Page 169 - January 2018

Embryo transfer began in the 1970’s. You could breed a mare, collect the embryo, put it in a surrogate mare and have a foal, while the donor mare could continue to reproduce.
“Then with some mares you come to the point where you can’t get embryos from them anymore. Maybe you have a really nice mare that is making you $100,000 a year with her foals, but now can’t. She may have a torn cer- vix, infected uterus, full of fluid, or whatever and you can’t get embryos from her anymore,” says Beck.
Then comes ICSI. “Through this proce- dure a mare can still give us foals. She might have all kinds of problems in her uterus, but these are totally irrelevant because we don’t need the uterus. We go directly to the ovaries and take the oocytes out of the follicles. As a result, it doesn’t matter how bad the uterus is or how many embryos have been flushed or what kind of infection she has. As long as she has ovaries that produce follicles, we can make babies,” he explains.
Another reason horse owners use ICSI is
to perpetuate the genetics of a good stallion. “If you have a stallion that has died or become infertile and you have a limited amount of fro- zen semen or you’ve used it all except for a few straws, we can take one straw of frozen semen and breed hundreds of mares,” says Beck.
A good example is the popular stallion Walk Thru Fire, who normally bred 170-plus mares each year, and then suddenly none of his mares were becoming pregnant. The syndicate owners decided to do ICSI with his semen. “We had 38 mares come here for the ICSI pro- cedure to breed to Walk Thru Fire and ended up with 35 pregnant ICSI recip mares. Some of the donor mares we didn’t get an ICSI embryo from, but from several of them we got multiple embryos,” says Beck.
The syndicate owners of Walk Thru Fire decided to do ICSI with his semen and ended up with 35 pregnant recipient mares from 38 donor mares.
More and more stallion owners are opting to use the ICSI procedure to preserve what lit- tle semen they might still have. Some deceased stallions continue to produce foals, using this technology. “We have semen here from Freckles Playboy and he died in 2003. The owners didn’t have enough semen left to breed a mare, but they sent us a couple straws of this old semen, and we now have a Freckles Playboy colt that’s 6 months old running around the pasture. We’ve also continued to produce some Smart Little Lena foals and now have semen from Doc’s Hickory—a famous foundation cutting horse, reiner, cowhorse stallion. His last foals were born some years ago, so it’s exciting to reintroduce some of these famous bloodlines and genetics,” he says.
To equip a lab for doing ICSI is very expen- sive. It also takes a lot of practice and experience to do this procedure because there are many variables in the chain of events that result in a pregnant recip mare when using this technology. “It’s not something you can do and still do a lot of other things. It’s difficult to run a veterinary practice and do ICSI. I shut down my veterinary practice and now only do reproduction, and I have another veterinarian who does the embryo work. ICSI requires a lot of quality control and constant supervision to grow the embryos in the incubator,” Beck explains.
The eggs are put in the incubator to mature and then injected with sperm--and then go back in the incubator. They remain in there for an average of 9 days and are then transferred into the recipient mare. “That period of time requires extensive quality control or it doesn’t work,” he says.
A foal bred from the semen of Freckles Playboy 14 years after his passing.
The Basics
Beck says most people don’t realize the difference between an embryo and an egg. The egg is unfertilized until it meets with sperm and becomes an embryo. With typical embryo transfer, this fertilization takes place in the mare—with Mother Nature fertilizing the
egg in the oviduct after sperm are deposited in the mare’s reproductive tract either by natural breeding or by artificial insemination.
“ICSI fertilization takes place outside the mare, using a microscope. I think it should have been called artificial fertilization, which is sim- pler for people to understand than ICSI. Many people don’t know what this is, and my girls in the office spends hours on the phone explaining to clients what they can expect,” says Beck.
It doesn’t work on every mare. There’s a certain percentage of mares, young and old, that it doesn’t work on. “We may harvest and do ICSI on many eggs from some mares and don’t get any embryos. At the other end of the scale, there are some mares on which it works incredibly well. We aspirated 17 eggs from one mare at one time and got nine embryos. We frequently get more than one embryo from one aspiration,” he says.
There are a number of eggs on the ovary that can be aspirated. “There are two different techniques. One is to harvest just the eggs that are ready—mature eggs from the big pre-ovu- latory follicles. This is the mature follicle that you’d wait for to breed a mare and then she ovulates and makes her own embryo. There are not very many of those.”
There are differences in mares and in breeds. “Warmbloods are an exception in the
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equine health