Abstract
The European honey bee (Apis mellifera L.) is known to be affected by such stress factors as pathogen load, poor nutrition and depressed immunity. Nosema ceranae is one of the main parasites that affect colony populations. The relationship between the stress factors and honey bee-bacteria symbiosis appears as an alternative to enhance bee health. The aim of this study was to evaluate the effect of the oral administration of bacterial metabolites produced by Lactobacillus johnsonii AJ5 on nutritional parameters, the N. ceranae development and the performance of A. mellifera colonies. Laboratory assays were performed and demonstrated that the bacterial metabolites did not have a toxic effect on bees. Field trial showed an increase of colonies population over time. Also, a decreasing trend of fat bodies per bee was detected in all colonies but there were no evident changes on abdomen protein content at the end of the assay. Lastly, N. ceranae prevalence showed a tendency to reduce with the organic acids. Future studies should be performed to increase our knowledge of the physiological effects of bacterial metabolites on the health of bee colonies.