Author(s): Supranee Wigraiboon, Nakao P Nomura and Niwooti Whangchai

Abstract: This study investigated the effects of essential oils from Houttuynia cordata Thunb as diet supplements on growth performance and immune responses of Hybrid red tilapia. H. cordata Thunb essential oils (HEO) were extracted using hydrodistillation and analyzed by gas chromatography-mass spectrometer (GC-MS). Beta-myrcene (44.220%) and 2-undecadone (21.985%) were the major components out of the 28 components present. The in vitro antibacterial activity of HEO showed minimal inhibitory concentration (MIC) against Aeromonas hydrophila, Streptococcus sp. and Flavobacterium columnare at 250, 250 and 500 ppm, respectively (Ampicillin sodium exhibited similar MIC values against the bacteria used). The in vivo analysis on growth performance of Hybrid red tilapia fed with three diet containing HEO 0, 1.5 and 3.0 g/kg showed no mortality after the 60 days experiment period. Also, weight gain and average daily growth of Hybrid red tilapia fed with HEO 1.5 g/kg were the highest among the other setups (p<0.05). Feed conversion ratio of HEO 1.5 g/kg was significantly (p<0.05) lower than the control and HEO 3.0 g/kg. It was also found out that the lysozyme activity of Hybrid red tilapia was improved in fish fed with HEO 1.5 g/kg (p<0.05), while the lowest values were obtained in the HEO 3.0 g/kg. However, no significant difference was observed in hematocrits, red blood cells and white blood cells values among all treatments (p>0.05). These results indicate that essential oils from H. cordata Thunb has a good potential as growth enhancer and can possibly replace antibiotics in enhancing fish immune response.

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