Farm Ireland

Tuesday 24 January 2017

Profits are in the genes

Dairy farmers have never had such strong breeding options but making the right choice is vital, says Teagasc's Donagh Berry

Donagh Berry

Published 09/03/2010 | 05:00

Genomic selection is being heralded as the most promising application of science in animal breeding since AI was introduced.

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The basis of the technology is similar to that used by the police and forensic scientists to solve crime or identify bodies. Both are based on the knowledge that everyone, with the exception of identical twins, has a unique signature of genes or DNA.

DNA is also passed on from parents to offspring. Therefore, the DNA of an unknown sample (eg a body) can be compared to the DNA of reference samples (eg relatives) and the identity of the individual can be determined. Furthermore, DNA can be measured in an individual from birth and does not change over their lifetime.

It is the DNA, interacting with the management on the farm, that determines whether an animal will yield more milk solids and will go back in-calf easily. Therefore, if we can determine which DNA is associated with the different performance traits, and we can measure the DNA of an animal at birth, then we can predict -- based on the DNA -- the genetic merit of the animal. This is the basis behind genomic selection.

A large number of proven animals are used to estimate the best signature of DNA for milk production, fertility, health, type, etc, for Irish production conditions. Once this is known, the DNA of a young animal can be compared to the optimal DNA and the performance of the animal is predicted. Genomic selection is currently only available in Ireland for Holstein Friesians.

The implication of genomic selection is an increase in EBI reliability for younger animals, especially young bulls and cows. It has no impact on the reliability or EBI of proven bulls. It can be done equally on males and females and is available to all Irish farmers; the cost is around €250 per animal.

Since last year, genomically selected bulls have been included on the Active Bull List. These bulls must have progeny calves to prove that they do not carry genetic defects and that their estimate of calving difficulty is of moderate to high reliability. Although the reliability of these genomically selected bulls is higher than before, it is not as high as some proven bulls. Also, the EBI reliability is not the same for all genomically selected bulls but is a function of the amount of DNA information available on the bull. The range in which the EBI of the bull can change as it becomes proven is also given on the Active Bull List.

Although the reliability of these bulls is lower than some others, the genomically selected bulls should, on average, be of greater EBI and should therefore consistently populate the top of the Active Bull List.

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The degree of uncertainty associated with low reliability can be overcome by using a team of bulls. The use of single genomically selected bulls is not recommended and a minimum of four bulls should be used in a bull team.

Although genomic selection is a relatively young technology, and has not been thoroughly proven, 35 layoff bulls that were genomically selected last year now have milking daughters. Comparing the daughters' milk production proofs -- these bulls have no daughters with fertility information yet -- with predicted milk proofs using genomic selection and the old traditional system of genetic evaluation, it is clear that genomic selection was the better predictor.

Some bulls did change relative to their predictions, but this is expected and is reflected in the range of EBIs on the Active Bull List.

Irish Independent