view - Department of Reproduction, Obstetrics and Herd Health

SUMMARY
Horse breeding has changed dramatically over the last century. Equine reproduction is no
longer dominated by natural breeding. All kinds of assisted reproductive techniques are now being
used for procreation of horses. To date, the most important of these techniques is artificial
insemination (AI), used for both cooled and frozen-thawed semen. Unlike human andrology, where
strict guidelines are followed concerning the handling, preparation and examination of an ejaculate,
veterinary andrology is characterized by a general lack of uniformity. This represents an important
problem for veterinarians involved in animal breeding, since every semen collection should be
followed by a standardized analysis of the quality of the ejaculate prior to the processing and
preparation of AI doses, to ensure the quality of the final AI dose.
So far, one of the most important in vitro sperm quality parameters remains sperm motility.
The subjective analysis of sperm motility highly depends on the operators’ experience and is very
often subject for discussion. Objective sperm motility analysis using computer assisted sperm
analysis (CASA) is well known and appreciated for its precision. As such, results of CASA motility
analyses should be comparable between laboratories, but since all laboratories perform CASA
analysis in a different way the opposite is true. Therefore, the first aim of this thesis was to
characterize and analyze the effect of technical motility settings and utensils on the outcome of CASA,
since no uniformity is present.
Additionally, when processing equine semen for either cooled storage or cryopreservation,
centrifugation is a frequently used technique in order to increase the relative sperm concentration
and to remove seminal plasma. Centrifugation, however, acts clearly as a double edged sword for the
two intended goals, namely to produce high yields of sperm combined with limited side effects for
sperm quality. Alternatively, centrifugation can also be used in combination with colloids to increase
the quality of a sperm sample by removing inferior sperm cells from the original aliquot. This superior
subsample might withstand cryopreservation in a superior way.
The general aim of this thesis was to identify how CASA results are influenced by settings and
utensils (Chapter 3.1 and 3.2) and by trying out a new device supposedly capable of analyzing equine
semen accurately and precise (Chapter 3.3 and 3.4). Additionally, the influence of different
centrifugation protocols on sperm yield and quality was analyzed (Chapter 4.1). A new selection
201