Advice for buying rams based on EBVs

Ram selection is key to a successful sheep enterprise, with trials showing that the right tup can be worth an extra £600 over his working lifetime.

With 50 years’ worth of performance-recording and new data from the RamCompare national progeny test, it has never been easier to select the right sire for an individual flock, says AHDB genetics specialist Samuel Boon.

With wider use of computerised tomography (CT) scanning for predicting carcass composition, and reliable performance recording data, there is no reason to take a gamble based on appearance alone.

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In fact, spotting the “good” sires by eye alone is impossible, given the large genetic differences between sires. Furthermore, high levels of feeding can easily mask poor-performing genetics, warns Mr Boon.

Below, he gives advice on selecting rams with the right estimated breeding values (EBVs) for your farm.

Advice for selecting traits: Where to start?

Farmers should first consider which EBV matters the most to their business and select rams accordingly.

Selecting rams with the right combination of traits should be a good match for business profitability, but remember that a ram’s EBVs should be halved when estimating how much of his genetic potential will be passed to his progeny, as the other half will come from the ewe.

Breeding information is often displayed on charts with the central line representing the average level of performance within the breed. The charts will list EBVs, indexes, and accuracy values.

Terminal traits to consider

RamCompare has clearly shown that a high scan weight EBV results in increased growth rates and reduced days to slaughter. High scan weight and muscle depth EBVs equal increased carcass weights.

The data has also shown that EBVs for superior muscle depth and gigot muscularity enhance carcass conformation. Fat depth EBV is a good indicator of the fat classification achieved by sire progeny.

Progeny performance data from RamCompare is already being used by Signet to enhance existing EBVs and support research to develop new ones for traits such as days to slaughter and carcass conformation.

CT data, which is funded by levy organisations such as AHDB, has also played a pivotal role in the improvement of terminal sire breeds.

CT measurements show the weight of fat, muscle and bone in the carcass; the distribution of muscle, including the percentage of muscle in the leg, loin, or chest; and spine length and vertebrae number. Intramuscular fat percentage and gigot shape are also measured.

This raw data is used by Signet Breeding Services to create nine EBVs that can enhance carcass yield and shape.

When buying rams, producers selling on a deadweight basis should take into account breeding values for scan weight, muscle depth, and CT lean weight.

Rams at an auction sale

© Tim Scrivener

Maternal traits to consider

Most flocks seek positive breeding values for eight-week weight, litter size, and maternal ability to influence early lamb growth rates; the number of lambs reared; and milking ability of female replacements.

Breeding values for traits influencing carcass conformation should be considered, too.

Some traits are breed-specific. For instance, the Lleyn and Scottish Blackface have EBVs for lamb survival, a trait that has high economic importance.

Another economically important trait is ewe longevity – it is a trait that considers the length of time when the ewe is productive in the flock, so it is actually an indicator of reproductive lifespan within a flock.

In recent years, breeders have become increasingly interested in enhancing the overall efficiency of the ewe, increasing her output without increasing her mature size.

New breeding values for ewe mature size, which have been developed as part of research funded by AHDB and the Centre for Innovation Excellence in Livestock, are being introduced to enable breeders to limit future increases in ewe mature size.

What to ask a breeder when buying a ram

Independent sheep specialist Kate Phillips advises on what to ask ram breeders and what quarantine procedures to carry out.

From vaccinations and fly treatments to nutrition and management, it is helpful to know as much as possible about a ram’s history.

There is no recognised document for cataloguing this information, but it would be a useful tool for ram buyers to have. Such a “clean bill of health” would be really useful, although it wouldn’t be a guarantee.

What information should the document contain?


  • Whether the ram is from a flock in a recognised health scheme and maedi visna-accredited, and whether it was monitored for enzootic abortion.
  • In the absence of that record, key information a buyer should request includes a vaccination record – what jabs a ram has had and when, and whether boosters have been given.
  • Rams should be up to date with clostridial and pasteurella vaccines with all the boosters in order.
  • A history of worm and flystrike treatments will inform policies on the purchaser farm and will prevent overuse of products.


  • Knowledge of how a ram was fed will ease its transition to its new environment.
  • If it has been fed large amounts of concentrates and is turned straight out to grass it would be under significant nutritional stress because it takes two or three weeks for the rumen to acclimatise to a grass-only diet.
  • Buy a ram that is compatible with your system – heavy concentrate feeding is not compatible with most commercial sheep systems and is counterproductive for the animal in the long term.


  • Vaccination against foot-rot will help avoid excess labour around foot health issues and keep them on their feet and working.
  • Inspect animals carefully – look at the feet to ensure there are no tell-tale lesions to indicate a history of contagious ovine digital dermatitis (Codd) or previous foot problems.

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  • Carry out a thorough physical check for any abnormalities. This should include making sure the testicles are normal and that there are no brisket sores that could prevent the ram from working.

See also: Ram buying guide: Choose the man, not the ram

New Scops guide

Sustainable Control of Parasites in Sheep (Scops) launched its new quarantine treatments guide in August. The key points are:

  • On arrival, yard or house the rams and treat with either a Group 4 (orange) or Group 5 (purple) wormer to remove resistant worms. Dose to the heaviest weight and check the drench gun accuracy.
  • If a significant risk of sheep scab is suspected, treat with an injectable that requires just one injection.
  • Liver fluke treatment may also be needed if the rams are from a risk area.
  • After 48 hours, turn rams out into a paddock where sheep have grazed earlier this season, where they should remain isolated for three weeks, if possible.
  • If rams are treated for sheep scab on arrival, two weeks after isolation use the Elisa blood test to check they are not still infected.