A project tested the use of locally-available essential oils as a safer and more natural way to improve the growth and disease resistance of saline-tolerant tilapia raised in hatcheries and nurseries.
Disease outbreaks and poor culture conditions continue to cause mortalities in tilapia farms. The use of antibiotics to control these diseases can also have negative effects on the environment thus, there is a need for alternative ways to protect farmed fish.
To address this concern, the project, “Development of Locally-Available Essential Oil as a Growth-Promoting and Antimicrobial Feed Additive for Saline-Tolerant Tilapia (Oreochromis niloticus),” developed essential oil-based feed additives that could help improve fish growth, health, and resistance to disease. The project is implemented by the University of the Philippines Visayas (UPV) and funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development of the Department of Science and Technology (DOST-PCAARRD).
(1:1 molar ratio of β-CD to citronella EO). (Image credit: UPV project team)
The project team screened around 15 essential oil products to determine whether they could fight bacteria commonly associated with fish diseases, including Aeromonas, Vibrio, and Pseudomonas species. At least three essential oils showed broad antibacterial activity, namely: citronella (Cymbopogon winterianus); calamansi (Citrofortunella macrocarpa); and lemongrass (Cymbopogon citratus).
After completing the screening process, the project also explored the development of an encapsulated product from the selected essential oils. Encapsulation is a process of coating the ingredients into a protective shell.
Results of the study revealed promising antibacterial properties of the natural essential oils. Although the calamansi essential oil showed reduced antibacterial activity after encapsulation, citronella oil, rich in Geraniol, exhibited antibacterial activity in a wide range of bacterial species-broad spectrum. Similarly, lemongrass oil, which contains Citral, showed an even stronger antibacterial activity. D-limonene, a major component associated with calamansi oil, is more volatile than the two compounds.
With these results, the lemongrass and levels of citronella essential oil (EO) were tested as feed additives for saline-tolerant tilapia during hatchery and nursery phases in UPV. The oils were tested in different forms, including as a feed premix and as a coating applied directly to the feed.
Based on the results, citronella essential oil supplementation at a certain dose shows positive impact on improving the growth performance of the tilapia through the enhancement of metabolic efficiency and modulating the gut microbiota, without disrupting microbial diversity or host immune balance.
These findings show that citronella EO has a potential as a functional feed additive in aquaculture. Additionally, lemongrass EO shows potential as a natural and sustainable alternative to antibiotic growth promoters in aquaculture, capable of improving host performance and health through integrated effects on immunity, gut morphology, and micro biome dynamics.
However, both citronella and lemongrass EO need to be further applied to larger sample sizes and subjected to functional analyses and validation, to better confirm the findings, refine application for commercial use, and confirm mechanisms of action and long-term effects. Additionally, the project noted that excessive EO supplementation may exert inhibitory effects, emphasizing the importance of dose optimization.