Issues around prediction bias, generational interval and the fact that, ultimately, genomics over-predicts EBI was first discussed in a breeding series in the Irish Farmers Journal back in May. Last week, the ICBF hosted a webinar in which it announced that it was going to reduce the amount of genomic data that can be used to calculate traits in a bull’s proof. These changes are designed to help improve the accuracy of the prediction and the ICBF says they are in line with global best practice.
Issues around prediction bias, generational interval and the fact that, ultimately, genomics over-predicts EBI was first discussed in a breeding series in the Irish Farmers Journal back in May.
Last week, the ICBF hosted a webinar in which it announced that it was going to reduce the amount of genomic data that can be used to calculate traits in a bull’s proof. These changes are designed to help improve the accuracy of the prediction and the ICBF says they are in line with global best practice.
The changes will take place in the October evaluation run. The youngest bulls will be affected most – 2020-born bull calves purchased by AI companies will see their EBIs fall by an average of €78 with a range from -€33 to -€125. The average EBI of these bulls will now be €300. For 2018- and 2019-born bulls (the most widely used AI bulls in 2020) the average drop in EBI will be €22 and €37, respectively.
The ICBF is working on details of the change on individual bulls
Certain bulls will drop more than others. The range of adjustment for 2018-born bulls (which dominate the 2020 active bull list) is between -€74 and +€50, meaning some bulls will go up and some bulls will go down. The ICBF is working on details of the change on individual bulls. The highest EBI bull on the current active bull list is Kilfeacle Pivotal, with an EBI of €345 while the highest EBI daughter-proven bull is Possextown Faithful with an EBI of €292, followed by the daughter-proven Jersey bull Superstition at €284.
Background
The reason for the change is due to the increased use of genomic bulls and the increasing number of milking cows with a genomic proof. The generational interval is getting shorter and we now have bulls, where not only is the sire genomic but the grand-sire is also genomic – ie doesn’t yet have a daughter proof.
To put this in context, Ross Evans from the ICBF said that, in 2008, the age difference between a calf and his or her maternal grand sire was 17 years, whereas in 2020 this age difference has reduced to eight years.
Evans said that the ICBF is now going to shrink the amount of genomic data that can be used when determining an animal’s EBI
While this has increased genetic gain, it has also built in a degree of uncertainty because a daughter proof is the ultimate test of a bull’s performance and it takes a number of years for a daughter proof to be realised, particularly for fertility.
Evans said that the ICBF is now going to shrink the amount of genomic data that can be used when determining an animal’s EBI. This will be carried out on a trait-by-trait basis with the fertility sub-index likely to be hardest hit as this is the trait that genomics has been over-predicting the most.
The fact that there has been no genetic gain for fertility in the parental average without genomics of the annual crop of AI bulls since 2011 is open to interpretation
Indeed, many 2020-born bulls have an EBI for fertility in excess of €300, while the Teagasc target for herd fertility is €120. As one farmer quipped to me recently, by right these young bulls should be getting cows in calf, even before they have been inseminated. The new changes to EBI will bring these evaluations back to a more expected level. An interesting slide presented by Evans showed that the traditional way of calculating EBI (without genomics) for the fertility sub-index of all AI sires has been more or less unchanged every year since 2011 at around €70.
The fact that there has been no genetic gain for fertility in the parental average without genomics of the annual crop of AI bulls since 2011 is open to interpretation.
Does this suggest that AI companies have en masse abandoned looking at parental average when picking AI bulls? Or is it the case that increases in the daughter proof for fertility just haven’t seeped down to bull sires and dams yet? Or, worryingly, is it the case that daughter-proven genetic gain for fertility has just flatlined since genomics was introduced? It is worth nothing that the traditional EBI for fertility was on an upwardly trajectory prior to genomics being introduced.
The ICBF is changing the way genomics is blended with parent average in calculating an animal’s EBI.Teagasc geneticist Donagh Berry said that genomic bias has always been present in the evaluations. The new changes will come into effect in the October evaluation run.The parental average EBI without genomics for AI bulls has not increased since 2011. Read more
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