Dr. Mennick has been freezing equine semen for seventeen years, and has taught courses to colleagues on the subject in New Zealand, Australia, Canada, and out of his facility. Our own unique, and very thorough test-freezing approach has been very successful, with 96% of sires frozen and pregnancy-tested to date having proven fertility. In fact, for more than fifteen years we have offered a money-back fertility guarantee, still unique in the business (see end of this section). Our in-house investigations continue, and we are now concentrating on developing solutions for those 4% of sires who retain little or no fertility despite our thorough protocol. We are beginning to obtain evidence that such fertility failure is not the fault of the sire; rather that of the processor, who has not selected a processing method which retains FERTILITY along with MOTILITY. In one recent instance, Dr. Mennick was able to refreeze a stallion whose postthaw motility from initial work was excellent, although none of six mares bred conceived. Upon refreezing, a different processing protocol was selected and tested. This time, despite somewhat lower motility postthaw, both test mares conceived with it; both on a single heat cycle, and both with a single straw. This investigative work was first presented at the Society for Theriogenology annual meeting (a worldwide organization of animal reproduction specialists) in 1991. Dr. Mennick presented an update on the subject to the same organization in 1997.

Unlike bulls, where a few "standard extenders" work quite reliably, a wide variety of extenders have been developed and used with equines. Each recipe has worked well, at one time or another, somewhere in the world, with a horse or two. For three decades, researchers have been looking for that "magic recipe" which would freeze nearly all stallions as reliably as bulls are frozen. However, each time that a new extender was developed, tried successfully with a couple of horses, and reported, others attempting to repeat the success would invariably run into sires which would not freeze well with it.

It became obvious several years ago that the "magic recipe" would probably never be found, and that the difficulties in repeating successful techniques were simply due to the significant, individual variations from one sire to another. These variations are much more evident with stallions (and boars), than with bulls, and is due to variations in seminal fluid components and amounts. In addition, seasonal variations in semen quality are more pronounced in horses, as most equine species are seasonal breeders, whereas bulls breed year-round and therefore have little seasonal variation. Some of the extenders we use with stallions are more likely than others to work well, but we still cannot predict in advance when one of the least-used recipes will prove to be the best.

We have thus developed, and continue to modify, an elaborate testing process, using many of the extenders developed over the years, along with several of our own design, to find the very best combination for each individual sire. Once we know the "favored recipe", this method seems to work well in later years, provided we refreeze that sire during the same season. If refreezing at a different time of year, complete retesting may be necessary in order to achieve good results. If, despite our selection of what we feel is the best method (based on postthaw MOTILITY), the sire happens to fall into the 4% where fertility with the product is unacceptable, we will reevaluate those extenders that may not have given quite the best motility, but which utilize different extenders and processing methods, and then retest fertility with the new combination. If this retesting and refreezing is required, our guarantee provides this work, including board at our facility, free of charge.

Jacks and zebras, so far, show similar individual variability from one sire to another. Our first "frozen mule" foal, born Easter Sunday, 1990, and featured on Sacramento's Channel 3 evening news the following week, has been followed by numerous other mule offspring. We now offer over two dozen jacks by frozen semen, and have several mules on the ground in England and New Zealand as well as many in North America.  Several of these jacks are now deceased, and are available only by frozen semen.

The advantages of breeding equines utilizing frozen semen are many. The mating of a chosen sire and dam over great distances becomes far less stressful and expensive, foals remain safe at home, bookings can be made anywhere in the world without the critical time-constraints associated with fresh-chilled semen, the mare owner saves substantial transport and board bills, while the sire owner has the opportunity to eliminate overhead associated with breeding and boarding facilities, and staff. A busy show or performance stallion can make his contribution to the next generation when most convenient for him, and without disrupting training or his competition schedule. Zoos and other organizations interested in procreating rare or endangered species must rely heavily on frozen sperm, as the opportunities to retrieve genetic material are often infrequent, rarely coincide with a female cycle, and must often be shipped to another zoo halfway around the world.

Disadvantages to frozen semen are, on average, a somewhat lower pregnancy rate per cycle compared to fresh semen (true for any species); with horses, frozen semen should average close to 50% pregnancy rates per cycle (some sires may consistently be a bit better, some a bit worse), as compared to the 65% rates expected with fresh or chilled semen. Frozen semen also requires a bit more in the way of training, equipment, and monitoring of the mare's follicular development to achieve good results; i.e. will cost the mare owner a bit more per cycle to use. In many cases, however, frozen semen may be the only method available for a particular sire, and is always an available backup if a sire is unavailable due to illness or competition. Our best three stallions, fertility-wise, have pregnancy rates of over 70% per cycle with frozen semen, over at least five years and many mares.

