Skip to the content

Using technology to breed lambs with more muscle


The yield of saleable meat in the carcase has a significant impact on carcase value. However great variation can be seen between sheep, including differences between breeds. This may be due to the influences of multiple genes that have a small impact on muscling on major genes that influence yield, such as those influencing myostatin expression which leads to increases in muscle in the carcase and a reduction in fat.

Selecting rams with high Scan Weight EBVs can increase carcase weights and reduce days to slaughter, but producers are also advised to select rams with superior breeding potential for muscling if they wish to enhance the carcase attributes of their flock and ultimately flock profitability.

To meet the needs of the commercial producer, ram breeders must select rams with the right carcase attributes, and this can be aided using EBVs to identify genetically superior animals. In order to assess muscling in the live animal, breeders can utilise measurement services such as ultrasound scanning and Computed Tomography (CT) scanning within their breeding programmes to find the best animals and make informed decisions. This work within pedigree breeding programmes is further supported by the RamCompare project, which is a progeny test for high genetic merit rams on commercial farms and collects progeny data such as abattoir records to enhance existing EBVs and create new ones.

Ultrasound Scanning

Many recording flocks use ultrasound scanning to identify sheep with superior muscling, while avoiding those likely to be excessively fat. Historically, scanning has been conducted around 21 weeks of age. However, in recent years, Signet has changed their guidance to focus on the weight of lambs at scanning rather than their age. Adjusting muscle and fat measurements for the weight of the lamb makes breeding values more commercially relevant and breeders now aim to scan lambs around 40 kg. Within maternal breeding programmes, this approach enables producers to breed lambs with a better yield of meat in their carcase without generating large increases in ewe mature size. This is an important consideration in breeding programmes that aim to enhance the efficiency of the breeding ewe.

CT Scanning

Since Signet introduced CT scanning into their genetic evaluations, more than 13,000 lambs have been put through the CT scanner, assessing carcase characteristics such a muscle and fat yield, spine length, loin area and intramuscular fat on live animals. Through AHDB Beef & Lamb-funded research these traits are now routinely evaluated allowing terminal sire breeders to measure the total quantity of muscle and fat in the carcase to a very high level of accuracy.

This service enables ram breeders to select breeding lines with superior yields of meat at a given liveweight, whilst accessing key measurements from the loin and gigot which we are unable to be measured via ultrasound.


RamCompare is the UK’s commercial progeny test for terminal sire breeds. The project has demonstrated the commercial value of genetic improvement by assessing the progeny of performance recorded rams of high genetic merit.

Pedigree breeders can use this data to improve their breeding programmes, focus their breeding decisions on commercially important traits and use the EBVs generated from RamCompare to market rams for sale.

These advances in ultrasound, CT and progeny testing provide breeders with in-depth data which can be used to make more informed breeding decisions and enhance the genetic merit of rams sold into commercial flocks. With a continued drive to improve efficiency and profitability on farms, the importance of using EBVs to make informed decisions and drive performance forward has never been greater.


About the author

Laura Eyles

Laura Eyles

Laura has joined the Signet team as a breeding specialist, she comes from an agricultural background having grown up on a sheep farm in Cornwall, where they keep commercial ewes and run a small flock of pedigree Charollais sheep.

Laura has a strong interest in animal breeding and genetics having studied Animal Science (BSc Hons) at Harper Adams University. During her time at Harper, she spent an industrial placement in Cumbria working for a sheep breeding company and some of our clients may recognise her from this role. Since graduating she has worked for a large cattle breeding company before joining us at Signet to lead on a number of Signet’s sheep breeding projects.