Artificial Insemination (AI) is now standard practice in many sports horse breeding programs. This story illustrates how the process works.

AI:101 Artificial Insemination. A Story of Two Mares
65 days after mare’s insemination
Photo from Elevage de Kezeg in Surzur, France

Arenberg Stud, France. Six o’clock in the morning. Mares, Pyjama, and Fleetie walk up the ramp into their trailer. They are on their way to the Elevage de Kezeg in Surzur, where a vet will artificially inseminate them with the previously frozen sperm of Jugano van de Vosberg.

AI:101 Artificial Insemination. A Story of Two Mares
Jugano van de Vosberg in Riemst
Photo courtesy of Gianne Verberckmoes

Pyjama, full name Wakayama, is an old hand at this, and Jugano is not her first frozen beau in a “straw.”

AI:101 Artificial Insemination. A Story of Two Mares
Mamma mare. Wakayama (Chin Chin x Sioux de Baugy) of the Arenberg Stud
Photo by Louise Morley

Look at this mare’s face! She knows we are talking about her. For Fleetie, full name Fleet Street van Arenberg, this is her maiden voyage.

AI:101 Artificial Insemination. A Story of Two Mares
Maiden mare – Fleet Street van Arenberg (Pall Mall x Amaretto d’Arco)
Photo by Louise Morley

There she is. Oblivious to the fact she is off to go through the process of artificial insemination by a world-class showjumper. Bless! The journey takes about 5 hours. On arrival, the mares, still in the trailer, join a lengthy queue of other mares “checking in”.

“There are often queues at the stud at peak breeding times. Start of a period of very good weather, all mares come into season… But now was very busy because of uncertainty about traveling breeding mares during lockdown.”

Louise Morley – Arenberg Stud. Producer of quality Belgian Warmbloods and owner of the mares

Pyjama and Fleetie‘s turn arrives. The mares had an internal exam to palpate their ovaries to check the size and maturity of the follicles. Next, an ultrasound to begin the monitoring of ovulation and follicular growth. The mares’ information is detailed on a board.

Mares can vary in what follicle size shows their ovulation. For most mares, it’s when the follicle reaches 35mm. But for some mares, it can be as large as 65mm. This is why the use of the same facility each time is good, as they will have a historical record of when your mares are ready for artificial insemination.

Maiden mare, Fleetie, has already ovulated while mamma mare, Pyjama, is not ready. So the mares are “turned out” into a field together until they are ready for artificial insemination. Had ovulation been imminent the mares would have been stabled to facilitate the ultrasounds every 6 hours.

Maartje Verberckmoes & Jugano van de Vosberg CSIU25 Z-Tour 201…

Ook Maartje Verberckmoes deed gisteren goede zaken in Lanaken bij de Z-Tour 2017 Zangersheide. Met Jugano van de Vosberg BWP van Ogano Sitte x Clinton I reed ze naar een 4de prijs in de 1,45m CSIU25 rubriek. Proficiat!

Posted by ClipMyHorse.TV België on Thursday, April 13, 2017
Maartje Verberckmoes & Jugano van de Vosberg CSIU25 Z-Tour 2017

Jugano “donated” his sperm, and it is now kept frozen in “straws” in liquid nitrogen tanks at Elevage de Kezeg. It is available for artificially inseminating mares on-site and sold worldwide.

They collected the semen at a collection facility in Belgium. Because he is an international sport horse, he visits there a few times per year during a break from showing, to collect enough semen to freeze for the year. The semen we are using now was from 2019. The quality differs each time depending on the time of the year, age and condition of the stallion.

Louise Morley – Arenberg Stud. Producer of quality Belgian Warmbloods and owner of the mares

Typically, the mares go through the artificial insemination process with defrosted semen within 6 hours of ovulation. Therefore, when mares Pyjama and Fleetie show signs of being in heat, the vet will monitor them every 6 hours and inseminate the mares upon release of the eggs.

Below is a video representation of what will occur with Arenberg Stud’s two mares:

Exclusively Equine Veterinary Services, Australia
Facility for the artificial insemination of mares

As you can see, the timing of artificial insemination of mares is crucial. This is why Arenberg Stud has the mares artificially inseminated at Elevage de Kezeg instead of at home.

Pyjama is very difficult to get in foal. It takes ages for a follicle to mature enough to ovulate. She also doesn’t seem able to get full with a foal at foot. Possible (sic) a temperament thing…

Louise Morley – Arenberg Stud. Producer of quality Belgian Warmbloods and owner of the mares

Many owners want to take their mares home with them directly after artificial insemination, but this isn’t advisable. The mares need monitoring to see if they are pregnant during an optimal time window, which is about 14-16 days. This way, if the original insemination did not work, it’s possible to catch the mare’s next ovulation.

A mare that had already gone through the process of artificial insemination with a “straw” of Jugano’s semen is confirmed pregnant. This mare loads into the trailer for the return journey home, while beginning the new journey of motherhood.

The circle of artificial insemination is complete.


For a more in-depth look at the artificial insemination of mares, this resource is great. For more information about palpation and ultrasound, check out this resource.