Horse sperm can now be stored unfrozen for longer

Scientists at the University of Newcastle (UoN) have developed a nutrient-rich liquid that enables collected horse semen to live for two weeks outside the body without the need to be frozen, in a breakthrough that is set to double the effectiveness of artificial insemination rates in horses and may also have implications for humans.

Chilling or cryopreserving sperm can be a damaging process where many viable cells die off, and surviving cells live for just a few hours once warmed up again. Furthermore, said UoN scientist Dr Zamira Gibb, the current process of artificially inseminating cryopreserved sperm can be expensive, labour-intensive and invasive for the mare.

For almost a decade, Dr Gibb and her colleagues carried out extensive research to understand how sperm cells metabolise energy and what sort of nutrients and antioxidants they required for optimal longevity. Their work commenced after industry partners at Australian Harness Racing approached the team for alternate methods to access genetics from around the world.

“Until now, the only way to access genetics from around the world was to import cryopreserved sperm or import the stallion on a seasonal basis, which can cost upwards of $40,000 including flights and boarding at quarantine stations,” said UoN scientist Dr Aleona Swegen.

“As fertility of cryopreserved sperm is quite low and the insemination process very labour-intensive, industry wanted a semen extender that could maintain sperm quality for a sufficient amount of time for it to be transported from America or Europe for use in a cost-effective insemination regime.”

The end result of their research is a liquid that supports sperm with molecules that help protect the cells and enable them to exist in their natural state for longer — in contrast to a method like cryopreserving, in which the sperm’s metabolism is suppressed. The new medium is also completely synthetic, eliminating the biosecurity threat of international importation and preventing samples from being held up at the border for longer than necessary.

“From a customs perspective, it was important that the medium be free of any biological materials, such as egg or milk, which are present in conventional semen mediums,” Dr Gibb noted.

The first foal bred using sperm stored in this medium was born in Tamworth on Christmas night 2018. Tinsel (pictured), the Welsh Mountain Pony cross Thoroughbred, was born a week early — which is normal in horses — and has not suffered any DNA damage or poor health as a result of the sperm’s longer storage time.

“This really is a game changer for our industry given our longstanding practice of utilising the benefits of artificial insemination,” said Australian Harness Racing Chairman Michael Taranto.

“We anticipate improved market access and breeding efficiencies, along with reduced costs, while also expanding the Australian Standardbred gene pool as a result.

“This extender has the potential to be widely adopted by breeders worldwide, not just for importation reasons, but also to reduce the need to collect semen from stallions so frequently, which is a real welfare advantage,” Dr Gibb added.

“In comparison to cryopreserved sperm, fertility rates could easily be doubled using this new method and the ability to use a more relaxed insemination regimen will potentially save breeders several thousand dollars per pregnancy.”

The team has also discovered that the extender can effectively be used to store spermatozoa from other species, including humans and cattle, and could be transferred to other equids such as zebras.

“We’re seeing exciting potential for the extender to help improve the conservation status of threatened species and be implemented as part of rare breed selective breeding programs to disseminate genetics from geographically distant locations,” Dr Swegen said.

“For many endangered species, no successful cryopreservation protocols have been established and little is known on how to transport sperm between facilities. This would be one way to address some of those issues.”

The sperm extender is currently undergoing independent testing by a biotech company in Europe and should be commercially available by September 2020.

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