STALLION MANAGEMENT

Lesson Ten

 

USE OF COOLED, SHIPPED STALLION SEMEN

 

          It takes particular expertise and teamwork to obtain a proper semen specimen from a stallion, so, once it is collected it is very important the sample is handled in a manner that does not cause excessive damage to the spermatozoa. (Many common semen handling techniques have been found to actually damage the semen; we don’t want that to happen.)

          The sperm cells of the horse are among the most fragile of any species when it comes to survival outside the animal (in-vitro environments). This is especially true when it comes to drastic changes in temperature----an obstacle that is difficult to avoid when collecting semen in the middle of winter. In its natural environment, sperm is kept at approximately 98 degrees Fahrenheit (37 degree celcius). That is a temperature much warmer than the atmospheric temperature during much of the breeding season.

          Care must be taken to have all contact surfaces warmed to near 100 degrees Fahrenheit. Keeping the bottles, pipettes, syringes, and extender media in an incubator will reduce the possibility of death due to cold shock, the term used to describe hypothermia in sperm cells. Overexposure to low temperatures causes the male gamete to develop a characteristic appearance: the tail bends backward in an arc toward the head. This causes the live cell to swim in a circular motion. This deviant movement prevents the cold-shocked sperm from being able to compete with the straight forward moving sperm in the race to fertilize the egg. Therefore, a cold-shocked sample decreases the fertilizing capability of an artificial insemination procedure and makes it more difficult to accurately evaluate the fertility of a horse.

          Ultraviolet light must be avoided.

          Place a semen sample in a clear container in direct sunlight and within minutes the mass slaughter of sperm cells will begin. To counter this problem, semen should be collected in containers that have ultraviolet ray filters and then be quickly moved into work areas devoid of ultraviolet light.

          The next two lethal conditions concern only those reproductive physiologists trying to protect the semen sample for a long period of time or breeders interested in preserving the semen for breeding mares in localities distant to the collection point. (AI with shipped semen).

          As the ejaculate waits to be processed, it becomes its own worst enemy. By-products of cell metabolism change the acidity of the environment. The waste produced by billions of cells becomes life threatening to all the cells in the beaker - a concept we are becoming increasingly aware of in our own habitat.

          In addition, as time lapses, the bacteria naturally found in this nutritive mix of sperm and seminal fluids begin to multiply at an ever-increasing rate, further adding metabolites that reduce the pH (a measure of the acidity or alkalinity of a solution), making the media more acidic. These bacteria are also in competition for the same nutrients as the sperm cells. Together these two factors, left unchecked, will eventually lead to the destruction of the fragile sperm.

          For ejaculates to be kept for more than half an hour, counteractive measures to these and other detrimental conditions should be taken.

          The first line of defense is to cool the temperature of the semen to slow the metabolic rate. To do this and prevent cold shock, the change in temperature should be regulated to drop at a rate of about 1 degree Fahrenheit per minute until the solution reaches refrigerator temperature which is about 39 degrees Fahrenheit).

          One way to do this is to take the semen which is in a baby bottle or a baby bottle liner and place it in a container of warm water. The water needs to be the same temperature as the semen. Place this unit in the refrigerator. The water bath will slow the cooling rate of the semen to about the correct level.

          Cold shock can be further reduced by increasing the volume of the sample through the use of a prepared solution (semen extender). The sperm should be placed in the appropriate extender medium before cooling. The correct procedure is to warm the extender and the ejaculate to the same temperature. Mix and then cool the extended semen at the rate given above.

          The extender medium can also be designed to help control the deleterious effects of the acid and bacteria. The addition of proteins to the solution will create a mild buffering of the acid. Antibiotics in the extender will help limit the replication of the bacteria.

          Many great equine semen extenders are readily available from companies dealing in AI products and equipment. Some of the best available are easily used powders that are reconstituted using distilled water.

          Remember that time determines which factor is most lethal to sperm cells. Initially, acidity is the biggest problem counteracted by the proteins in the extender. After 24 hours, however, significant sperm death can be attributed to the build-up of bacteria populations. Samples that need to be kept longer than 24 hours may need to be inoculated with antibiotics.

          There are other reasons to have more pathogen-free samples. For example, some mares seem to have little resistance to pathogens found in semen. For these mares, it may be desirable to use artificial insemination techniques with semen incubated in an antibiotic extender to retard the growth of these negative bacteria.

          Unfortunately, however, our ever-fragile equine sperm cells also find these antibiotics detrimental to their health. So the extender must balance the positive effect of the antibiotics against the bacteria versus the negative effects of the drug on the sperm cells themselves. Most available extenders today have antibiotics included that have no or minimal deleterious effects on the sperm.

          Nutrition for the sperm cells and obtaining the proper osmolarity of the liquid are two other considerations in the development of a proper equine extender media. This has been taken into account with all commercially available extenders on the market today.

