Performance record makes finding best tups an easier job
By Jessica Buss
FLOCKMASTERS can be sure they buy genetically superior rams this autumn by selecting them from breeders recording through the Signet Sheepbreeder scheme.
Signet breeding services manager, Sam Boon, says 60-70% of the schemes breeders have managed to scan lambs, despite foot-and-mouth restrictions. Most others have continued weighing lambs. Figures, therefore, are available from this years lamb crop. About 600 flocks, with 27 different breeds, are registered on the scheme.
Scheme members can choose to complete within-flock comparisons or co-operate in a breed Sire Reference Scheme (SRS). "SRS members must use AI from specific rams to give a genetic link with other flocks," he says. This allows breed averages to be calculated. The resulting Estimated Breeding Values (EBVs) can only be used to compare breeding progress within a breed. "EBVs relate to a base population of the breed at a certain time and those bases are different. There would need to be a genetic link between breeds, involving breeding crossbreds, to compare one with another," he adds.
Ram buyers should aim to buy from the top 5% of a breed. In SRS flocks EBV results would be printed on blue cards in the market, differentiating them from within flock recorded stock. "When buying directly from breeders ask whether they are in an SRS. If not, ask about the genetic progress being made within the flock to ensure animals are better than a few years ago and compare EBV ranges."
The average for these flocks is always 100. Results are usually in the 0 to 200 range. As a rough guide, rams with indexes above 165 are likely to be in the top 10% of that flock, he says.
When flocks are in an SRS, figures may be directly compared with breed averages (see table for the three largest SRS results), these are available from Signet.
The differences between average and top 10 % stock are becoming clear in the better established schemes. "Charollais SRS figures reveal that a top 10% ram offers a scan weight EBV of almost 3kg higher than an average one, so his lambs should be 1.5kg heavier as well as better muscled and leaner."
EBV scores for carcass and growth traits help make up a Scheme Index for each breed to highlight superior genetic merit in rams for finished lamb production. But the index is only a starting point, says Mr Boon. "Look closely at the individual EBV score to select a ram which suits your system. For terminal sires select on scan weight, muscle depth and fat depth, indicating potential for growth, muscularity and leanness.
"Do not be unduly influenced by the actual measurements made at scanning. These can be influenced by many factors, including feeding and age at scanning. The EBV formula takes these into account, as only the rams genes will influence his offspring.
"When selecting a ram to breed ewe replacements, growth rate is still important, but also look at EBVs for litter size – indicating prolificacy of offspring – and maternal ability, which shows how milky progeny will be," he says. *
Signet has developed a Pedigree Directory of Sheepbreeder flocks to help buyers identify superior rams in all areas of Britain. It is available free on-line www.signetfbc.co.uk
Sheepbreeder recorded flock averages for 2001 lambs
Charollais Suffolk Texel
Average Top 10% Average Top 10% Average Top 10%
Scan Weight EBV (kg) 5.07 7.94 6.32 9.03 5.03 7.99
Muscle Depth EBV (mm) 1.91 3.23 2.06 3.43 1.51 2.77
Fat Depth EBV (mm) 0.04 -0.73 0.18 -0.26 0.10 -0.30
Scheme Index 226 292 225 295 183 242