Transforming the cow

The ability of scientists to improve health and disease management of cattle and enhance the nutritional value of beef and dairy products has received a major boost with the release of the most complete sequence of the cow genome ever assembled.

Developed by an international consortium of research organisations, including CSIRO and AgResearch New Zealand, the bovine sequence contains 2.9 billion DNA base pairs and incorporates one-third more data than earlier versions.

Differences in just one of these base pairs can affect the functioning of a gene and mean the difference between a highly productive and a poorly performing animal. Over two million of these SNPs, which are genetic signposts or markers, were identified as part of the project.

Australia's representative on the US $53 million Bovine Genome Sequencing Project, CSIRO's Dr Ross Tellam, said the new map marks the end of the sequencing phase of the project, with the focus now on analysing the available data.

"This is very valuable information," Tellam said.

"We could potentially achieve as much improvement in cattle breeding and production in 50 years as we have over the last 8000 years of traditional farming."

Cattle geneticists will use the bovine genome as a template to highlight genetic variation within and between cattle breeds, and between cattle and other mammal species.

"We can use this data to identify those genes that are involved in important functions like lactation, reproduction, muscling, growth rate and disease resistance," Dr Brian Dalrymple, head of bioinformatics research at CSIRO Livestock Industries, said.

The Hereford breed was selected for the bulk of the sequencing project, which began in December 2003. Holstein, Angus, Jersey, Limousin, Norwegian Red and Brahman animals were also sequenced to detect specific genetic differences between breeds.

"This is just the beginning of a revolution in the way we produce our animals and food," Dalrymple said.

"Once we have a complete set of genes that influence tenderness, for example, we will be able to predict that animals of a certain type, fed a particular type of pasture or grain, will consistently produce meat of a particular standard of tenderness and marbling."

He also noted that despite the centuries of inbreeding involved in developing different cattle breeds, most maintain a "surprisingly large" degree of genetic diversity.