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

## TL;DR

This study shows that feeding honey bees a syrup with beneficial bacteria improves their gland development and gut health, which could help beekeepers maintain healthier colonies.

## Contribution

The study introduces a direct-fed microorganism syrup containing lactic acid bacteria that enhances hypopharyngeal gland development and gut microbiota in honey bees.

## Key findings

- Bees fed with direct-fed microorganism syrup showed improved hypopharyngeal gland development.
- DFM syrup increased microbial protein content and digestibility in bees.
- Lactobacillus brevis in the syrup significantly enhanced gland acini size compared to controls.

## Abstract

Honey bees are essential insects that help produce valuable foods like honey and royal jelly, which also provide health benefits for humans. However, bee health and productivity face various environmental challenges. This study investigated the beneficial bacteria naturally found in the digestive system of worker bees. Lactic acid bacteria were isolated, identified, and incorporated into sugar syrup in direct-fed microorganism (DFM) form to test their potential effects on bee health. The results demonstrated that bees fed with DFM syrup developed hypopharyngeal glands in their heads that are crucial for royal jelly production. These findings suggest that supplementing bee diets with beneficial bacteria can enhance protein digestibility and gut microbiota composition, which benefits overall health. This approach could help beekeepers improve their colony care and support sustainable production.

Honey bees (Apis mellifera 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 Apilactobacillus kunkeei (AK), Lactiplantibacillus sp. (LP), and Lactobacillus brevis (LB). Three species of lactic acid bacteria were investigated for potential probiotic properties by supplementing 50% (w/w) 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 L. brevis (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.