Abstract

This study examined the effects of dietary supplementation of nevadensin, a flavonoid isolated from rice paddy herb (Limnophila aromatica), ongrowth and physiological parameters of hybrid catfish (Clarias macrocephalus × C. gariepinus). Fish (initial weight of 5.00±1.00 g) were fed with the diets containing 0 (control), 10, 30, and 50 mg nevadensin/kgfeedfor 8 weeks. Growth parameters,feed intake, and feed efficiency were significantly improved (P<0.05) by the diets containing30 and 50 mg nevadensin. Survival rate and organosomatic indices for the intestine, gill, heart, kidney, and spleen were notsignificantly different (P>0.05) among the groups. However, the hepatosomatic index in fish fed with 30 mg nevadensin/kg diet was significantly increased (P<0.05) when compared with the control. A significant improvement (P<0.05) in villi heights, muscular thicknesses,goblet cells,and microvilli heights was detected infish fed with nevadensin containing diets. Villi widths, total enterocyte heights, and supranucleus heights decreased significantly (P<0.05) in fish fed withnevadensin supplemented diets. Red blood cells and white blood cellsin fish fed with supplemented diets were significantly higher (P<0.05) thanthose in fish fed with the controldiet. Hemoglobin and hematocrit significantly increased (P<0.05) in fish fed with 50 mg nevadensin/kg diet compared to the control. The highest level of lymphocyte was observed in fish fed with10 mg nevadensin. Blood biochemical valueswere not significantly different (P>0.05) in any of the treated groups compared to the control. In conclusion, the results indicate that nevadensin could be used as a natural feed additive to improve somatic growth and physiological parameters of hybrid catfish. By using the second-order polynomial regression analysis, the optimal concentration of nevadensin for cultured catfish was estimated to be between 30.64 and 31.14 mg/kg diet.

Keywords: Flavonoid, Fish, Intestinal histology, Growth promoters,Phytogenic compounds