A possible step forward for semen freezing?
DNA damage might be one of the reasons that frozen-thawed stallion semen is less fertile than chilled or fresh semen. A group from the University of Northern Colorado (Burns et al, 2009) have done some interesting investigations where they have been adding plant extracts to commercially available freezing extender. Initial results with 4 stallions shows that additions of these extracts appears to significantly reduce DNA fragmentation that occurs during the freezing (and thawing) process.
No fertility data (pregnancy rates) is available, and this is important to keep in mind. Previous work had suggested that addition of cholesterol to the sperm membrane could improve freezability. However, work since then has shown that while increasing the cholesterol content of the sperm membrane does improve post-thaw motility, it actually causes a reduction in pregnancy rates. This is probably due to the added cholesterol reducing the sperm’s ability to undergo capacitation.
Hopefully we’ll see some fertility data using frozen-thawed semen from this trial at some point in the not-too-distant future.
