Horse breeding expert explains the unique equine embryo

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More than a decade after they were collected, samples of equine embryonic losses from early studies are proving useful to researchers today.

The value of long-term studies is well understood by researcher Dr Keith Betteridge, who has been involved with Ontario Veterinary College equine reproduction studies since 1986.

Since graduating as a veterinarian from Bristol University, England, in 1959, Betteridge has seen reproduction technology evolve with the introduction of ultrasound in the 1980s and, most recently, RNA sequencing which has been used to better understand how the equine embryo develops.

“Pregnancy was always looked at as though the embryo was just a passenger in the uterus,” Betteridge said.

“It has gradually emerged since the 1960s that the embryo is a very active participant in pregnancy. If the embryo is not communicating with the mare, the pregnancy won’t develop.

“Understanding the two sides of the conversation between the embryo and the mare is absolutely vital to understanding how pregnancy will develop normally and how, when an embryo is lost, the pregnancy will fail.”

Betteridge said that long-term studies using the embryonic loss samples collected in 2008 gave researchers an opportunity to “really follow those embryos”.

“The ‘lemons’ from the lost pregnancies in early studies turned into lemonade as new techniques came along which we could use to further investigate those samples,” Betteridge said.

In the above video, Betteridge looks at studies on equine reproduction and describes how the equine embryo is truly unique with its unusual coating (called a capsule) which allows the embryo to move around in the uterus.

With ultrasound, an embryo can be detected as early as nine days in. Betteridge said about 17% of equine pregnancies fail and 70% of those losses will occur in the first six weeks of pregnancy.

RNA sequencing has provided new methods of finding out which genes are active in the lining of the uterus at a particular time. The ‘dialogue’ from the mare’s side has been examined and future studies will hopefully reveal the ‘conversation’ from the embryonic side.

With continued research, information is gradually building up that will help the horse breeder reduce the number of pregnancies that are lost.

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