The Effect of Different Extenders on the Quality Characteristics of European Red Deer Epididymal Sperm Stored at 5 °C

SIMPLE SUMMARY: The use of commercial extenders for storing cervid epididymal spermatozoa in a liquid state can contribute to popularizing this method of semen preservation in cervid farms. The aim of this study was to assess the effect of various extenders (Bovidyl(®), BoviFree(®), and BioXcell(®)) on the quality of European red deer epididymal spermatozoa stored at 5 °C. The analyses demonstrated that the tested extenders and storage time significantly affected sperm motility and functionality of different sperm structures. The Bovidyl(®) extender containing chicken egg yolk exerted the most beneficial influence on the quality of stored sperm. Spermatozoa stored in the Bovidyl(®) extender were characterized by satisfactory motility (above 60% on storage day 9) and the functionality over a long period of time. In turn, extenders containing plant-based ingredients and glycerol (BioXcell(®) and BoviFree(®)) significantly decreased membrane integrity and mitochondrial activity of spermatozoa already on the first day of storage. These results indicate that European red deer epididymal spermatozoa can be stored in commercial extenders, but their viability and functionality are significantly influenced by the composition of the applied extenders. The extender containing chicken egg yolk without glycerol produced the most satisfactory results. ABSTRACT: The aim of this study was to evaluate the effect of different extenders on the quality of European red deer epididymal sperm stored at 5 °C. Epididymal spermatozoa were collected post mortem from 10 stags and diluted with three extenders (Bovidyl(®), BoviFree(®), and BioXcell(®)) and stored at 5 °C. Sperm motility (TMOT), motility parameters (system CASA), plasma membrane integrity (SYBR-14(+)/PI(−)), acrosomal membrane integrity (FITC-PNA(−)/PI(−)), mitochondrial activity (JC-1/PI), viability, and apoptotic-like changes (YOPRO/PI) were evaluated. The analyses were conducted on the first and successive days of storage (D1–D7). The applied extender, storage time, and the interactions between these factors significantly (p < 0.001) affected most of the analyzed parameters whose values were highest in sperm samples stored in Bovidyl(®), regardless of storage time. In Bovidyl(®), BoviFree(®), and BioXcell(®) extenders, TMOT values were estimated at 83%, 63%, and 59%, respectively, on D3. The extenders significantly influenced DNA integrity on D7. The percentage of dead sperm increased from D3. The quality of stored sperm cells was significantly influenced by the extenders’ biochemical composition. BoviFree(®) and BioXcell(®) contain glycerol which could contribute to deteriorating the quality of spermatozoa stored at 5 °C. Sperm cells stored in the egg yolk-based extender (Bovidyl(®)) were characterized by the highest viability and functionality.