New research shows key role of nutrients in salmon health

New research has shown the importance of various nutrients in feed to achieve optimal health and growth in salmon.

Scientists in Norway studied the interplay between the lipid cholesterol and saturated fat, and between the mineral zinc and the omega-3 fatty acids EPA and DHA.

As fish oil has been gradually replaced with vegetable oil in feed over the past decades, salmon's requirement for saturated fat has not received sufficient attention, said Nofima scientist Nini Sissener.

Greater impact

“Saturated fat has a greater impact on fillet quality than previously thought. Fishmeal and fish oil possess a unique composition of omega-3, saturated fats, and cholesterol.

“It is therefore important to assess what these changes mean for the quality of salmon raised on today’s plant-dominated feed,” said Sissener, who conducted her research while employed at the Institute of Marine Research.

The results revealed that frozen salmon fillets lost more liquid during thawing when sourced from fish that had received insufficient saturated fat during the growth phase. Additionally, low cholesterol level in the feed reduced the fillet’s firmness and red colouration.

Resilience

In another study, Nofima scientists looked at how zinc levels affect health and resilience in small salmon in the freshwater stage.

High zinc and omega-3 levels have positive effects on scale development, wound healing in the skin, increased bone density, and overall growth.

“Together with omega-3, zinc enhances skin health, and more omega-3 improves the utilisation of zinc,” said Bente Ruyter, senior scientist at Nofima. “They are truly a powerful duo in salmon feed and act synergistically.”

Robust growth

For robust growth under optimal conditions in land-based tanks, research showed that six per cent omega-3 of total fatty acids in the feed is sufficient.

Trials were also conducted on larger salmon in sea cages, where scientists found that fish lost minerals and had lower harvest weights when fed low zinc diets. However, mineralisation improved when both omega-3 in the feed increased, and total fat levels decreased.

The research showed that salmon raised under challenging conditions in sea cages require more omega-3 for optimal growth, health, and fillet quality than those kept under ideal conditions in land-based tanks.

Feed intake

For example, salmon that received 11 per cent omega-3 of total fatty acids in the feed resumed feeding more quickly after delousing than those fed 6.5 per cent. Since feed intake typically drops after delousing, Ruyter said that a rapid return to feeding is essential.

“What’s exciting about these findings is that the interaction between nutrients plays a key role in skin health, red coloration, energy metabolism, membrane fluidity, and the salmon’s ability to adapt to new production environments,” said Ruyter.

"Today’s production involves various technical solutions, warmer seas, and more sea lice. To thrive through the production cycle with good growth, health, and fillet quality, salmon need the right feed.’