Frozen For 50 Years, World's Oldest Semen Manages To Successfully Impregnate Sheep

For many newly-married couples, they're not ready to have a baby right then.

However, they're also worried about it being harder to conceive when they try later, so they sometimes save and freeze their sperm and eggs as a backup. Turns out that stuff has quite a shelf life.

Images courtesy: University of Sydney

In a laboratory at the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney, researchers were trying to carry out a record-setting experiment. They were going to take an old frozen sample of sperm from a ram and try to impregnate some female sheep to see if it would take.

The kicker was that the semen they were using was fifty years old, believed to be the oldest sample in the world.

The original donor ram "Sir Ferdinand"

As it turns out, the little guys still had plenty of life to them. Once defrosted and implanted into the ewes, the researchers found that 34 of them became pregnant. "We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring," said Dr Jessica Rickard from the University of Sydney.

To test the sample, the researchers had to first thaw some of it out. Which was frozen and stored as small pellets in vats of liquid nitrogen at minus 196 degrees. "What is amazing about this result is we found no difference between sperm frozen for 50 years and sperm frozen for a year," Rickard said.

Of the 56 ewes inseminated, 34 were successfully impregnated. That's a 60 percent success rate, which is fantastic for sperm that old. The researchers were trying to recreate the wool output of sheep breeds from the last century that have been bred out.

It's still not clear if this knowledge is in any way helpful for humans freezing their sperm for later, but it's still a pretty cool factoid to share at the very least.