12 May 2000



By Shelley Wright

SIRE reference schemes probably have as much, if not more, to offer commercial sheep farmers as they do breeders of pedigree terminal sires.

Geoff Simm, head of SACs animal breeding and genetics, believes that after more than 10 years of rapid progress in terminal sire genetics, commercial producers can now benefit from that work.

Back in the early 1980s, any recording that was done in sheep revolved around the liveweight of animals, says Prof Simm.

"But sheep breeders were becoming increasingly aware of the need to reduce carcass fatness, so we began to see more use of ultrasound scanning, in conjunction with liveweight recording."

It was about this time that Prof Simm and his colleagues began trying to develop a sire reference scheme using an SAC flock of Suffolk sheep in Edinburgh.

"We looked at every sort of measurement under the sun, gradually reaching the point where we could have good accuracy using ultrasound scans and liveweight measurements.

"As far back as 1984 we looked at hiring a computed tomography (CT) scanner, but it was too expensive."

SAC now has its own CT scanner, located at the Bush Estate, Edinburgh – the only facility in the country where sheep can be CT scanned.

And Prof Simm believes that CT scanning – which produces a much more accurate carcass evaluation than ultrasound scanning – will be one of the keys to further improvements in sire reference schemes and genetic improvement in the UK sheep flock.

From the roots of sire reference schemes back in the 1980s, there are now more than 20 breed societies involved, accounting for about two-thirds of performance tested sheep in the country, says Prof Simm.

"I think the most impressive achievement over the past 10 years, is that the larger schemes have achieved about 1.75% improvement each year in lean index.

"That sort of improvement is more than you would see in the dairy sector selecting for increased milk yield, and the same sort of rate of genetic improvement that would be expected in intensive pig and poultry production, so the advance has been really encouraging.

In fact, Prof Simm reckons that this level of genetic progress in the UK sheep flock is up there with the best in the world.

Yet, despite this, sire reference schemes remain largely a tool used by pedigree terminal sire breeders. "They really have been the driving force. But we are now starting to see more and more commercial producers beginning to appreciate what these schemes offer."

More choice

Because breeders have worked so hard – with little financial reward – on introducing reference schemes, there is now much more choice and accuracy of estimated breeding values on offer for commercial producers, he says.

"When you look at the economics of lamb production, those who are involved in flock recording make more progress than those who dont." And equally, making use of sire reference schemes offers faster development, adds Prof Simm.

"Its definitely worthwhile for commercial flocks. We have done much trial work in the past eight years looking at high and medium index flocks, and assessing genetic progress on grass-based finishing systems.

"There is no question that high index lambs reach a fixed carcass weight quicker and are leaner than lower index animals."

For commercial lamb producers, often criticised for failing to produce what the market wants, SAC results show the improvement, and financial reward, that can be achieved.

"In our own Suffolk flock, after nine years of selection, about 75% of lambs achieved the preferred MLC carcass classification for fatness of 2-3L." This compares with 40% achieving the target in the low index flock. At todays prices that is worth about £2 lamb more, he adds.

The next step towards convincing commercial producers of the benefits of genetic improvement is to take recently developed indexes for hill breeds into the field.

Twin benefits

"Its more complicated because we need to build in aspects like lamb survival, number of lambs weaned and maternal instincts. Were looking for the twin benefits of reducing lamb loss and improving carcasses," says Prof Simm.

"I think this is a good way of trying to improve farms financial performance. In the longer term it is one way of reducing producers dependence on subsidies."

One of the most important tools in the short term, he believes, is increased use of CT scanning. But, although much more accurate, the technique is also more expensive than ultrasound, costing up to £75/sheep.

However, Prof Simm and his team hope to work out a realistic compromise. "Ultrasound scanning is much cheaper where large numbers of animals are involved. But if we selected say the top 10 -15% of a flock and sent them for CT scanning, we would see exciting progress in genetic improvement." &#42

CT scanning offers a really exciting chance to accelerate sheep genetic improvement, says Geoff Simm (inset).


&#8226 World leading genetic progress.

&#8226 CT scanning will lead to greater gains.

&#8226 But more expensive.

See more