The SBS network of affiliates is the acknowledged leader in the field of cryopreservation of equine semen. Each year we freeze thousands of ejaculates equating to tens of thousands of doses. In fact, this year the SBS Network will surpass the 50,000 ejaculate milestone since the company’s founding in 1987. When SBS was founded the company leadership made a commitment to quality of the finished product above all else. We wanted to put technology to use to help grow the equine frozen semen AI industry in the most responsible manner possible. It was clear early on that one of the major factors limiting the application of frozen semen in the horse industry was inconsistent quality of the product being put on the market. Breeders and veterinarians experienced frustration with attempts to use expensive semen that in many cases was of very poor quality. We knew that in order for breeders to realize the full potential of frozen semen technology they would have to be convinced that by applying strict standards for quality, frozen semen could be produced to achieve results similar to cooled semen. We also knew that these results would have to be produced in an efficient and economical way. Quality became the cornerstone upon which we would build our business.
When a client brings their stallion to an SBS facility for semen freezing they are entrusting us with one of their most valuable assets. This is a responsibility we take very seriously. Our promise to these customers is that we will use our more than 25 years of experience and all of the latest technology to produce the best possible frozen semen from their stallion. What we do behind the scenes is what makes us successful.
Because equine spermatozoa are very fragile and susceptible to damage from any number of factors, our QC program must deal with all phases of the process. Regardless of how sophisticated your cryopreservation procedures are, the quality of a thawed sample is directly dependent on the initial quality of the collected semen sample. In addition to the inherent semen quality from an individual stallion the collected semen can also be influenced by many factors such as collection frequency, collection technique, number of mounts required for ejaculation, AV contamination, temperature shock (inappropriate AV, laboratory, and incubator or water bath temperatures), improperly calibrated equipment, etc. and many other often overlooked factors. All SBS labs routinely measure and maintain logs of numerous such details so that they are never factors that contribute to a poor result.
SBS cryopreservation extenders are proprietary formulations that have been developed over the last 30 years and have been used in conjunction with our freezing protocols to process literally tens of thousands of ejaculates of stallion semen. The cryopreservation media may be the single most important factor for success and that is why all extenders for North American Labs are produced at our main laboratory in Maryland and shipped complete and frozen on dry ice to our affiliates as they are needed. In 2017, SBS and Minitube GmbH in Germany formed a partnership to produce SBS extenders for use in Europe and extenders for Australasia are produced by a single laboratory in Australia. All extenders are made with the finest cell-culture grade reagents and ultra-pure (18 megOhm) sterile distilled water. Furthermore, each lot of extenders is tested and adjusted to provide pH and osmotic pressure within a narrow critical range or the batch is discarded.
Analysis of Equine Frozen Semen
One of our founding principles is that all parties in frozen semen transactions should be treated fairly and that means providing detailed and accurate information concerning semen quality. When a mare owner or their veterinarian receives a shipment of frozen semen from SBS they also receive detailed instructions on use of the semen for maximum success and a Frozen Semen Transaction Report that details the expected quantity and quality of spermatozoa in the frozen semen doses. Veterinarians and mare owners have come to rely on the open, objective and detailed information provided when semen is shipped from an SBS lab. Our strict post-thaw evaluation protocols are second to none and involve thawing two “test straws” from every single ejaculate frozen. The thawed semen is cultured for potential mare pathogens and counted using a NucleoCounter SP100 (fluorescent cell counting device) to verify sperm numbers. An aliquot of the thawed semen is diluted in extender, incubated for 30 minutes at 37C to provide a “thermal stress test” and then analyzed for critical motility characteristics using a sophisticated Hamilton-Thorne CEROS model computer assisted semen analyzer (CASA). Use of CASA (photo above left) provides detailed, accurate and most importantly objective measurements of sperm motility thus eliminating the bias or discrepancy between individual technicians that is inherent in subjective estimates of sperm motility.
Although many of the SBS Affiliates have their own CASA systems, our Quality Control program for affiliate labs requires that QC straws from all test freezes and a minimum of 25% of all subsequent ejaculates are sent to the SBS central laboratory for evaluation as described above. In addition, all data sheets and freeze records for the samples are sent to the central lab so they can be evaluated for stallion management, implementation of SBS Standard Operating Procedures and assistance in troubleshooting difficult freezing stallions for each of the labs. Site visits, frequent communication, use of the resources on our company-wide intranet site and annual technical meetings for all network affiliates round out the Affiliate Quality Control Program.
Properly stored frozen semen can maintain viability for many decades and perhaps longer but improperly stored frozen semen will deteriorate and result in lower quality and fertility. The most troubling aspect of this reality is that there is no way to determine if straws of frozen semen have been improperly stored or handled without thawing and assessing semen quality. And in some cases the damage may be to structures in the sperm membrane that are very difficult or impossible to detect. SBS maintains the largest inventory of equine semen in North America and possibly in the world. We take this responsibility very seriously. All semen is stored immersed in liquid nitrogen containers (photo above left) that are measured weekly and logged and filled to maintain semen quality at maximum level. Monitoring nitrogen consumption in liquid storage containers allows us to detect when a container may be losing vacuum and failing well in advance so that the semen can be transferred to another container before valuable inventory is lost due to container failure.
In the end everything we do is geared towards success for our clients. Frozen semen is a wonderful, efficient technology that removes geographical and time limitations when breeding superior horses but realizing this potential requires deliberate, steadfast adherence to quality standards. SBS has led the way in establishing these standards and will continue to raise the bar for the benefit of our clients as we head into the future.