Honey bee colonies provided with natural forage have lower pathogen loads and higher overwinter survival than those fed protein supplements

Malnutrition is a major cause of colony losses. In managed hives, bees are fed protein supplements (PS) during pollen shortages. If bees were provided with natural forage instead of PS, would they have lower pathogen levels and higher queen and colony survival? We addressed this question by either providing colonies with forage (Brassica rapa—rapini) or feeding them PS from November to February. Soluble protein concentrations in the PS were lower than the rapini pollen as were levels of most amino acids. Nurse bees digested less of the protein in PS than the pollen. Hemolymph protein titers in nurse bees and colony growth did not differ between those fed PS or foraging on rapini. However, colonies fed PS had higher levels of black queen cell virus and Nosema and greater queen losses, indicating that natural forage might improve overwintering survival.