Evaluation of Citronella Essential Oil as a Functional Feed Additive for Improving Growth Performance, Nutrient Utilization, Tissue Health, and Antioxidant Defense in Common Carp (Cyprinus carpio)

Abstract

The current study evaluated the impacts of supplementation of Citronella Essential Oil (CEO) on feed utilization, macro nutritional profile, liver histology, and detoxifying enzyme activity in common carp (Cyprinus carpio). Eighty healthy fingerlings were randomly assigned to four treatment groups and fed diets supplemented with different levels of CEO: 0% (G₁ Control) 0.5% (G₂), 1.0% (G₃), and 1.5% (G₄) for a period of 10 weeks. The parameters of growth performance, feed utilization, free amino acids, total lipid levels, liver histological observations, and the level of detoxifying enzymes were measured at the end of the trial. Fish fed with 1% CEO diet (G3) not only had the best feed conversion ratio (4.77 ± 0.18), but they also exhibited the greatest weight gain (34.33 ± 1.24 g), specific growth rate (0.716 ± 0.021% day^-1), feed intake (163.67 ± 1.53 g), and efficiency of feed conversion ratio (0.210 ± 0.013) compared to the non-CEO supplemented diets. In addition to the results mentioned above, fish in the CEO-supplemented groups showed significantly elevated amounts of free amino acids and total lipids relative to those in the P diet group. Histological examination revealed mild hepatic alterations in CEO-treated fish, although overall liver architecture remained preserved. In addition, there were significant increases in detoxifying enzyme activities of glutathione-S-transferase and total esterases in both supplemented groups. Based on the results, it is concluded that citronella essential oil can be used as a natural feed additive to improve growth rate, nutrient utilization, physiological health, and metabolic performance of common carp; G3 fish with 1% CEO had the best results.