Maxwell Awumah, GNA
Ho, March 21, GNA - Over 50 years old semen stored in a laboratory in Sydney has been defrosted and successfully used to impregnate 34 Merino ewes.
The resulting live birth rate is said to be as high to that of a sperm frozen for just 12 months.
Out of 56 ewes inseminated, 34 were successfully impregnated compared to a recently frozen semen from 19 sires used to inseminate 1048 ewes of, which 618 were successfully impregnated.
This gives a pregnancy rate of 61 per cent for the 50-year-old semen against 59 per cent for recently frozen semen, a statistically equivalent rate, according to a research published in Science Daily and copied to the Ghana News Agency (GNA).
Professor Simon de Graaf from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney said "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."
"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.
Dr Jessica Rickard, a co-author 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."
Professor de Graaf said that it was the reproductive biology and genetic aspects of unpublished findings that were of most interest to him.
"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, adding that, "this gives us a resource to benchmark and compare."
Dr Rickard who is a post-doctoral McCaughey Research Fellow in the Sydney Institute of Agriculture 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.
She did the original work to determine if the stored semen were viable for artificial insemination which involved thawing the semen, which is stored as small pellets in large vats of liquid nitrogen at -196 degrees.
Dr. Rickard 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," she said.
The original semen samples were donated in the 1960s from sires owned by the Walker family.
The 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 programme at the University of Sydney.