For a conversation on our reproduction services contact us on 02 4405 5658.

Specialised reproductive management of mares and stallions is one of our core services. 

We breed horses through:

  • natural service
  • artificial insemination (AI) with fresh, chilled and frozen semen
  • embryo transfer.

We specialise in problem mares and stallions ranging from warmbloods (dressage and showjumping), Australian Stock Horses, quarter horses, paint horses, standardbreds, ponies, eventers and draught horses through to thoroughbreds.

Artificial insemination (AI)

Artificial insemination is the manual deposit of live motile spermatozoa into the mare’s uterus at the optimum time. This can include fresh, chilled, or frozen semen. 

Advantages of AI include:

  • Breeding a large number of mares with one ejaculate.
  • Transporting semen from distant places. 
  • Adding extenders and antibiotics to semen to increase the fertility of some stallions.
  • Not having to transport the mare to the stallion.
  • Breeding more mares to a stallion.
  • Reducing the risk of disease transmission.
  • Greater access to stallions.
  • Earlier detection of fertility problems.
  • Decreased risk of injury to the mare, stallion and personnel.
  • May be easier to breed the mare at the proper time.

There are some disadvantages of AI, namely needing increased knowledge and skills in mare and stallion management, and the equipment required.

Embryo transfer (ET)

Embryo transfer is the process in which the donor mare is bred and a surrogate mare (recipient) carries the pregnancy. ET is most successful with a fertile donor mare and a stallion with known fertility. 

Where fertile mares and stallions are used, an embryo is recovered around 70 per cent of the time. Embryo recovery in older mares – who have older and fewer oocytes (eggs), or who have had reproductive problems – is around 30 per cent.

Embryo transfer steps:

  1. The donor mare is reproductively evaluated to ensure a reasonable chance of success.
  2. The donor mare is bred using fresh, chilled or frozen semen. Conception rates may vary between these methods, depending on both the mare and stallion.
  3. The embryo is removed from the donor mare’s uterus typically six to eight days after ovulation.
  4. The embryo is located and evaluated under a microscope for appearance, shape and size.
  5. The embryo is non-surgically transferred into a recipient mare.
  6. The recipient mare is checked for pregnancy around a week after the transfer.

Infertility examination for mares and stallions

Evaluating the reproductive tract of a mare can involve:

  • Thorough evaluation of reproductive history.
  • Trans-rectal palpation.
  • Ultrasonography.
  • Endometrial culture and cytology of swabs.
  • Endometrial biopsy.
  • Hormonal evaluation.
  • Hysteroscopy.
  • Laparoscopy. 

Examining stallions for breeding purposes can include:

  • Performing ultrasonography of the genital organs.
  • Collecting and evaluating semen to assess fertility.

Twin reduction

Twin pregnancies are almost always resolved when identified at the first pregnancy scan. If twins are not identified until much later, various options are available, including:

  • manual reduction
  • trans-vaginal puncture
  • cranial cervical dislocation.

We offer a referral service for mares with twins.

Fetal sex determination

Ultrasound examination is used to determine fetal sex to a high degree of accuracy. Our preferred window is between 58 and 65 days from breeding. This service is available to permit breeders in order to assist with marketing and breeding strategies.


Laparoscopic surgery can be used to diagnose and treat a range of infertility problems in both mares and stallions. Mares with blocked oviducts can be treated by applying Prostaglandin E gel on the oviducts using laparoscopy.

Removal of endometrial/uterine cysts

Cysts are fluid-filled structures usually projecting outward or away from the surface of the endometrium into the uterine space. 

In some cases, the presence of one or more large endometrial cysts can:

  • cause fluid retention post-breeding
  • impede motility of the early pregnancy
  • deprive a pregnancy of vital nutrients, resulting in early embryonic death.

We offer a range of treatment options for cyst removal.


Willinga Park Vet Hospital
02 4405 5658