Protein supplementation of Africanized honey bee colonies improves drone and semen quality
Honey bee (Apis mellifera) drones reared in protein-supplemented colonies may have reproductive advantages over drones reared in non-supplemented colonies. Additionally, climate and genotype can influence drone and semen quality; however, the studies conducted till now have been carried out in temperate climate countries with European honey bee subspecies. Furthermore, it is not known what minerals are associated with sperm quality in honey bees. Therefore, the objective of this study was to evaluate the effect of a protein diet supplement fed to Africanized honey bee colonies on drone and semen quality, as well as on the mineral content and concentration of their semen. The experimental colonies were fed sucrose syrup and a commercial protein supplement, while control colonies were fed only sucrose syrup. Drones reared in these colonies were weighed and their thoraxes and abdomens measured. Ejaculated semen collected from the drones was evaluated for volume, sperm concentration, sperm viability, morphological abnormalities, and mineral content. Mineral analyses were also made of drone seminal vesicles. Drones reared in colonies supplemented with the protein diet were significantly heavier and larger than drones from control colonies. Semen volume did not differ significantly between treatments (P > 0.05), but the sperm concentration and viability of drones reared in supplemented colonies were significantly higher relative to the control. Furthermore, the rate of abnormalities of sperm cells was significantly lower for drones of supplemented colonies (P < 0.0001). There were no differences between treatments for concentration of Mg, P, Cu, Zn, and Se in the ejaculated semen; however, P was significantly more concentrated in seminal vesicles of drones of supplemented colonies. Most of these minerals had not been reported in bee semen before. We conclude that protein diet supplementation provided to Africanized honey bee colonies improves the quality of drones and their semen.