More horse owners than ever before have begun using transported chilled semen in their breeding programs. Shipping semen makes it possible to breed your mare to a stallion just about anywhere in the country without the expense, stress, and time of hauling your mare. This technique has been in use for over 10 years, but only recently have most breed registries allow its use. The procedures for using shipped semen and artificial insemination are not particularly difficult, but do require very careful attention to detail. In this article, we’ll describe the use of shipped semen, common complications, and try to help you decide if it’s suitable for your mare.

As clarification, shipped chilled semen refers to the practice of breeding mares with semen which is chilled - not frozen. Chilled semen is usually fertile 1-3 days while frozen semen has indefinite “shelf life”. Breeding mares with frozen semen is significantly more time consuming and less available than breeding with chilled semen. The time consumption comes predominantly from the increased palpation requirements needed for successful AI (artificial insemination) with frozen semen. For frozen semen it is necessary to palpate mares every 6 hours while chilled semen necessitates every day or every other day palpation. This article will only cover chilled semen.

Although using transported semen is a very effective, successful, and simple procedure, it is not necessarily the best method for all mares and stallions. Fertility rates are somewhat lower compared to AI of fresh semen and live cover. There are many possible causes for the lower fertility of transported semen. From the male prospective, not all stallions produce semen that will survive the cooling process and transport well. When considering the female causes, “problem mares” requiring several cycles to become pregnant, may have a smaller “window of opportunity” because the egg’s lifespan may be the limiting factor. When examined from a management perspective, breeding with shipped chilled semen definitely requires more intensive and accurate palpation of the mare, and excellent communication between everyone involved: mare owner and veterinarian, in concert with the stallion handlers and their veterinarian.

If you want to breed your mare with shipped semen, you must first find a farm prepared to collect and ship semen. Inquire about the stallion’s success, percentages (conception, pregnancy, and live foal), (percentages) as well as semen characteristics with shipped semen. Some relevant questions to ask are: %motility, % motility at 24, 48, & 72 hours, total conception for last season (namely # conceptions / mares bred), # live foals last season, % conception per shipment, # cycles per pregnancy, # breedings per conception. If the farm does not have any firm statistics, have your veterinarian open a line of communication with the farm manager or veterinarian. These fertility statistics are very important, and you should have them in hand BEFORE signing any contracts. At the very least, they indicate how closely a farm is monitoring (the) shipments, at best it will give you some idea of how successful you may be with a particular stallion.

Regarding contracts: read these carefully as huge variations exist. Ask for semen quality guarantees, inquire about refunds for mares not pregnant at the end of the season, and get it in writing. Paying with credit card helps you in the event of a contract dispute.

Once you have found the right stallion, expect to pay a booking fee and, for some farms, produce a clean uterine culture from your mare. Uterine cultures are requested to minimize the number of futile attempts a stallion would make trying to impregnate a mare with uterine disease. Although helpful, cultures are not as diagnostic as other techniques in the detection of problem breeders, but tradition is hard to change in the equine industry. Culturing of maiden mares is not warranted, but it can be a huge headache for stallion managers to know which mares are maiden and which aren’t.

Another farm expense will be shipping fees. These shipping fees cover the expense of collecting, preparing, and shipping the semen. Common fees average in the range of $200 and up. If the shipping fee is much higher, say $500, the farm is most likely using this fee as a source of income. Because re-breeding is common, you should carefully consider high shipping expenses.

The usual scenario to breeding mares with shipped semen is as follows: your veterinarian must first determine the stage of your mare's cycle. This can be accomplished by rectal palpation, sometimes ultrasound, and teasing with a stallion. Once this is determined, the mare is palpated near the beginning of anticipated heat. When the mare is near ovulation, your veterinarian will request that semen be shipped. Most farms require at least a one days notice, others only collect certain days of the week. This must be determined before the mare is in heat. If not, you might find that the cycle will be lost! Usually, if the farm cooperates, you can have the semen collected the same day and shipped either overnight or the same day. Same day shipping via commercial airlines is great, but usually requires more work from all involved.

The need for accurate timing of AI, as well as good communication between farms, is best illustrated by several facts. The life of the egg is 12 hours. Semen survives for 1-3 days, but often begins deteriorating after 24 hours. Ideally, a mare should be inseminated as few times, and as close to ovulation as possible, preferably not after ovulation. The common practice of saving a portion of the semen sample to use the next day is not advised for several reasons. First, insemination always causes a uterine inflammatory response that peaks 24 hours after breeding. Inseminating into an inflamed uterus is unsuccessful. That is why the practice of breeding every other day produces better results than breeding every day. Second, there is ABSOLUTELY NO EVIDENCE to suggest that semen stores in the container better than in the mare; common sense would indicate the mare is the best "storage". Third, although some stallions will store well for 3 days in the containers, I like definite confirmation of this from a veterinarian before I use it in this way. Usually, if the mare doesn't ovulate, I request a fresh shipment.. It is always a good idea to “push” the mare to ovulate with an injection of HCG (human chorionic gonadotropin), a hormone, which will stimulate a mature follicle to ovulate.

A word about the containers used to transport chilled semen. Several commercial containers are sold on the market with Equitainer‘, the most frequently used. A very recent university study compared Equitainer‘, ExpectaFoal‘, and Equine Express‘. All three containers worked equally well for the transport of chilled semen when storage time was approximately 24 hours. Equitainer’s‘ were more effective at maintaining an optimum temperature when storage was extended to 60 hours.

Use of chilled shipped semen allows you to choose from many stallions without the trouble, expense, and stress of shipping your mare. A breeding program using this convenient technology requires closely monitoring the mare's reproductive cycle and excellent communication between mare and stallion owners as well as all veterinarians involved. It’s a great advance for horse breeding but requires attention to detail. If you would like more in depth information on equine reproduction, chilled and frozen semen, please don’t hesitate to contact our office.

This article was published In Horseman's Marketplace magazine, Nov. 1997