Growth performance of Clarias gariepinus (Burchell, 1822) Fed Diets Fortified with Lemongrass (Cymbopogon citratus)

The utilization of synthetic antibiotics in the production of food fish is a concern globally due to the development of antibiotic-resistant bacteria and the residual effects of these drugs. This study investigated the in vitro antimicrobial activity and growth-promoting effects of lemongrass meal (LGM) in Clarias gariepinus fingerlings. The fish were fed diets (40% crude protein) fortified with 0, 5, 10, and 15gLGM/kg lemongrass meal, and a 3g Oxytetracycline (OTC)/kg diet was used as the negative control for 70 days. Data on the zones of inhibition (ZI), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and optimum inclusion level was obtained. Higher ZI was obtained from OTC against Aeromonas hydrophila, while higher ZI was obtained from lemongrass extract against Pseudomonas putida. Feeding C. gariepinus fingerlings with 10gLGM/kg diet significantly enhanced WG, SGR, and PER, compared to the control treatments. The FCR (1.40) was significantly reduced in fish fed a 10gLGM/kg diet, compared to the control and other LGM-fortified treatments. The quadratic regression analysis showed 0.83% and 0.86% as optimum inclusion levels for WG and FCR, respectively. The results from this study suggested that lemongrass possesses antibacterial properties and that the meal could be included in the fish diet at 10 g/kg as a natural growth promotant.