Common Reasons for Failure with Transported Semen
A successful transported semen (TS) program requires careful attention to detail. Some procedures may vary from your customary artificial insemination.
Not all stallions are good candidates for transported semen. Prior to shipping, it is important to perform a trial run of the complete procedure and then observe the motility of the semen at 24-hours post-collection.
The goal of semen preservation is to maintain the functional ability of sperm for a prolonged time. Cooling and storage of semen will not improve semen quality.
The effects of subtle errors in semen handling are greatly magnified when the semen is stored rather than used after collection. There is also variability between stallions. Some have hardy semen which can survive faulty procedures for hours. However, most have sperm that is highly sensitive to any form of insult. Sperm from healthy stallions will demonstrate better longevity and fertility if the semen is handled properly. Strict attention to detail in processing semen is critical.
Some essential criteria for successful cooling, transportation and insemination are:
Avoidance of Exposure to Toxic and Spermicidal Substances
Many materials commonly used in artificial insemination are known to be spermicidal to equine sperm. Some of these materials will significantly reduce 24-hour viability after less than one minute of contact with the semen.
Sperm sensitivity to these substances vary greatly between stallions. As evidenced in tests against controls, the reaction may range from rapid loss of motility and sperm death to decreased survival during storage, morphological damage and reduced velocity.
Some of the following materials (American products only) known to be spermicidal are:
Monoject and Becton Dickinson disposable syringes
All injectable antibiotics containing preservatives
Some brands of disposable gloves and sleeves
Some insemination pipettes
Bacteriostatic injectable sterile water
Many brands of plastic vials
Many laboratory bottle tops
Detergents, disinfectants, tap water
Skim or powdered milk containing preservatives
Another source of exposure to toxic substances is the AV. Careless washing and rinsing procedures may leave spermicidal substances on the inner surface of the AV or rubber liner. Residues from detergents, disinfectants and tap water may be highly detrimental to the survival of the sperm. Use of a spermicidal lubricant will also cause problems.
The best way to avoid contamination of the in the Av is to use disposable AV liners. However, not all stallions will accept these type of liners. If this is the case, AV and rubber liners must be scrupulously washed and rinsed with distilled water to avoid presence of harmful residues.
Avoidance of Temperature Shock
Stallion sperm are very sensitive to fluctuations in temperature. Sperm in unextended semen are particularly susceptible to cold or heat shock resulting in immediate alterations in motility and reduced survival. A severe decline in motility is caused by incorrect temperatures in items such as the extender, incubator, ballast bags, and collection packs and bottles.
Maintaining the unextended semen at 37°C for more than 15 minutes after collection will give a marked reduction in motility at 24 hours. Therefore, the semen should be extended as soon as possible, with extender that is also at 37°C. Once extended, the semen may be kept at room temperature until you are ready to pack the Equitainer. The packaging of the extended semen and placement in the Equitainer should occur within 15 minutes of collection.
Use of an Extender/Antibiotic Combination that is Compatible with the Stallion's Semen
Another potential source of problems is the semen extender and antibiotic used. Incorrectly prepared or improper extenders may create a hostile environment, which can reduce survival of the sperm. The use of untested antibiotics may also result in problems.
In preparing extender, attention to detail is important, especially if you are making your own. Only recommended ingredients, in the precise amounts, should be used. Ingredients should be properly stored and not used after the expiration date. Pay particular attention to the type of water used since some sterile water contains preservatives that are spermicidal.
Since sperm of certain stallions may extend best with one antibiotic over another, antibiotics that are used should be tested prior to shipping. To do so, several aliquots of extender should be prepared, each with a different recommended antibiotic. One ejaculate from the stallion should then be split and stored in each extender/antibiotic combination and the motility tested at 24 hours. This will allow you to chose the antibiotic that works best for your stallion. This same type of test may also be used to compare different types of commercially available extenders.
Correct Cooling Rates and Thermal Control in Transit
For proper cooling during transport, it is essential that the components of the Equitainer are properly stored and at the correct temperature, otherwise the cooling process may proceed too quickly or too slowly.
Once the sample is cooled, thermal control of the contents is the next concern. If the coolant cans were not adequately frozen, the internal temperature will not be maintained as long. In addition, exposure to extremes of temperatures during shipping may be detrimental, especially if using the disposable variety of semen shipper. Research has shown that the internal temperature of semen transport containers is affected by the temperature of the environment.
Good Mare Management
The stallion owner must keep in close contact with the mare owner and their veterinarians. There may be a great variation between mare owners in their breeding experiences. While some mare owners are well-versed in breeding with cooled semen, others may not have much experience and will require extra support.