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CHAPTER 1.1
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In the next paragraphs, the state-of-the-art concerning the analysis of (equine) semen is
reviewed. Where possible, the comparison is made with the guidelines according to the World Health
Organization (WHO). The WHO laboratory manual for the examination of human sperm and sperm-
cervical mucus interaction was published for the first time in 1980. This guideline was developed in
response to a growing need for the standardization of procedures for the examination of human
semen. The manual has ever since provided global standards for human semen analysis and has been
updated on numerous occasions based on new understandings and developments. In 2010 the fifth
edition was published.
1.1.2 Gross evaluation of equine semen quality
Following ejaculation the gel is separated from the remainder of the semen in the laboratory
if no inline filter was applied during collection. The color and consistency of the semen are recorded.
Normal semen should be white, grayish-white to slightly cream coloured and this provides a rough
estimate of sperm concentration. Usually, larger volumes are more watery instead of a creamy
consistency and this will be reflected in low sperm concentrations. A deviant color of the ejaculate
may indicate the presence of admixtures, such as blood, urine or purulent material (Estrada and
Samper, 2007; Binsko et al., 2011). The conventional semen analysis consists of the evaluation of
semen volume, spermatozoal concentration, morphology and motility. Additional evaluations using
more recent techniques might improve the predictive value of the examination (Varner, 2008).
1.1.3. Volume
The volume of an ejaculate is most often determined by pouring the semen from the
collection bottle into a tilted, pre-warmed graduated cylinder (Jasko 1992; Picket, 1993; Squires et al.,
1999). This is in sharp contrast with human andrology, where it is advised to weigh the empty and
filled container in order to calculate the volume based on the density of semen (WHO, 2010). For
human samples, it is not recommended to aspirate or to decant the sample into a graduated cylinder.
Anyhow, by decanting a part of the sample will get lost and sample losses have been reported to vary
between 0.3 and 0.9 mL (Brazil et al., 2004; Iwamoto et al., 2006; Cooper et al., 2007). Obviously,
these losses weigh heavily when handling small volume samples in human andrology with a total
volume of about 4.0 mL, when compared to equine ejaculates in which a 10 times larger volume is
most often present (Picket, 1993; Squires et al., 1999). In species with lower volume ejaculates (bulls,
rams,…) losses due to decanting will be more important.