           Today, the male sperm of many species of animals, including the horse, can be stored, shipped and even frozen for future use. Today the stallion seed, designed to live 24 to 72 hours once deposited in the reproductive tract of the mare, can be extended and placed in a refrigerator where it is likely to remain capable of fertilizing an ovum for 48 hours.

          Even longer storage can be obtained by freezing the sperm at very low temperatures. The major difficulty in this delicate procedure is the formation of ice crystals as the liquid changes into the solid state as the temperature drops to -196 degrees Celsius.

          The addition of an ingredient such as glycerin will prevent crystal formation by causing the liquid to freeze in sheets----a consequence that renders less damage to sperm cells. At best, one should expect that freezing semen will reduce the number of live normal cells by 50 percent.

          The number of live normal cells in an ejaculate is an extremely important number in the calculation of the number of mares that can be inseminated from a collection.

          Research has shown that it takes approximately 500 million live normal cells deposited in the uterus of the mare to present the best opportunity for a pregnancy.

          The following formula can be used to determine the number of farm mares that can be bred from one fresh ejaculate.

 

Percent Live Cells X Volume X Concentration X Normal Cells

500 X 106 (10 to the 6 power)

 

 

          For the purpose of this discussion, let's suppose that this ejaculate had 50% live cells, the volume was 100 cc with a concentration of 250 x 106, and 90% of the live cells were normal. Put these values in the above formula.

 

Calculate:

 

0.5 x 100 x 250 x 106 x 0.9

500 X 106

 

…and we can see that this ejaculate has the potential to breed about 22 mares.

 

 

          In addition, we know that each insemination procedure is best performed with at least 10cc of fluid. Therefore to breed these 22 mares, we need a total volume of 220 cc.

          The addition of 120 cc of extender to the 100 cc of raw semen will supply the additional fluids.

          Now let’s assume that we are going to prepare this ejaculate for shipment. We can expect about 50% death loss during overnight delivery so this ejaculate should be capable of breeding approximately 11 shipped semen mares.

          Semen also ships better in more fluid so let’s assume that we are going to ship about 30cc per insemination dose. This means that we need a total of 330 cc of semen and extender. The ejaculate is 100 cc so 230 cc of extender needs to be added to the ejaculate in order to make 11 doses of 100 million live normal cells in 30cc of fluid.

          There are many advantages associated with breeding with collected semen.

          Stallions with a large book of mares often have more than one mare ready to breed on any given day. Collecting and extending the ejaculate allows several mares to be bred from a single collection. This saves stallion power and presents the opportunity for more pregnancies. It would be a major feat for a stallion to service 3 mares a day for any extended period of time.

          Extended cooled semen also provides the opportunity to book the stallion to mares outside the immediate area.

          There are many stallion semen shippers on the market.

          Shipping stallion semen can be as easy as filling a syringe with the extended semen, placing the syringe in the shipping container, having the container picked up by an overnight delivery service that will deliver the semen to the mare owner the next day.

          The skill in breeding with shipped semen falls mainly to the breeder of the mare.

          The reproductive specialist in charge of the mare is responsible for calling for the shipment so that the semen will be there when the mare is ready to ovulate.

          The job of the stallion owner or manager is to provide the mare owner with a semen dose that has at least 500 million live normal cells upon arrival. Using the techniques that have been discussed provides the stallion manager with the ability to get semen to the mare owners that is capable of creating a pregnancy.

 

Summary of the use of Shipped Cooled Semen

          Use of Shipped Cooled Semen

              A.  Sending from Stallion

     1. Normal collection procedure

     2. Determine insemination dose for single mare (500 million progressively motile sperm).

     3. Prepare two doses

     4. Place into Equitainer or similar device which will cool semen to 4-8 degrees centigrade. (This is the same as a normal refrigerator.)

     5. Ship to destination via air transport. (Usually arrives within 24 hours; semen will be viable for 72 hours.)

              B. Arriving for Mare

     1. Have courier pick up from airport.

     2.  Preplanning should leave you with a mare that is in estrus and ready to ovulate within 24 to 48 hours.

     3. Inseminate mare with one dose immediately and one dose within the next 24 to 48 hours depending on ovulation determination.

     4.  HCG (human chorionic gonadatropin) often used to stimulate the mare to ovulate within 24 to 48 hours

              C.  Use of Frozen Semen

          This technique is successful, but is not as successful as using cooled, shipped semen at this time. The technique is being perfected and may eventually take over the shipment of cooled semen, which would allow for much less preplanning and deadlines.

 

ASSIGNMENT (No Quiz)

Send your report to Dr. Sales at jsales@horsecoursesonline.com

Include your full name and email address on the document. 

Please answer each question as completely as possible. Resources other than the written text are encouraged as well as personal experiences.

1.  When would a cooled, shipped semen program be used in the horse breeding industry?

2.  Describe, in detail and step by step, what techniques would be followed in order to prepare a semen sample for shipment to a single mare owner that is anticipating the insemination of that semen into that mare within 24 hours.