Page 138 - Speedhorse February 2018

ICSI – AdvAnCeS In equIne RepRoduCTIon
“A lot of mares that people want to use are perfectly healthy, young broodmares, because it’s a semen issue rather than a mare issue.”
Part Two – Mare Issues
by Heather Smith Thomas
even though most breeders utilize ICSI as a way to get foals from a stallion that is no longer able to breed mares, a growing number of mare owners
are using this as a way to get more foals from a valuable or favorite mare. “In Europe, interestingly, the warm- blood breeders have started using ICSI for convenience, which is something I am concerned about,” says Katrin Hinrichs, DVM, PhD, Texas A&M. “If you are breed- ing via ICSI, you bring the mare in periodically to the veterinarian and have her follicles aspirated to collect eggs. You don’t need to give her a break from training, have her ultrasounded every day or order semen for a certain day as you would for a natural conception cycle. From the mare owner’s side, it seems simple. You just bring her in once every 2 weeks or once a month to aspi- rate the follicles, then you take her home and continue doing whatever you were doing with her before,” she says. The mare doesn’t need to be in heat for the process.
The follicle aspiration procedure is not without risk, however, and is not like putting semen into the uterus. This is an invasive procedure in which a needle punc- tures repeatedly through the vaginal wall and into the ovaries. “We’ve done studies on this and have shown that the complication rate is very low (about one in 300). However, follicle aspiration could potentially lead to peritonitis, an ovarian abscess, or even death. Would people want to take this risk with a valuable mare for no reason?” Hinrichs asks.
Warmbloods have a large number of follicles compared to other breeds, so the efficiency is high. “The people doing ICSI with warmbloods are getting more blastocysts (embryos at the stage that they can be transferred to the uterus of a recipient mare) per aspira- tion than if they were doing embryo recovery from the uterus,” she explains.
“Warmblood mare owners are looking at this
in terms of not having to fuss with the mare and at the same time getting more embryos transferred per cycle, but I think they have to consider the risks to the mare also. There doesn’t seem to be as many breeders doing ICSI for convenience in the U.S. Perhaps this
is because ICSI is so expensive compared to embryo recovery and transfer, and maybe because the follicle numbers in Quarter Horses are not as high, so the number of oocytes recovered is lower.”
Only a small proportion of recovered oocytes actually develop into blastocysts. “Thus, the average numbers of blastocysts produced for Quarter Horse- type mares per cycle with ICSI is typically 1 to 1 1/2, which is not a lot higher than that for standard embryo recovery,” says Hinrichs.
A blastocyst is an embryo that has reached the stage at which it can be transferred to the uterus of a recipient mare.
RIsks To T he MaRe
One of the first questions people ask when trying to decide whether to try ICSI is if this procedure will hurt their mare. “A lot of mares that people want to use are perfectly healthy, young broodmares because it’s a semen issue (trying to get a foal from a certain stallion) rather than a mare issue,” says Dr. Rick Beck, whose In-Foal Inc. practice in Hemet, California is one of only two private practices in the U.S. that does ICSI. “Mare owners don’t want you poking needles in their mare’s ovaries if it will ruin the mare. These mares are worth a lot of money, so we’ve done a lot of work to answer that question, try- ing to demonstrate the safety or lack of safety with this procedure,” says Beck.
He has a nice cutting horse mare of his own that he bought a couple of years ago and used for multiple aspirations. “When we harvest immature follicles, you don’t have to wait for the mare to cycle and have a big follicle. You can aspirate eggs about every 10 days because mares just keep creating a bunch more little follicles. You take those eggs out and then come back again and the mare has a bunch more little fol- licles because she never did ovulate,” he explains.
“So, we aspirated this mare 31 times in one year and made 23 embryos. We transferred 11 of them and froze the rest. I had eight yearlings to sell this year from that mare. That’s an exceptionally good success story,” he says.
After all those aspirations, he bred that mare last spring for an embryo transfer, flushed an embryo out
Heather Smith Thomas
136 SPEEDHORSE, February 2018
equine health