Abstract: Koi carp Cyprinus carpio with initial body weight of(52.99±1.95)g was reared in net cages at a density of 30 fish per cage and fed six isonitrogenous(38.5%-38.6%,crude protein)and isocaloric(12.2 MJ/kg)diets containing 0(control,D1),3%(D2),6%(D3),9%(D4),13%(D5),and 14%(D6)dry duckweed meal replacing corresponding rapeseed meal at water temperature of(29.0±1.1)℃or 8 weeks with triplication to evaluate the effects of dietary duckweed levels on growth,antioxidant ability,and digestive ability of koi carp.The results showed that there were significantly higher weight gain rate(WGR),specific growth rate(SGR),protein efficient ratio(PER)and condition factor(CF)and significantly lower food conversion ratio(FCR)in the fish in group D6 than those in the control group and in group D2(P＜0.05).The koi carp fed the diet containing 14%duckweed had significantly higher activities of protease and lipase than the fish in other groups did(P＜0.05),without significant differences in amylase activity(P＞0.05).There were significantly higher activities of superoxide dismutase(SOD)and catalase(CAT)in hepatopancreas,kidney,spleen and serum in the fish fed the diets containing 9%and 14%duckweed meal than those in the other groups(P＜0.05),with significantly lower contents of malondialdehyde(MDA)in the fish fed the diets containing 14%duckweed(P＜0.05).The findings indicate that supplementation of 14%duckweed replacing corresponding rapeseed meal can improve the growth,and meet requirements for antioxidant ability and digestive capacity of koi carp.
2017, Vol. 32 
