

Speaking at the IFFO’s annual conference in Lisbon this month, Dr Prabhu urged a renewed focus on marine-based osmolytes in salmon feed to address health challenges linked to cold temperatures, such as dehydration and increased susceptibility to disease.

“It’s crucial to adjust feed formulations to meet the fish’s health needs,” he stressed, emphasizing that certain health benefits can only be provided by marine ingredients.

Aquaculture producers are facing tougher conditions, he said. Norwegian authorities reported that over 62.8 million salmon, or 16.7% of the population, died ​​in 2023, primarily due to disease and osmoregulatory dysfunction.

This is where osmolytes can play a role. These naturally occurring compounds are critical for the health of carnivorous species like salmon. "Osmolytes are essential for hydration and cell integrity, and marine ingredients are their primary source."

Salmon, originally evolved in freshwater, rely on osmolytes to retain cellular water, which is crucial in cold and saline environments like Norwegian waters, where dropping winter temperatures increasingly threaten salmon health, according to Dr Prabhu.

"Fish are composed of 70–80% water, and even a 2% drop can result in severe dehydration. In colder waters, reduced metabolic rates lead to less drinking, making salmon more vulnerable to dehydration, ulcers, and disease, thus heightening their dependence on osmolytes for cellular protection."

Benefits of targeted supplementation of marine osmolytes 

Dr Prabhu noted that as plant-based feed alternatives have increased and marine-derived osmolytes in salmon feed—especially in grower diets—have declined, winter-related issues like ulcers and dehydration have become more prevalent. He advocates for osmolytes to be recognized as essential nutrients in the industry rather than non-essentials.

To address these issues, the scientist is leading OsmoProtect, a Norwegian Research Council-funded project starting next year and running through 2028. This initiative aims to produce data supporting the idea that targeted supplementation of marine osmolytes in feed can reduce winter wounds, prevent ulcers, and enhance overall salmon welfare.