Intensive culture systems are pivotal for meeting the growing demand for fish production. However, these systems often expose fish to stressful environmental conditions, which can compromise growth performance and reduce resistance to infectious diseases, particularly those caused by bacterial pathogens. In response to concerns over the use of traditional chemotherapeutics, recent research has increasingly focused on essential oils as sustainable and effective alternatives for disease management in aquaculture. The present study evaluated the efficacy of the microencapsulated lemongrass essential oil (EO) as a growth-promoting and antimicrobial feed additive for the hatchery phase of saline Oreochromis niloticus.
A three-week feeding trial was conducted to assess the effects of varying concentrations (0.5%, 1.0%, 2.0%, 4.0%, and 8.0%) of lemongrass-EO on growth performance, feed utilization efficiency, muscle growth-related gene expression, and gut microbial load compared to untreated control groups.
Results demonstrated dose-dependent effects, with optimal growth performance observed in groups receiving 0.5% lemongrass-EO supplementation, while growth was significantly suppressed at 8.0% inclusion levels. Feed utilization efficiency negatively correlated with dietary inclusion rates exceeding 4.0%. Molecular analysis revealed that 0.5% lemongrass-EO supplementation significantly upregulated the expression of myogenic regulatory factors, with 124% and 240% increases in myoD and myoG gene expression, respectively, compared to controls. Conversely, expression levels of these genes decreased by 38% (myoD) and 26% (myoG) in the 8.0% treatment group. Despite variable effects on growth parameters, fish survival was not negatively affected across all treatment groups. Microbiological analysis demonstrated significantly reduced bacterial loads in the gut of fish fed lemongrass-EO-supplemented diets compared to control groups.
This study demonstrates the potential of essential oils, specifically microencapsulated lemongrass oil, as sustainable alternatives to conventional antimicrobial agents in aquaculture feeds, with optimal inclusion rates of 0.5% promoting both enhanced growth performance and reduced bacterial load in O. niloticus during hatchery production.