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The financial impact of using performance recorded rams

Selective breeding is not a new concept. Humans have been selecting livestock with desirable traits since the days of Robert Bakewell, who was the first to implement selective breeding of livestock in the 1700s. 


However, our ancestors only had the opportunity to do this by eye. While this results in genetic progress over a long period of time, an animal’s appearance may not reflect how its progeny perform.

Using Estimated Breeding Values (EBVs) and indexes to select a performance-recorded sire is a more efficient way of making genetic progress than selecting stock by eye.

Emma Steele, Signet specialist breeding adviser, says: “EBVs and indexes are produced from performance data collected from the individual and its relatives, giving an estimate of its genetic potential and how its progeny are expected to perform. These help inform selection decisions and increase the rate of genetic progress.”

Improved lamb performance means increased financial returns. If more lambs meet specification at reduced days to slaughter this generally means a higher premium for carcases and reduced feed and maintenance costs for the lambs.

Ms Steele says: “A ram’s index provides an overview of its genetics for a desired breeding objective, for example producing prime slaughter lambs. Purchasing terminal sires with a high index means the sire is likely to produce lambs which have high early growth rates and improved conformation. It is estimated financial returns can be expected to increase by at least £3-£4 per lamb when high index sires are used, which is more than £1,000 in a ram’s lifetime.”

Traits to look for

Performance-recorded rams come with EBVs which describe how well an animal’s progeny is expected to perform for individual traits.


  • Eight-week weight and scan weight EBV – these indicate the genetic potential of a ram’s progeny for early growth rates to slaughter weight. A ram with a scan weight EBV of +6 is estimated to produce lambs which are 3kg heavier at 21 weeks than a ram with an EBV of 0

  • Muscle depth EBV – an indication of muscling across the loin. A ram with an EBV of +4mm is estimated to produce lambs with loins 2mm deeper at 21 weeks than a ram with an EBV of 0

  • Fat depth EBV – an indication of fatness across the loin. A ram with an EBV of -1mm is estimated to produce lambs with 0.5mm less fat across the loin at 21 weeks than a ram with an EBV of 0

Most terminal sire breeders also make use of computed tomography (CT) scanning, allowing them to assess carcase characteristics in fine detail.


CT lean weight EBV – breeding potential for weight of muscle in the carcase
CT fat weight EBV – breeding potential for weight of fat in the carcase
CT gigot muscularity EBV – breeding potential for width of the gigot

Choosing the right EBVs for your system

It is important to remember that different EBVs will suit different systems.


Ms Steele says: “An early lambing flock where lambs are creep fed to aim for the Easter market may place high importance on early growth rates. It will therefore make sense to pay particular attention to the eight-week weight and scan weight EBVs. An extensive grass-finishing flock, however, may place more importance on selecting a ram with EBVs for higher conformation and muscling, with a slightly positive fat depth EBV, to ensure lambs have the required level of finish.”


Finding a recorded ram


Every Signet performance-recorded ram in the UK can be found online at, which can be accessed by anyone. Search for rams by identification number or by using the ‘EBV search’ function, selecting the breed and traits of interest. At sales the breeder will advertise stock with their EBV charts in pens.

This year Signet has launched the ‘Seek the Standard’ campaign. Breeders recording with Signet have the option to display silver and gold identifiers on their stock at the point of sale. A gold identifier shows an animal with an index in the top 10 per cent of its breed, while a silver identifier indicates those with a top 25 per breed index.


In 2018 Signet will be producing EBVs for:

  • Vertebrae number and spine length
  • CT-predicted intramuscular fat (IMF) percentage
  • Eye muscle area across the loin

Ms Steele says: “These will be generated from data collected from past, present and future CT images, allowing us to make the most from what we have.
“There is variation between breeds for all these traits. Total vertebrae number varies between 18 and 21, whereas lumbar vertebrae number varies between six and seven. We believe this could enable us to select for longer sheep with an extra lamb chop in the future.”


For more information go to

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