Veterinary Q&A: Embryo Transfers
Dr. Sabrina Jacobs, of Performance Equine Vets in Aiken, recently took time out of her busy schedule to offer insights and advice on using Embryo Transfers to improve a breeding operation. In a Q&A interview with The Aiken Horse, Dr. Jacobs talks about the costs, medical issues and pitfalls one should expect when considering embryo transfers.
We hope this interview will provide our readers with a greater understanding of these particular services and how better to use them in a successful breeding operation.
AH: Explain briefly the Embryo Transfer (ET) process, starting with how an egg is fertilized.
SJ: In the donor mare an egg is released from the ovary and travels into the fallopian tube where it meets the sperm and fertilization takes place. After fertilization the embryo enters the uterus in approximately 6 days. Once in the uterus the embryo is mobile and moves around quite a bit. We are flushing and transferring the embryo in this mobile stage. Approximately 16 days after transfer to the recipient mare, the embryo will physically attach to the recipient’s uterus. The embryo’s movement throughout the uterus is actually very important and is thought to play a role in maternal recognition of the pregnancy.
AH: How old is the embryo when you transfer it to the recipient?
SJ: 7 days typically although that can vary with different mares and stallions.
AH: How long does it take on average, start to finish, to complete an ET and confirm a pregnancy? How many days should a client expect to wait for an ET to be completed?
SJ: The Donor mare cycle will typically last 3-7 days, she is then flushed at 7 days and we can determine if the recipient mare is pregnant 4-5 days later. This is 11-12 days from the ovulation date. The entire process can take a month sometimes to complete if a mare is “dirty” and needs to be cleaned up for her next cycle. We do have the ability to short-cycle a mare, meaning that we can shorten the time between cycles. This is sometimes done if stallion semen is delayed and we miss our window of opportunity to inseminate the donor mare.
AH: Can I use my own mares as recipients? What are the problems with using the mares at my farm?
SJ: The synchronization of the donor and recipient is one of the most important aspects. The recipient mare MUST ovulate in a very small window in order to receive an embryo from the donor mare. Attempting to manage this process on a client’s farm is difficult and costly. Daily farm calls just to cycle and medically manage a client’s recip mares runs up the cost dramatically. The mares I keep in the PEVS recip herd have an ideal uterus. They are young, usually under 10 years of age. The key to having a high success rate for embryo transfers depends on the ability to transfer a CLEAN embryo into a CLEAN uterus and have it maintained in that environment till term. At PEVS, our recipient mares are managed on a daily basis to perform that function.
AH: What is the success rate at PEVS for ETs?
SJ: Each mare’s fertility is quite variable so pregnancy rates are not the same for every mare. Currently, our success rate for transferring a viable embryo into a recipient and having it stick is about 85%. There’s always the risk that a client falls into the 15% which don’t take. When this happens the cost increases. But, by utilizing the embryo transfer process, a client with a valuable mare can recover and transfer multiple embryos in a single season, greatly increasing the number of foals produced.
AH: Briefly explain how your recipient herd is managed to maximize results for ETs done at PEVS.
SJ: All of our recipient mares are considered ideal. If I don’t like them, we don’t use them. Each mare is checked daily and kept current on vaccinations and deworming. They are cultured before and during the breeding season to insure they are clean. They are given medications to speed up their cycle and sometimes slow it down in order to synchronize them with the donor mare. We treat our recips with anti-inflammatories and antibiotics at the time of transfer to improve our success rates. People often ask about the quality, temperament and behavior of the PEVS recipient mares. Our mares are all gentle, halter broke mares. They are in excellent condition and ready to go home with clients once a pregnancy is confirmed.
AH: What are some of the drugs used when doing ETs?
SJ: There are a wide variety of drugs that we use to manage the ET process. Here are a few examples. Prostaglandins are most commonly used to shorten the interovulatory period or short-cycle the mare. Progestogens or Progesterones (ie. Regumate) can be used for multiple reasons such as shortening the duration of transitional season, synchronization of ovulation among multiple mares, maintenance of pregnancy, and also suppression of estrus. Oxytocin is used quite frequently, mostly for uterine evacuation but can also be used to accelerate uterine involution and even to promote milk production in the mare post foaling. Deslorelin is our drug of choice to induce ovulation but hCG is also used sometimes. We use various antibiotics to treat uterine infections, the choices depend on the culture results obtained. The ones we use most frequently are SMZ, Naxcel, Penicillin, and Timentin.
AH: What is the average cost for an ET? What typically increases the average cost?
$4500-$5500 is typical. The cost can increase due to mare difficulties including abnormal cycles or uterine infections, reproductive conformation, and body condition to name a few. Stallion factors can also increase the cost. Poor semen quality, poor fertility rates, and unreliable semen shipments can cause delays. Delays in time arrising from these problems can lengthen the entire process, and that directly affects the cost.
AH: From a Vet’s point of view, what is the #1 problem with doing ETs?
SJ: The most important part of the entire process is the transfer of the embryo. It is often discussed in Veterinary circles that your first 100 transfers are just practice until you get your technique down and get good at the process. It is nearly impossible to be proficient at transferring embryos unless you do them all the time. Our success with embryo transfers is directly related to the fact that we have years of experience getting the job done.
AH: How can a breeder use the ET process to improve their operation?
SJ: The most common reason is to produce offspring from valuable mares that are still in their prime show career. Another reason is to increase foal production from valuable stallions and mares during the season. The embryo transfer process allows you to recover multiple embryos in a single season. If you’ve got a good mare – stallion combo, simply increasing production of that pair can greatly improve the bottom line for a breeding operation.
