The impact of winter feed type on intestinal microbiota and parasites in honey bees

The intestinal microbiota of honey bees consists of only few bacterial species and may have effects on health and pathogen resilience. Honey is usually harvested and replaced by sugar syrup. We hypothesized that replacing honey may change the composition of the intestinal microbiota, and therefore compromise pathogen resilience. Fifteen colonies were fed with wheat starch syrup, sucrose syrup, or blossom honey. 16S-based bacterial community analysis was performed on three individuals per hive in summer and winter, and Nosema ceranae and Crithidia/Lotmaria levels were assessed by qPCR. Seasonal differences in the intestinal microbiota and N. ceranae were found; however, microbiota and parasite levels were very similar between the feed types. Rhizobiales and Bifidobacteria were found to be increased in the bees that had received honey or wheat starch syrup, as compared to sucrose syrup. In conclusion, intestinal microbiota and parasites were found to be largely unaffected by the winter feed type.