Effect of dietary nanosilver on gut proteases and general performance in Zebrafish (Danio rerio)

The present study was conducted to evaluate the effect of dietary inclusion of silver nanoparticle on general performance and digestive proteases in zebra fish. Four experimental diets were designed with a concentration of 5, 20 and 40 parts per billion (ppb) nanoparticles in the diet (named S5, S20, and S40, respectively) and control group without any nanoparticles (S0). There was no significant difference was observed in FI and FCR between the dietary treatments. At the end of the experiment, S20 exhibited highest WG and SGR followed by S40 compared with other treatments while, there was no significant difference observed between S0 and S5. Similar trends were also observed in total protease enzyme activity. To evaluate the protease enzyme patterns on gut extract, substrate SDS-PAGE was performed and the inhibition of zymogram was studied. The results showed that there was no difference in banding patterns between S0 and S5 with EDTA treated samples whereas two extra bands of molecular weight (MW) 67 and 37 appeared in S20 and S40, were inhibited by EDTA indicating the presence of metalloprotease in those dietary regimes. There were no differences in the banding patterns of PMSF treated samples suggesting that the total serine protease remains unaffected by the dietary regimes. To conclude, we found 20 ppb inclusion of silver nanoparticle in fish diet improves general performance and induces metalloprotease activity in fish. Further detailed study is required before establishing dietary inclusion of silver nanoparticle for industrial purposes.