The search for natural additives to sustainably improve aquaculture production is a key objective for the industry. In this context, herbal essential oils (HEOs) are emerging as a promising alternative to synthetic additives. A recent study, published in Frontiers in Veterinary Science, has evaluated the impact of a blend of these compounds on the performance of Nile tilapia (Oreochromis niloticus) fry, revealing significant improvements in growth, health, and efficiency.
Key findings
- Supplementation with 30 and 60 mL/kg of herbal essential oils (HEOs) significantly improved the growth and feed efficiency of Nile tilapia.
- Higher doses (120 and 240 mL/kg) were detrimental, resulting in decreased growth and survival rates.
- The optimal doses strengthened the immune and antioxidant responses, reduced cholesterol and triglycerides, and improved blood parameters.
- HEOs positively modified intestinal morphology by increasing the nutrient absorption surface area and regulating key genes related to growth, immunity, and stress resilience.
Study design
The research, conducted by scientists from Kafrelsheikh University, Shanghai Ocean University, the Agricultural Research Center, Al-Azhar University, and Princess Nourah bint Abdulrahman University, among other organizations, focused on determining the effects of supplementing the diet of Nile tilapia fry with a blend of herbal essential oils. Over 72 days, the fish were fed five different diets:
- A control group without HEOs.
- Four groups with increasing doses of the supplement: 30, 60, 120, and 240 mL per kilogram of feed.
The HEO blend contained bioactive compounds known for their beneficial properties, such as carvacrol, oregano oil, 1,8-cineole, thymol, α-pinene, β-pinene, and limonene. The researchers measured key parameters including growth performance, feed efficiency, blood health indicators, immune and antioxidant responses, intestinal morphology, and the expression of related genes.
Impact on growth and feed efficiency
The results clearly demonstrated a dose-dependent response. The groups that received 30 and 60 mL/kg of HEOs showed the best outcomes, with a significant increase in final body weight, weight gain, and specific growth rate compared to the control group.
Furthermore, a crucial metric for any producer, the Feed Conversion Ratio (FCR), improved markedly at these two doses, indicating that the fish utilized the feed more efficiently. Conversely, the higher doses (120 and 240 mL/kg) not only failed to improve performance but were detrimental, negatively affecting growth and the survival rate.
Improvements in health and immune response
Supplementation with HEOs at the optimal doses (30 and 60 mL/kg) not only boosted growth but also enhanced the overall health of the fish. The following benefits were observed:
- Blood parameters: Increased levels of hemoglobin and higher red and white blood cell counts, suggesting improved oxygen transport capacity and immunocompetence.
- Lipid metabolism: A decrease in serum cholesterol and triglyceride levels was recorded.
- Immune system: Lysozyme activity and the phagocytic rate, two key indicators of the innate immune response, increased significantly. The concentration of Immunoglobulin M (IgM) was also higher, pointing to a more robust adaptive immune response.
- Antioxidant defense: The activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) was enhanced, indicating that the fish were better protected against oxidative stress.
Intestinal health: The key to better absorption
One of the most significant revelations of the study was the effect of HEOs on the intestinal structure. Histological analysis showed that fish fed the 30 and 60 mL/kg diets developed taller intestinal villi, with greater branching and a larger absorptive surface area.
Stay Always Informed
Join our communities to instantly receive the most important news, reports, and analysis from the aquaculture industry.
This morphological improvement is fundamental, as a healthier intestine with a larger surface area allows for more efficient nutrient absorption, which directly explains the enhanced growth and reduced FCR observed in these groups.
Gene expression analysis: What do the genes tell us?
To understand the molecular mechanisms behind these benefits, the researchers analyzed the expression of several genes. The findings confirmed the physiological observations:
- Growth genes: The expression of key genes in the growth axis, such as the growth hormone receptor (GHr) and insulin-like growth factor I (IGF-I), increased significantly in the 30 and 60 mL/kg groups.
- Intestinal integrity genes: Genes such as ZO-1 and occludin, which are responsible for maintaining a strong and tight intestinal barrier, also showed higher expression, corroborating the improvement in intestinal health.
- Stress gene: The expression of the heat shock protein 70 (HSP70) gene, a known indicator of cellular stress, was reduced in the groups with optimal doses, suggesting greater resilience and well-being.
Conclusion
This study conclusively demonstrates that supplementation with a blend of herbal essential oils, within a range of 30 to 60 mL/kg of feed, is a natural and effective strategy for improving the productive performance, health, and efficiency of Nile tilapia farming.
HEOs act on multiple levels by enhancing nutrient digestion and absorption, strengthening the immune and antioxidant systems, and positively regulating the expression of key genes. These findings offer producers a valuable tool to optimize their operations and advance toward more sustainable and profitable aquaculture.
Reference (open access)
Khalafalaa, M., Shehab, S. M., Aboraya, M. H., Amer, A. A., Farrag, F., Abdelghany, M. F., Alotaibi, B. S., Abdelmegeid, M., Shukry, M., & Elolimy, A. A. (2025). Herbal essential oils improve growth, antioxidant response, and gene expression in Nile Tilapia fingerlings. Frontiers in Veterinary Science, 12, 1620632. https://doi.org/10.3389/fvets.2025.1620632
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
