Effect of Uncoated Magnetic Nanoparticles on Stallion Sperm Parameters: Influence of Semen Quality

The aim of this study was to evaluate the effect of uncoated, non-functionalised magnetic nanoparticles (MNPs) on stallion sperm and to determine whether these effects depend on initial semen quality. Ten cooled ejaculates from 3 stallions were exposed to different MNP concentrations ([MNPs] = 0, 5, 25, and 50 mg/mL), agitated, and exposed to an external magnet to recover the unbound sperm fraction. Ejaculates were classified as high- or low-quality groups according to initial evaluation sperm quality index (HSQi and LSQi), and the effect of [MNPs] was evaluated within groups using GLM. The 5 mg/mL concentration preserved sperm motility, membrane integrity and morphology regardless of initial sperm quality. In contrast, [MNPs] ≥ 25 mg/mL reduced sperm motility and recovery rate in both groups. These results indicate that the primary detrimental effect of MNPs is reduced sperm motility, consistent with observations in other species. In brief, nanopurification using 5 mg/mL MNPs can be used in high- and low-quality ejaculates and may provide a useful reference for future nanopurification protocols in stallions.