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  Discussion on Cooled semen viability
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Posted on Wednesday, Jun 19, 2002 - 4:17 am:

Hi Dr. O,
My understanding is that sperm live in the mare's uterus for approx 48 hours. When you ship cooled semen, does the age of the semen start with collection, or with insemination? For instance, on a stallion with exceptional semen (40% forward motility at 72 hours), if you inseminate with semen that is 48 hours or 72 hours old, will it still live another 48 hours in the mare? Or does the "life" of the semen decrease with time like the motility decreases?
Thanks,
Linda

Posted on Wednesday, Jun 19, 2002 - 7:13 am:

Hello Linda,
Though most people believe that 2 day old cooled sperm will last 2 days post insemination, research is fairly clear: you will get more mares pregnant if you handle it like it doesn't.

Sperm live much longer than 48 hours in the mares reproductive track and mares have settled when inseminated one time 5 days prior to ovulation, but you can't make a living doing it. Fertilization is optimized when insemination occurs in the period of 48 hours before or just after ovulation.

Cooled semen is the same deal, it is not an all or nothing thing at 48 hours and its ability to survive following cooling dependent on how well it is handled, the extender used, and probably varies from stallion to stallion. Cooled semen begins loosing its vitality the moment it is collected and this becomes significant after about 40 hours of cooling. Once inseminated it continues to lose vitality in the reproductive tract of the mare. Some stallions, in some extenders have been shown to be about 48% potent after 72 hours of cooling out (2/3rds as potent as when used at 48 hours) but these inseminations occured around ovulation. Add to days more to ovulation and pregnancy rates will be very low but probably not zero.
DrO
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