Friday, January 17, 2020

Motility versus Fertility

The most usual question for semen shoppers to ask is "what's the motility?" Unbelievebly enough, we often do not receive motility percentages from our suppliers, but must extrapolate from the number of straws per dose. For example, three straws per dose indicates approximately 50% motility and four straws per dose about 40% motility. When selling single straws, we do however, usually get a motility report. 
Breeders often rely on their veterinarian or technician for a motility count, and share information between themselves or via our database. But just take a look at our Conception Database (you must sign up to use it) to see how the reported motility of the same stallion can vary wildly. Our experience has been that even semen from the same collection can vary. It would seem that it's not an actual variation of the semen, but perhaps that it has been compromised by handling and thawing, or by a flawed assessment when looked at on a slide.
The most reliable assessment of semen motility is provided by CASA (computer assisted semen analysis).
And while good motility is never a bad thing and often bodes well, the far more important question is "what's his fertility rate?" We've seen stallions with 5-10% motility settle mares at a high rate and stallions with 75% motility that didn't work at all.
We built our Conception Database so breeders have access to important data to use in making informed breeding choices. So, if you haven't entered your results or you have searched the database, please do! And if you don't see the information you're looking for, call us. We often have information that is not entered in the database. The database information is only entered by breeders.