LEMONGRASS and citronella essential oils could help improve tilapia growth and health while offering an alternative to antibiotic-based feed additives, according to research funded by the Department of Science and Technology (DOST).
The study, conducted by the University of the Philippines Visayas (UPV) and funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD), examined the antibacterial properties of locally available essential oils and their potential use in feeds for saline-tolerant tilapia.
In a report published Sept. 30, DOST-PCAARRD said tests found that citronella oil supplementation at a particular dose improved the growth performance of tilapia, while lemongrass oil showed potential as a natural alternative to antibiotic growth promoters. Researchers said further testing is needed before the oils can be considered for commercial aquaculture.
The project team initially screened about 15 commercial essential oil products for activity against bacteria associated with fish diseases, including Aeromonas, Vibrio and Pseudomonas species. Citronella (Cymbopogon winterianus), lemongrass (Cymbopogon citratus) and calamansi (Citrofortunella macrocarpa) showed broad antibacterial activity.
Researchers also explored encapsulation, a process that encloses an ingredient in a protective material to help preserve its properties. Encapsulated citronella and lemongrass oils retained antibacterial activity, while calamansi oil showed reduced activity after the process.
The team then tested lemongrass and citronella oils as feed additives for saline-tolerant tilapia during the hatchery and nursery stages. The oils were incorporated into feed premixes or applied as coatings directly onto the feed.
Citronella oil contains geraniol, a compound associated with antimicrobial activity, while lemongrass oil contains citral. The researchers reported that citronella supplementation at a specific dose improved fish growth, potentially through better metabolic efficiency and changes in the gut microbiota, without disrupting microbial diversity or immune balance.
Lemongrass oil also showed potential benefits for fish performance and health through effects on immunity, gut structure and microbial communities, the report said.
The research addresses concerns about antibiotic use in aquaculture, where the drugs may be used to control bacterial infections and promote growth. Inappropriate or excessive use can contribute to antimicrobial resistance and the spread of resistant bacteria, while residues can affect the environment and food safety.
Plant-derived essential oils are being investigated as possible alternatives because they contain biologically active compounds that may help control pathogens and support animal health. Their effectiveness, however, depends on factors including composition, delivery method and dosage.
DOST-PCAARRD said the findings require validation using larger sample sizes and additional functional analyses. Researchers also need to determine the oils' mechanisms of action, refine application methods and establish their long-term effects.
The report cautioned that excessive essential oil supplementation could inhibit rather than improve fish performance, making dose optimization essential before commercial application.
The project, titled “Development of Locally-Available Essential Oil as a Growth-Promoting and Antimicrobial Feed Additive for Saline-Tolerant Tilapia (Oreochromis niloticus),” seeks to develop feed additives that could improve production efficiency and fish health while reducing reliance on conventional antibiotics.