25 July 1997

TARGETING UKS MAIN BREEDS…

STRATEGIC targeting of genetic testing for scrapie at those breeds which have greatest influcence on the national flock is whats needed to control incidence of the disease in the UK.

Thats the view of Oxon sheep producer Tony Good, who runs 2000 early lambing Finn Dorset Milksheep at his 202ha (500-acre) all grass Warborough Farm, at Letcombe Regis, Wantage.

Mr Good has been involved in MAFFs Central Vet Laboratory scrapie research programme since its initiation three years ago.

Good record keeping, and an incidence of the disease in his own flock made him a natural collaborator with CVL, he says.

Need for approach

"I could see the need for this sort of approach to breeding – both to satisfy pressures from retailers and improve the prospects of the British sheep industry for exports abroad.

"We notify CVL of all our scrapie cases; we have also been blood testing rams over several years to identify which are genetically resistant to scrapie and will pass on – as far as we know – resistance to forms of scrapie encountered in this country.

"Over the last two years we have been breeding replacements from scrapie resistant rams, so within five years virtually all females will be scrapie resistant," maintains Mr Good.

"Whats important is that our rams test R/R at codon 171; these are going to be scrapie resistant, and will produce scrapie resistant offspring. They are, therefore, the ones we use to breed replacement breeding stock," he says.

Flock replacements born in 1995 and 1996 at Warborough Farm, where the ewes lamb to AI in December, were sired by R/R rams, and these 1000 ewe lambs and shearlings will also be tupped with R/Rs. "This should mean their offspring are at least R/R and R/Qs."

Mr Good is conscious that breeding for scrapie resistance could compromise selection for other traits, but he has seen no detrimental effects so far.

"We have had one crop of lambs from our Dec 1995 born ewe lambs, and theres no evidence that prolificacy or conformation have suffered."

But access to sufficient bloodlines has meant testing Finn Dorset rams in other flocks and using those which test R/R.

"Use of AI across the flock also helps," explains farm manager David Barber. "We need only six rams per 1000 ewes, whereas with natural mating wed need nearer 25 per 1000."

Mr Good believes sire reference schemes and breed societies should be concentrating on breeding for scrapie resistance as well as individual breeders such as himself. "Now we have the tools to do the job, the sheep industry has a responsibility to use those tools to breed scrapie resistance into the national flock."

More breed societies – particulary the Bluefaced and Border Leicester, whose sires are used to produce crosses for the lowland sheep breeding flocks – should be concentrating on identifying scrapie resistant sires.

"This would ensure we can rapidly produce scrapie resistant lowland breeding ewes – and that will be the quickest way to produce a scrapie free national flock."

Mr Good acknowledges that there could be difficulties in sourcing sufficient scrapie resistant rams initially. But suggests AI could enable use of targeted rams over more of the draft ewes.

Likewise, he maintains that sire reference schemes – whose aim is to identify the best rams in the breed – should only admit rams which are scrapie resistant.

Two ram classes

Mr Good also believes that there should be two classes of ram in all pedigree sales. "One should be for rams certified as resistant and one for those which are not. Real money will be made by the resistant rams, and that will put pressure on breeders to do something about scrapie. Unless it hits your pocket, you wont do anything about it."

But he recognises that one concern the NSA must address is how to certify that a ram is resistant. "It might require regular random blood testing, with producers struck out of the flockbook if they are found to be cheating," he says.

As for his sheep AI service, he is making semen from his R/R Finn Dorsets rams available to other producers, and hopes to start using R/R Suffolks this year.

"When theyre available wed like to use R/R rams from other major breeds, so all semen is from scrapie resistant rams.

"Its only now that the industry is waking up to the need to address concerns over scrapie. It must act to address those concerns."

Farm manager David Barber with a high indexing scrapie resistant (R/R) Suffolk ram.

Tony Good (left) and farm manager David Barber – breeding scrapie resistance into their flock of 2000 early lambing Finn Dorset Milksheep.