Farm Ireland
Independent.ie

Tuesday 26 September 2017

Forecasting the future with genomic selection

Huge strides in gene technology give farmers a chance to identify which traits young calves have inherited from their parents -- and provide a clearer view of their performance potential

DNA is the building block of life and differences in DNA control the differences among cattle and humans
DNA is the building block of life and differences in DNA control the differences among cattle and humans

Donagh Berry

Genomic selection is the term used to describe the new method of evaluating the genetic merit of animals. This new approach exploits direct information from the DNA of the animal and the traditionally used information from its relatives.

DNA is the building block of life and differences in DNA control the differences among cattle and humans. DNA is present in all cells and is identical in every one in the same animal. It also does not change over the lifetime of an animal. Because DNA is transmitted from parent to offspring, it can also be used to identify human remains.

The transmittance of DNA from parents to offspring also allows animal breeders to trace what DNA an animal received from each parent and what its effect will be. Knowledge of what pieces of DNA are transmitted is important because the transmitted DNA from each parent is not the same for all offspring.

Example are the bulls Etazon Addison (EZA) and Etazon Slogan (ESZ), both of which are full brothers from Bismay S-E-L Mountain and Tidybrook Elton Steph. Slogan has an EBI of +€69, which includes a milk sub-index of +€28 and a fertility sub-index of +€43. His full brother, Addison, on the other hand, has a negative EBI of -€16, which includes a milk sub-index of +€60 and an extremely poor fertility index of -€94. Despite having exactly the same pedigree these bulls are very contrasting in genetic merit because they received different pieces of DNA from their parents.

Past breeding programmes, based primarily on progeny testing, required several years to identify such differences among bulls based on daughter performance. Imagine if by sampling the DNA of Slogan and Addison at birth, through a few hair follicles, we could determine, more accurately, the expected performance of each bull. This is the basis behind genomic selection which tries to identify, using the DNA of young calves, which animals, male and female, are most suited to individual farming systems.

Genomic selection in Holsteins was launched in Ireland last year and now constitutes the official genetic evaluation in most other countries, including Ireland. Although it is only early days in the implementation, the improvements in accuracy of evaluating animals are obvious, although further research is needed to address some issues. Such issues include the implementation of genomic selection in pure Friesians (and other dairy breeds). Because genomic selection relies on the estimation of the effect of different DNA profiles from proven bulls, the lack of pure Friesians in the Irish reference population to estimate these effects currently hinders its applicability in pure Friesians.

In recent months a campaign to increase the number of Friesian bulls in the training population to estimate the effect of different DNA profiles has taken place. The impact of this campaign on the ability to undertake genomic selection in Friesians is under investigation.

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