Sir Freddie. Photo credit: Walker family

Potential fathers who truly struggle with their decision to start a family can now delay that decision by decades.

Biologists in Sydney, Australia, recently thawed out sheep semen samples taken in 1968 and used it to impregnate Merino ewes. Out of 56 ewes inseminated, 34 were successfully impregnated, for a statistically equivalent pregnancy rate of 61% for the 50-year-old semen against 59% for sperm frozen for only 12 months. The pregnant ewes also experienced a live birth rate just as high as with the more recently frozen sperm.

“This demonstrates the clear viability of long-term frozen storage of semen,” says Associate Professor Simon de Graaf from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney.

Beyond the long-term storage finding, Dr. de Graaf and his colleague,  Dr Jessica Rickard say that the reproductive biology and genetic aspects of these as-yet unpublished findings are of most interest to them.

“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,” says Professor de Graaf. “This gives us a resource to benchmark and compare.”

The original semen samples were donated in the 1960s from sires owned by the Walker family, who maintain a close and proud relationship with the animal breeding program at the University of Sydney.

So for those truly unable to commit to a family, your can now put your decision on ice for at least 50 years, although that level of procrastination may affect your family potential in other ways.