Linkage – What does it mean?


Flock linkage or flock connection refers to the genetic connectivity (similar bloodlines) between Sheep Ireland performance recording flocks.

Genetic linkage is crucial for accurate genetic evaluation as it allows fair and accurate comparisons between flocks. Flocks become linked by sharing rams with other LambPlus flocks within the same  season (see below for 3 different options). The subsequent lambs should also have weights recorded on them at the recommended times for the best results. All performance recording flocks should also use more than one sire each year in order to keep their linkage levels high. If only one ram is used in the flock then it is very difficult for the evaluation to determine if the subsequent lamb performance is due to the sires genetics or due to the environment the lambs have been raised in.

Flocks that are unlinked essentially only have within flock evaluations and once these flocks/animals become linked they are likely to see fluctuations in their evaluations which is not desirable by anyone and the best way to avoid this is to remain linked at all times.

In the example below Link Ram 1 is the most connected ram as he has been used in the most flocks including the CPT, this ram is likely to have the highest accuracy, meaning his evaluation will be more dependable. Home Ram A, B, C & D have all only been used in one flocks but are still linked because a second ram has also been used in the flock and that second ram has also been used in another linked flock. Home Ram F is not linked, therefor the lambs in this flock will not be linked and the data collected in this flock will be of limited use in the evaluation.


When it comes to flock linkage, there are three possible categories;

  • Linked – The ideal situation for performance recording flocks. Your flock is being compared to all other performance recording flocks within your respective breed
  • Weak Linkage – Your flock linkage status is weakening. You may have been linked last year. You should act during the next mating season to prevent your flock becoming unlinked.
  • Unlinked – Your €uroStar evaluations are within flock evaluations and are not comparable to other breeders within your respective sheep breed, this will be reflected in how your €uroStars will be displayed in 2020.

Some key Q & A on linkage: 

If my flock is ‘linked’, what does that mean?

This means that your flock is genetically linked to all other performance recording flocks within your breed. Sheep Ireland refers to this as ‘The Central Hub’. The €uroStars being provided to you are calculated based on all performance records available to the Sheep Ireland database from all breeders within your respective breed. This is the best possible situation for you and more importantly for your customers.


If my flock is ‘unlinked’, what does this mean?

This means that Sheep Ireland cannot accurately compare the data being recorded by your flock with other breeders within your breed. Your flock is not linked to ‘The Central Hub’. The €uroStar evaluations being provided to you are within flock genetic evaluations. This is not a good situation for you as a breeder or for those purchasing rams from you as these within flock €uroStar evaluations are not a true reflection of your animal’s genetic merit within your respective breed.


How do I become linked to another flock?

To link with another flock, the same sire (genetics) must be shared by two breeders. This sharing must take place in the same year and weights must subsequently be recorded from the shared sire’s progeny in both flocks.

Warning – Linking to another flock does not guarantee linkage to ‘The Central Hub’.  If two ‘unlinked’ flocks share a ram and become linked to each other, they are still both unlinked to ‘The Central Hub’.


How do I become linked to ‘The Central Hub’?

To link your flock to ‘The Central Hub’, you must share a sire (genetics) with another flock that is already linked to ‘The Central Hub’.


How do I know if I am linked or unlinked currently?

Sheep Ireland will notify all LambPlus breeders about the linkage status of their flocks in the coming weeks.


If my flock is unlinked, what are my options to become linked?

There are a number of options available to you;

  • Share a sire with another linked breeder in the same year, and ensure progeny are weighed in both flocks
  • Use AI on a number of your ewes, ensure that you are using semen that is also being used by at least one other linked LambPlus breeder. Again ensure progeny are subsequently weighed in both flocks.
  • Purchase inlamb females from a linked flock. Ensure the source flock will also have progeny from the sire used across the inlamb ewes. Again ensure progeny are subsequently weighed in both flocks.


What will happen if my flock remains unlinked?

Unfortunately, for unlinked flocks, the genetic evaluation information available to ram purchasers is severely compromised, thus is it is incumbent on Sheep Ireland to address this issue. It is critical that unlinked flocks take action during the 2018 mating season to establish linkage with ‘The Central Hub’.

For the 2018 season the Sheep Ireland board has taken a decision to clearly highlight where €uroStar evaluations originate from an unlinked flock. This will be highlighted in sales catalogues and all other locations where €uroStar evaluations appear. This decision has been made for the benefit of all Irish sheep farmers, to ensure that the best possible information is being provided to users of the €uroStar evaluations.

Figure 1. Stars for linked and weak linked flocks will be displayed as normal as seen above.

Figure 2. How stars will be displayed for unlinked flocks.