Farm Ireland

Monday 11 December 2017

New developments in breeding strategies

Genomic selection is currently implemented in Ireland by measuring the DNA profile of animals at more than 50,000 locations or markers along the animal's DNA.

This number of markers is not sufficient to undertake genomic selection across breeds, but a new technology measuring the DNA profile of an animal at 777,000 locations along an animal's DNA is now available.

This will be crucial for the successful implementation of genomic selection in beef as well as across the different dairy breeds. Simultaneous with the development of DNA panels with a larger number of markers, was the development of lower cost panels with less that 3,000 DNA markers.

The objective of the research was to evaluate whether the entire 50,000 DNA markers could be predicted from the 3,000 markers on the small panel.

This prediction is called 'imputation' and is based on the knowledge that chunks of DNA are inherited from parents to offspring and knowledge of some of the markers inherited can help fill in the gaps of the inherited markers not known.

Results clearly show that the entire 50,000 markers can be predicted with 97pc accuracy using just the 3,000 markers.

Equally, this means that the genomic predictions of an animal based on the 3,000 markers is 97pc as accurate as those based on the entire 50,000 markers.

However, of utmost importance is that the computer programmes developed must have previously seen a similar DNA profile to that of the animal being tested with the 3,000 markers. Since individuals inherit DNA from their sire and dam, having information of the 50,000 markers on both the sire and dam is key to successful predictions.

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When the sire and dam both have information on the 50,000 markers then the accuracy of prediction is 99.5pc.

However, what is more likely in reality is that knowledge of the 50,000 markers is available on the sire and maternal grandsire (ie, sire of the dam) of the individual; the accuracy of prediction in this scenario is 97.6pc.

Therefore, the 3,000 marker panel should not be used unless both the sire and maternal grandsire (or dam) have information in the Irish Cattle Breeding Federation database on the 50,000 markers.

Accurate genomic selection using this approach is then feasible.

Irish Independent