The oldest embryo transfer (ET) foals we have produced are now five years old. Jim believes that “Luke”, our first ET foal is almost certainly the best horse he has ever bred. He now has three full brothers from the same mare, all by ET and is keeping the youngest as a colt at the moment. Meanwhile the mother has been ridden and played polo every year including during the ET process.
ET gives you a chance to breed more than one foal from each of your best mares every year and using healthy but not necessarily spectacular recipient mares to carry and rear the foals. From one client mare we produced three foals in the first season (from only two inseminations!) and two foals are due from the same mare this year. Meanwhile the mare is back at home being ridden and competed regularly.
The foals will inherit all of their genetics from the donor mare and stallion, whilst the recipient mare provides all the nutrients for the foal to grow. Many people seem concerned that the foal’s temperament will be influenced by the recipient. We have no evidence of that. So far all the ET foals we have experience of have been very similar in temperament to their genetic mothers with a variety of different recipients.
The recipient mare can influence the size of the foal but probably less than the genetics of the foal. In research studies putting embryos from the same mares into two groups of recipients, a herd of 13.2 mares and a herd of 16.2 mares the foals on average were a few inches different in height. Individual variation is much greater than this anyway so we try and use recipients as close to the dam’s size as possible but a hand either way probably won’t influence foal size noticeably.
As well as offering the full service here we will also do embryo transfer on mares mated elsewhere. If you wish to do this you need to contact us and we need to liaise with your vet. The mares need to be regularly monitored as we need to know the time of ovulation to within at least 24 hours, and we need to ensure that we have suitable recipients synchronised with the donor mare.
Embryo transfer can also be done with fresh, chilled or frozen embryos. So far we have only carried out fresh transfers here but pregnancy rates for overnight cooled shipped embryo are very comparable to fresh transfer, with the best centres achieving about 85% post transfer pregnancy rates with both. We have achieved 9 pregnancies form the last 10 embryos we have transferred to July 2012.
Freezing equine embryos is still very much in its infancy and success rates are very variable and poor at the moment compared to fresh transfers. We are not proposing to freeze embryos commercially at the moment but we may try some later this year if we have surplus embryos from our own mares.