Preparation
This review will not go into depth on collection and evaluation of
semen; however, it is important to recognized that semen collection and
evaluation can greatly impact the quality of the semen after processing.
Two important factors in collecting semen which could impact the semen
quality are proper washing of the penis (Bowen et al., 1982; Dascanio,
2014) and lubrication of the artificial vaginal. Proper washing reduces
smegma in the ejaculate, which, even in small qualities, can be greatly
increased if centrifugation is required. Water is recommended for
washing, since detergents and disinfectants can increase the risk of
pathogenic bacteria colonizing the penis (Bowen et al., 1982).
Lubrication of the AV is important, but caution should be taken to
minimize the amount of lubricant to reduce contamination of the
ejaculate. A non-spermicidal lubrication should be used, but all
lubricants are spermicidal to some extent. Clarity brand lubrication has
been shown to have the least impact on sperm quality (Serafini et al.,
2019). Finally, if more than 2 collection attempts are required with an
artificial vagina (AV) to obtain an ejaculate, we recommend a replacing
the used AV with a clean, freshly prepared AV to reduce dirt and
bacterial contamination.
When evaluating semen, one should look at the color of the ejaculate and
a raw sample to determine the presence of sperm or other material such
as blood, white blood cells or urine crystals as these can not only
impact the accuracy of the evaluation but also the longevity of the
sperm. Concentration can be evaluated using a hemocytometer,
sphectrophotometer (Equine Densimeter, Spermacue®, etc) or fluorescent
based system (nucleocounter®). Each system to measure concentration has
its advantages and disadvantages which should be recognized as this can
impact accuracy. The hemocytometer allows differentiation of cells
(sperm vs other) but is subject to human error either in dilutions,
counting sperm or mathematical mistakes. A spectrophotometer-based
system works will in situations with little contamination of the
ejaculate that is reading on the middle of the standard curve. This
system will overestimate sperm numbers if debris, red blood cells, urine
or other material is present such as extenders. Additionally, this
system is not accurate in cases of low sperm concentration or high sperm
concentration. Fluorescent-based systems stain the DNA of the sperm.
Thus, non-cellular or red blood cell contamination will not interfere
with the accuracy. In cases of pyospermia, this system will overestimate
sperm numbers. In situations where the spectrophotometer and
fluorescent-based systems are inaccurate, we recommend evaluation with a
hemocytometer to try to gain a more accurate sperm concentration. For
more in-depth reviews on semen processing and evaluation please see
(Jasko, 1992; Love, 2016).