What are the nuts and bolts of embryo transplantation, ICSI and a surrogate mare? Hans Hurkmans from the Netherlands is specialised in embryo transplantation (ET) and intracytoplasmic sperm injection (ICSI) in horses and cows. His company also takes care of the storage and dispatch of embryos. He gives an overview of the process.

When will a breeder choose ET and when ICSI?

Embryo transplantation is interesting when you have a valuable mare and you want more than one foal from her in one year. When a mare is active in the sport, ET can also be a good choice.

The mare does not have to carry the foal herself but you can still use the breeding value of the mare. You can use ICSI, for example, for older mares that have already proven themselves in the sport, that can not get in foal anymore and for which flushing is difficult.

ICSI is also used when the sperm is scarce. You can still use proven, but already deceased, stallions such as Heartbreaker and Chacco Blue.”

Over the past few years ET and ICSI have boomed in horse breeding. What is your experience?

Our turnover of ET and especially ICSI has gone up by 50 to 60%. We have to work really hard to meet the demand. You see that more and more people go for ICSI instead of flushing, because only one treatment can produce two or three embryos.

To get that same result you would have to flush several times. Our main client circle are people with a show jumping mare that left the sport or has very interesting breeding (70%). Then there are the Arabians and Quarter horses (15%), followed by dressage mares (15%).

What should a breeder consider before using ET or ICSI?

That those two methods are far more costly than a normal service. They should determine if it is worth the investment or whether they want to make a profit from it. When you sell one or two foals, you can earn your costs back and you get your other foals for free.

In the case of ET you need an average of three flushes to get one foal, because it does not always work the first time. Then there are the costs of the recipient mare. ICSI is more expensive, but then you want to create more embryos to have a better chance of at least one embryo growing into a foal.

Are there any mares for which you would advise against ET or ICSI?

Sure! Last year I used a number of three-year-old mares for ICSI, mares who had never foaled before. I advise against this now, because these horses sometimes get complaints from the Ovum Pick Up (OPU).

This is because the ovaries of young mares are harder to reach with the OPU-probe, the instrument with which the oocytes (eggs) are harvested. In a mare that has foaled before, everything inside is more loose and you can easily reach the ovaries.

But in mares with womb troubles, such as chronic uteritis or a badly closing cervix, ET will not always be successful. Fertilisation and flushing can be problematic. Such mares are more suitable for ICSI.

When is an embryo transplanted in a recipient mare?

You can stimulate a recipient mare to get in heat and follow it from the moment she is in heat. In the case of ET, this has to be closely combined with the cycle of the donor mare.

An ICSI-embryo can be transplanted on day four or five after the ovulation of the recipient mare, flushed embryos on day five, six or seven after ovulation.

The recipient mares can also be used when they are spontaneously in season. Then the frozen embryo can be thawed and transplanted on the desirable day.

Are all mares suitable to be recipient mares?

No, not all of them. You need mares with a solid fertility cycle, aging three to 15-year-olds. It is also important that the recipient mare is not too small. French trotters are very suitable as recipient mares. They are fertile and have often been used in the sport, so they are easier to handle and to work with.

What should you look for when buying a recipient mare?

It is an advantage when the mare has had a foal before, for then you know if she will be a good and careful dam. I advise to have the womb of the recipient mare checked upon purchase. The mare should have been properly vaccinated, have a good condition and have no stable vices.

What are the average costs - besides the stud fee - of ET?

What are the costs of ICSI?

(on average €3,500 to €4,500 per foal)

*Note: Not all embryos will be accepted by a recipient mare, you may have incurred expenses yet you get no foal. The lease of a surrogate mare often starts from 45 days of gestation to four to five months after the foal is born.