Breeding for scrapie resistance according to the current National Scrapie Plan (NSP) strategy does not affect lamb performance, but could compromise the national flock's ability to withstand future scrapie strains.

Richard Moore of Roslin Institute told delegates at last week's BSAS conference, York, that a study comparing PrP genotype of more than 3500 Charollais lambs with performance recording data from Signet, showed no significant link between performance and genotype.

"In particular, alterations to the PrP genotype frequencies [following the move from ARQ to ARR allele] in this breed will have negligible impacts on lamb performance."

But Dr Moore did admit a move to a more limited genetic base, tilted in favour of one genotype could reduce the rate of improvement in flocks.

Meanwhile, similar studies in both Blackface and Swaledale flocks also reached similar conclusions, explained Rami Sawalha and Nicola Man, respectively.

Dr Sawahla though did find that Blackface lambs carrying the VRQ allele took 10 days longer to finish than lambs with other genotypes, although this wasn't statistically significant.

While in Swaledales, Dr Man found lambs carrying the ARR allele were slower to reach slaughter weight, again this was statistically insignificant.