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It’s not every day you come across a 50-year-old batch of frozen sheep sperm. So when Australian scientists rediscovered this little time capsule, left behind by a previous researcher, they did what any curious researcher would do: they tried to create lambs. According to Smithsonian, they succeeded.
The sperm, originally collected from several prize-winning rams, had been frozen in 1968 by Dr. Steve Salamon, a sheep expert from the University of Sydney. After thawing the sample and conducting a series of lab tests, the researchers found that both its viability and DNA integrity were preserved. With the sperm ready, they decided to put it to the test: Would it result in a pregnancy? The sperm was artificially inseminated into 56 Merino ewes, and remarkably, 34 of them became pregnant, leading to the birth of healthy lambs.
This wasn’t just a fun experiment; the researchers were keen to test whether sperm frozen for decades in liquid nitrogen at -320°F would still be suitable for breeding. Surprisingly, the older sperm had a slightly higher pregnancy rate (61 percent) compared to sheep sperm frozen for just 12 months, which achieved a 59 percent success rate in another experiment.
"We believe this is the oldest viable preserved semen of any species in the world, and certainly the oldest sperm ever used to produce offspring," said researcher Dr. Jessica Rickard in a statement.
The researchers also note that this experiment provides an opportunity to evaluate the genetic progress made in selective breeding over the past fifty years. "Over that time, our goal has been to create better, more productive sheep for the wool industry," said Associate Professor Simon de Graaf. "This gives us a valuable reference point to benchmark and compare."
