Revolutionizing Salmon Feed: The Triple Benefits of Zinc Coating
Innovative Approach to Zinc Supplementation
“We need to rethink how we incorporate zinc into salmon feed,” states Antony Philip, a researcher at Nofima. This change promises enhanced absorption and health benefits for salmon, reduced environmental emissions, and a more circular use of sludge.
The Importance of Zinc in Fish Nutrition
Zinc is an essential mineral for fish, playing a crucial role in processes such as wound repair. However, the current method of adding zinc to salmon feed results in a low retention rate, with a significant portion directly lost to aquatic environments.
The European Union aims to mitigate zinc emissions, which has prompted the salmon farming sector in Europe to adhere to stricter regulations regarding zinc levels in feed. As of now, the allowed limit is 180 mg per kilogram for salmonids and 150 mg for other species. The European Food Safety Authority (EFSA) has suggested a further reduction to 150 mg/kg for salmon.
Enhancing Zinc Digestibility
“To overcome this challenge, we must boost the digestibility of zinc in feed so salmon still receive sufficient amounts, even with reduced content,” emphasizes Philip.
The Feed Production Process
Currently, zinc is added to the feed in a premix prior to extrusion—a process involving high heat and pressure to create pellets. Typically, after the extrusion, the pellets are coated with oils under vacuum. This coating allows for the inclusion of temperature-sensitive additives, but minerals are usually omitted as they can withstand high temperatures. Unfortunately, essential minerals like zinc can become trapped in rigid protein structures formed during this treatment, limiting their availability.
The Shift to Coating
Philip proposes moving zinc supplementation from the premix stage to the coating stage. His extensive background in mineral nutrition, coupled with a dual Ph.D. in fish mineral nutrition from the Netherlands and France, has led him to this conclusion. Since joining Nofima, he has been dedicated to exploring various zinc sources, environmental influences, and salmon physiology.
Documented Benefits of Zinc Coating
At Nofima’s Feed Technology Centre, Philip initiated a project to test this innovative supplementation method on post-smolt salmon (200-280 grams) in seawater tanks. The results were promising: the digestibility of zinc improved by up to 15 percentage points, and zinc excretion in feces decreased by nearly 25%.
The Triple Win
- Improved zinc absorption leads to better health outcomes for the fish.
- Reduced zinc emissions to the environment through higher absorption rates.
- Lower zinc concentrations in aquaculture sludge, enhancing its potential for reuse and value creation.
Looking Ahead: The TOP-zinc Project
Building on these findings, Philip is now advancing the TOP-zinc project, focused on determining optimal strategies for zinc absorption and understanding the implications for fish health during long-term sea-cage trials. This initiative involves collaboration with renowned institutions including the Institute of Marine Research, Akvaplan-niva, MOWI Feed AS, Huvepharma NV, and NIVA, with funding from FHF – the Norwegian Seafood Research Fund.
Renate Johansen, R&D Director at FHF, acknowledges the environmental risks posed by excessive zinc and states, “As the climate crisis grows, our need to minimize negative impacts is critical.” She highlights the urgency in addressing potential zinc deficiencies as regulatory measures become more stringent.
Preparing for Regulatory Changes
This novel method can help meet the zinc nutritional requirements for salmon, even in light of new EU regulations. While these new limitations are still forthcoming, Philip emphasizes the potential benefits for feed companies and farmers who experiment with this technique in smolt facilities.
“By adapting this method, feed manufacturers can improve zinc absorption, lower emissions, and cut feed costs. The TOP-zinc project is examining strategies for zinc supplementation throughout all phases of salmon growth,” he concludes.
Conclusion
The issue of inadequate zinc digestibility has shifted from a purely biological concern to an operational challenge, intensifying the industry’s pursuit of effective solutions.
Image: A feed pellet’s pores allow oils to be absorbed through the coating process—marking the transition of zinc addition to this stage. Nofima
