Effects of dietary supplementation with Lippia sidoides essential oil on the growth, histopathological and hematological parameters of koi carp (Cyprinus carpio linnaeus, 1758)

The aim of this research was to evaluate the effects of dietary supplementation with Lippia sidoides essential oil on the hematological, histopathological and growth parameters of koi carp (Cyprinus carpio). A total of 300 fish with an initial average weight of 3.56 ± 0.68 g were randomly distributed in 15 net cages and fed twice daily with diets containing 0.0, 0.25, 0.5, 0.75, and 1.0% essential oil, all in triplicate. Histological and hematological analyses were conducted after 30 and 60 days of feeding, along with growth performance assessment at the conclusion of the 60-day period. No mortalities were observed during the period. Fish in the 0.75% treatment exhibited significantly lower final weight and specific growth rate (p = 0.012 and p = 0.011) compared to fish in the 0.25% treatment and the control group. Histological analysis of renal tissue revealed a significant increase (p < 0.05) in capillary dilation in fish that were fed diets containing 1.0% L. sidoides essential oil compared with those fed diets containing 0.25%, 0.50%, and 0.75% essential oil. Hematological parameters were not altered at any of the essential oil concentrations. Supplementing the diet with L. sidoides essential oil was found to be safe and did not result in any mortality over a 60-day period. Among the treated groups, the 0.25% dose resulted in improved growth. Nevertheless, it is advisable to exercise caution when using higher dosages approaching 1.0%.