Bringing artificial breeding techniques to life
In recent years, embryo transfer has been gaining popularity with horse breeders across Australia.
The procedure involves the collection and transfer of a fertilized embryo from one mare (the donor) into another (the recipient) who carries the pregnancy to term, and then raises the foal to weaning.
Camden Equine Centre’s client J and R Equestrian have undertaken embryo transfer to produce foals from Olympic gold winning stallion Big Star and their mare Chatina. See pictures at right.
There are a number of advantages to embryo transfer including: enabling breeding from mares that cannot maintain their own pregnancies; the ability to achieve multiple pregnancies in one season from one horse; and allowing owners to breed from mares while they continue with competition careers.
While the foal’s size at birth may be influenced by the recipient mare, the foal receives all of its genetics from the donor mare and stallion and thus should be no different at yearling age and beyond to one from the same stallion/mare combination carried without embryo transfer.
There are several steps involved in embryo transfer including:
- Reproductive evaluation of the donor mare to ensure a reasonable chance of success and in order to optimise fertility
- Insemination of the donor mare using fresh, chilled or frozen semen
- Removal of the fertilized embryo from the donor mare’s uterus by non-surgical flushing between six and nine days after ovulation
- Washing and evaluation of the embryo under a microscope for appearance, integrity and size
- Non-surgically transferring of the embryo into the recipient mare
- Pregnancy testing of the recipient mare around one week after the transfer
- Carrying of the foetus to term by the recipient and raising of the foal to weaning.
Two main considerations when looking into embryo transfer are costs and success rates.
Costs for embryo transfer are considerably higher than standard breeding because the procedure involves synchronizing multiple recipient mares per breed, the flush and transfer process and in the case of a successful pregnancy, recipient mare leasing fees. It is generally considered appropriate to work on the total veterinary and recipient mare costs falling between $3500 and $5000 for a successful attempt.
Regarding success rates, as a guide it is considered appropriate to reduce the expected success rate for a given breed (mare/stallion fertility and chilled vs frozen semen) by 10 per cent when accounting for embryo transfer. Thus while the success rate may be as high as 70-80 per cent in young, fertile mares using chilled or fresh semen of optimal fertility, it can be as low as 20 per cent in infertile mares with frozen semen of reduced fertility due to lower embryo recovery rates and poorer quality embryos.
A variety of options are available to our clients when it comes to the use of recipient mares for embryo transfer. Some of our clients have sourced their own recipient mares while most clients lease a suitable mare from one of a pool of highly fertile mares available, which often must be returned when the foal is weaned. These sources of highly fertile mares include a recipient herd established locally by The Oaks Sport Horses as well as two large recipient herds in NSW and VIC with which we collaborate and ship embryos to via air freight. In 2016 we established a small recipient herd maintained at the University which we will continue to expand leading into the 2017 breeding season.
We are very pleased to be offering this advanced breeding technique. Our ambulatory reproductive service can customize this service to suit different client needs. We offer the service from October to March. So far, in the current 2016-17 season we have harvested 35 embryos from 18 mares with a per cycle harvest rate of over 80 per cent and a per cycle pregnancy rate of 75 per cent.
If you are interested in discussing embryo transfer options for your mare with Camden Equine Centre, you may call or text Dr Ed Annand on 0439 572 329 or via the hospital office on 02 4655 0777.