Investigation of the effects of Dictyota ciliolata extract on growth performance, feed utilisation, haemato-biochemical indices, hepatic antioxidants activities and immune responses of Clarias gariepinus

Seaweeds and their derived products represent huge resources that are still underexploited as functional ingredients in fish feeds. This study evaluated the growth performance, nutrient utilisation, antioxidation status, and immunity of Clarias gariepinus fed diets containing Dictyota ciliolata extract (DCE). Ethanolic extract of the brown seaweed D. ciliolata was obtained using the Maceration extraction method. Afterwards, four diets were prepared with DCE at inclusion levels of 0 g/kg (control), 0.25 g/kg (DCE-0.25), 0.5 g/kg (DCE-0.5) and 1.0 g/kg (DCE-1.0). One hundred and twenty fish (14.47 g/fish) were allotted to four triplicate groups (10 fish per group) and fed thrice daily with diets containing DCE at various graded levels. At the end of the feeding trial, there were no statistical differences (p > 0.05) in final weight, weight gain and specific growth rate among the dietary group. Fish fed DCE-based diet had lower feed conversion ratio and higher protein efficiency ratio that differs significantly (p < 0.05) from the control. Erythrocytes and leukocytes were significantly higher (p < 0.05) in C. gariepinus fed DCE-0.25 and DCE-0.5 diets in comparison to the control. The liver function enzyme alkaline phosphatase was higher (p < 0.05) in fish fed DCE-0.5 and DCE-1.0 diets than the control and DCE-0.25 groups. Dietary DCE improved antioxidant activities and decreased peroxidation of lipid in the hepatic tissue of C. gariepinus. The cytokines (Tumour Necrosis Factor – alpha, Interleukin-6, Interleukin-1 Beta) were significantly elevated (p < 0.05) in the liver tissue of C. gariepinus fed DCE-based diets. Therefore, these results indicate that fish fed DCE diet had better nutrient utilisation, enhanced antioxidants activities and immune responses, suggesting the high suitability of D. ciliolata extract as a functional ingredient to improve the welfare of C. gariepinus.