BLUP MOVES ON AND UP THROUGHOUT SHEEP AREA
Pedigree and commercial sheep producers now benefit from BLUP analysis of performance records. Sue Rider reports
UK sheep breeding is now moving ahead rapidly and the pay-off for the genetic progress is cash benefits for breeder and commercial lamb finisher alike.
Top breeders are seeing increased demand for terminal sires that produce prime quality finished lambs. And the commercial producer is now prepared to pay extra for sires of proven transmitting ability because they can count on the extra cash obtained producing leaner and heavier sheep without incurring carcass penalties.
Use of high indexing rams, says Meat and Livestock Commission sheep strategy manager Stewart Hall, is worth £2 a commercial lamb, according to Scottish Agricultural Research.
Much of the credit for this genetic improvement goes to the sire reference schemes set up by the MLC (see pS24). Its farm consultancy service, Signet, also promotes flock recording and runs the Sheepbreeder service. Records from recorded Signet Sheepbreeder flocks fall into two categories – sire reference scheme flocks and other recorded flocks.
The sire reference concept is based on best linear unbiased production (BLUP) analysis of records for stock across participating flocks and of their ancestry records. The index is compared against a base year (1990) and updated as the group progresses. Comparisons are possible because each flock uses a proportion of similar sires by AI.
"Sire reference schemes enable us to identify rams with proven transmitting ability," says MLC sheep strategy manager Stewart Hall.
SRS rams transmitting ability is measured using best linear unbiased predictions. BLUP provides estimated breeding values (EBVs) for traits such as muscle score and backfat measured by Signet using its sheepbreeder service.
EBVs indicate an animals genetic advantage over the base year in terms of kg weight, mm eye muscle depth or reduced mm fat depth. An individual will pass on half of its genes – and, therefore, on average half of its genetic worth – to its offspring.
EBVs are more accurate than other performance records, says Mr Hall, because BLUP separates the genetic and non-genetic effects which influence a rams performance. It also makes fuller use of relative information. And the added bonus is that EBVs for sire reference scheme flocks can be compared across flocks and between years. The significance for the commercial producer is that they can ensure the sires they select are better than those used in previous years.
EBVs are measured by the sheep breeder service for four key traits (see diagram above).
SRS rams are ranked on a combination of the EBVs for weight, eye muscle, and loin fat depth known as the scheme index. Due to genetic improvement made by breeders the average scheme index of SRS rams is now around 130 depending on the breed.
From this year performance of non-SRS flocks recorded under the Signet sheepbreeder scheme has also been analysed by BLUP. EBVs for scan weight, eye muscle depth and loin fat depth are provided. But for scanning flocks not in an SRS scheme, EBVs are combined in a lean index. Unlike the scheme index used for SRS flocks, the lean index of lambs and other sheep from different flocks cannot be compared.
As a guide, the top 25% of lambs in a flock have lean indexes over 126, and the top 10% are 150.
Mr Hall is keen to increase flock participation in recording schemes – and aims to increase SRS membership by 20% a year. He is confident this target will be achievable as more and more commercial lamb producers recognise the value of buying high indexing sires. A producer wishing to sell into the Easter market can, for example, identify rams which score well for growth rate. The producer selling late lambs will put more emphasis on rams with good weight EBVs.
Next year maternal traits for sheepbreeder recorded flocks will be analysed using BLUP and EBVs for litter size, maternal ability and mature size produced.
"Producers will, for example, be able to monitor the prolificacy of ewes in their own flock," says Mr Hall. *
• For more information on sheep breeding and the Signet sheepbreeder service visit, the MLC stand at Smithfield or contact Signet Farm Business Consultancy, PO Box 603, Milton Keynes MK6 1BR.
Top breeders are seeing increased demand for terminal sires with the proven transmitting ability to produce prime quality finished lambs.
MLC sheep strategy manager Stewart Hall: "Sire reference schemes enable us to identify rams with proven transmitting ability.