Page 141 - Speedhorse February 2018

AUTO-TRANSFER
Another innovation currently being done at Colorado State University is transfer-
ring the embryo back into the donor mare. Patrick McCue, DVM, PhD, Diplomate ACT (Equine Reproduction Laboratory, Colorado State University) says this is some- thing he thinks will become more common in the future.
“We’ve recently done this at CSU several times. We collect an oocyte from a young, fertile mare and do sperm injection utilizing a stallion that has limited numbers of sperm. We utilize ICSI on that egg and put it in an incubator and let the embryo start to develop and then transfer that embryo back into the donor mare and let her carry her own preg- nancy.” This is analogous to what is being done in humans to enable a woman to have
a pregnancy.
“In the horse, using a recipient mare is
standard for traditional embryo transfer to generate pregnancies, but auto-transferring back to the same mare certainly can be done and we have done it here. This procedure has not taken off yet in our breeding industry and I think people need to know it can be done and that there’s the possibility for the mare to carry her own pregnancy.” There would be some advantages to this for breed- ers, who would rather have their own mare have her own foal.
Dr. Katrin Hinrichs (left, with Cicily Grady) and her team at Texas A&M work constantly to improve the rate of blastocysts produced from doing ICSI on oocytes.
work. In general, however, mares under 20 are a good risk, while mares between 20 and 25 have more issues. Mares over 25 have a pretty low success rate,” he says. It’s always a gamble with the older mare and can be a lot of work with no results.
COST
“We do the aspiration, sperm injection and culture for free. The client only pays us when we get a pregnant recipient mare. When we do the first pregnancy check, the client pays us $5,000 if the recipient is pregnant. When she is 45 days pregnant, they pay us another $5,000 and take her home. If she loses the pregnancy in that early window, we give them their original $5,000 back. In other words, we offer a $10,000 guarantee for a 45-day pregnant recipient mare or they don’t pay for anything except the board on the donor mare while she is at our place. This means the pressure is on us. If we don’t make it work, we don’t get paid. So, we go out of our way to make it work and our success rate improves every year. We are continually fine-tuning our procedures.”
ONGOING RESEARCH
Dr. Hinrich’s team at Texas A&M works constantly to improve the rate of blastocysts produced from doing ICSI on oocytes. “We made some changes earlier this year and over the last six months our blastocyst rate per injected oocyte has been consistently around 40%, which is the highest we’ve ever had. We also just completed a study on using the con- ventional method for ICSI versus the method we’ve used for the past 17 years, the Piezo drill.
We found no significant difference in blas- tocyst production between the conventional method and the Piezo method,” she says.
The Piezo is a drill that takes out a piece
of the covering (zona) around the oocyte and the conventional method uses a sharp pipette to just poke through it. “Our senior embryolo- gist, Dr. Renato Salgado, directed the project and is the first author of the paper that we have submitted for publication on this important study,” she says.
“In another study last year, we used a differ- ent medium for the last half of embryo culture and this resulted in a higher pregnancy main- tenance rate in our clinical cases. Our earlier pregnancy loss rate had been of concern to me, about 20% of the pregnancies produced from these ICSI embryos were lost. Last year, with our new culture system, we got that down to about 10%, which is about the same loss rate as for normally conceived embryos, usually about 8%,” says Hinrichs. Fine-tuning some of these methods is making better chances for success with ICSI.
Beck is also studying different media for growing embryos, transferring them and for freezing. “This is another issue. If you get 5 embryos and you were only planning on one baby, now what do you do? We recommend that you transfer two of them (because based on the law of averages, you’ll probably only get one) and have a plan for what to do with the second one if you get lucky and have two, and then freeze the rest. This has worked out very well,” says Beck.
“Our pregnancy rate is not as good with fro- zen embryos. The pregnancy rate is about 50%. We are working on increasing this percentage and we’ve found that some embryos freeze a lot better than others. Some mares that we freeze have an extremely high success rate on the transfers, while some don’t have much success at all. That’s another unknown. Why do some of them freeze so well and others don’t?” This is something they hope to find out.
“From the end of the breeding season until mid-November 2017 we have frozen 65 com- mercial embryos that we will transfer in early spring. This is another tool that mare owners can use, especially if they have a difficult mare and don’t want to have a June foal. They can bring her here and let us work on her in the off season and freeze a couple embryos. Then we can put those into a recipient mare in February and if she has a foal, it will be in January. This option is attractive to a lot of people for a lot of reasons,” he says.
“It’s also attractive to us because it spreads our year out a little more and it takes some of the pressure off early spring because, if we already have the frozen embryos, all we have to do is thaw them out and transfer them,” says Beck.
SPEEDHORSE, February 2018 139
EQUINE HEALTH