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Ram Semen Stored Frozen In 1968 Successfully Impregnates 34 Sheep

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Back in the 1960s, a researcher Australia froze a ram's sperm and stored it in a time capsule.

Fifty years later, researchers inseminated 56 sheep with the sperm in an effort to establish its viability.

Samples Of Ram Semen Frozen For 50 Years

A team of researchers from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney in Australia recently defrosted samples of a male sheep's semen that was frozen way back in 1968, and with it, successfully impregnated more than half of the sheep inseminated.

The sperm samples came from four rams that were owned by the Walker family on their Ledgworth property in the 1960s. Dr. Steven Salamon, who was then a researcher at the University of Sydney, was the man responsible for freezing the samples.

Salamon froze and stored the semen in huge vats of liquid nitrogen at -196 degrees, according to the researchers. The main reason for preserving it in frozen form was to establish whether sperm could still be viable after "long-term frozen storage."

Fertility Rates Remained High

The team used the sperm to inseminate 56 ewes, 34 of which became pregnant. They then made a comparison between this success rate, which is 61 percent, and those that had been preserved for just one year. The recently preserved semen managed to impregnate 618 ewes out of 1,048 sheep, which is a 59 percent success rate.

The researchers concluded that fertility rates of the ram semen frozen for 50 years have remained as high as the semen frozen for just one year. This means that there is no difference between semen frozen for five decades and semen frozen for 12 months.

"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 Associate Professor Simon de Graaf from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney.

"We can now look at the genetic progress made by the wool industry over past 50 years of selective breeding. In that time, we've been trying to make better, more productive sheep," added de Graaf. "This gives us a resource to benchmark and compare."

The World's Oldest Viable Preserved Semen

The researchers believe the semen to be the world's oldest viable stored semen of any species and the oldest frozen semen to be used to produce offspring.

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