With most stallions, freezing work can be successfully accomplished year-round, although sperm production, and hence speed with which we can fulfill an order, are generally higher during the warmer months of the year. Extreme summer heat (much over 100 degrees F / 39 degrees C) can cause a temporary but severe drop in semen quality and freezeability. For extended projects in the wintertime, we can always keep a sire "under lights" at night, thus stimulating summertime levels of sperm production about two months later. If the sire has not been recently and actively breeding, it is important to collect (and discard) semen a couple of times prior to the freezing procedure. This "flushes out" old, dead sperm that accumulate during periods of sexual inactivity, and also assures us that the sire has normal semen quality suitable for cryopreservation. We can then provide the sire owner with an estimate of the number of doses we might obtain per collection.

The freezing process itself involves the addition of one of several possible centrifuge media; a solution of energy-providing sugars, plus salts or buffers, to the freshly collected semen. This mixture is then centrifuged at 300G to separate out the sperm. After discarding the liquid portion, the sperm "pellet" is resuspended in a separate freezing medium, generally a more complex mixture of salts, sugars, buffers, egg yolk, a special detergent, and glycerol, the protective agent which dehydrates the cell sufficiently to prevent ice-crystal formation during the freezing process. Otherwise, the ice crystals would rupture the cell membrane, killing it much like an autumn frost wilts tender vegetation. On rare occasions, the centrifuging process is skipped, when this method proves to provide the best results.

High-quality plastic straws are used to package the semen for storage in liquid nitrogen. We can use either the tiny, 0.5ml "bull" straws, or the larger "macrotubes" which hold 5ml (about the size of a soda straw). There are advantages and disadvantages to each straw size, so final selection is based upon a discussion with the client. The larger straws are more convenient for the inseminator to use, and are slightly more forgiving with small errors in thawing time or temperature, but because they take up more space, are also more expensive to store. The small straws are more economical to store, but generally dictate the use of multiple straws per insemination dose, and are very unforgiving if a handling mistake is made. We do not freeze in pellets, which cannot be stored in a method ensuring freedom from contamination, nor in plastic packets, which are awkward to store, brittle, and prone to cracking.

Each and every straw is labelled with the sire's name, Registration number and breed, the date of collection, and our own individual freezing code, which readily identifies us as the business responsible for producing that straw.

Filled straws are cooled at the selected cooling rate either in nitrogen vapor, or in a chest-type refrigerator prior to freezing in liquid nitrogen. Small straws are packaged into plastic goblets attached to metal canes; larger straws are stored on end directly in the tank cannisters. Each sire has his own tank and cannister location allowing quick retrieval. When ready to ship or use, the desired straws are withdrawn, reinspected in a nitrogen bath, and either transferred to a thawing bath for insemination, or carefully packed in a cryogenic shipper tank for shipment. A straw from every batch that we freeze is thawed after production, to critically assess motility, count, and culture. On rare occasions, potentially pathogenic microorganisms may be present in the semen, and these survive the freezing process along with the sperm cells. Knowing their presence helps avert potential infection in the receiving mare.

Once frozen, we ALWAYS recommend test-breeding a mare with the frozen semen in order to obtain a pregnancy, thus proving fertility, regardless of how "good" it looks under the microscope. This also insures that the sire owner is offering a "tested and proven" product. Oftentimes, clients agree to provide that "test mare" as part of a regular booking, in which case we add an addendum to the breeding contract allowing a full refund of the stud fee, at the client's request, if the mare does not conceive. We hope one day to complete a detailed computer program which will be able to collate and analyze all of the data we have amassed over the years, thus allowing statistical investigation of our various processing methods and the results.

Obviously, our approach to this procedure involves a fair amount of time, expensive equipment, and very careful, clean, and precise handling of the semen and extenders at every step. We prepare our extenders from "scratch", using the highest quality, purified chemicals; weighing them individually on an electronic balance to the nearest hundredth of a gram (a grain or two of salt). Liquid ingredients are then added, measured equally carefully in temperature-compensated cylinders, to make liter-sized batches, thus further minimizing any variation from batch to batch. This "pre-extender" is then divided into smaller aliquots, and frozen in sterile, amber bottles until needed. Just prior to use, we add fresh egg yolk (from a local egg farm), and an appropriate antibiotic. This extender must be freshly prepared within hours of use, and unused extender is discarded.

We are often asked "how many doses can I expect per collection?" This varies considerably from sire to sire, and breed to breed. Sperm production is best in late spring and summer, decreasing by a third or so in winter. As with bulls, stallions with larger testicles produce, on average, more sperm per day than stallions with smaller ones. Size alone is not the only criteria, however; younger sires have, on average, firmer and more productive tissue, such that a younger horse with smaller testes may outproduce an older individual with larger gonads. We have seen a range in production of from six to nearly one hundred doses per week; the average stallion producing about thirty per week; the average jack forty.

