Ram sperm frozen for 50 years successfully used to impregnate 34 ewes

World's oldest semen still viable
Researchers who thawed 50 year old sheep semen and successfully impregnated 34 ewes Associate Professor Simon de Graaf and Dr. Jessica Rickard. Pictured here with the healthy progeny from the semen. Credit: Morgan Hancock/University of Sydney

Semen stored since 1968 in a laboratory in Sydney has been defrosted and successfully used to impregnate 34 Merino ewes, with the resulting live birth rate as high sperm frozen for just 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 ," said Associate Professor Simon de Graaf from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney.

"The lambs appear to display the body wrinkle that was common in Merinos in the middle of last century, a feature originally selected to maximise skin surface area and wool yields. That style of Merino has since largely fallen from favour as the folds led to difficulties in shearing and increased risk of fly strike," Associate Professor de Graaf said.

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

Associate Professor de Graaf said that it was the and genetic aspects of these as-yet unpublished findings that were of most interest to him.

Sheep semen thawed after 50 years under a microscope. Credit: 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," he said. "This gives us a resource to benchmark and compare."

Dr. Rickard is a post-doctoral McCaughey Research Fellow in the Sydney Institute of Agriculture. She is continuing the strong animal reproduction research tradition in veterinary and biological sciences at the University of Sydney through her work in the Animal Reproduction Group.

Dr. Rickard did the original work to determine if the stored semen was viable for artificial insemination. This involved thawing the semen, which is stored as small pellets in large vats of liquid nitrogen at -196 degrees. She and her colleagues then undertook in vitro tests on the sperm quality to determine the motility, velocity, viability and DNA integrity of the 50-year-old sperm.

"What is amazing about this result is we found no difference between sperm frozen for 50 years and sperm frozen for a year," Dr. Rickard said.

World's oldest semen still viable
'Sir Freddie,' one of the original semen donors, in 1969. Credit: Walker family

Out of 56 ewes inseminated, 34 were successfully impregnated. This compares to recently frozen semen from 19 sires used to inseminate 1048 ewes, of which 618 were successfully impregnated. This gives a pregnancy rate of 61 percent for the 50-year-old semen against 59 percent for recently frozen , a statistically equivalent rate.

The original samples were donated in the 1960s from sires owned by the Walker family. Those samples, frozen in 1968 by Dr. Steven Salamon, came from four rams, including 'Sir Freddie' born in 1963, owned by the Walkers on their then property at Ledgworth.

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

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Citation: Ram sperm frozen for 50 years successfully used to impregnate 34 ewes (2019, March 17) retrieved 19 August 2019 from https://phys.org/news/2019-03-ram-sperm-frozen-years-successfully.html
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User comments

Mar 17, 2019
Uh oh - another commodity for traditional Chinese medicine-

Mar 17, 2019
Merino sheep are valuable for their wool production. The ram in the photo would probably be gone now, but his offspring live on.
Yes, Life is Positive, which was meant to be.

Mar 17, 2019
Well. 59% to 61%"meant to be,
With the best available monitoring & veterinary care for the stock.

Sexual Reproduction is a crapshoot. An unpredictable process in the stochastic reality of Biology.
Even with the careful selection of specimens with proved desired characteristics.

They managed barely above flip of the coin for young surviving birth.
The next tests will be how successful the breeding line does over the next few generations.

It would be interesting to have autopsies of the failed births & any ewes that died during & after pregnancy.
Might garner some clues as to why the success rate was only slightly above random average.

Mar 17, 2019
50 years of potential DNA degradation there is no telling what hidden damage there is.

Mar 17, 2019
Ok, since no one else is going to say it.
Sir Freddie is a mule in sheep's clothing.


Mar 17, 2019
Sexual reproduction is always "hit or miss". If it wasn't that way, the land masses of the Earth would be so full of people and animals that it would be too crowded. Calls for euthanasia would result.
Oh wait. That's happening now, isn't it. It's called Abortion and Infanticide on already-born babies. New York and Virginia have passed it into law.
Doubtful they would pass such a law on sheep as sheep can be slaughtered for...
Oh wait. Infanticide is slaughter too, isn't it.

