Introduction
The ideal method for processing semen for use with either fresh or
cooled-shipped breeding would maximize the number or sperm per mL,
maximize total number of progressively motile sperm, minimize the volume
needed to breed a mare, not be deleterious to sperm function or
longevity and minimize seminal plasma. Based on these criteria, cushion
centrifugation is currently the best method. Cushion centrifugation
maximizes sperm recovery compared to sperm filters(Roach et al., 2016)
and centrifugation without cushion. Seminal plasma is removed, which can
be deleterious to sperm longevity(Braun et al., 1994; Jasko et al.,
1991), allows for the semen to be reconstituted more concentrated than
simple dilutions, which reduces the volume of the breeding dose while
increasing the number of sperm which inseminated into a mare.
Simple dilution of semen is perhaps the oldest method to extended semen
for artificial insemination with either fresh or cooled. This was
developed prior to the optimization centrifugation techniques for semen
through a combination of trial and error and research. Simple dilution
is a faster method to process semen, easy to use and works in many
circumstances. A variety of other techniques have been developed, such
as density gradient centrifugation, which can be used to remove abnormal
sperm and sperm filters which may be useful when a centrifuge is
unavailable. This review will discuss these techniques in the
application of processing equine semen for either fresh or
cooled-shipped use.