Bactocell and Levucell probiotic formulas promote spring brood production in honey bee colonies

The aim of this study was to assess three probiotic treatments and their effects on overwintering

survival, spring performance and Nosema spore loads in honey bee colonies. Colonies treated with the commercial formulas Bactocell and Levucell gained 77% and 90% more spring brood, respectively, than control colonies.

Some authors suggest that probiotic-treated colonies produce more brood because treatment stimulates egg laying (Audisio and Benítez-Ahrendts 2011; Sabate et al. 2012). However, no mechanism identified so far supports this hypothesis. The observed increase in brood suggests higher larval survival

in colonies supplemented with probiotics.

A first factor that may have improved larval survival was greater food availability and quality. In a study of Bombus terrestris microcolonies using Lactobacillus kunkeei as a probiotic—now reclassified as Apilactobacillus kunkeei (Zheng et al. 2020)—treated colonies increased their population when available food was poor in quality (Billiet et al. 2017). The authors hypothesised that A. kunkeei enhanced digestion and food assimilation, allowing those colonies to thrive and rear more larvae. Secondly, many researchers have shown that endogenous and commercial Lactobacillus strains can improve colony performance by increasing worker populations and honey production (Audisio and Benítez-Ahrendts 2011; Sabate et al. 2012; Patruica and Hutu 2013; Audisio et al. 2015; Alberoni et al. 2018; Khaled et al. 2018).

In our experiment, probiotic treatments did not significantly affect Nosema, although lower spore loads were detected: B. apis and Levucell showed a trend towards fewer spores per bee. Cage trials previously showed lower spore counts in bees fed B. apis, formerly called P. apium, than in untreated bees (Corby-Harris et al. 2016).

El Khoury et al. (2018) also found that Bactocell and Levucell could improve survival in Nosema-infected honey bees. Treated bees had the same spore load as untreated bees but significantly higher survival. This tolerance could reflect protection of the intestinal epithelium by some probiotics (Oelschlaeger 2010) and stimulation of bee immune responses (Janashia et al. 2016). In the present study, two of the three probiotic treatments, B. apis and Levucell, showed a nonsignificant trend towards reduced spore loads. Therefore, higher probiotic

concentrations, additional treatments during overwintering or alternative delivery methods (Daisley et al. 2023) should be investigated to validate their potential efficacy in reducing spore loads.

Overall, our results support current knowledge about the benefits of probiotics for bee performance. Three individual beneficial microbial strains were tested in honey bee colonies during overwintering. Colonies treated with Bactocell and Levucell showed a significant increase in spring brood. These findings indicate that probiotic treatments may play an important role in beekeeping.

Adapted from Commercial probiotic formulas Bactocell and Levucell promote spring brood production in Apis mellifera L. (Hymenoptera: Apidae) colonies — N. Bleau et al., Journal of Insect Science (2023) 23(6): 17; 1–8 https://doi.org/10.1093/jisesa/iead099