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CHAPTER 4.2
subpopulation of superior sperm is cryopreserved. These sperm are more likely to withstand the
cryopreservation protocol; additionally the harmful effect of seminal plasma is eliminated since
almost all seminal plasma is discarded during the selection procedure and the subsequent washing of
the pellet. It is likely that some poor freezing stallions might have experienced additional benefit if
heterologous seminal plasma from a good freezing stallion is used instead of the homologous
seminal plasma that was added back in the present study, this was however not the intention of the
present study. Nevertheless it is clear that Androcoll-E can be beneficial to successfully cryopreserve
stallion semen. Stallion selection however, plays a key role in the eventual outcome.
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In conclusion, sperm selection using Androcoll-E prior to cryopreservation resulted in an
overall increased post-thaw sperm quality. Stallions that produce ejaculates with low post-thaw PM
might benefit from sperm selection prior to cryopreservation. As such only the best population of
sperm is cryopreserved, which could result in good frozen semen. Androcoll-E can be beneficial to
successfully cryopreserve stallion semen, but stallion freezability plays a role in the eventual
outcome. Additional experiments need to be performed to evaluate the in vivo fertility of frozen
thawed equine semen, selected with Androcoll-E prior to cryopreservation.