Keeping fish healthy is crucial for aquaculture, and researchers are exploring innovative ways to boost their immune system and combat infections. The study investigates the potential of “functional feed ingredients”: special additives that offer health benefits beyond basic nutrition.
Researchers from the University of Stavanger (Norway), Skretting AS, and Bremnes Seashore evaluated the feasibility of in vitro methods to assess the qualities of functional feed ingredients, using the fish cell line RTgill-W1, which has never been used in fish nutrition, and the culture of Paramoeba perurans. The study focused on Complex Gill Disease (CGD), a major health challenge in salmon farming. CGD has multiple contributing factors and no single cause.
The Power of Functional Feeds
Traditionally, fish feeding focuses on providing essential nutrients for growth. However, functional ingredients can go a step further and offer benefits such as:
- Enhanced immune system: Helps fish combat diseases more effectively.
- Improved gut health: Promotes better digestion and nutrient absorption.
- Stress reduction: Leading to healthier fish and potentially higher yields.
Testing New Tools: In Vitro and In Vivo
This study explored two new methods for evaluating functional feed ingredients:
- Fish cell line assays: Using a previously unused fish cell line (RTgill-W1), researchers could assess the impact of different ingredients on cellular health and antioxidant activity. This helped identify optimal ingredient concentrations for future feed formulations.
- Amoebicidal activity: By culturing a specific parasite (Paramoeba perurans), the study tested whether the ingredients could kill this harmful microbe.
Promising Results: From Lab to Fish Farm
Five functional ingredients were chosen for analysis, including:
- Arginine (an amino acid): arginine, which plays a role in immune function.
- β-glucan (a type of fiber): Carbohydrates that can stimulate the immune system.
- Vitamin C
- Two plant-based additives (phytogenic feed additives)
In vitro tests showed positive results for most ingredients, suggesting their potential to improve fish health. Notably, the three ingredients tested for amoebicidal activity (arginine and the two plant-based additives) showed efficacy against the parasite.
Field Trial Success: Gill Protection
The study then tested a commercially available feed containing these functional ingredients (Protec Gill, Skretting AS) in a real-world setting. Fish suffering from complex gill disease were fed this special diet for three weeks. The results were encouraging:
- Reduced pathogen load: The level of harmful microbes in the fish significantly decreased.
- Improved gill health: Histological examination revealed a notable improvement in gill tissue condition.
- Slowed disease progression: The overall progression of the disease slowed, suggesting that the functional feed offered some protection.
A Better Future for Fish Health
This study highlights the potential of functional feed ingredients to improve fish health and combat diseases like complex gill disease. By combining in vitro screening methods with real-world trials, researchers are developing new tools to optimize fish feed formulations. This can lead to healthier fish populations, better aquaculture practices, and ultimately a more sustainable fishing industry.
Conclusion
“The in vitro model, which can be implemented with additional assays and cell line types, appears to be a suitable alternative for selecting ingredients, reducing the number of in vivo trials for a more sustainable aquaculture practice,” the researchers concluded.
While this study provides promising results, further research is needed to fully understand the long-term effects of functional feeds on fish health and the optimal combinations of different ingredients.
Contact
Matteo Vitale
Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger
Stavanger, Norway
Skretting Aquaculture Innovation
Stavanger, Norway
Email: matteo.vitale@uis.no
Reference (open access)
Vitale M, Hoel E, Yousaf MN, Kambestad MA, Mullins J, Lagos L, et al. (2024) Effectiveness of functional ingredients to enhance gill disease in Atlantic salmon (Salmo salar, L.). PLoS ONE 19(6): e0304112. https://doi.org/10.1371/journal.pone.0304112
