DNA blueprint for healthier and more efficient cows

Ground breaking findings by an international consortium of scientists who sequenced and analysed the bovine genome, could result in more sustainable food production. The findings, published in two reports in the journal Science today, will have a profound impact on Australia's livestock industry.

CSIRO scientists were among the 300 researchers from 25 countries involved in the six-year Bovine Genome Sequencing Project designed to sequence, annotate and analyse the genome of a female Hereford cow called L1 Dominette.

The scientists discovered that the bovine genome contains 2,870 billion DNA building blocks, encoding a minimum of 22,000 genes. Of major interest to scientists are the differences in the organisation of the genes involved in lactation, reproduction, digestion and metabolism in cows compared to other mammals.

One of the lead authors of the report on the project's latest findings, CSIRO Livestock Industries researcher Dr Ross Tellam said the bovine genome has about 14,000 genes which are common to all mammals and these constitute the 'engine room' of mammalian biology.

"The team found that cows share about 80 per cent of their genes with humans, also providing us with a better understanding of the human genome," Dr Tellam said.

"One of the surprises in the analysis was that cow and human proteins have more in common than mouse and human proteins, yet it is the mouse that is often used in medical research as a model of human disease conditions."

Dr Tellam said the research provides an insight into the unique biology and evolution of ruminant animals and helps explain why they have been so successful as a species.

One of the major findings was that the cow has significant rearrangements in many of its immune genes and presumably an enhanced natural ability to defend itself from disease.

"This may be an evolutionary response to an increased risk of opportunistic infections at mucosal surfaces caused by the large number of bacteria and fungi carried in the rumen (the largest of the four compartments that make up the bovine stomach)," Dr Tellam said.

"The second possible explanation is that ruminants and cows are typically found in very large herds, and in these herds there is a greater propensity for disease transmission, so you need to be better equipped to withstand diseases."

These new findings will point the way for future research that could result in more sustainable food production.

Dr Tellam said the US$53 million Bovine Genome Sequencing Project – led by the Human Genome Sequencing Centre at Baylor College of Medicine (BCM-HGSC) in Houston, Texas – is an example of major achievements that can only be realised by substantial international scientific cooperation.

Using the complete genome sequence from L1 Dominette, the female Hereford cow, scientists also undertook comparative genome sequencing for six more breeds to look for genetic changes.

The resulting bovine HapMap – a literal map of genetic diversity among different populations – is also published in today's edition of the journal Science.

"Domestication and artificial selection appear to have left detectable signatures of selection within the cattle genome yet the current level of diversity within breeds is at least as great as that found within humans," CSIRO Livestock Industries scientist and one of the project's group leaders, Dr Bill Barendse, said.

The implications of the genome project for the beef and dairy industries are enormous.

"The availability of very large numbers of single nucleotide polymorphisms (DNA changes in the genetic blueprint) has allowed the development of gene chips that measure genetic variation in cattle populations and will allow the rapid selective breeding of animals with higher value commercial traits.

"This technology is quickly transforming the dairy genetics industry and has the potential to dramatically alter beef cattle industries as well," Dr Barendse said.

These new genetic tools may provide a means to select more energy-efficient animals with a smaller environmental footprint, particularly animals that produce less greenhouse gas.

Source: CSIRO Australia