Effect of zinc oxide sources and dosages on gut microbiota and integrity of weaned piglets.

Abstract

Zinc oxide (ZnO) supplied at pharmacological dosage in diets of weaned piglets improves growth performance. However, it causes environmental contamination and induces bacterial antibiotic resistance, yet this practice is debated. The effects on gut microbiota and integrity in weaned piglets of conventional ZnO at nutritional and pharmacological dosage (110 and 2,400mg/kg Zn, respectively) were compared to an alternative ZnO source at 110 and 220mg/kg Zn. Each of the four treatments was applied to four pens (two piglets/pen; weaning age, 20days) for 15days, and piglets were sampled on day 15 to determine indices of gut integrity. Feeding conventional ZnO at 2,400mg/kg Zn reduced coliforms and Escherichia coli in distal small intestine as compared to conventional ZnO at 110mg/kg (-1.7 and -1.4 log10 cfu/g, respectively), whereas the alternative ZnO reduced only coliforms, irrespective of dosage (-1.6 to -1.7 log10 cfu/g). Transepithelial electrical resistance of distal small intestinal mucosa was higher for pigs fed the alternative ZnO source as compared with groups fed 110mg/kg Zn of conventional ZnO, in line with a trend for higher gene expression of claudin-1 and zona occludens-1. Interestingly, the alternative ZnO source at 110 and 220mg/kg Zn increased intestinal alkaline phosphatase gene transcript as compared to conventional ZnO at 110mg/kg Zn, whereas the alternative ZnO source at 110mg/kg Zn exhibited higher Zn concentrations in mucosa (2,520μg/g) as compared to conventional ZnO at 110mg/kg Zn (1,211μg/g). However, assessing alkaline phosphatase activity, no significant effects were found. In conclusion, the alternative ZnO reduced digesta Enterobacteriaceae numbers and improved gut integrity, albeit similar or better, depending on the dosage, to the effects of pharmacological dosage of conventional ZnO.