 Roast beef is not only a food, noted American novelist Edna Ferber once said, it is a philosophy.
“Seated at Life's Dining Table, with the menu of Morals before you, your eye wanders a bit over the entrees, the hors d'oeuvres, and the things a la though you know that Roast Beef, Medium, is safe and sane, and sure,” she wrote.
Today, roast beef is more “sure” than ever, thanks to the development of a cow’s genetic blueprint by a team of international scientists, including Australia’s CSIRO.
A humble Hereford cow living on a research farm in Montana, known to scientists as Dominette 01449, has become the genetic equivalent of a bovine Eve.
The mapping of Dominette’s DNA took six years to complete, and details were published in April 2009, although her genetic information has been in the public domain for the use of scientists since 2006.
It turns out the bovine genome contains some 22,000 genes and 2,870 billion DNA building blocks and is much the same size of the human genome.
Dominette’s genetic blueprint has been mapped a number of times to ensure detailed coverage, and compared to other breeds – Holstein, Angus, Jersey, Limousin, Norwegian Red and Brahman.
This information is stored on public databases and studied by geneticists to identify genes and genetic areas (or markers) associated with important production traits, such as milk production, reproduction, digestion and metabolism.
This will lead to cattle breeding programs where genomic information is used in conjunction with phenotypic information – the physical performance characteristics of the animal, such as its weight and growth rate – to help cattle producers breed better beef.
Beef Cooperative Research Centre (Beef CRC) CEO, Dr Heather Burrow, said the cost of mapping the genomes of animals used to cost in the order of USD $50 million.
“Today you can almost map your own genome for USD $50,000 – in fact, an engineer at Stanford University has invented new technology to do exactly that," she said. "And the cost just keeps coming down.”
Dr Burrow said chips of DNA markers, known as “single nucleotide polymorphisms” (SNP or “snip”) chips, can now be used in conjunction with the ‘phenotypes’ to identify the relationships between thousands, or even hundreds of thousands, of DNA markers and productive or adaptive traits in cattle.
Dr Burrow said the Beef CRC has already developed DNA marker tests for tenderness.
“The tender beef DNA tests have been shown to work consistently across a wide range of cattle breeds and the tenderness test is providing major benefits for the Australian industry,” Dr Burrow said.
Beef CRC has also recently identified a diagnostic test for polled cattle – cattle born without horns.
Identifying the marker for genetically polled animals which don’t pass horns on to the next generation of calves is a major breakthrough in animal welfare, as it will avoid the need to de-horn young cattle.
However discovering and validating DNA markers associated with other important production traits such as feed efficiency and female reproduction is proving far more complex.
“Our research shows there are thousands of genes from all over the genome involved in these important production traits, all of which have a very small effect,” Dr Burrow said.
“That means we have had to change to way we develop and commercialise DNA markers.”
Dr Burrow said the Beef CRC, which has operated in the cattle industry for over 18 years and includes major industry players such as breed societies, Meat & Livestock Australia, CSIRO Livestock Industries and state departments of primary industry, had initially expected to follow on from its early success with the tenderness markers by delivering around 5-10 DNA markers for each economically important trait.
“Before the bovine genome sequence became publicly available in 2006, we expected those markers would collectively account for around 50 percent of genetic variation for each trait,” she said.
“However, genomics technologies have changed vastly since 2006, and the price of the DNA testing is now in freefall,” she said.
“In 2008, a SNP panel that can test 50,000 DNA markers simultaneously became available. It cost us around US$250 per animal to use that panel. We now can access that panel for US$100 and we are expecting it to reduce even further in price as the size of the SNP panels increases to around 500,000 markers or even more.”
Dr Burrow said the Beef CRC would continue testing for carcase and beef quality, feed efficiency and female reproductive attributes using these new, much denser SNP chips as soon as they became available in 2010.
“It is clear we have to revise our research and commercialisation strategy. We also need to ensure all of our tests are independently tested in appropriately-sized cattle populations to understand the amount of genetic variation that the test accounts for, as well as any trade-offs that might need to be made through selection for the markers before those tests are released to industry.”
Based on results already available from use of the 10,000 and 50,000 SNP chips, Dr Burrow said that Beef CRC was confident that by 2012,it would commercialise DNA markers accounting for at least 15 percent of genetic variation for a range of traits such as marbling, tenderness, saleable meat yield, feed efficiency and female reproduction.
However the tests that would be commercialised would be a prediction equation best used through Australia’s beef genetic evaluation scheme, BREEDPLAN, rather than a DNA test for a single gene.
“DNA tests accounting for 15 per cent of genetic variation for any of these very difficult-to-record traits would provide beef producers with cost-effective ways of genetically improving their cattle herds and better meeting beef market specifications,” she said.
Dr Burrow said it was critical beef producers continued to measure the performance of their cattle herds though, to ensure an ongoing source of industry-relevant information by which new DNA markers could be properly evaluated in future.
|
