10 Steps for Successful Artificial Insemination for Horses
Artificial insemination (AI) is today's breeding standard for many types of horses. To find out how to make our readers' artificial insemination programs more successful, The Horse went to two recognized experts in equine artificial insemination--both of them pioneers in their field.
Christine Aurich, DVM, PhD, Dipl. ECAR, professor at the Centre for Artificial Insemination and Embryo Transfer and Graf Lehndorff Institute for Equine Science and at the University of Veterinary Sciences in Vienna, Austria, has published or presented more than 50 scientific publications worldwide on equine reproduction. Her recent discoveries are leading to significant improvements in handling and transporting sperm. Robyn Woodward, BVSc, MVSc, MRCVS, who operates Equivet Australia's Equine Breeding Centre, in Queensland, performed the first successful equine embryo transfer in Australia. During the off-season she leads insemination programs in breeding facilities throughout Europe, specializing in frozen semen inseminations.
With their help, we've put together a "top ten" list of hints so that your next artificial insemination project will as successful as possible.
1. Choose the right mare
Regardless of her age, a mare should be examined for reproductive soundness before breeding, according to Aurich. An exam of the reproductive organs is sufficient for young mares, whereby the veterinarian checks for malformations or cervical dysfunction. The practitioner should routinely culture the uterus and assess uterine cytology in broodmares of all ages, and in older broodmares it's important to perform an endometrial biopsy to determine if any alterations exist that could affect fertility.
"Maiden" mares--those that have never foaled--are a particular risk group when they are of advanced age, says Woodward. "The lining of their uterus, if they haven't used it, does deteriorate, and their cervix might not dilate as much as that of a younger mare during estrus." While these mares could still be successfully inseminated, more post-insemination treatment of the uterus might be required. Therefore, they are often poor candidates for frozen semen insemination, which, as we will explore further in a moment, presents a host of challenges of its own and is a much more invasive process for the mares.
Know in advance some of the risks of breeding your particular mare. This will help you make wise choices and have realistic expectations. The right mare for breeding depends largely on your budget, your accessibility to breeding farms and/or referral clinics for reproductive issues, and your flexibility in choice of stallion.
2. Choose the right stallion
They all look magnificent on the glossy pages of the stallion catalog and as they trot to music on the stud farms' promotional DVDs. But when it comes to getting your mare pregnant, you also want a stallion with strong semen quality. "It doesn't matter how fertile the mare is; if the semen is of poor quality, it's probably not going to work," Woodward says.
Ask the stud farm owners about the stallion's fertility, requesting results from any semen quality tests. According to veterinarians, the per-cycle pregnancy rate (percentage of mares that conceive per estrus) provides the most useful information. "You should also always find out what happens if the mare doesn't get pregnant," says Aurich. "If they have a very high stud fee and they don't have any provisions for nonpregnant mares, then you should be very suspicious." Some stud farms will offer a "live foal guarantee," meaning they will refund the stud fee, or at least part of it, if the mare does not produce a living foal.
You should also consider the long-term genetic consequences of breeding with low-quality semen. "There's a real question at the moment about whether we're creating a breeding stock of reproducers with poor-quality semen (through assisted breeding), and this is a serious problem," Aurich says.
Different countries, regions, and even states have varying requirements on testing shipped semen for contagious equine metritis and other venereal diseases. While most countries require breeders to designate a stallion's disease status and test his semen before shipping, it's important to ensure the shipper meets these testing requirements.
3. Choose the right place to breed
The right place to breed your mare via AI might be your very own farm. This is particularly true if you have a young, fertile mare that is easily stressed by separation from her pasturemates. But in many cases, the preferred location is a high-quality breeding facility. According to Aurich, a breeding clinic often provides more attentive care, better results, and lower costs.
If you choose to keep your mare at home, make sure you're working with veterinarians who are qualified to conduct AI in horses, says Aurich. Find out if they have diplomate certification in theriogenology (animal reproduction) and if they do any kind of continuing education. In Europe and the United States, veterinarians who specialize in reproduction can acquire the status of "diplomate" by passing an ambitious exam provided by the European College of Animal Reproduction and the American College of Theriogenologists, respectively. Also get recommendations from other breeders.
