Rainbow trout (Oncorhynchus mykiss) is a vital species in aquaculture, particularly in regions such as Pakistan, where environmental stressors like elevated water temperatures and increased turbidity can compromise fish health.
A recent study published in Animal Feed Science and Technology explores the benefits of dietary supplementation with selenium (Se) and vitamin E (VE) to enhance the growth, hematological profile, and disease resistance of rainbow trout. The findings provide valuable insights for fish farmers seeking to improve production efficiency and fish health.
The importance of selenium and vitamin E in fish nutrition
Selenium and vitamin E are essential micronutrients that play a crucial role in fish physiology. Selenium is a key component of selenoproteins, which protect cells from oxidative damage and support thyroid hormone regulation, essential for growth. Vitamin E, a fat-soluble antioxidant, stabilizes cell membranes and protects against lipid peroxidation, which is particularly important in fish diets rich in polyunsaturated fatty acids.
The interaction between selenium and vitamin E is synergistic, enhancing each other’s metabolic functions. This synergy is especially beneficial in intensive aquaculture systems, where stress factors such as high stocking densities and environmental fluctuations can increase disease susceptibility.
Study design and findings
Researchers from the University of Veterinary and Animal Sciences, Purdue University, University of the Punjab, and University of Galway conducted a 90-day trial with rainbow trout fry, evaluating seven experimental diets supplemented with different levels of selenium and vitamin E, both individually and in combination. The diets included:
- Control: No supplementation
- 3S and 6S: Selenium at 3 mg/kg and 6 mg/kg
- 160E and 280E: Vitamin E at 160 mg/kg and 280 mg/kg
- 1.5S/80E and 4.5S/90E: Selenium and vitamin E combined at 1.5 mg/kg + 80 mg/kg and 4.5 mg/kg + 90 mg/kg
Growth performance
Fish fed selenium and vitamin E combined (1.5S/80E and 4.5S/90E) exhibited significantly higher final weights, net weight gains, and specific growth rates compared to the control and single-nutrient diets. The 1.5S/80E diet resulted in the highest weight gain percentage, indicating that moderate levels of selenium and vitamin E are optimal for growth.
Hematological parameters
Hematological analysis revealed that diets supplemented with selenium and vitamin E, particularly the 1.5S/80E and 4.5S/90E combinations, significantly improved red blood cell counts, hemoglobin levels, and other blood indicators. These improvements suggest enhanced oxygen transport and overall fish health.
Disease resistance
A pathogen challenge with Aeromonas salmonicida, a common fish pathogen, demonstrated that fish fed the 1.5S/80E and 4.5S/90E diets had the lowest mortality rates (~20-22%), compared to 68% in the control group. This indicates that combined supplementation significantly enhances disease resistance.
Phagocytic activity
Phagocytic activity, a measure of immune response, was significantly higher in fish fed selenium and vitamin E combined diets. This suggests that these micronutrients strengthen the innate immune system, providing better protection against infections.
Practical implications for aquaculture
The study highlights the importance of selenium and vitamin E in diets to improve the growth, health, and disease resistance of rainbow trout. For fish farmers, particularly in regions with environmental stressors, supplementing diets with these micronutrients can lead to:
- Improved growth rates: Increased weight gain and better feed conversion ratios.
- Better health: Enhanced hematological profiles and immune responses.
- Reduced mortality: Lower susceptibility to common pathogens like Aeromonas salmonicida.
Conclusion
Incorporating selenium and vitamin E into rainbow trout diets offers a practical strategy to mitigate environmental stressors and improve overall fish health and productivity. The 1.5S/80E diet, in particular, proved to be the most effective, providing optimal growth performance, hematological benefits, and disease resistance.
For fish farmers, this research underscores the potential of micronutrient supplementation to enhance aquaculture outcomes, ensuring healthier fish and more sustainable production practices.
Contact
Noor Khan
Department of Fisheries & Aquaculture, University of Veterinary and Animal Sciences
Lahore, Pakistan
Email: noorkhan@uvas.edu.pk
Reference (open access)
Shah, S. J., Khan, N., Fatima, M., Bano, S., Tanveer, A., Nazir, S., Asghar, M., Mustafa, A., Tahir, M., Aftab, S., Wan, A. H. L., & Davies, S. J. (2025). Enhancing defense and production efficiency in rainbow trout (Oncorhynchus mykiss) through prophylactic dietary selenium and vitamin E fortification. Animal Feed Science and Technology, 323, 116296. https://doi.org/10.1016/j.anifeedsci.2025.116296
