Frozen Boar Semen Can Be Successfully Stored at −80°C, Reducing Need for LN ₂ Storage Containers

ABSTRACT

This study explores alternative freezing approaches aimed at reducing or avoiding the use of liquid nitrogen (LN ₂ ) to store boar semen. Sperm‐rich fractions from three boars were pooled and frozen in 0.25‐ and 0.5‐mL straws using four different protocols: a conventional method (Control; LN ₂ vapours followed by immersion and storage in LN ₂ ), FT1 (as Control but stored at −80°C), FT2 (LN ₂ vapours followed by storage at −80°C), and FT3 (direct transfer from 5°C to −80°C plus storage at this temperature). Sperm quality and intracellular H ₂ O ₂ production were evaluated at 30‐ and 150‐min after thawing. Sperm motility and viability in FT1 and FT2 were similar to Control, whereas FT3 showed poorer sperm quality and higher intracellular H ₂ O ₂ generation. Straw size also influenced cryosurvival, being lowest in 0.5 mL straws. In addition, sperm quality deteriorated alongside post‐thaw incubation time. In contrast, storage time (one week vs. one month) did not show a clear effect on the evaluated parameters. In conclusion, these findings suggest that freezing protocols based on LN ₂ vapour cooling, combined with storage at −80°C, could be a practical alternative for short‐term storage of boar semen, reducing LN ₂ use.