EFFECT OF DIETARY NANO-ZINC OXIDE ON GROWTH AND CALPAIN ACTIVITY OF Pangasianodon hypophthalmus (SAUVAGE, 1878)
Zinc is one of the important micronutrients required by all organisms throughout their life in minor quantities to perform a wide range of physiological functions. Fishes accumulate zinc both from water and dietary sources. However; dietary zinc is more efficiently absorbed than waterborne zinc. Calpains are important proteolytic enzymes which hydrolyze myofibrillar proteins which contributes to rapid softening of flesh. The dietary zinc can chelate the available calcium in the body and thus make it unavailable for the calpain to act. In the present study, an attempt was made to investigate the role of nano-zinc oxide (nano-ZnO) as a dietary supplement and its effect on the growth and calpain activity of Pangasianodon hypophthalmus against a control group fed with normal inorganic zinc.
A 30 day feeding trial was conducted to study the impact of dietary nano-zinc oxide on the growth and muscle development in P. hypophthalmus. Three experimental feeds were prepared with different concentration of nano-ZnO (30, 65 and 100 mg nano-ZnO Kg-1 Diet) based on LC50 value against a control feed (T0) with inorganic zinc (30mg kg-1).One hundred and twenty fishes with an average weight of 7.5 ± 0.5g were randomly distributed in four treatments with triplicates.
Specific Growth Rate (SGR) data shows highest growth was shown by the control group compared to all other groups followed by the group fed with 65 mg nano-ZnO Kg-1 diet. The least growth was shown by the group fed with 100 mg nano-ZnO Kg-1 diet (T3) due to its toxic effects.The calpain activity was higher in T1 group which showed the lowest zinc accumulation. The low zinc concentration in carcass with high calpain activity in T1 indicate the chelation of calcium by zinc is less in this group and the calcium dependent calpain activity was least in T0 group due to strong chelation of available calcium by zinc. Overall, it can be concluded that nano- ZnO reduce growth in high concentration. However, 65mg kg-1 nano-ZnO can be incorporated in P. hypophthalmus diet without any detrimental effect on growth and calpain activity.
