The oldest frozen ram semen in existence has been thawed out and used to successfully impregnate 34 Merino ewes in a world first.
The semen has been stored in a Sydney laboratory since 1968, with the sample used this year as part of University of Sydney’s Balmoral sire evaluation program.
Pregnancy scanning results indicated that despite 50 years of storage the semen was as fertile as the day it was frozen, with pregnancy and scanning rates no different to the overall average of all sires in the program.
University of Sydney’s Institute of Agriculture and School of Life and Environmental Sciences’ Associate Professor Simon de Graaf said the results demonstrated the clear viability of long-term frozen storage of semen.
‘‘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,’’ he said.
It is believed this is the oldest viable stored semen of any species in the world and the oldest sperm used to produce offspring.
‘‘We can now look at the genetic progress made by the wool industry over the past 50 years of selective breeding. In that time, we’ve been trying to make better, more productive sheep,’’ Prof de Graaf said.
‘‘This gives us a resource to benchmark and compare.’’
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 per cent for the 50-year-old semen against 59 per cent for recently frozen sperm, a statistically equivalent rate.
The original semen samples were donated in the 1960s from sires owned by the Walker family from Yass in NSW.
The samples were frozen in 1968 by Dr Steven Salamon and came from four rams, including Sir Freddie born in 1963, then owned by the Walkers on their 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.