Section: Semen Collection Methods
Semen from stallions is most commonly collected with the aid of an artificial vagina while mounting a mare in heat, an ovariectomized mare or a dummy mount. There are several types of artificial vaginas, and the most commonly used in the United States are the Missouri, Colorado State University and the Japanese or Nishikawa. Other methods of semen collection are available, including collection of semen with the stallion standing on the ground or manual stimulation instead of an artificial vagina. These are good alternative methods in some cases, particularly with special needs stallions, but have not been used widely for routine semen collection and require special training.
The choice of artificial vagina to be used depends on the preference and experience of the semen collection technician. For example, the Missouri model is easy to handle and wash and most stallions respond well with this type of vagina. Additionally, the length of this vagina fits with the length of the penis of most stallions avoiding the heat shock of the sperm that will result if semen is exposed to the inside water jacket of the vagina. The design also eliminates the possibility of water contamination of the semen sample.
Preparing the Artificial Vagina
Prior to semen collection the inside of the vagina should be clean and dry.
A sterile whirl-pack bag or other type of receptacle (i.e. baby bottle or baby bottle liner) is secured to the distal end of the artificial vagina to collect the semen during ejaculation.
The inside of the artificial vagina is lubricated with a non-spermicidal water-soluble sterile lubricant (i.e. KY Jelly is not acceptable because it contains a bactericidal substance that can affect sperm viability). The lubricant is spread by inserting the operator's arm into the vagina protected by a clean shoulder-length palpation sleeve. The vagina should only be lubricated to about two-thirds of its length to avoid excessive contamination of the semen sample with lubricant.
The water jacket of the vagina is then filled with hot tap water at around 50 to 55 degrees Celcius. A non-breakable thermometer can be used to measure the temperature inside the opening of the vagina, but be sure to remove the thermometer prior to semen collection! A final temperature of 42 to 48 C is appropriate for most stallions. Many stallions do not appear to get enough stimulation to ejaculate at lower temperatures. Temperatures higher than 50 C may burn the penis of the stallion resulting in a long-term negative experience.
Once the artificial vagina is at the right temperature, the outer leather shell is secured and the pressure of the inside of the vagina is adjusted by releasing water according to the size of the penis and pressure preferences of the stallion to be collected. Some stallions require more pressure than others for adequate stimulation and only by working with a stallion in a regular basis one can learn his individual preferences. As a general rule, one should be able to fit their arm comfortably inside the lumen of the vagina and make a fist with the hand.
Cleaning and Care of the Artificial Vagina
The artificial vaginal should be thoroughly cleaned after semen collection to avoid both cross contamination between stallions and contamination of the semen sample. The exact cleaning steps vary among farms and laboratories.
Most people first clean the rubber liner with tap water only. Then the rubber liner is submersed in an alcohol bath (70 percent isopropyl alcohol) for about 20 minutes for disinfection and is then hung in a clean cabinet for drying. Most detergents will leave spermicidal residues even after thorough rinsing, so should be avoided altogether. Rubber products are particularly vulnerable to harboring spermicidal residues. Spermicidal agents can have varying degrees of damage to sperm. Some kill sperm immediately, some slowly. So you may not detect damage even under a microscope before semen is inseminated but damaged sperm may not yield expected pregnancy rates.
