Dietary zinc oxide is often used in pharmacological concentrations to promote
health as well as performance of weaned piglets due to its bacteriostatic
effects. This study was conducted to provide an in depth analysis of the
bacterial composition in weaned piglets fed different amounts of dietary zinc
oxide. Piglets were fed diets containing 57 (low), 164 (medium) or 2425 (high)
mg/kg dietary zinc. Zinc above the basal dietary level was supplied from
analytical grade zinc oxide (ZnO). DNA was extracted from stomach and ileum
digesta samples of 32 and 53d old animals (n=4 per group) and used to generate
bar-coded 16S ribosomal DNA amplicons for deep sequencing analysis. A total of
9 phyla, 40 orders, 75 families and 328 genera were detected in 8.76 x 105
sequencing reads. Firmicutes, Bacteroidetes and Proteobacteria were the
dominant phyla, but no significant differences between treatment groups were
observed. Lactobacillales (16.3-59.9%), Bacteroidales (2.2-59.1%),
Clostridiales (0.05-70.2%) and Selenomonadales (2.6-17.5%) were found as the
dominating order. Noteworthy changes on the order level were found for
numerically or significantly increased ratios of Clostridiales, but
significantly decreased Lactobacillales in the high dietary zinc group. The
bacterial diversity for the high dietary zinc diet was significantly higher
for the total microbiota than the medium or low zinc diet. However,
Lactobacillales diversity decreased, while Clostridiales and Enterobacteriales
diversity increased significantly. Principal component analysis confirmed
changes in the microbiota, most notably for the high dietary zinc treatment.
This study has shown that pharmacological doses of high dietary zinc can
drastically alter the bacterial composition and development of the microbiota
in weaned piglets. The quantitative shift of bacterial groups due to high
dietary zinc was most pronounced one week after weaning, while the more
developed microbiota in older animals seemed to be able to adapt to high
concentrations of dietary zinc