Semen frozen for 50 years used to breed 34 healthy lambs in breakthrough study

Amazingly, the sperm resulted in birth rates comparable to semen frozen for 12 months.


Sperm is one of the shortest-lived cells in the animal kingdom, with just 5 days of life in the best of conditions before it dies out or gets recycled by the body. Now, scientists have managed to revive semen stored in a lab since 1968 and used the cells to get 34 lambs pregnant.

Amazingly, the sperm resulted in birth rates comparable to semen frozen for 12 months, which is an established benchmark timeline for current freezing tech.

Semen frozen for 50 years used to breed 34 healthy lambs in breakthrough study

One of the new lambs born from 50-year-old semen. Image credit: Morgan Hancock

"This demonstrates the clear viability of long-term frozen storage of semen," Professor Simon de Graaf from the University of Sydney, said in a press release.

All the semen used in the study came from four rams — Sir Freddie, born in 1959, two rams born in 1963, and a ram born in 1965. Their sperm was used to revive lambs with wrinkles on their body — a feature common in Merino rams in the mid-20th-century. The wrinkles meant a larger skin surface area and better wool yields, which eventually grew tedious to manage and sheer.

The success bodes well not just in the veterinary sciences, but also human medicine. As de Graaf told Inverse, "What is true for the sheep is also true for humans."

There’s no reason to believe that human sperm will behave any differently than sheeps'. The researchers will have to keep a close eye on those wrinkly lambs to make sure they develop normally. But as far as scope for the future, this success means hope for people at risk of losing their fertility (like males undergoing chemotherapy).

This could also be great news for breeders of purebred dogs — the genetic diversity in many dog breeds is down to worrying levels, which means more abnormalities and poorer health with every successive generation. One of the most awesome of its applications is making (existing or extinct) animals and people parents long after their death.

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