Staining mixtures comprising viable spermatozoa, a composition which regulates oxidation/reduction reactions intracellularly or extracellularly, and a DNA selective dye are disclosed. The cells contained in such suspensions tend to have a greater capacity for enduring the various process steps typically associated with the sorting of sperm cells into gender enriched populations, thereby resulting in post-sort compositions with an increased number of viable or motile sperm. Processes for staining sperm cells comprising the formation of a staining mixture are also disclosed.