Graduate Thesis Or Dissertation
 

Evaluating the Potential of Protein Supplements and Probiotics for Improving Honey Bee Health and Understanding Honey Bee Behaviors Related to Social Immunity

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  • Managed honey bees (Apis mellifera) play a vital role in pollinating cultivated crops worldwide. Honey bee colony declines reported in the past two decades have been associated with stressors such as pests and diseases, pesticide exposure, and poor nutrition. In the wake of these colony declines, beekeepers have strived to improve honey bee nutrition by feeding probiotic and protein supplements to their colonies, but there exists a significant gap in knowledge regarding the efficacy of these nutritional supplements. The primary objective of this thesis is to evaluate the potential benefits of protein supplements and probiotics that are commonly used by beekeepers to improve honey bee health and survival. Most studies to date have evaluated protein supplements by measuring colony level parameters, such as colony growth and survival. In our first study, we assessed protein supplements by measuring several physiological parameters directly related to colony fitness. Utilizing both lab and field experiments, we measured several common physiological markers of honey bee health in adult bees raised in colonies that had access to natural pollen and compared them to bees raised in colonies with restricted access to pollen and were instead fed a commercial protein supplement. We measured survival rates, overwintering success, reactive oxygen species, head protein levels, and vitellogenin gene expression in these two groups of experimental colonies. Head protein and reactive oxygen species levels were similar between the two treatments groups. While expression of vitellogenin, which functions as an antioxidant to promote longevity in overwintering bees, was not significantly different between the treatment groups after overwintering, the pollen treatment group experienced a higher increase (33-fold) compared to the protein supplement treatment group (6-fold). Our results suggest that protein supplements could be beneficial during times of limited pollen forage and offer short-term benefits, but are not as effective in sustaining colonies to the same extent as natural pollen. In a second study, we evaluated the efficacy of a commercial probiotic in improving honey bee health and mitigating pesticide toxicity. The treatments in this study consisted of a combination of a probiotic, lambda-cyhalothrin, and a multifloral pollen. Samples of live bees were obtained to measure head protein levels, reactive oxygen species levels, and microbiome taxa. Survival data revealed that that treatment groups that received the probiotic had lower survival, and the probiotic did not meaningfully affect head protein or reactive oxygen species levels in bees that were exposed to lambda-cyhalothrin. Analysis of gut contents revealed that pollen, rather than the probiotic, played a larger role in influencing the microbiome structure. Our results indicate that the commercial probiotic did not have the desired effects in mitigating pesticide toxicity. In our final study, we examined honey bee worker behaviors related to social immunity and attempted to collect potential evidence for the behavior of altruistic self-removal. We observed and recorded the behaviors of infected and uninfected bees in experimental observation hives and also examined potential self-removal by monitoring the presence of experimental bees at regular intervals. Our results showed no significant differences in the frequencies and durations of specific interactive behaviors (antennation, inspection, trophallaxis, etc.) among the infected and uninfected bees. Throughout the study, numbers of infected bees were lower compared to the uninfected group. There appears to be a weak, but not conclusive evidence for self-removal, given that there are other important factors contributing to these low numbers. Therefore, it is difficult to discern altruistic self-removal behaviors with the experimental design used in our study.
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