The present study was conducted to investigate the effects of different dietary zinc sources on growth performance, survival, and body composition of larval rainbow trout, Oncorhynchus mykiss. A total of 3240 larvae with an average weight of 82.3 ± 11.6 mg were randomly divided into four groups by three replicates and were fed for 70 days. Organic zinc (Zn-proteinate, Bioplex Zn®), mineral zinc (ZnSO4), and nanoparticulate zinc (ZnO-NPs) were each added to the basal diet at 50-mg/kg diet. In all of the zinc-supplemented groups, final body weight (FBW) and weight gain (WG) increased significantly (P < 0.05) compared to the control at the termination of the feeding trial. There was no significant difference in specific growth rate (SGR) in experimental groups. Fish fed with mineral and nanoparticulate zinc, respectively, demonstrated the highest and lowest survival rates (P < 0.05) as compared to other experimental diets. Feed conversion ratio (FCR) significantly decreased (P < 0.05) in groups fed with organic and mineral zinc. There were no significant differences in protein, lipid, moisture, and ash content among fish fed the experimental diets. Fish fed mineral zinc showed the highest (P < 0.05) zinc content in the whole body than the other groups. The data of the present study confirm positive effects of the use of 50 mg kg−1 of zinc sources in early diet to enhance growth performance of rainbow trout larvae.