Currently accepted standards for frozen equine semen vary slightly around the world, but most commonly set a minimum level of 25 or 30% postthaw motility and 250 million motile sperm per dose. Data accumulated by us continues to suggest more strongly that the most important factor is the total number of normal, motile cells per insemination, NOT the motility percentage. We often use "substandard" straws on the sire owner's mares, for example, and have obtained pregnancies from semen having only 6 or 7% motility by combining many straws to make an adequate dose. We do not charge anything for straws produced which do not meet our minimum commercial standards of 25% postthaw, progressive motility, AND 250 million motile sperm per dose. Ideally, we aim for 300 to 350 million motile cells per dose, and most sires will produce semen with over 30% postthaw motility; sometimes over 50%.

In order to maintain consistent collection and laboratory conditions, which help us produce a uniform and predictable product, we encourage clients to bring their sires to our main facility in northern California. We also have arrangements with other adequate facilities near San Diego and Seattle, and can provide freezing services there if we get enough clients together. We can, by special arrangement, bring our laboratory to any facility in the world, provided that adequate collection and laboratory facilities are available, and have hauled our equipment overseas before. Stallions to be frozen for export will probably have to come to our USDA-approved facility, depending upon the current regulations of the country of destination. We have exported semen all over the world; from England to Czechoslovakia, the Phillippines, Brazil, and Sri Lanka. New Zealand currently has among the toughest regulations in existence, and our facility is inspected twice annually by the USDA, and is approved, to meet these exacting standards. Semen frozen to New Zealand protocols can be exported to almost any other country.

Most people, upon seeing the flushing and testing process from start to finish (average of ten to twelve days to accomplish), are surprised at how much time and equipment is involved, and only then understand why we prefer that sires be brought to our facility. We have frozen semen in stock from sires that were brought to us from as far away as Iowa, Oklahoma, and Edmonton, Alberta.

The most fertile of straws creates nothing if not handled carefully and competently. Equine females are not the most fertile creatures on earth, either, and some consideration should be given to the mare's past and current fertility before undertaking a breeding program with frozen semen. Conception rates with frozen semen are directly related to mare fertility, straw handling technique, and the skill of the inseminator. Because the best conception rates are achieved by breeding the mare within 12 hours prior to, and 6 hours after ovulation, the ability of the veterinarian to predict ovulation time can substantially affect the results, and the number of doses used per heat-cycle. We have two recommended protocols which both give good results, depending upon the skill of the veterinarian involved, their schedule, and the cost of the semen involved. The first is to check the mare's follicle every 12 hours as ovulation approaches, and begin insemination when you believe that ovulation is imminent. Rebreed every 12 hours, including the first postovulatory check. This normally uses up two or three doses per cycle.

The second method involves more frequent checking, but uses only one dose per cycle. Check the follicle every six hours (yep, that DOES mean somebody gets up at 2 am!!) and inseminate one time immediately post- ovulation. Regardless of the method selected, WE STRONGLY RECOMMEND THAT THE VETERINARIAN WHO IS TO PERFORM THE PROCEDURES BE SOMEONE WITH SPECIAL EXPERTISE IN EQUINE REPRODUCTION! In our experience, results with "general practitioners" have been noticeably lower.

Most semen imported into the United States is sold "by the dose", without any live-foal guarantee. This is fine, where rigorous testing, and proof of pregnancy production provide the mare owner with a good assurance of fertility. We always recommend to a mare owner that they inquire as to pregnancy RATES with a given sire, before purchasing semen by this method. We advise the stallion owner, on the other hand, that offering (proven) frozen semen with the usual live-foal guarantee will encourage bookings, at least until a substantial fertility track record has been established. On average, 6 or 7 doses will be required to obtain a pregnancy, under well-managed conditions, using the "breed every 12 hours" method. Hence, a stallion owner might reasonably offer a sire with a $2000. stud fee by live-foal guarantee, at $300. per dose, no guarantee. In the long run, either method works out comparable to the other for both mare and stallion owner, but it does offer the breeder two options to "gamble" with, depending upon their confidence in their mare and their veterinarian. We have a client who has bought straws "by the piece", and has obtained two successive foals from two straws purchased out of an Olympic competitor, at a small fraction of the "live-foal guarantee" stud fee. On the other end of the spectrum, we have shipped semen for two whole breeding seasons to mare owners without a pregnancy being obtained (both by frozen and chilled semen).

Breeding horses in general is not for the faint of heart!

