Skip to the content

Duncan Nelless

Thistleyhaugh data reveals a £5/lamb benefit from careful ram selection

Reducing days to slaughter and increasing lamb values by £4-£5 can have a major impact on sheep enterprises when you invest the time to understand the breeding values of rams and how they can work in your lamb enterprise. Using Duncan Nelless and his commercial lamb enterprise at Thistleyhaugh Farm we explain how you can get the best out of recorded genetics on a forage based system.


High quality forage, high genetic merit Lleyn ewes and a high flock health status all contribute to the high levels of lamb performance achieved at Thistleyhaugh, with half the lamb crop finished off grass in under 3 months in a typical year. However, even in this high performing flock, ram selection can influence margins by £5/lamb. Testing rams from five different breeds as part of RamCompare, Duncan has seen major differences in the days to slaughter, carcase weight and conformation grade of their progeny, which can be directly attributed to the Estimated Breeding Values (EBVs) of the sires he has used over the last four years.

Read how the genetic merit of his rams has influenced flock performance and how the same principles can be applied in any commercial flock.

The commercial flock located at Thistleyhaugh Farm in Northumberland has been involved in RamCompare from the beginning. Just completing their fifth lambing season.

In the first four years at Thistleyhaugh, 32 rams have been on test producing over 2,500 lambs with data from birth to slaughter. This dataset shows clear relationships between the breeding values produced in ram breeding flocks and the performance of lambs sired by recorded rams when they go to the abattoir.

Sourcing new ram purchases from a performance recorded flock and targeting specific EBVs will provide a guide to a sires genetic potential making significant savings quickly and easily. First you need to identify the goal for your lamb enterprise:

  • Increase speed of finish
  • Improve economic value of carcase
  • Increase carcase weight
  • A combination of them all
Targeting early finishing lambs with high growth rates

At Thistleyhaugh, lambs are born from the end of March/April. Natural service rams are used across 70+ ewes each, often over more than one season. Such large progeny groups provide a rigorous performance test for each sire with 40-100 lambs per sire group slaughtered.

Lambs are managed as one uniform group and daily live-weight gains are recorded fortnightly, achieving growth rates up to weaning of over 0.3kg/day. Thistleyhaugh lambs are finished quickly from clover-rich organic leys.

Lambs are drawn in large batches from just 10-weeks post lambing, as seen in the graph below, 90% of his total lamb crop are sold within an eight week period in a standard year, with an average slaughter age of 140 days. The last lambs are sold by September. Lambs, drawn from 36+kg, are selected in batches of around 100 with 94% achieving grade R2L or better over the four years.

Only rams associated with the RamCompare project have abattoir derived breeding value but all performance recorded rams have a Scan Weight EBV. If you want to reduce days to slaughter, select rams with high Scan Weight EBVs.

Top performing rams at Thistleyhaugh include Suffolk sires, Ortum Supersire ’05 (78X:F49), Bentley Xcellent 239:16:02039 and Bentley 239:N42 and two Hampshire Down rams, Court Contender 73R07739 and Court General 73R12077. These have all performed well with progeny finishing 2 – 4 weeks ahead of those by slower growing sires. 

Using carcase weight to predict improved yield

Lamb carcase weights are strongly influenced by the genetic merit of their sires.

We see in the graph below that the leading rams on tests at Thistleyhaugh include Texel ram Roxburgh Shot Gun Willie EJR1101108 (2016), two Hampshire Downs originating from the Court flock (2017), Texel ram Handbank Super Nova PRH1100114 (2018) and Charollais ram Rainbow Statistician 17XPU02870 (2019). This demonstrates that a ram’s Breeding Value for Carcase Weight is a good indicator of his genetic potential for increasing progeny carcase weights.

Economic value of the lamb carcase

There is a strong correlation between Carcase Merit Index (which combines the attributes of carcase weight, conformation grade and fat class) and the average carcase value for the sire progeny groups.

Sires with a high value for Carcase Merit will produce lambs with a higher carcase value. There are clear benefits shown from rams on test here, with Rainbow Statistician producing progeny carcase values that were on average worth £10 more than the lowest performing sire – and about £5/head more than the flock average. Other rams such as Texel AI sires Roxburgh Shot Gun Willie, Handbank Super Nova, Avon Vale Yale MQZ1602438 and Court Hampshire Down sires are amongst the leading sires used in terms of carcase value.

Remember all the sires were in the top 20% of their breed, so even selecting within top-recorded sires there is a marked difference.  For a flock of 800 commercial ewes this can make a huge difference to the profit from your lamb enterprise.

This shows a robust argument that selecting sires with a high Carcase Merit Index, combining weight and quality attributes, will provide an improved carcase value of over £4-£5/head.

Duncan Nelless, Thistleyhaugh Farm, Partner farmer says, “Through RamCompare, we have seen the benefit of using high index sires. Over four years, our lambs have consistently killed out with heavier carcases, drawn at the same weight and a higher percentage fall into the 2-3L specification. We are convinced of the significance of a rams individual EBVs and would choose future replacements based on this.”

He added, “Throughout the project we have recorded thorough data, part of this has been tracking ewe weight and body condition four times a year. We have found this information has proved invaluable in identifying high performing ewes and has highlighted those who should be culled. This is an unintentional benefit of being involved in the project and has helped us to fine tune the ewe management making our commercial sheep enterprise more economical.”


Key messages:
  • Consider your lamb enterprise objectives to target ram purchasing decisions (including their speed of finishing, carcase weight and conformation for overall carcase value).
  • Use EBVs to select sires with superior genetic merit. Information is readily available at and (for Texels). Remember in many cases the ranking of the ram within the breed will often outweigh any breed differences.
  • Both the speed with which lambs finish and their overall value is important. There is often a trade-off between these two aspects of performance when selecting rams – but through the use of EBVs, rams can be found which do both.
    • To reduce Days-to-Slaughter select rams with High Scan Weight EBVs (from 2-4 weeks)
    • Increase Economic Yield using the sires Carcase Weight EBV (increasing carcase weight by 1-2kg)
    • For higher value carcases select rams with a high Carcase Merit Index (gain £4-£5/average)
  • Ensure rams are structurally sound and healthy, so that this investment in genetic merit is repaid for many years to come.