Effects of dietary kaffir lime, Citrus hystrix DC, leaf powder on the growth performance, digestive enzyme, hematology, antioxidative response, and disease resistance against Edwardsiella tarda infection in African catfish, Clarias gariepinus

Abstract

This study evaluated the effects of kaffir lime (KL), Citrus hystrix, leaf powder on growth performance, digestive enzyme activities, blood and antioxidant parameters, and disease resistance in African catfish, Clarias gariepinus. A total of 450 healthy juveniles (10.5 g) were randomly distributed into five groups and fed diets containing 0% (control), 1%, 2%, 3%, and 4% of KL for eight weeks. At the end of the feeding trial, 10 healthy fish from each group were challenged with Edwardsiella tarda infection. The study findings demonstrated significant differences in all growth parameters, including final weight, weight gain, specific growth rate, feed conversion rate, hepatosomatic percentage, and viscerosomatic index between dietary KL and control groups, with the group fed 2% and 3% KL exhibiting superior performance (p < 0.05). Dietary KL significantly increased white blood cells, red blood cells, hemoglobin, and hematocrit (p < 0.05) in African catfish, with the highest values observed in the 2% and 3% KL groups. Meanwhile, there were no significant differences in mean corpuscular hemoglobin and mean corpuscular hemoglobin concentrations between treatments. Furthermore, dietary KL significantly increased digestive enzyme activities, including lipase, amylase, and protease (p < 0.05), and the highest activities were observed in fish fed 2% and 3% KL. Antioxidative responses, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in KL-treated fish, were also significantly higher than the control group (p < 0.05). Finally, the highest and the lowest cumulative survival rates following a challenge with E. tarda were 3% KL and control groups, respectively. Based on the study results, 2% or 3% dietary KL could improve the growth and health of African catfish, thus enhancing aquaculture production.