No bull: personal genomics for cattle

Home Technologist Online No bull: personal genomics for cattle

The recent decoding of 234 bull genomes is set to speed up the scientific quest to breed cattle with more efficient milk and beef production and fewer hereditary diseases.

A cow's eye

Since the entire genetic code or genome of a cow – written in 3 billion pairs of DNA ‘letters’ – was first cracked in 2009, researchers of cattle genetics have taken advantage of the ever-cheaper and faster DNA sequencing technologies in a bid to meet cattle breeders’ future needs.

Scientists from Australia, Canada, Denmark, France, Germany, the Netherlands and the United States have joined forces in an international collaboration known as the 1000 bull genomes project.

They recently reported the first 234 genome sequences that will become part of a comprehensive database of genetic variation for all cattle breeds around the world.

Genetics to improve productivity, health and welfare

“Information gathered from this research will allow cattle producers to make better predictions of the breeding merit of young bulls or heifers and the impact that genetics have on milk production, fertility, and other traits that affect farm profitability,” says a key project leader, Ben Hayes, in a press release from the Australian Department of Environment and Primary Industries. Hayes is corresponding author of the landmark study published in Nature Genetics.

According to Hayes, the massive sequencing effort will also help improve the health and welfare of future herds. “The sequenced genomes have already identified genetic defects that are known to reduce fertility and cause severe dwarfism in cattle. This information will now be immediately deployed in breeding programs to reduce or eliminate such disorders…,” he says.

“Unprecedented scale for a livestock species”

The 234 bulls that had their genomes sequenced represent some of the most commercially important cattle breeds – Holstein, Jersey and Fleckvieh. Collectively they have tens of millions direct descendants spread across the globe.

With intense selection of elite bulls and widespread use of artificial insemination in cattle breeding, it’s not unusual for a single bull to sire a hundred thousand offspring. Now equipped with the genetic blueprint of influential ancestors, breeders can deduce the descendants’ DNA sequence by analysing a collection of single DNA sites, without having to sequence the entire genome. That way, they can identify genetic variations and mutations associated with certain traits, for instance high fat content in milk, and choose to pass on those traits – or not – in breeding programs.

In the 10,000 years of cattle breeding, this really is something new, according to researchers from the Technische Universität München (TUM), who contributed to the project with data on 43 Fleckvieh bulls, originating from the Bavarian Alps.

“Whole-genome sequencing of founder animals on this scale is unprecedented for a livestock species,” says Ruedi Fries in a TUM press release. “Our results provide the basis for individualised cattle genetics, one might say ‘personal genomics’ for cows.”

by Lillian Sando

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