Effect of zinc supplementation on the quality of cooled, stored equine sperm

Context Collecting, cooling, and cryopreserving semen is essential for accessing genetically superior stallions. However, preserving stallion sperm presents unique challenges compared with other species. Aims This study aimed to investigate the effect of zinc (Zn) supplementation on the quality of equine sperm during cold storage. Methods Various factors contributing to sperm quality were assessed at 24 and 48 h after cooling, and after subjecting the sperm samples to a heat-resistance test. In Experiment 1, four experimental groups were examined, each with different concentrations of Zn sulfate, as follows: 0, 1, 2, and 3 mM. Subsequently, Experiment 2 involved testing a wider range of concentrations (0, 0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 mM), including evaluation of samples after incubation for 240 min at 37°C (heat-resistance test). Key results The addition of different concentrations of Zn to the extender INRA96 did not yield substantial improvements in sperm-quality parameters for cooling stallion semen after 24 or 48 h. Moreover, no protective benefits were observed when samples underwent a heat-resistance test. Concentrations of Zn surpassing 3 mM had an adverse effect on sperm-quality parameters. Conclusions and implications These findings have contributed to the understanding of Zn supplementation as a strategy for improving semen preservation in stallions.