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Irish National Sheep Breeding Indexes

Teagasc & Sheep Ireland Researchers, Nóirín McHugh, Fiona McGovern, Eamon Wall, Kevin McDermott and Aine O’Brien, explain how to use genetic indexes when selecting rams while emphasising the importance of commercial data in strengthening the national breeding indexes

Main Messages

  •  Genetic indexes should be used as a selection tool when selecting rams and pay careful attention to:
  1. Across breed € value for the index of interest
  2. Accuracy of the indexes
  3. Star ratings of important traits for your production system
  • A large proportion of commercial data is now feeding into the genetic indexes to allow for more accurate selection of rams that will perform in a commercial environment


Animal genetics is a powerful tool that allows farmers to identify superior (and inferior) animals to become the parents of the next generation. The national genetic indexes are crucial to enable farmers to make more informed breeding and selection decisions for their flock. Previously a large proportion of the data generating the sheep genetic indexes was originating from pedigree flocks however in recent years there has been a large emphasis placed on the collection of commercial data. This commercial data allows for pedigree rams to be evaluated in a true commercial environment.

€uro-star indexes

The Sheep Ireland €uro-star indexes aim to identify a low cost, easy-care sheep with good maternal characteristics, but that also produces a good quality lamb that reaches slaughter at an early age. Each animal’s index is calculated based on its individual animal performance (such as lambing information and weights) and the animal’s relatives (i.e. sire and dam).

The establishment of a genetic index involves two main steps, firstly a list of traits or animal characteristics that influence the selection of an animal must be identified, thereafter each trait is weighted based on its economic value (€/lambs born) to farm profitability. A star rating is assigned to each trait that allows farmers to visualise the ranking of animals within their breed (1 star = bottom 20%; 5 stars = top 20% of the breed). The Sheep €uro-star indexes provide a measure of the genetic ability of the animal’s progeny to generate profit at farm level for a combination of traits. The Sheep €uro-star breeding indexes are split into two indexes:

  1. Terminal index - ranks animals based on their ability to produce live, fast growing terminal progeny with little lambing difficulty. This takes into account the progeny’s growth rate, carcass characteristics, lambing and health data.
  2. Replacement index - ranks animals on the expected maternal performance such as milk yield, lambing and health data, however it also includes some terminal growth and carcass traits to account for the efficiency at which animal’s progeny are finished.

The current emphasis placed on each of the trait groups within the Terminal and Replacement indexes are highlighted in Figure 1.

Figure 1. Relative emphasis of each trait group in the Terminal and Replacement indexes.

Irrespective of the type of animal that is needed, careful attention should be placed on the €uro-value, star rating and the accuracy associated with the index or trait of interest. The higher the accuracy (Acc) the greater the information that is known about the animal and the greater the confidence we have that their index value which will reflect their true performance potential. The €uro-value is the predicted extra profit that will be generated for the animals progeny compared to an ‘average’ lamb, from 2019 onwards this value is now calculated across all breeds. Therefore this value can be used to compare the index value of a Charollais to a Suffolk ram. The Data Quality Index (DQI) is an index that ranks each flock based on the quality and quantity of the data recorded on the flock over the previous year. This index can be used to help commercial farmers to identify pedigree flocks that are recording a large amount of data as accurately as possible.

Role of Commercial Data

A number of programmes are on-going to ensure that accurate data is recorded on a number of commercial flocks including the CPT (central progeny test flocks), the Teagasc Better farms, Teagasc research flocks and independent commercial flocks.

Currently, 10,000 ewe and 15,000 lamb records are produced annually (Figure 2) from these commerical flocks, including detailed lambing, lamb growth performance, health and ewe fertility data. This data feeds directly into the evaluations of the rams that are evaluated on these commercial flocks but also close relations of these rams. Data from commercial grass-based flocks now makes up 50% of all data entering Sheep Ireland each year. This ensures that pedigree rams are tested in a pure commercial environment.

Figure 2. Number of lambs recorded on both pedigree and commercial flocks annually.


The €uro-star indexes are an essential tool available to sheep farmers to allow them to make a more informed decision prior to buying a ram for use in their flock. The large amounts of commercial data now feeding into the €uro-star indexes ensures that rams are ranked on their potential performance in a commercial environment.