Half a century later
With the help of sheep sperm frozen for 50 years, 34 sheep were fertilized
Dmitry Mazalev, Naked Science
The oldest sperm in the world, stored since 1968 in a laboratory in Sydney, was thawed and successfully used to fertilize 34 Merino sheep. According to the researchers, this demonstrates the obvious viability of sperm during long-term storage in frozen form.
According to Simon de Graaf, an employee of the Institute of Agriculture at the University of Sydney, fertility can be preserved even after 50 years of storage frozen in liquid nitrogen. The results of the study are available on the university's website (World's oldest seed still viable).
On the body of the born lambs, scientists found wrinkles and folds familiar to merinos of the middle of the last century, which increased the surface area of the skin and wool cover. Since then, this style of merino has largely lost popularity, as the folds created more difficulties associated with collecting fur and problems with insects.
These sperm samples became the oldest viable samples among all the species in the world and definitely the oldest samples used to produce offspring. According to scientists, the genetic aspects of this achievement are of the greatest interest to them. According to de Graaf, we can now look at the genetic progress made over the past 50 years of selective breeding. During this time, experts have tried to breed better and more productive sheep — now we can visually compare the two species.
First, the researchers determined whether the preserved sperm was viable for artificial insemination. To do this, the samples were thawed — they were stored in the form of small granules in large vats with liquid nitrogen at a temperature of minus 196 degrees Celsius. The scientists then conducted in vitro tests on sperm quality to determine the motility, speed, viability and DNA integrity of 50-year-old sperm. To their surprise, they found no difference between sperm samples frozen for 50 years or a year. Of the 56 inseminated sheep, 34 were successfully fertilized.
"Sir Freddie", one of the first sperm donors, in 1969 / © Walker family
This is comparable with other results: the sperm of 19 male donors frozen for a year was used to inseminate 1,048 sheep, of which 618 were successfully fertilized. This gives a pregnancy rate of 61% for 50-year—old sperm versus 59% for sperm frozen for 12 months - the two results are practically equivalent to each other.
Samples frozen in 1968 by Dr. Steven Salamon were obtained from four sheep, including Sir Freddie, born in 1963. They belonged to the Walker family. Now the Walkers have eight thousand sheep on their farm in Ledgeworth and work closely with the animal breeding program at the University of Sydney.
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