"You can lose a lot of time and money through bad veterinary management," says Klaus Kuhlemann, a physician and owner of a Trakehner breeding farm in Alpen-Veen, Germany. "We once had to change veterinarians when excessive exams and inseminations led to more than 4,000 euros ($5,000 USD) to inseminate a single mare."
Stallion owners also benefit from a professional center, because semen collection could be dangerous for the stallion and the handlers if not carried out under optimum conditions. "You can also do a lot of detrimental things to semen during collection and processing," says Aurich. "It's very important for both the stallion and the personnel to be well-trained."
4. Prepare your horse for the breeding season
Any horse entering a breeding season should above all be healthy, Woodward says. Make sure your stallion or mare is up-to-date on all vaccinations; have the hooves examined and trimmed by a qualified farrier; get the teeth evaluated and, if necessary, floated. Check for parasites using a fecal egg count test and follow a deworming program that your veterinarian recommends. Also ensure your horse's body condition remains between desired Henneke body condition scores of 5 (moderate) and 7 (fleshy).
As mentioned before, a uterine culture can be useful--an annual culture can reveal the presence of pathogenic bacteria in the mare's reproductive tract before breeding attempts start. If infection is found, it must be treated with antibiotics prior to breeding. Treatment can be difficult, especially in older barren (nonpregnant) mares, and it might be necessary to postpone breeding.
Lactating mares that foaled earlier in the year without complications can be induced to have a short cycle just after the foal heat (the first estrus that occurs after a mare delivers a foal) and before peak lactation. "Sometimes their bodies prefer producing milk to thinking about having babies again," Woodward says. The foal heat also is a prime time to check for fluid (which could interfere with insemination) and infection, she added. Some mares, especially those with poor vulvar conformation, might also need a temporary Caslick procedure (surgical closing of the upper part of the vulva) just after foaling to prevent new contamination via aspiration of air, dirt, or debris.
In addition, maiden mares, especially young ones, can benefit from pre-breeding training, says Aurich. "Get them used to being transported and having gynecological exams," she says. "It will keep their stress levels down later when fertility is impor-tant."
5. Choose the right semen presentation
The pros and cons of each kind of semen presentation (fresh, chilled, or frozen) must be weighed against the reproductive strengths and weaknesses of your mare or stallion.
Fresh semen This undergoes minimal or no processing and always has the highest fertility. It's longer-lasting once inseminated, the inseminated mare requires less frequent veterinary checks prior to conception, and it's usually the least expensive method. However, as it can't be transported and must be used almost immediately, mares and stallions need to be at the same location for insemination.
Chilled semen Mare owners order chilled semen and can have it transported inexpensively overnight by carrier or postal services using Styrofoam boxes or the more cost-intensive Equitainer. It usually retains good viability for 24-30 hours plus an additional 24-48 hours once inseminated. Ordering, shipping, and delivery must be well-managed to respect the semen viability time constraints, and the mare owner must order new semen if the mare does not ovulate within 24-48 hours after insemination.
Frozen semen Liquid nitrogen tanks can preserve frozen semen for years, which allows it to be ready and on hand whenever your mare ovulates. Special transporters, known in the U.S. as dry nitrogen shippers, can deliver frozen semen worldwide, and new one-way shipping containers provide a less expensive and more convenient way to transport frozen semen, Aurich says. Even so, frozen semen remains the most expensive and least successful AI method.
Not all stallions can have their semen frozen or even chilled, Aurich says; up to 20% of breeding stallions have sperm that are easily hampered by processing and cold temperatures. Sometimes the extender, which dilutes and nourishes the sperm, can be adjusted to improve survival. But if your stallion is among that 20%, you should probably encourage mare owners to accept it fresh.
6. Choose the appropriate ultrasound/insemination program
Ultrasound the mare every day or every other day if you plan to use fresh or chilled semen. When the ovarian follicle reaches a size of 35 mm and the mare shows strong signs of heat, she should be inseminated every 48 hours until she ovulates, according to Aurich. The veterinarian can induce ovulation with a luteinizing hormone analogue--human chorionic gonadotropin (hCG)--injection or, if available, a drug that stimulates the secretion of the mare's own luteinizing hormone (such as the GnRH analogue deslorelin) to help limit the number of inseminations.
