Vaughn W. Henry

 In the most basic terms, a stallion's function is to deliver viable sperm cells to impregnate a mare. One of the stallion manager's principal concerns is to identify potential failures in the breeding stallion and correct them, if possible. Over the years, laboratory examinations have been able to provide some insight on the manufacture and delivery of those critical sperm cells, but not every farm does it well. Since the manager can't just turn a tap and gather a semen sample, a fair number of procedures have evolved to allow those sperm cells to be collected and evaluated. The first primitive techniques allowed the stallion to naturally service the mare and then a sample was either retrieved from the mare's tract or the post-ejaculatory dribbles were stripped from the penis and examined microscopically. While it's true that this method is easy and does not require much training or equipment, it does have some disadvantages:

• Possible contamination of the sample from the female's tract
• A complete sample is not available
• It requires a female in estrus to accept service
• There are relatively few sperm cells in the post-ejaculate fraction, so it's not a representative sample

 The next level of technique is to use a condom. While this provides a complete and representative sample, it too has drawbacks:

• It requires a mare in estrus to accept service
• There is a significant opportunity to lose both a portion of the sample and the condom during the dismount
• There is no means to filter out the gel in the post-ejaculate

 

Although it's technically possible to masturbate a stallion to ejaculation, it's not always an easy process. For those unwary individuals who would attempt to use a bovine electro-ejaculator on a stallion, be prepared for an unpleasant response. Most stallions are vigorously opposed to any electrical stimulation and there's ample opportunity for injury to the horse and the technician, since complete restraint is difficult and muscle spasms are an unpleasant side effect. To that end, the artificial vagina (AV) has been the preferred means for the last 40-50 years. The first models, like the Mississippi model, were not very effective, but improvements have been made over time. Today, most farms use one of three basic types. In the U.S. the primary choices are the Missouri - USDA horse model or the pony model or the Colorado model or the less widely used Japanese model. All of these models have different manufacturers, each with their own modifications; but there are some farms still building their own AVs from materials found in hardware stores and plumbing shops.

 

While the presence of sperm cells in a semen sample doesn't guarantee fertility, the consistent absence of sperm cells pretty much guarantees sterility. To determine the potential for reproductive success, a stallion's semen needs to be collected and evaluated on a routine basis. For the sample to be meaningful, a well designed and maintained AV needs to be available. Whether you use a commercially manufactured product or build your own artificial vagina, there are a number of requirements that need to be met.

• Stallion genitals come in varying sizes, so the AV must be adjustable to accommodate individuals.
• It must be easy to hold and of a light enough weight that the employees in the breeding shed can easily manipulate it. The AV must be durable, as it will be exposed to a wide range of treatment. Some rubber products are susceptible to damage from UV light and disinfectants, so quality components are important.
• It must be easily disassembled, cleaned and disinfected. There are a number of venereal diseases in horses and unsanitary breeding procedures and equipment can spread disease rapidly.
  
• It must be able to maintain the internal temperatures to properly stimulate the stallion. This is especially true in climates with extreme temperature ranges. Some models even have insulated covers to preserve the heat.

• It should filter the post-ejaculate gel fraction in the semen sample, preferably as the stallion is actually delivering the sample to avoid mixing with the sperm rich earlier fractions. The gel clogs up equipment, contains few sperm cells and generally isn't useful in an AI program, so it's discarded.
• The AV must be able to protect the sperm cells from light and temperature fluctuations (both high and low) that may damage fragile cells. This is of major concern for those breeders in cold climates or those collecting outdoors.
  
• The ejaculatory response in the stallion is controlled by temperature, pressure and friction. So the AV must be able to hold a temperature of 38 to 45 degrees Centigrade, without actually exposing sperm cells to temperatures higher than 33 to 38 degrees Centigrade or to ultraviolet light which damages them.

• The AV components must not be spermicidal. Although this seems obvious, there are a number of chemicals present in rubber that have been known to kill sperms cells and soap residue in the collection bottles is a common contaminant.
• The AV lubricants must be water soluble, sterile and non-spermicidal. Any soaps or disinfectants must be easily removed by a water rinse and not have residual properties that damage sperm cells.

 

Sexual behavior is learned, so the training process needs to be consistent, patient and persistent. If a particular AV is used, then recreating the favorable environment for the stallion is important. One way to do that is through the trial and error process to find the exact conditions of temperature, pressure (amount of water) and friction (liner texture and lubrication) that favor positive responses. Keep a set of records, and note the modifications and model that works best. Given the preferences of some stallions, sometimes changing the personnel leading and collecting makes a difference, make note of those factors.

Generally the process starts off with inspection and pre-breeding sanitation. The stallion's penis and abdominal area need to be clean; while some managers prefer to just use plain water, it doesn't remove accumulated dirt well. A few breeders use disposable gloves and a nearly pre-surgical level of sanitation to reduce the spread of disease. Many other breeders will get by with a mild water-soluble soap, disposable cotton and then thoroughly rinse the genitals with clean water. If more than one stallion stands at the farm, then separate buckets and washing materials should be used. Also do not wash the stallion and then go back and forth into the wash bucket cross-contaminating the water or cotton washing material if it's to be used elsewhere. A little extra patience and the stallion manager can make the washing a tolerable, even enjoyable experience. On the other hand, vigorous disciplining or striking the horse on the penis creates poor associations with the horse's breeding shed work habits. If washing is made a routine part of the procedure, it is well tolerated and not difficult.

The actual collection and evaluation process follows, and is covered in part II of this series.

E-mail VWHenry@aol.com

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