Advanced Reproduction

Hawkesbury Equine Vet Centre are proud of our exceptional team of experienced advanced equine reproduction vets. We provide a full range of services to our clients from our thoroughbred stud work and setting up mares for walk-on service to advanced procedures including embryo flushing and transfers. We have excellent success rates with frozen semen and embryo transfer. Our aim is to help produce happy healthy foals. Some of the services we provide for our clients include;

• Embryo Vitrification
• Reproductive Surgery
• Mare fertility evaluations
• Insemination Techniques
• Stallion Fertility Evaluations
• Emergency Foaling Assistance
• Embryo Recovery and Transfer
• Management of Problem Mares
• Examination and Management of Sick Foals
• Evaluation of Foal Conformation, Corrective Shoeing
• Semen Collection and Evaluation for Chilling and Freezing
• Management of Mares for Breeding Naturally or by Artificial insemination
• Artificial Insemination with Fresh, Chilled or Frozen Semen including Deep-Uterine, Low Dose

Some of these services can be accomplished on an “out-patient” basis, by appointment. Others require the mare/stallion to be agisted in our safe facilities.

What is Embryo Transfer (ET)?

Embryo transfer is a procedure where we inseminate your valuable competition mare and 7 – 9 days later we flush the early embryo (blastocyst) from her uterus and transfer it into the healthy uterus of a recipient (surrogate) mare.

Advantages of ET:

• ET enables the embryo donor mare to continue her competition career while the recipient mare carries the pregnancy to term.
• It is possible to obtain more than one pregnancy per year from a mare. You may choose to inseminate your mare with the same stallion each time or use different sires for each estrous cycle. We usually recommend that you aim for 1 – 3 pregnancies from each donor mare each season.
• If you have a mare with an old, subfertile uterus who is prone to losing pregnancies after 15 days then it is beneficial to transfer her embryo into a healthy uterus of a younger mare.
• The fertility of an embryo transfer programme is similar to a normal breeding programme.
• The whole procedure is non-surgical
• There is no increased risk of embryo loss or birth defects from ET foals than from foals in the normal population.
• New embryo freezing technologies enable us to achieve satisfactory pregnancy rates from frozen-thawed embryos. See our page on embryo vitrification for more information on freezing embryos.

Disadvantages of ET:

• It is more expensive that conventional breeding programmes.
• The procedure requires considerable skill and experience in meticulous embryo handling procedures.
• The synchronisation of recipient mares is challenging (but fun!) and therefore 2-3 embryo recipient mares are required for every donor mare. This does contribute to the cost of the programme.

The results of Embryo Transfer:

• We recover embryos from >70% of cycles. The embryo recovery rate is however, dependent upon the fertility of the mare and the stallion and whether fresh or frozen semen is used.
• Of all the (Grade 1) embryos recovered we achieve 90% embryo survival after embryo transfer.
• In the 2015/16 season HEVC had a record year with more than 93% of embryos surviving after transfer!
• This gives us a 55 – 60% per cycle pregnancy rate.
• Therefore, it is recommended that you budget for 2 cycles per pregnancy.

What is Embryo Vitrification, why would you do it, and what does it involve?

Here are a couple of foals that were vitrified, stored in liquid nitrogen and later thawed by the vets at Hawkesbury Equine Veterinary Centre… On left is a warmblood filly. She was the first embryo vitrified back in 2012 at Hawkesbury Equine Veterinary Centre and then implanted into a recipient mare in 2013. The foal on the right was an embryo vitrified in 2013 and then implanted into a recipient in 2014. The resulting foal, a stunning chestnut colt went on the win multiple futurities as a weanling.

What is Embryo Vitrification?

Embryo vitrification is a process by which a 6 to 6.5 day embryo that measures less than or equal to 300 micrometers is frozen by an ultra-rapid freezing technique. Pregnancy rates following transfer of small vitrified embryos have improved compared to routine freezing and have been demonstrated as high as %65 to %75. Thus there has been an increased interest in embryo vitirification in the equine breeding industry.

There are several situations in which embryo vitrification may be warranted and beneficial to a breeder. Performance mares that are in training or on the performance circuit can be bred in their off season and embryos transferred the following spring. In addition mares that are bred late in the season and would like to have a pregnancy early the following year, can have their initial embryo vitrified for transfer early next year and maintain the following pregnancy herself. Finally, it can be used in breeding diversification in which a mare can be bred to different stallions during one breeding season and potentially have different embryos to transfer the next year.

The process is similar to routine embryo transfer except the embryo is flushed from the donor mare’s uterus earlier, at day 6-6.5 post ovulation. This is important so that the embryo size is small and the capsule not present allowing cryoprotectants to enter the embryo which is imperative for survival.  Once the embryo has been retrieved from the donor, identified, graded and washed it then goes through a number of steps during which it is transferred to increasing concentrations of cryoprotectants and substrates. This four step technique increases the efficacy and ease of the vitrification process. The embryo is then loaded into a 0.25ml straw and a 0.5 ml straw attached to the open end for labeling and identification purposes. The embryo is then frozen by being placed in liquid nitrogen vapor and then being plunged into the liquid nitrogen. Once frozen the straws can be placed for long-term storage in a liquid nitrogen tank.

Thawing and transfer of vitrified embryos occurs with the use of a water bath for thawing and a Cassou gun for embryo transfer into the recipient. Recipient mares should be screened and synchronized as in the embryo transfer process however transfer will occur one day earlier into the recipient. Recipient mares can be provided by Hawkesbury Equine Veterinary Centre or by individual mare owners.