Frozen in 1968 by Dr Steven Salamon of the University of Sydney, the pool of semen included four rams of Ledgworth, Merryville and Boonoke genetics, owned at the time by the Walker family of Ledgworth at Yass.

In celebration of the semen's 50th year and the late Dr Salamon's 100th birthday the semen was thawed and inseminated in ewes as part of the the 2018 Balmoral Sire Evaluation Group, a trial into leading sires suited for fine wool production in Western Victoria. 

The Boonoke ram, known as Sir Fred, was born in 1959 and sold to Ledgworth in 1961 for 345 guineas or $659.30 in today's currency.

The Merryville ram, born in 1963 was bought by Ledgworth in 1965 for 1000 guineas or $1911 today while the other two sires were F1 progeny of the Boonoke and Merryville rams and crossed with Ledgworth ewes from 1963 and 1965.

Interestingly, semen from all four rams was frozen in a pellet together with researchers unsure of exactly which of the rams will have inseminated the ewes. 

The semen was initially frozen to prove sperm could survive several years storage in liquid nitrogen at -196°C and is now the oldest sheep semen in existence in the world and the oldest to be inseminated. 

Used alongside a number of modern rams in the trial, the historic semen recorded higher pregnancy and scanning rates of its younger counterparts.

Of the 56 ewes inseminated with the 50-year-old semen, 34 were scanned pregnant or 61 per cent. This was compared with 59 per cent in the other sires with 618 of 1048 ewes pregnant.

In the fetus scan, the older semen had an 82 per cent scanning rate while other sires were at 80 per cent. 

Early findings from the trial have found the sperm was as fertile as the day it was frozen.

"Pregnancy and scanning rates (were) no different to the overall average of all sires who were also artificially inseminated in the Balmoral program,” an information brief said. 

“The high fertility of this semen demonstrates that long term frozen storage of sperm is safe and reliably preserves genetics for future use in the agriculture industry.

“This trial offers a remarkable opportunity to open a window to the industry’s past and in doing so also contemplate the future of sheep selection and genetics and what we might expect to see in 50 years’ time.

“Beyond insights into artificial breeding and semen freezing technology, use of this semen also stands to showcase 50 years of genetic progress of the Australian wool industry."

The performance and appearance of the progeny of the 50-year-old semen will be compared to the modern rams in the Balmoral program over the next few years with the first report available after the first shearing in March. 

The progeny were on display at the Balmoral Merino Sire Evaluation Field Day on Friday at Kooringal in Victoria.

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