Effects of Low-Density Lipoprotein Supplementation on Post-Thaw Quality and Fertility of Honeybee Semen (Apis mellifera L.).

Introduction: Long-term storage of bee semen by freezing is a critical process for both the preservation of the genetic material and the sustainability of beekeeping activities. It has been observed that low-density lipoproteins (LDLs) increase sperm quality after freezing and thawing. Although studies have been conducted on the use of LDL for this purpose in different animal species, no research has been conducted on honeybee semen to date. Objectives: This study aimed to evaluate the potential effects of using LDL instead of egg yolk (EY) on sperm quality and fertilization rate by examining the effects of different LDL ratios (2.5%, 5%, 10%, 25%) on bee semen. Methods: Sperm collection was conducted using a Schley-type device, resulting in six distinct groups, including both no-supplemented and experimental groups. In the first experiment, sperm collected from 36 drones were diluted with varying LDL concentrations before being frozen and thawed; motility, membrane integrity, viability, and longevity were measured. In the second experiment, a total of 56 virgin sister queens, 8 from each group, were inseminated. Results: In the group containing 25% LDL, a significant increase was observed in the motility, membrane integrity, and viability rates of frozen-thawed honeybee sperm. In the group containing 25% EY, there was a clear decrease in these parameters; moreover, the lifespan of the sperm was significantly reduced. In the groups, the highest value in terms of fertility was observed in the 25% LDL group, and the lowest value was determined in the 25% EY-added group. Conclusion: The findings demonstrated that the addition of 25% LDL significantly enhanced both sperm quality and fertility rate in honeybees.