Advanced fertility techniques could aid endangered horse breeds

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Twemlows Little ICSI with his surrogate mother, Victoria.
Twemlows Little ICSI with his surrogate mother, Victoria.

The recent birth of two test-tube foals in Britain as part of a project led by leading fertility experts could ultimately help benefit rare breed conservation and horses with fertility problems.

The births mark the successful completion of a three-year programme, led by the University of Liverpool, the University of Surrey and Twemlows Stud Farm. The aim was to establish and offer advanced breeding methods not routinely available in Britain.

It is thought these processes could have further use in breeds under threat of extinction and for valued horses that have died, or in cases where mares or stallions have specific fertility problems.

One of the methods, called intracytoplasmic sperm injection (ICSI), has the potential to allow greater numbers of offspring to be produced from individual mares and from stallions where sperm samples are limited, allowing breeds to continue in larger numbers.

Importantly, this method could allow the embryos of rare breeds to be “frozen”, creating a safety net of “reserve animals” should anything threaten the existing stock.

The chief executive of the Rare Breeds Survival Trust, Tom Beeston, said breeding numbers of all British native equine breeds continued to decline.

“If not halted soon, our gene bank may be needed to reconstitute a breed. It really is that serious. Being able to freeze embryos as well as semen will mean we can do this completely and faster. This project is by far our best hope of being able to do this soon.”

Niamh Lewis, a veterinarian researcher at the University of Liverpool, who managed the project, said: “These are complex methods which are currently offered by only a very few centres worldwide.

“The ability to perform these techniques reliably offers new hope to help overcome various fertility issues in stallions and also provides opportunities to create offspring from valuable mares who have died unexpectedly or cannot conceive in their own right.”

Foals have been born in Britain using the two different specialist breeding techniques at the centre of the research. In June, a foal named Twemlows Simba became the first foal in Britain to be born using Oocyte Transfer, a technique that involves oocytes (eggs) being collected from a donor mare and then transplanted into a surrogate female before being fertilised.

A second foal, called Twemlows Little ICSI, was born earlier this month using ICSI. This technique is already used with great success for infertile human couples and involves a single sperm being injected into an egg through a thin glass pipette to create an embryo which is then transferred to a surrogate female.

In this case the egg had been harvested from the ovary of a mare that died 11 months ago and was then matured in the laboratory ahead of the procedure.

If rare breed embryos can be reliably frozen, as opposed to just semen, then breeds under threat could potentially be resurrected by returning the embryos to surrogate mares.

Professor Caroline Argo, from the University of Surrey, who was the academic lead for the project, adds: “At the moment, we can freeze stallion sperm reliably but not horse eggs or embryos.

“However, ICSI embryos are smaller and more robust to the freezing process. Now that this method has proved successful, it could be possible to use it more routinely and widely for the purposes of conservation.”

The project was jointly funded by the government’s Technology Strategy Board and Twemlows Stud Farm in Shropshire.

It was described as a major collaborative effort, which included working with consultant clinical embryologists in human medicine.

Edward Matson, of Twemlows Stud Farm, said the collaboration with academic and clinical partners had allowed it to extend its service to include the advanced techniques.

“Until now, clients wishing to embark on these methods were largely dependent on shipping animals to overseas clinics.”

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