Impact of Direct-Fed Microorganism Syrup on Honey Bee (Apis mellifera L.) Hypopharyngeal Gland Development, Protein Digestibility and Gut Microbiota Composition

Honey bees (<i>Apis mellifera</i> L.) are considered highly significant economic insects. It is a source of valuable food and medicinal products such as honey, bee pollen, royal jelly, bee brood, and beeswax, which possess excellent nutritional and pharmacological properties. Nevertheless, honey bee health and productivity were often challenged by various environmental factors. Therefore, bee colony management is of the utmost importance. In this light, bee supplements and gut microbiota are crucial to ensure that bees receive sufficient nutritional value to maintain their health and productivity. In this study, we isolate and characterize lactic acid bacteria from the hindgut of the worker bee. 16S rRNA sequencing revealed that three isolated bacteria were <i>Apilactobacillus kunkeei</i> (AK), <i>Lactiplantibacillus</i> sp. (LP), and <i>Lactobacillus brevis</i> (LB). Three species of lactic acid bacteria were investigated for potential probiotic properties by supplementing 50% (<i>w</i>/<i>w</i>) sucrose syrup in the form of a direct-fed microorganism (DFM). The supplement with DFM had no negative effect on average lifespan. Examination took place of the impact of probiotics on the development of the hypopharyngeal glands (HPGs) in the bee's head at days 3, 6, and 9 post-treatments. The cage-bees fed by pollen and DFM syrup exhibited acini surface areas ranging from 0.020 to 0.023 mm². The <i>L. brevis</i> (LB) group exhibited enhanced HPG development, with an average acini size of 0.027 ± 0.007 mm² at day 6, while the non-treatment control had an average acini size of 0.023 ± 0.006 mm². The significant size differences were maintained throughout the 9-day period. In addition, the DFM syrup enhanced microbial protein content in the bee head, digestibility, and community complexity compared with the negative control groups. Therefore, the DFM syrup with a potential strain of probiotic may enhance overall honey bee health status.