There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
The effects of different freezing and thawing rates on the post-thaw motility and
membrane integrity of boar spermatozoa, processed as split samples in Maxi-straws
or flat PET-plastic packages (FlatPack) were studied. A programmable freezing device
was used to obtain freezing rates of either 20, 50 or 80 degrees C/min. Thawing of
the samples was performed in a bath of circulating water; for 40s at 50 degrees C
or 27s at 70 degrees C for Maxi-straws and 23s at 35 degrees C, 13s at 50 degrees
C or 8s at 70 degrees C for the FlatPacks. Sperm motility was assessed both visually
and with a computer assisted semen analysis (CASA) apparatus, while plasma membrane
integrity was assessed using the fluorescent probes Calcein AM and ethidium homodimer-1.
Temperature changes during freezing and thawing were monitored in both forms of packaging.
Values for motile spermatozoa, sperm velocity and lateral head displacement variables
were significantly (p<0.05) higher for samples frozen in FlatPacks than in Maxi-straws,
with superior results at higher thawing rates. Freezing at 50 degrees C/min yielded
better motility than 20 or 80 degrees C/min, although the effect was rather small.
Neither freezing rate nor thawing rate had any effect on membrane integrity (p>0.05).
A significant boar effect was seen for several parameters. The most striking difference
in temperature courses between containers was a 4-5-fold lowering of the thawing rate,
between -20 and 0 degrees C, in the center of the Maxi-straw, compared with the FlatPack.
This is apparently due to the insulating effect of the thawed water in the periphery
of the Maxi-straw. The improvement in sperm motility seen when using the FlatPack
appears to be related to the rapid thawing throughout the sample, which decreases
the risk of cell damage due to recrystallization during thawing. Since sperm motility
patterns have been reported to be correlated with fertility both in vitro and in vivo
it is speculated that the use of the FlatPack might improve the results when using
frozen-thawed boar spermatozoa for artificial insemination.