The dose makes the poison: feeding of antibiotic-treated winter honey bees, Apis mellifera, with probiotics and b-vitamins

Honey stores of Apis mellifera colonies are replaced with sugar water by beekeepers, which may result in malnutrition. Nutritional supplements have been developed, but the importance of bacterial probiotics and vitamins is poorly understood. Given that supplementary feeding with vitamins and probiotics enhances worker weight and longevity, this would suggest a feasible approach to mitigate winter colony losses. Here, we conducted a laboratory hoarding cage study with freshly emerged winter bees, which were treated with the antibiotic tetracycline to reduce gut bacteria and subsequently assigned to feeding regimes: sucrose only, sucrose + pollen, probiotics (low and high dosage), probiotics + pollen (low and high dosage), or b-vitamins (low and high dosage), (N=8 treatments, 29 workers/cage x8 replicates). In parallel, controls remained on their frame (=Frame) to establish their gut microbiota and were subsequently fed with sucrose only or sucrose + pollen (N=2 treatments, 29 workers/ca...