Effects of Dietary Supplementation of Zinc Oxide Quantum Dots on Growth Performance and Gut Health in Broilers

This study aims to investigate the effect of different levels of zinc oxide quantum dots (ZnO-QDs) on the growth performance and gut health in broilers. A total of 1125 1-day-old Ross 308 broilers were randomly divided into five groups with 15 replicates of 15 chicks each. The broilers were fed basal diets supplemented with 0, 40, 80, 120, or 160 mg Zn/kg as ZnO-QDs for 6 weeks. The results showed that dietary 80 and 120 mg Zn/kg ZnO-QD supplementation increased (P < 0.05) average daily gain (1.4-1.7%) and reduced feed conversion ratio (1.3%) compared to the basal diet group during various experimental periods. Meanwhile, 80 mg Zn/kg ZnO-QD supplementation increased (P < 0.05) trypsin activity (25.4%), villus height, and the ratio of villus height to crypt depth in the jejunum. Moreover, 80 mg Zn/kg ZnO-QD supplementation increased (P < 0.05) the activities of glutathione reductase (47.7%) and superoxide dismutase (30.9%), while 120 mg Zn/kg ZnO-QD supplementation decreased (P < 0.05) glutathione peroxidase activity (27.1%) in the jejunum. Furthermore, 40 mg Zn/kg ZnO-QD supplementation down-regulated (P < 0.05) the expression of genes; interleukin-2, transforming growth factor beta (TGF-beta), Cathelicidin-1, Cathelicidin-2, Cathelicidin-3, and Occludin, while 80-160 mg Zn/kg ZnO-QD supplementation up-regulated (P < 0.05) Claudin-2 expression in the jejunum. In conclusion, dietary ZnO-QD supplementation improved growth performance of broilers potentially by enhancing their intestinal health status. Based on nonlinear regression analysis, the appropriate level of ZnO-QD supplementation would be from 98.2 to 102.5 mg Zn/kg.