Polyvinylpyrrolidone can effectively improve the efficiency of resiquimod in sorting bovine Y sperm.

Objective: The X/Y sperm separation technique plays a crucial role in gender control. The objective of this experiment is to investigate the effect of polyvinylpyrrolidone (PVP) concentration (A: 0%, B: 1%, C: 3%, D: 5%, E: 7%, vol/vol) on Y sperm sorting efficiency, based on the specific binding of Resiquimod (R848) to toll-like receptor (TLR)7/8 receptors on the tail of X sperm.

Methods: The different concentrations of PVP were added to the R848 sperm sorting solution to facilitate the separation of Y sperm. Subsequently, the isolated sperm were subjected to quantification and motility assessment using computer-assisted semen analysis system. The X/Y sperm ratio is then analyzed by flow cytometry. The sorted sperm were evaluated for acrosomal and plasma membrane integrity. The spermatozoa were then subjected to immunofluorescent staining through immunofluorescence (IF) techniques, which preceded the quantification of the negative sperm rate. The proportion of male embryos was determined through embryonic sex identification after in vitro fertilization.

Results: Flow cytometry analysis results showed that when the PVP concentrations were 3%, 5% and 7%, the proportion of Y sperm was not statistically significant, (p≥0.05). However, these percentages were significantly elevated compared to those obtained with 0% and 1% PVP concentrations (p<0.05). The IF staining results demonstrated that the proportion of TLR7/8-negative sperm remained statistically unchanged across PVP concentrations of 3%, 5%, and 7% (p≥0.05). However, these percentages were significantly elevated compared to those obtained with 0% and 1% PVP concentrations (p<0.05). The generation of male blastocysts was significantly higher at a PVP concentration of 3% compared to 0% and 1% (p<0.05), but showed no significant difference from 5% and 7% (p≥0.05).

Conclusion: Selecting a 3% PVP concentration not only ensures sufficient sperm yield but also promotes effective selection of Y-sperm. These findings provide empirical evidence supporting the high-efficiency separation of X/Y sperm in livestock.