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The sperm ram frozen for 50 years has been successfully used to impregnate 34 ewes

Researchers who thawed 50 years old sperm and successfully impregnated 34 ewes of Professor Simon de Graaf and Dr. Jessica Rickard. Pictured here with a healthy offspring from seed. Credit: Morgan Hancock / University of Sydney

Sperm stored at the Sydney laboratory in 1968 was thawed and successfully used to impregnate 34 Merino ewes, with the resulting fertility of live birds frozen for only 12 months.

"This demonstrates the clear viability of long-term frozen semen storage. The results show that fertility is maintained over 50 years of frozen liquid nitrogen storage," said Professor Simon de Graaf of the Institute of Agricultural and School Life in Sydney and Environmental Science at the University of Sydney.

"The lambs have wrinkles that occurred in Merinos in the middle of the last century, a feature that was originally chosen to maximize the surface of the skin and the yields of wool. This Merino style has since largely fallen out of favor. and the increased risk of a hit, "said Professor de Graaf.

His colleague on this project, Dr. Jessica Rickard said, "We believe this is the oldest viable stored sperm of any kind in the world, and certainly the oldest sperm used to produce offspring."

Professor de Graaf said that it is primarily the biological reproduction and genetic aspects of these unpublished findings that are most interesting to him.

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

"We can now look at the genetic progress that the wool industry has been developing over the past 50 years of selective breeding. At that time, we tried to make better, more productive sheep," he said. "That gives us a source of comparison and comparison."

Dr. Rickard is a post-doctoral researcher at McCaughey Research at the Sydney Agricultural Institute. She continues her strong tradition of animal reproduction research at the University of Sydney through her work in Animal Reproduction.

Dr. Rickard did the original work to see if the stored semen was viable for artificial insemination. This included the thawing of semen, which is stored as small pellets in large liquid nitrogen containers at -196 ° C.

"On this result, it is amazing that we did not find any difference between sperm frozen for 50 years and sperm frozen for one year," he said. Rickard.

Sir Freddie, & # 39; One of the original seed donors, in 1969. Credit: Walker Family

Of the 56 fertilized ewes, 34 were successfully impregnated. This is comparable to the recently frozen semen from 19 nobles used to inseminate 1048 ewes, of which 618 have been successfully impregnated. This gives pregnancy 61 percent for a 50 year old semen versus 59 percent for recently frozen sperm, a statistically equivalent rate.

Original sperm samples were donated in the 1960s by Walker family sponsors. These samples, frozen in 1968 by dr. Steven Salamon, they came from four rams, including "Sir Freddie", born in 1963, owned by Walkers on their then estate at Ledgworth.

The Walkers now run 8000 sheep at Woolaroo, at Yass Plains, and maintain a close and proud relationship with the animal husbandry program at Sydney University.

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