Stallion Management – Semen Collection and Evaluation

Stallion Management – Semen Collection and Evaluation

Stallion Management – Semen Collection and Evaluation

Vaughn W. Henry

┬áThe most effective process of semen collection requires the stallion use an artificial vagina to collect a representative semen sample for either fertility evaluations or insemination. The training process can be somewhat involved, but consistency is a major part of a successful collection program. While some farms will mount the stallion on a receptive mare, most commercial farms have increasingly made use of a “dummy” or “phantom mare”. Why?

  • The “phantom” is always “receptive”; there’s no need for a mare to be mounted. In early training usually a mare in heat is nearby or positioned in front of the phantom to encourage the stallion to express interest. After successfully mounting and ejaculating, the stallion soon associates the phantom with breeding shed activity and may no longer need a mare to be in the same area. This consistency is critical to success
  • The phantom is safe. A well-padded phantom with a durable and washable cover is sanitary and comfortable for the stallion’s use. The phantom should be designed to withstand a lot abuse, and the padding should be high density foam so the stallion can slide off without getting stuck in a too soft mattress type pad.
  • The phantom removes one unnecessary horse and one or two extra people from the area. This reduces the risk of injury to both the stallion and the handlers.

Once the stallion has attained an erection and is brought to the phantom to mount, the handler and collector need to coordinate their actions. Some breeders like both individuals on the left side, but my preference is to have the handler on the left shoulder of the horse and the collector near the horse’s right hip. In this way, they can “funnel” the horse to the phantom and help position him so the artificial vagina (AV) can be easily worked. As the horse approaches the phantom the handler “checks” the horse’s progress so he doesn’t rush up and the collector simultaneously moves in from the side to deflect the penis into the AV. The handler needs to avoid the forefeet of the horse as he mounts and still maintain contact with the horse’s shoulder to steady and stabilize him once mounted on the phantom. The collector rotates to keep pressure against the horse’s flank and allows the stallion to thrust into the AV as it’s rested against the side of the phantom. Let the phantom take most of the weight and step in closely to keep the horse secure. Although any work with an animal weighing 1,000 to 1,500 lbs. is risky; generally it’s best to stay close and take a “push” instead of trying to be a little farther away and take a full strike from one of the stallion’s legs. To avoid a damaging blow to the handler’s head, a lot of farms require a helmet and as a prudent measure to keep injuries down, it’s a pretty good idea to use one. This is one time that being very close to the work makes sense from a safety viewpoint, as there is a better sense of what’s happening and more control of the situation.

Once the horse starts to ejaculate, lower the back end of the AV to ensure the sample runs into the bottle instead of onto the floor. The stallion’s penis will soften and the horse will start to back off of the phantom, so the collector needs keep the AV in place and help drive the horse back by keeping body contact with the horse’s flank and abdomen. Meanwhile the handler on the left side makes sure the horse doesn’t rear or twist during the dismount or suddenly pivot and try to kick the collector. Again, this is another reason to have staff working on both sides of the horse to prevent the handler from pulling the horse inadvertently over on top of the person collecting. Once the horse is backed off from the phantom, the AV and the semen sample is taken to the lab for processing and evaluation. In the meantime, the horse’s genitals are rinsed and he’s returned to his stall, a day’s work done in the breeding shed for him. Different horses respond to different stimuli, and no one system works for every horse on every farm, so expect a little trial and error to find the right response. Since horses never read any of the “books” that purport to explain horse behavior, be prepared to adapt.

Calm, quiet and consistent handling is the primary rule and selecting a site free of obstructions and suitable for this work is important. The flooring should provide traction, but keep dust and contamination minimized. The walls should be smooth, as there is ample opportunity for wrecks in this business of collecting horses. A lot of horses don’t necessarily feel there’s a need for people to be involved and object to the best organized plans of the breeding crew, so safety is always a concern. Qualified personnel are important if the stallion is to have a positive response to all of these efforts to control every aspect of the breeding process. If you collect and breed indoors, then a ceiling of ample height and lined walls to protect the building are required. Besides having laboratory space with room to store needed equipment and supplies, some farms go so far as to provide observation areas and video cameras to satisfy owners who want to view the process from a safe vantage point.

Once the semen arrives in the laboratory, it should be immediately processed and protected. Generally the filter is removed with the trapped gel fraction and is discarded. The gel-free portion of the semen sample is measured for volume and a small portion is set aside for motility and concentration studies. The rest is placed in a pre-warmed water bath or incubator, the temperature of which should be set at body temperature or slightly below 38 degrees Centigrade. To avoid the risk of heat damaging the semen sample, set the temperature controls to 32 – 34 degrees Centigrade, rather than risk higher temperature shocks. Any heat stress on sperm cells is extremely damaging and should be avoided. By keeping the sample at the same temperature of the testes, that is 5-7 degrees lower than body temperature, the incubator mimics the effect of scrotal cooling mechanisms. The small semen sample outside the incubator is quickly evaluated microscopically for motility and progressive (quality of movement) motility. This procedure is done at 100X – 400X power setting on a decent quality microscope. Rather than look at a swarm of moving sperm cells, it’s generally easier to dilute them slightly and look at two or three sperm at a time in different areas of the slide. If you consistently see 1 of 2 sperm moving in a straight line, but don’t always see 2 of 3 sperm cells so inclined to movement, then you can note the motility is between 50% and 66%. Likewise, if 2 of 3 sperm are always moving but 3 of 4 aren’t, then the motility rating is between 66% and 75%. After much practice, it becomes easier to be consistent in this evaluation process. As for concentration studies, a microscope and grid-like hemocytometer can be used, but most farms opt for a machine that measures light transmission through a diluted semen sample and compares it to a known standard. The primary advantage is that it’s fast and accurate, but the machines can be a little expensive for those breeders who don’t do a lot of semen evaluation or artificial insemination work. Why go through all of these gyrations? The motile and normal sperm output is one of the deciding factors on the stallion’s ability to impregnate mares. If the stallion produces enough semen to impregnate only 3 mares and there are 10 to breed, then priorities can be assessed and management decisions will need to be made. Without the information to make good decisions, it becomes difficult to improve reproductive efficiency on the breeding farm.

Other studies may include morphology (cell structure) to determine the proportion of normal vs. abnormal cell types, cell cultures for bacterial organisms causing infertility, procedures to identify blood or urine in the sample and longevity studies, especially important for those breeders who ship semen. All of these procedures should be logged and monitored for each stallion. Very often a drop in motility is an early warning to either look to contamination in the equipment or for the possibility that the stallion has experienced an illness that increased body temperature enough to affect sperm development. Remember that it takes 45 days to manufacture a sperm cell, so any illness today may impact on the fertility of the working stallion for six weeks or more.

The design and use of an artificial vagina is covered in part I of this series.