Effect of Honey and Syrup Diets Enriched with 1,3-1,6 β-Glucans on Honeybee Survival Rate and Phenoloxidase Activity (Apis mellifera L. 1758)

• Published in: Veterinary sciences Vol. 8; no. 7; p. 130
• Main Authors: Sagona, Simona, Fronte, Baldassare, Coppola, Francesca, Tafi, Elena, Giusti, Matteo, Palego, Lionella, Betti, Laura, Giannaccini, Gino, Guglielminetti, Lorenzo, Felicioli, Antonio
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 13-07-2021; MDPI
• Subjects: Apis mellifera; Beekeeping; Bees; Communication; Diet; Dietary supplements; Food; Glucans; Glucose; Honey; Immune system; Immunomodulation; innate immune system; Innate immunity; Invertebrates; Investigations; nutrition; Oral administration; Phenoloxidase; phenoloxidase activity; Survival; Syrups; Workers (insect caste); β-Glucan; β-glucans
• ISSN: 2306-7381; 2306-7381
• DOI: 10.3390/vetsci8070130

β-glucans can activate the animal innate immune system by acting as immune-modulators and inducing various stimulatory effects. The aim of this study was to investigate the effect of 1,3-1,6 β-glucans administered orally for 96 h on Apis mellifera workers (newly emerged and nurse bees). β-glucans were included in honey and syrup. Survival rate and phenoloxidase activity were measured. In both newly emerged and nurse bees, β-glucans supplementation did not affect survival rate (p > 0.05). Conversely, phenoloxidase activity was higher in both newly emerged bees (p = 0.048) and nurse bees (p = 0.014) fed with a honey diet enriched with β-glucans compared to those fed with only honey. In both the newly emerged and nurse bees, no statistical differences in phenoloxidase activity were recorded between the group fed with a syrup-based diet enriched with β-glucans and the control group (p > 0.05). The absence of significant variation in survival suggests that the potential negative effect of β-glucans in healthy bees could be mitigated by their metabolism. Conversely, the inclusion of β-glucans in a honey-based diet determined an increase of phenoloxidase activity, suggesting that the effect of β-glucan inclusion in the diet of healthy bees on phenoloxidase activity could be linked to the type of base-diet. Further investigations on β-glucans metabolism in bees, on molecular mechanism of phenoloxidase activation by 1,3-1,6 β-glucans, and relative thresholds are desirable. Moreover, investigation on the combined action of honey and β-glucans on phenoloxidase activity are needed.