A New Method for Evaluating Stallion Sperm Viability and Mitochondrial Membrane Potential in Fixed Semen Samples.

Multiparametric assessment of stallion sperm quality using flow cytometry can be a useful adjunct in semen evaluation; however, the availability of flow cytometers in veterinary practice is limited. The ability to preserve and transport sperm samples for later flow cytometric analysis using fixable probes would potentially facilitate this process. In the current study, we validated the combination of live/dead Zombie Green® (a fixable dye used to assess live and dead sperm) and MitoTracker Deep Red® (used to assess mitochondrial membrane potential). The assay was validated against classic, non-fixable, membrane assays (SYBR-14/PI). Our results demonstrated the feasibility of the assay. In conclusion, stained and fixed semen samples stored for 72 h obtained equivalent results to the exam on the same day; this new protocol shall facilitate the wider use of flow cytometry in stallion andrology in the future.