Effects of zinc oxide supported on zeolite on growth performance, intestinal barrier function and digestive enzyme activities of Nile tilapia

A total of 720 Nile tilapia fingerlings were allocated to four treatments and used to investigate the effects of zinc oxide supported on zeolite (Z-ZnO) on growth performance and intestinal function. The basal diet (control) was not supplemented with zinc and contained 60 mg Zn kg(-1). The other three groups were added 30 mg Zn kg(-1) to the basal diet, in which zinc was supplemented as Z-ZnO, Z + ZnO (mixture of zeolite and ZnO) or ZnSO4, respectively. As compared to the control, supplemental Z-ZnO improved (P < 0.05) specific growth rate, protein efficiency ratio (PER) and survivor ratio; increased (P < 0.05) villus-height-to-crypt-depth ratio and transepithelial electrical resistance; decreased (P < 0.05) mucosal-to-serosal flux of dextran 4 kDa; and improved (P < 0.05) intestinal activities of protease, amylase, lipase and alkaline phosphatase. Fish fed with Z-ZnO had higher (P < 0.05) specific growth rate and PER, and better intestinal barrier function than those fed with ZnSO4 or Z + ZnO. The zinc concentrations in whole body and vertebrae were not affected by dietary treatments. The results indicated that Z-ZnO improved intestinal morphology, barrier function and digestive enzyme activities. Such changes in intestinal health in the presence of Z-ZnO might contribute to its improvement in growth performance.