Semen which has been stored in a lab since 1968 has successfully impregnated 34 sheep, a study claims.
Samples were taken from four rams, including one called Sir Freddie, in 1968 and were frozen for fifty years.
Australian researchers describe it as the world’s oldest sample of frozen semen successfully used to produce offspring.
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Semen which has been stored in a lab since 1968 has successfully impregnated 34 sheep, a study claims. Samples were taken from four rams including one called Sir Freddie, pictured here, in 1968 and were frozen for fifty years
The defrosted samples, taken by scientists from the University of Sydney, inseminated 56 Merino ewes – and 34 became pregnant.
The 61 per cent success rate was higher than that of sperm frozen for only a year – which impregnated 59 per cent of inseminated ewes.
The team said that their research shows that there is ‘no difference between sperm frozen for 50 years and sperm frozen for a year’.
‘This demonstrates the clear viability of long-term frozen storage of semen,’ 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 results show that fertility is maintained despite 50 years of frozen storage in liquid nitrogen.’
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.
‘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.’
The University said that the samples were kept as small pellets in large vats of liquid nitrogen at 196 degrees.
Sheep semen thawed after 50 years under a microscope. The team said that their research shows that there is ‘no difference between sperm frozen for 50 years and sperm frozen for a year’
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
They were then defrosted and tested for its velocity, viability and DNA integrity.
The success will bolster hopes that plunging eggs and sperm into the deep freeze is a credible long-term means of providing endangered species with a lifeline.
The original semen 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.
HOW DOES ARTIFICIAL INSEMINATION WORK?
Researchers in Illinois recently used an artificial insemination procedure to, hopefully, impregnate a wolf (file photo)
Artificial insemination is among the slew of new reproductive medicine techniques that has come out recently.
Human couples who opt for the technology see specialists who use ultrasounds, blood tests or ovulation kits to check to see if a woman is ovulating at the time of her procedure.
A sample of sperm is then required from the woman’s chosen donor; the doctor puts the sample in a catheter that is threaded through the woman’s vagina and cervix before reaching her uterus.
The success rate for the procedure varies. The following can affect the chances a woman has of becoming pregnant thanks to artificial insemination:
- the woman’s age
- the quality of the sperm and egg
- a condition called endometriosis
- fallopian tube damage
- fallopian tube blockage
Scientists near Chicago recently tried to use artificial insemination technology to impregnate a wolf.
Their hope is that the technology can revive the species, which has been considered endangered since 1976.