Effects of Replacing Pharmacological Levels of Dietary Zinc Oxide with Lower Dietary Levels of Zinc Oxide Nanoparticles for Weaned Piglets

Pharmacological dosage (3,000 mg/kg) of zinc oxide (ZnO) in pig nursery diets was commonly used to improve growth performance and gut health. However, high zinc excretion in animal wastes poses environmental contamination. Zinc oxide nanoparticles (nano-ZnOs) with small size and bigger specific surface area is potential to be used as a substitute of pharmacological ZnO. This study aimed at comparing the effects of nano-ZnOs with conventional ZnO. One hundred and fifty crossbred (Landrace × Large White × Duroc) weaned piglets (9.37 ± 0.48 kg BW) were randomly allotted to 5 dietary treatments with 3 replicates for 21d, including a basal diet (BD), the BD + 150, 300, or 450 mg/kg Zn from nano-ZnOs, and the BD + 3,000 mg/kg Zn from conventional ZnO. After the feeding trial, six pigs from BD, 450 mg/kg nano-ZnOs, and 3,000 mg/kg ZnO treatments were selected and slaughtered to collect samples. All studied parameters were analyzed with one-way ANOVA taking into account the experimental treatment as the main factor with α level of 0.05. Supplementation of either 300, 450 mg/kg nano-ZnOs or ZnO increased (P < 0.05) ADG, ADFI, and G:F compared with pigs fed the BD. Pigs diarrhea incidence in treatments of 300, 450 mg/kg nano-ZnOs and 3,000 mg/kg ZnO was significantly decreased (57.24, 79.14, and 58.09%, respectively; P < 0.05) compared with that in BD treatment. Supplemental nano-ZnOs and ZnO improved (P < 0.05) the concentration of Zn in serum, heart, liver, spleen, and kidney. Compared with the BD, villus height (V), crypt depths (C), and V/C ratio in pigs supplemented with 450 mg/kg nano-ZnOs exhibited greater (P < 0.05) improvement, and C and V/C ratio of 3,000 mg/kg ZnO were also improved (P < 0.05). The abundance of Escherichia coli community of 450 mg/kg nano-ZnOs was reduced in the cecum, colon, and rectum (13.85, 13.03, and 11.13%, respectively; P < 0.05). The abundance of Lactobacilli, Bifidobacterium and Salmonella community in different large intestine segments did not differ between the treatments. The results indicated that the nano-ZnOs product in low dosage (450 mg/kg) is potential to exhibit beneficial effects in weaned pigs, which are similar to or better than that of pharmacological dosage (3,000 mg/kg) conventional ZnO. Nano-ZnOs may reduce Zn excretion, which consequently may lower the environmental challenges.