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World's Oldest Frozen Semen Successfully Impregnates Dozens Of Sheep


Madison Dapcevich

Staff Writer

clockMar 17 2019, 06:00 UTC

Sheep semen thawed after 50 years under a microscope. University of Sydney

It’s 2019, and if you don’t believe that we are living in the future then GTFO.

Researchers at the University of Sydney have taken the world’s oldest known frozen semen and used it to impregnate not one, not two, but 34 ewes last year. The sperm was retrieved from four rams – one of whom was named Sir Freddie, mind you – in a 1968 trial to prove that sperm could survive storage in liquid nitrogen at a temperature of -196°C (-320°F).


"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 researcher Jessica Rickard in a statement. A biologist and veterinary­­ scientist, Rickard initially determined if the stored semen was viable for insemination by thawing the sperm and then conducting in vitro tests to determine its motility, velocity, viability, and DNA integrity.

The new lambs appear to have a body wrinkle that was common in Merinos from the 1950s and 60s – right around the same time the sperm was frozen. The feature was bred into sheep as a way to create more skin on each animal, thus more wool. Since then, breeders have moved away from skin folds because it makes shearing a sheep much more difficult.

'A 1969 photo of Sir Freddie, donor of the world's oldest viable semen. Courtesy of the Walker family

Of 56 ewes artificially inseminated with the ram-quad sperm, 34 were successfully impregnated. That means Grandaddy Freddie’s sperm had a 61 percent success rate after 50 years, compared with a 59 percent success rate of modern ram sperm – virtually “no difference” in fertility measures.


"This demonstrates the clear viability of long-term frozen storage of semen. The results show that fertility is maintained despite 50 years of frozen storage in liquid nitrogen," said lead researcher Simon de Graaf.

Even though it’s been in the freezer for 50 years, the sperm is as fertile as the day it was collected, something researchers say demonstrates that the long-term frozen storage of sperm may be a safe and reliable method for future families, such as applications in future genetics testing and human medicine, particularly young male cancer patients who may need to store semen prior to beginning chemotherapy or radiation treatment.

The offspring were on display last month in Australia looking alive and well, just like any other adorable little lamb.  

A doctor artificially inseminating a sheep in the 1960s. 
Can you see the resemblance? Merino lamb in 2018 from 50-year-old semen. Morgan Hancock 

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