Effects of Nano-zinc and Nano-zinc-polysaccharide on Growth and Immunity in Rainbow Trout Oncorhynchus mykiss

A feeding trial was conducted to evaluate the effects of nano-zinc and nano-zinc-polysaccharide on growth and immune in rainbow trout(Oncorhynchus mykiss). Three hundreds individuals of rainbow trout with body weight of(120±3.0) g were randomly allotted to 5 groups(3 replicates and each 20 fish), and injected 1000, and 3000 mg/kg nano-zinc and nano-zinc-polysaccharide according to 1 μL/g body weight and fed a basal diet supplemented with nano-zinc and its polysaccharide for 10 days. The results showed that nano-zinc and nano-zinc-polysaccharide differently promoted the special growth rate(P<0.05). The percentage of NBT in the 1000 mg/kg nano-zinc-polysaccharide was increased by 22.3%(P<0.05) on the third day, with the maximal phagocytic percent in the 3000 mg/kg nano-zinc-polysaccharide on the sixth day. The serum bactericidal percent in the 3000 mg/kg nano-zinc was increased by 19.4%(P<0.05) on the third day, but that in the 3000 mg/kg nano-zinc-polysaccharide was increased by 32.43%(P<0.05) on the sixth day. The activities of catalase(CAT) and NOS in the serum of rainbow trout in the 1000 mg/kg nano-zinc-polysaccharide group were 26.39 U/mL and 43.38 U/mL(P<0.05) on the third day;the activities were 29.9 U/mL in SOD, 201.4 U/L in ACP, and content of 3.19 nmol/mL in MDA(P<0.05) on the sixth day. After the feeding trial, Aeromonas salraonicida injection challenged during 7 d was executed to test the effects of nano-zinc and nano-zinc-polysaccharide. There was mortality of 30% in the 1000 mg/kg nano-zinc-polysaccharide group. It is concluded that supplementation of nano-zinc and nano-zinc-polysaccharide can improve the immunity of rainbow trout, and that 1000 mg/kg nano-zinc-polysaccharide is the optimal dose.