view - Department of Reproduction, Obstetrics and Herd Health

CHAPTER 1.2
Recently, a new technique for concentrating equine semen was described. Based on a filter
with a hydrophylic synthetic membrane that does not allow sperm passage. Following filtration, up
to 95% of sperm cells could be recovered without affecting sperm motility and viability (Alvarenga et
al., 2010).
Selection of spermatozoa
Different techniques are available for separation and selection of spermatozoa. Separation is
the most straightforward procedure, in which the only objective is to separate the spermatozoa from
the seminal plasma. This is done by centrifugation and can be achieved as described above (Henkel
and Schill, 2003). In contrast, selection aims at simultaneously separating the spermatozoa from the
seminal plasma and selecting a sperm subpopulation based on sperm quality characteristics.
Migration, filtration and colloid centrifugation are three techniques available for sperm selection
(Morrell and Rodriguez-Martinez, 2009).
→ Migration
Sperm selection by migration relies on the ability of motile spermatozoa to move from one
suspension into a medium of a different composition. The original sperm population (diluted semen
or a washed sperm pellet) can be either underneath, on top of or beside the migration medium.
During an incubation stage the spermatozoa migrate actively into the selection medium (Morrell and
Rodriguez-Martinez, 2009) indicating this technique selects spermatozoa based on motility rather
than on morphology, chromatin integrity, viability and acrosome integrity (Somfai et al., 2002). The
major disadvantage of migration is the low recovery rate, rendering it impractical for clinical use for
preparing AI doses (Morrell and Rodriguez-Martinez, 2009).
→ Filtration
Filtration is achieved by the interaction of spermatozoa with the different filter substances.
Non-viable spermatozoa adhere more to the filter substrate compared to motile spermatozoa, as
such increasing the quality of the sample following filtration (Bussallou et al., 2008). Filtration allows
for processing of relative large volumes, but leukocytes and debris also pass by the filtration process.
Additionally, the sperm remains suspended in the same volume containing the seminal plasma, as
such requiring an additional centrifugation step (Henkel and Schill, 2003), or possibly a filtration to
increase the concentration (Alvarenga et al., 2010).
35