In this episode of the Disease Du Jour podcast, Carly Turner-Garcia, DVM, DACT, discussed ovum pickup (OPU) and intracytoplasmic sperm injection (ICSI). She explained some of the advantages of these procedures, the overall success rate, and the risks involved.
Advantages of OPU and ICSI for Horses
Ovum pickup is a technique used to harvest oocytes straight from the horse’s ovary. Intracytoplasmic sperm injection involves injecting a single sperm cell into a single egg to fertilize it in the lab.
In many situations, OPU and ICSI are more advantageous than traditional breeding or embryo transfer in horses. Mares with chronic endometritis, semen allergies, cervical problems, and other reproductive issues that would struggle to become pregnant or carry a foal can often reproduce successfully through OPU and ICSI.
OPU can be more practical than embryo transfer for competition mares because owners don’t have to wait for them to come into heat and don’t have to wait for the embryo flush. “If they have enough follicles, you can just bring the mare in, have OPU done, and then she can leave the same day if everything goes well,” said Turner-Garcia. “Usually, I just say give them 24 hours off [after the procedure].”
OPU and ICSI are more likely to produce multiple embryos compared to embryo flushing. The procedures are also valuable when breeding to subfertile stallions or stallions with very limited semen available. “You can stretch a stallion’s genetics and lineage a lot longer using him for ICSI than you could breeding traditionally,” Turner-Garcia said.
What Types of Mares Are Ideal Candidates for OPU?
“Fertility is fertility,” said Turner-Garcia. “Your most fertile mares are going to be your sexually mature, younger mares anywhere from the age of 4 up until the age of about 13.” After that point, your odds of success with anything breeding-related start to trend down. Older mares in their 20s probably won’t have many follicles, so there are fewer opportunities to be successful, but Turner-Garcia says you can still get it done.
“I’ve seen embryos made on 26-year-old mares, but in general, it’s going to take a little bit more time, a little bit more financial investment, and some pretty fertile stallions to get success on your older mares that are in their mid-20s,” she said.
Turner-Garcia said OPU might be more successful in the fall when mares are transitioning out of their natural season.
OPU is also possible on deceased mares. Turner-Garcia said your best chance of success is to put the mare under anesthesia and take the ovaries prior to euthanasia. However, if the horse dies unexpectedly, you can still be successful if you can get the ovaries or oocytes to a lab within six hours. After 12 hours, your odds of success drop off significantly.
Success Rates for OPU and ICSI in Horses
Turner-Garcia shared success figures for OPU and ICSI based on data from the Lazy E Ranch, where she performs OPU, and their sister lab, Reliance In Vitro, which has achieved more than 7,000 ICSI pregnancies and more than 15,000 ICSI embryos. Both facilities are located in Guthrie, Oklahoma.
Turner-Garcia explained that success depends on the setup for the procedure. Veterinarians who travel to a farm and perform OPU on all the mares that day might recover between six and 10 oocytes from each mare.
She has many mares that live with her for the full season or year-round. She can monitor these mares, manipulate their cycles, and perform OPU when they have the most follicles, which has resulted in an average of 15 oocytes retrieved per OPU. They typically have a 70% maturation rate and, of that 70%, about an 85-90% cleavage rate. Reliance In Vitro successfully makes embryos 93-94% of the time. Overall, they average four embryos per OPU session, but that rate varies based on the lab.
Risks Associated With OPU
Turner-Garcia has been performing OPU heavily for seven years, and she said she very rarely sees anything happen to the mares. However, this is largely dependent on the experience of the veterinarian driving the needle.
She occasionally sees mares get crampy, but these are mares that are also painful when in heat. They usually feel better after six to 12 hours. Another potential side effect is contamination when transferring the needle from the vagina to the abdomen if the mare is dirty, so she cleans mares up as much as possible before the procedure if they have chronic endometritis. There is a small risk of rectal tearing, but Turner-Garcia says this happens more often with flushing embryos than with OPU procedures.
“Overall, I think it’s actually a pretty safe procedure, especially if you have someone do it that’s skilled and has had a lot of practice,” she said.
About Dr. Carly Turner-Garcia
Carly Turner-Garcia, DVM, DACT, is currently the head veterinarian at the Lazy E Ranch, in Guthrie, Oklahoma. She is board certified in theriogenology, and her areas of specific interest are advanced equine reproduction and equine neonatology. She graduated veterinary school from the University of Georgia, completed an internship at Rood and Riddle in Kentucky, and completed a residency at Texas A&M University. She has a passion for horses and teaching people about them. She and her husband also own Top Cat Genetics, where they raise cattle and registered Boer goats and train and trial working American Border Collies.
Related Reading
- Historical Perspectives in Equine Reproduction: Pioneers in the Age of Discovery
- Breeding Problem Mares
- How To Synchronize Recipient Mares on the Farm
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