More horse owners than ever before are using transported chilled semen in their breeding programs. Shipping semen makes it possible to breed your mare to a stallion anywhere in the country without the expense, stress, and time of hauling your mare great distances. This technique has been in use for more than 20 years but it is until the last decade or so that almost all breed registries (with the major exception of the Jockey Club - racing Thoroughbreds) allow its use. The procedures for artificial insemination (AI) of shipped semen 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 can significantly more time consuming and somewhat more expensive. Time and expense are comes predominantly from the increased palpation requirements needed for successful AI of frozen semen. One protocol for breeding mares with frozen semen requires the palpation of mares every 6 hours while chilled semen necessitates every day or every other day palpation. Another basic protocol for using frozen semen advanced by Colorado State University involves timed AI using 2 doses of frozen semen. This article will only cover chilled semen. If you’d like more information on frozen semen, please refer to our article on Breeding Your Mare With Frozen 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 or in some cases live cover. There are many possible causes for the lower fertility of transported semen. From the stallion prospective, not all stallions produce semen that will survive the cooling process and transport well. When considering the mare causes, “problem” or infertile 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 accurate palpation and ultrasound exams of the mare, and excellent communication between everyone involved: mare owner and veterinarian, in concert with the stallion management.
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, THIS IS IMPORTANT: (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, 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. For more information on this subject please see Questions to Ask the Stallion Manager.
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 contract dispute.
Equine Viral Arteritis (EVA) is a disease which can be transmitted by live cover, and AI of both chilled and frozen semen. Click here to read more.
It is fairly simple to control with the following protocol. Ask the stallion owner about the EVA status of the stallion. Stallions can be vaccinated against this disease, but must test negative before vaccination. If breeding to an EVA positive stallion, vaccinate your mare at least 30 days before breeding. These mares should be tested prior to vaccination and should be isolated from direct contact of non vaccinated horses. If breeding to an EVA negative stallion no action is necessary. If EVA status of the stallion is unknown the risk of this serious disease to your mare is unknown.
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 frequently not as diagnostic as other techniques such as uterine cytology or ultrasound 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 follows: your veterinarian must first determine the stage of your mare's cycle. This can be accomplished by rectal palpation and ultrasound examination, as well as 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 would 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. Many shipments arrive with 2 doses of semen. Some breeders recommend the practice of saving the 2nd semen sample for use the next day. We do not routinely advise this practice for several reasons. First, insemination always causes a uterine inflammatory response that peaks 24 hours after breeding. Inseminating into an inflamed uterus can be less successful. Second there is no evidence to suggest that semen stored in the container is better than in the mare; common sense would indicate the mare is the best "storage". Third, although some stallions will store well for 2 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. Having said all this I have successfully bred some mares in this manner.
In order to use the fewest doses it is a standard practice to induce the mare to ovulate with an injection of HCG (human chorionic gonadotropin) or desorelin, hormones which will stimulate a mature follicle to ovulate. These agents take 24-48 hours to work so I prefer to inject them the day before AI.
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 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.
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