Age-Dependent Impact of Dietary Supplements on Gross Energy Content in Worker Honey Bees (Apis mellifera carnica, Pollmann 1879)

Nutritional supplementation with pollen and protein-based patties is widely used in apiculture to support honey bee (Apis mellifera carnica) colonies during periods of limited natural forage, particularly in early spring and late summer. This study evaluated the effects of different supplemental diets on the survival, food intake, and gross energy content of caged adult worker bees of mixed ages under controlled laboratory conditions. Worker bees were fed four different diets: sucrose syrup (control), sugar patty, protein patty, and pollen patty. Survival, food intake, and gross energy content were assessed over an 18-day experimental period. Survival differed significantly among dietary treatments in both spring and summer experiments, with the highest final survival observed in bees receiving sugar patty (HBP). Aged-related differences in survival were treatment-dependent. Descriptive calorimetric data showed that bees receiving the pollen-enriched patty (HBP-PO) had the highest mean GE of bee body (22.05 ± 0.38 MJ/kg), with similarly high values observed in the 18-day old bees (22.28 ± 0.18 MJ/kg) and 20-day old bee workers (22.26 ± 0.23 MJ/kg). Notably, the GE content of the experimental diets did not correspond directly to the GE measured in bee bodies: the sucrose syrup had the highest dietary GE (16.56 ± 0.01 MJ/kg), whereas bees fed pollen-enriched patty showed the highest descriptive mean GE despite this diet having the lowest GE among the tested patties. These findings indicate that dietary caloric density alone may not predict the energetic status or survival of worker bees and suggest that diet composition and worker age contribute to different physiological responses to supplemental feeding. The experiment was conducted under controlled cage conditions; further studies at the colony level under apiary conditions are needed to determine whether these individual-level responses are maintained within functioning honey bee colonies.