Effect of trehalose and month of collection on DNA fragmentation in Holstein bull semen during dilution, cooling and thawing.

摘要

We report optimal levels of trehalose in diluents for freezing bull semen monitored by fragmentation of DNA during dilution, cooling and post thawing during October, November, December and January. Ejaculates with 50-55% or more individual sperm motility were collected weekly by artificial vagina. Semen was diluted with Tris containing 50, 100, 150 or 200 mM Trehalose to provide 80 million spermatozoids per ml. Semen was cooled to 5C° over 4h, packed into 0.25 ml straws and freeze stored 48hr in liquid nitrogen. DNA fragmentation was evaluated after dilution, cooling and thawing. After dilution, fragmentation in 50 (4.7%) or 100Mn (4.8%) Trehalose was less (P < 0.05) compared with 200nM (6.7%) or controls (6.7%). After cooling, fragmentation increased (P < 0.05) in all samples but in those with 50nM was 6.6% less (P < 0.05) compared with 200nM (8.1%) or controls 10.2%. After thawing fragmentation increased in all samples but in those kept in 100nM Trehalose (7.4%) was less (p<0.05). Our findings suggest that 50-100nm Trehalose in Tris-dilution may reduce DNA fragmentation in sperm and ameliorate damage due to cooling or freezing. We found that in semen collected in November and December, fragmentation was less compared with other months.