Dorset sheep breeders take carcase traits to a new level

This isn’t their sole focus as they have made important gains in maternal traits like milk and prolificacy, but by measuring lamb growth rates and ultrasound scanning prime lambs to assess muscling, they have transformed the carcase attributes of Dorset-sired lambs.

The challenge with this approach is that it has always focused on proxy measures for the traits of interest. A better approach would use measures of days to slaughter, carcase weight and carcase conformation to generate more informative breeding values – and in the last 12 months this is exactly what they have done.

To date, 7,000 abattoir records have been supplied for pure-bred Dorset lambs. Using genetic approaches established through the RamCompare project, these records are being analysed as part of the National Terminal Sire Evaluation, with records for individual sheep viewable at www.signetdata.com.

What has the evaluation of abattoir data shown?

The latest AHDB-funded research, due for release this autumn, shows exactly what the breed has achieved in selecting for on-farm performance.

Increases in breeding values for scan weight (an indicator of liveweight gain) have led to reductions in days to slaughter of over a week, accompanied by additional increases in carcase weight (Figure 1). Selection for muscling has increased carcase conformation with little change in carcase fatness.

Selecting for traits measured on farm has boosted the value of the average Dorset-sired lamb by £3/head, with the leading Signet-recorded sires regularly showing a genetic advantage of £6–7/head.

Figure 1. Genetic trends for Dorset sheep – reducing days to slaughter and increasing carcase value 

How can ram buyers use this data?

When buying Dorset rams, producers should select stock sires with high Estimated Breeding Values (EBVs) for Scan Weight and Muscle Depth if they want lambs to finish quickly and receive a premium for conformation.

In addition, ram buyers should start using the new breeding values for abattoir traits, such as days to slaughter and carcase conformation, to capitalise on the best genetics the Dorset breed has to offer.

Further information can be found in the Signet publication Dorset sheep − Bred for commercial sheep production.

Members of the Signet team will be at the following Dorset sales:

• 5 April 2024 – Centurion Ram Sale
• 7–8 May 2024 – Dorset May Fair