There are many reasons and techniques for collecting a fractionated ejaculate from a stallion. In this article we will discuss some reasons why and demonstrate the technique we have used in our laboratory to manage a stallion with excessive gel fraction that contaminates ejaculates collected using standard in-line filter equipment.
The stallion ejaculate is made up of several fractions which are ejaculated in numerous “jets”. The different fractions contain fluids that are contributed by different parts of the reproductive tract. The first fraction is the pre-sperm fraction which contains fluids primarily from the bulbourethral glands and are often secreted by the stallion during stimulation prior to ejaculation during washing or teasing.
The number of jets in the ejaculate may vary slightly among stallions although the first 2-3 jets usually contain the vast majority of all the sperm and so are termed the sperm-rich fractions. These fractions contain fluids from the testes, epididymides and ampullae. The remaining jets contain few sperm (sperm-poor fractions) and are comprised of fluids from the seminal vesicles and prostate glands.
Collecting individual fractions separately can be used to diagnose the origin of abnormalities in the stallion ejaculate. Diagnosis and treatment of conditions such as pyospermia (purulent debris, leukocytes, etc. in the semen) and hemospermia (blood in the semen) can be aided by determining which fractions of the ejaculate are contributing the blood, puss or bacteria to the semen. Treatment can then be directed to the affected part of the stallion’s reproductive tract.
One or more of the sperm-poor jets can contain a fluid from the seminal vesicles termed “gel”. Some stallions have ejaculates that contain little or no gel while others can produce copious amounts of gel (in some cases more than 100 ml) that ranges in consistency from thin and watery fluid to a thick gelatinous glob. Standard collection equipment employs an in-line filter inside the collection bottle that traps the gel fraction which is ejaculated in the last jets, preventing contamination of the sperm-rich fractions which pass through the filter first. In some cases, the gel contaminates many fractions of the ejaculate and mixes with the sperm-rich fractions despite the use of an in-line filter making it very difficult to analyze sperm quality. 
In some rare cases the contaminating gel is very toxic to the sperm causing a rapid loss of sperm motility. Below is a description of one such case of extremely toxic and difficult to filter gel which prevented this stallion from being used in a cooled or frozen semen artificial insemination program.
Case Study
Our approach was to use an open-ended artificial vagina for collection which allowed for the stallion’s glans penis to protrude through the back of the artificial vagina (AV) so the individual jets could be isolated and collected. We used a 19 inch Colorado model AV. The inner latex bladder was thoroughly cleaned and disinfected using our standard protocol for reusable latex AV liners. The AV was filled with warm (50C water and the bladder was lubricated using a non-spermicidal lubricant (photo above). A sterile fingerless palpation sleeve was affixed to a wire loop with a handle (photo below) to catch the sperm-rich fractions.
The stallion mounted the phantom as usual and the collector places the AV on the penis. A second technician positions the collection device at the back of the open-ended AV to visualize the glans penis and the jets of semen as they were ejaculated. The collector places two fingers on the base of the penis in order to feel the urethra to alert the second technician as to when the jets were happening. The collector calls out the jets. After jets 1, 2, 3 are collected the second technician closes off the collection bag with their hand and removes the device, allowing for the remaining gel-contaminated jets to fall to the ground (video clip). For diagnostic purposes the remaining individual fractions can be collected by quickly exchanging a second collection bag/device after the sperm-rich fractions were collected.
Using this technique, we were able to properly evaluate the semen from this stallion, prevent any gel contamination and successfully manage him in a cooled transported and frozen semen AI program.
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