Evaluation on sperm quality of freshly ejaculated boar semen during in vitro storage under different temperatures

The purpose of this study was to assess the sperm quality of fresh ejaculated boar semen stored under different temperatures for up to 48 h in order to use the fresh semen efficiently. Spermatozoa were evaluated by 4 methods: Using trypan blue staining, the viability of spermatozoa stored at 39, 20, 15 and 4 °C for 48 h were 1.6, 46.9, 42.0 and 31.0%, respectively. Employing the hypoosmotic swelling test (HOST) showed 1.7%(39 °C), 28.7%(20 °C), 24.1%(15 °C), and 20.1%(4 °C) coiled-tail spermatozoa following 48 h storage. With Coomassie blue staining, the rates of acrosome-intact spermatozoa stored for 48 h were 4.5%(39 °C), 35.3%(20 °C), 55.7%(15 °C) and 22.8%(4 °C). Using fluorescein isothiocyanate-peanut agglutinin (FITC-PNA), the percentages of acrosome-intact spermatozoa stored for 48 h were 4.3%(39 °C), 43.2%(20 °C), 17.3%(15 °C) and 14.8%(4 °C), respectively. The cytoplasmic droplets were found in 18.66% of the spermatozoa in fresh semen and were gradually shed during storage. The results of these 4 methods were highly correlated and could be used to characterized sperm-cell quality effectively. These findings indicated that both membrane integrity and viability of spermatozoa could be preserved well during in vitro storage at 20 °C and 15 °C for 24 to 48 h.