Aside from individual Breed Registry stipulations, which may change from year to year, there are no restrictions on the use of frozen semen in North America. The requirement for International Health Certification for shipments to Canada was dropped early in 1997. We routinely test ALL sires frozen for Equine Infectious Anemia (Coggins Test), Equine Viral Arteritis (EVA), and Vesicular Stomatitis (VS), so that we can certify the semen as being free of these diseases, and allow export to many countries, even if regulations change next year. This testing is included in our test-freezing fee. Some countries, such as New Zealand, Australia, and the European Union, may require additional testing, and perhaps bona fide quarantine under USDA scrutiny. If export of straws to any country outside North America is anticipated, we should know this in advance of the freezing process in order to check on the latest requirements, and ensure proper export testing.

Providing a quality product and assisting both mare and stallion owner in reaching their breeding goals is not the end of our commitment. Besides ongoing and self-supported research efforts, Dr. Mennick has been part of two committees in the Society for Theriogenology; one which developed a standard, recommended protocol for a breeding soundness examination of the stallion, the other which is attempting to set standards for frozen semen quality control. He has served on the Board of Directors for the American Livestock Breeds Conservancy, and acts as one of three National genetic storage banks for this organization. He has also volunteered his expertise to the San Diego Zoo for their onager breeding program, and more recently has assisted with semen cryopreservation efforts from the endangered white rhinoceros. While Dr. Mennick feels comfortable 'entertaining' 1400 pound stallions and 2800 pound bulls, he has yet to be persuaded to get underneath a white rhino!

From a more commercial perspective, Pacific International Genetics offers a complete range of equine breeding services for mares, jennies, jacks, and stallions. Our frozen semen inventory now exceeds 200 sires, and we believe our selection of jacks by frozen semen is the largest in the world. We offer complete breeding and promotional programs for sires, including Website sire pages, can handle breeding contracts, mailing of videos and brochures, plus Registry paperwork, at whatever level of client involvement is desired. One of our specialties is the management of problem mares, and we perform embryo transfer, GIFT (gamete / oocyte intrafallopian transfer), embryo cryopreservation, and video-monitored / veterinary-attended foaling. We ship (fresh) semen seven days per week (six for frozen), cooperate closely with other specialists as required, and Dr. Mennick is available by pager 24 hours per day during the breeding season for urgent consultation.

Our custom-designed facility consists of a variety of paddocks and pens, five oversized box stalls, and a plenty of pasture. The laboratory, completed to our specifications in 1999, is as modern and well-equipped as that at any University. Our proximity to state USDA offices, three commercial airports, and Interstate highway 5 offers convenience to haulers, owners, clients, and visitors.

Additional questions, or requests for visitation appointments, are welcome, and Dr. Mennick is frequently in the office until well into the evening. Our desire is to provide the best possible service, and the best possible results. Unlike most doctors, we truly believe that ALL of our patients enjoy the visit!

Finally, 2005 marks our fifteenth year offering the equine industry a guarantee still unique to Pacific International Genetics. This guarantee offers a money-back guarantee that our frozen equine semen will be fertile, and offers additional work free of charge should this occur:

No one can absolutely guarantee that frozen semen, regardless of its appearance postthaw, WILL retain its fertilizing capacity. To our knowledge, however, we remain the only business offering the following guarantee: From any stallion having a normal semen evaluation, as disclosed during the initial test-freezing process, we will produce straws which meet or exceed minimum commercial standards of 25% postthaw motility (visual assessment under phase-contrast microscopy) AND 250 million, progressively motile sperm per dose (Unopette dilution and hemacytometer count) AND WHICH, AT LEAST IN OUR HANDS, can result in a pregnancy. If this cannot be accomplished, we will offer additional attempts at successful freezing at our California laboratory, AT NO CHARGE, INCLUDING BOARD, until either such further work is successful, or we have exhausted our attempts. If this refreezing work is still unsuccessful (our insemination of two mares in "good reproductive condition" over two cycles each), then we will fully refund the original test-freezing and straw fees. This is the limit of our guarantee, and we are not responsible for any consequential damages or expenses of any kind, directly or indirectly related to our work. To date, pregnancies have been acheived with approximately 96% of the stallions that have been adequately tested. We reserve the right to require test-breeding by us, in our hands, at our facility. This normally consists of two cycles each on two mares of "reasonable fertility", at sire-owner's expense, prior to issuing any refunds. We will take into account test-breeding work done elsewhere to some degree, depending upon that parties' level of expertise. All frozen semen should be tested for viability by obtaining a pregnancy with it prior to commercial use!! The costs of such testing are not included in our freezing fees, nor in our guarantee.

We believe that it is our very thorough testing that allows us to offer not only this guarantee, but the best possible product in the first place.