Mar 17, 2019
oh, sillyegghead, you do love your lies.
& those fake, crocodile tears of yours? Are particularly hypocritical when you are part of the agitprop campaigns against science & education.

Together with the anti-vaxxers, you despicable traitors are contributing to the actual deaths of actual; children.
who actually exist as Human Beings. With the misfortune to have had ignorant & gullible parents. Past Tense!

Not the photoshoped mannequins your cult of bigots & death worshipers wave about.

Jow do we prove you are a liar?
What are you doing for educating pubescent children in the Sciences of Hygiene & Human Reproduction?
& supportive Mental Health training teaching children they can say NO! to you religious perverts?
& Grossly Obscene Pederasts?

Mar 18, 2019
@Thorium Boy, your comment is very significant.

It is more than likely that old sperm was frozen in liquid nitrogen. That is around -340 F. That is how all sperm, ova and embryos are stored today, so there is not significant degeneration in the DNA, or the overall macrostructure of the nucleus. But it may take time to tell for sure with each animal created this way.

And it cannot just be dunked into the liquid nitrogen. It is ramped down at a slow rate to prevent ice crystals from forming rapidly and tearing through the tissue, which usually destroys most nuclei. This was discovered by trial and error, and the requirements are pretty precise. I believe the thawing has to be ramped up as well.

This is why it is doubtful they will ever clone animals frozen in the wild, or stuffed ones in museums. Too "warm" long-term storage, or dehydration, destroys nuclear structures. Would love to hear from anyone who knows more about cryogenic tissue storage.

hello again @rrwillsj!

Mar 18, 2019
Clarification of temperature. Missed the temperature line from the article on my first post. Rereading says these were indeed stored in "large vats of liquid nitrogen at -196 degrees". That value is in Centigrade. Fahrenheit is about -240ish. I used F because most people, even myself, relate to it much more easily. It is freakin' cold!

Mar 18, 2019
howdy dfj. I appreciated reading both your comments.
For the details I did not know or had forgotten. Been a while since I've had to deal with breeding stock.
& we sure didn't have any of these fancy procedures or technology.

"Okay Jose! Open the chute gate & let'im at'er!"
"!Arriba! Mu Chacho!"

Man that was a long time ago. So far back, the last Real Republican, Eisenhower, was President!

& good on you dfj!
For encouraging seu to find a better nature. Even if he has to borrow it fro, a neighbor for the weekend.

Mar 18, 2019
The most significant post here remains that of @Thorium Boy. His comment about the potential danger is not at all understood. Human studies on people born from cryogenic storage either as sperm, ova or embryos is not possible yet since it is so new. Will they grow up with a higher risk for disease or disability? There is limited data on this I have to believe.

Not enough time has elapsed since this tech has been developed. Surely they have data from mice and rats, but they remain a far cry from humans. Time will tell.

Of course livestock is not a good measure since most are eaten before anything bad can happen. Again, we need an expert who has some data on all this to get a real answer.

I hope Thorium Boy returns for more commentary.

Mar 18, 2019
Getting eaten isn't bad enough?
If the pseudo-science of eugenics was correct?
Stock would breed flesh poisonous to Human consumption.

It took natural selection paired in a three-legged race with plain blind stupid luck, billions of years from algae to multi-celliar, multi-organ complexity.

Considering all the competition?
Our algae are the very best algae!
Those expecting to artificially induce "superior" Human beings?
Might want to ponder "Sometimes, moderate, modest, conservative effort is a good enough a measure of success."

I realize the Modern American motto is
"Excess is Never Enough!"
With the matching slogan for Capitalist Plutocracy
"If it was worth doing?
It must mean that it is worth overdoing!"

dfj, try not to fet your hopes up too high with either tb or seu.
As the saying goes: "Wishful thinking causes more disasters than we choose to believe."

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