Influence of Pollen Patty Composition and Carbohydrate Types on Honey Bee Longevity and Physiological Health

The Western honey bee (Apis mellifera) plays a critical role in global agriculture through crop pollination and ecosystem stability. However, recent population declines have raised serious concerns. Among the contributing factors, poor nutrition is a major contributor to colony losses, prompting beekeepers to supplement carbohydrate and protein sources during periods of nectar and pollen dearth. In this study, we evaluated the combined effects of two carbohydrate sources (corn syrup and sugar syrup) and three pollen types (rapeseed, kiwi, and mixed pollen) on honey bee longevity and physiological responses. Bees fed corn syrup (CS) exhibited significantly longer lifespans and larger hypopharyngeal glands (HPG) compared to those fed sugar syrup (SS). Among the pollen types, rapeseed pollen (RP) supported higher survival rates and vitellogenin expression than kiwi pollen (KP), while mixed pollen (MP) yielded the best overall outcomes, including enhanced survival, larger HPG size, and increased vitellogenin gene expression. Bees receiving the corn syrup-mixed pollen combination (CS-MP) showed the longest lifespans, highest survival rates, and lowest food consumption, indicating improved nutritional efficiency. This group also exhibited the most developed HPG acini and elevated vitellogenin levels, reflecting superior physiological condition. Gut microbiota analysis further revealed that diet significantly influenced microbial composition. Bees fed CS had higher abundances of Commensalibacter while higher abundances Snodgrassella observed in SS-fed bees. Furthermore, MP-fed bees exhibited significantly higher levels of Lactobacillus. These findings underscore the importance of optimizing both carbohydrate and pollen sources in honey bee diets to promote longevity, physiological health, and gut microbiota balance, offering valuable insights for enhancing colony management and resilience.