The goal with frozen semen is to inseminate immediately after (within six hours of) ovulation, Aurich says. This reduces the number of inseminations, usually to just one, but it means the veterinarian must increase the frequency of ultrasound scans to once every six hours, day and night.
"We inseminate as soon as the follicle is gone (indicating the egg has been released)," she says. "Then we are quite sure that we have inseminated her within six hours after ovulation."
A less labor-intensive option is to give the mare hCG or deslorelin and then inseminate 24 and 40 hours later.
7. Get the timing right
The timing of ultrasounds, ovulation induction, semen shipping, and insemination is critical.
During heat, a mare's uterus shows characteristic signs of edema (fluid swelling) because of endocrine changes related to estrus. The veterinarian can detect this easily by examining the reproductive tract with ultrasonography. Don't give an hCG shot unless the mare shows these clear signs of heat in addition to a large follicle, Aurich says. And check with the stud farm first to be sure they can ship semen that day.
Order chilled semen at the same time as you give the hCG injection, says Aurich. The semen should arrive in about 24 hours, the mare should be inseminated immediately, and she should probably ovulate about 12 hours after that.
To be on the safe side when dealing with the unknowns of shipping overseas or cross-country, many breeders wait until the semen is in hand, then give hCG and inseminate. Good pregnancy rates can still be achieved with this method.
Frozen semen might take longer to arrive, so never induce estrus or ovulation until your order is waiting in the tank. "These shots are indispensable tools in equine reproduction," Aurich says. "But if they're going to be productive, they have to be used wisely."
8. Fight bacteria
With proper management, sexually transmitted diseases and bacteria such as Streptococci will have been controlled prior to the breeding season. However, there is always some kind of bacterium present during breeding.
"It's never a sterile process, no matter how clean you keep it," says Aurich. "You always have bacteria on your fingers or tools, and the mare has it in her vagina. Stallions have it on their penises, and it can come from the dummy (the phantom mare used when collecting semen) and the tools used in sperm processing."
The effects of bacteria on a mare are usually minimal as long as she is healthy. But a susceptible mare (one with signs of persistent endometritis) will need medical assistance clearing her uterus of bacteria within hours after insemination so infection does not interfere with her fertility.
For sperm, bacteria can be deadly. "It can completely destroy the spermatozoids during storage," Aurich says. Fortunately, keeping semen cool will stop the negative effects of bacteria. "Our research has shown that when you keep semen at 5°C (41°F), the bacteria appear to be neutralized," she says. Once the temperature rises to even 15°C (59°F), however, it becomes active--and destructive--again, and adding antibiotics to the extender isn't always very helpful. Semen extenders always contain antibiotics to prevent excessive bacterial growth during storage and shipment, according to Aurich, but this isn't always enough.
Bacteria-infected semen is easy to recognize under a microscope (the bacteria themselves are visible, and the semen have very poor motility) and should be refused.
9. Stick to the program
A common AI pitfall is not being vigilant about following the mare's status after insemination.
"A lot of people want to take their mares home as soon as they've been inseminated, but post-service treatment is very important," says Woodward. "Post-service treatment assists the mare in evacuating the uterus well if she is showing signs of inflammation or infection."
Some owners also neglect to have their mares checked for pregnancy within the optimum 14-16-day window, when it's still possible to catch the next ovulation. "If you're just waiting to see if she goes into heat again, it's often too late," Aurich says.
This time frame also makes it easier and safer to reduce a twin pregnancy if necessary, Woodward adds.
10. Keep stress to a minimum
Studies show that normal stress related to the breeding process, including transportation, separation, dummy mounting, and examination and insemination procedures is not significant enough to negatively affect fertility, according to Aurich. However, each horse and each situation are different. Keeping horses calm and cool is generally a good rule of thumb when breeding.
Working and competing horses also tend to be less fertile, Woodward says. The fertility level varies from one horse to another, so owners should be mindful to monitor fertility rates with a working horse and to modify the program if necessary.
Most of the keys to successful AI involve making wise choices. Armed with good information and a competent team, you can feel confident that your next AI procedure will be a positive experience for you and your horse.
About the Author
Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.