Preservation of tomcat (Felis catus) semen in variable temperatures

The aim of our study was to estimate the viability of cat epididymal sperm in short time storage at +4 degrees C and in long term storage at -196 degrees C and to assess the percentage of live sperm in fresh semen using eosin/nigrosin staining compared to the flow cytometry method. The testes with epididymides were obtained after routine castration procedure. The sperm for further research were collected after flushing the epididymides using extender consist of: Tris 2.4 g, citric acid 1.4 g, glucose 0.8 g, 0.06% (w/v) Na-benzylpenicillin, 0.1% (w/v) streptomycin sulphate and distilled water. Half of each sample was equilibrated with the dilution and loaded in 0.25 ml plastic straws. The straws were placed on a rack in liquid nitrogen vapour at -120 degrees C for 10 min, plunged in liquid nitrogen for 10 min, replaced to marked goblets and loaded into canes for long term storage in liquid nitrogen at -196 degrees C. Sixty percent of motile spermatozoa was accomplished after thawing. However, the percentage of the sperm with intact acrosomes was decreased and the share of cells with midpiece and tail defects was increased. The storage of sperm flushed from epididymides at +4 degrees C for a short time and the usage of sperm during 2-3 days after collection seems to be better than cryopreservation. In our study, normospermia was present in 72.7 +/- 8.8% of fresh semen. The most common defect was the presence of distal droplets, imperfect heads or abnormal acrosomal outline. The motility of fresh sperm flushed from epididymides achieved 77.9 +/- 6.8%. The viability of sperm amounting to 52.5 +/- 13.8% was achieved on third day of conservation in the liquid extender. The percentage of viable sperm in fresh epididymal spermatozoa was 84.9 +/- 7.8%. Compared to these results, the percentage of live cells using SYBR-14/propidium iodide staining was insignificantly lower (82.2 +/- 8%). The live, non-apoptotic cells were 79.0 +/- 7.8%. The share of live, early-apoptotic spermatozoa and late-apoptotic spermatozoa was, respectively, 2 +/- 1.4% and 1.5 +/- 0.9%. The viability of sperm estimated by eosin/nigrosin staining was confirmed by the flow cytometry method. There was no statistical differences between the staining. The usage of apoptosis detection kit revealed, that the percentage of early-apoptotic and late-apoptotic cells was insignificant.