Courtesy of Michael D. MacNeil, USDA ARS
DNA from a Hereford cow named "L1 Dominette 01449," pictured here with her calf, was used by scientists to sequence the entire bovine genetic code.
DNA from a Hereford cow named "L1 Dominette 01449," pictured here with her calf, was used by scientists to sequence the entire bovine genetic code. Courtesy of Michael D. MacNeil, USDA ARS
After six years of close observation, a cow is finally getting her 15 minutes of fame. Her name is L1 Dominette 01449, and she is a 1,300-pound brown and white Hereford who grazes on a ranch in eastern Montana.
Scientists have been closely studying L1 Dominette 01449, combing through her DNA to try to find out what makes a cow a cow. And her DNA has been used to produce the first full sequence of the bovine genome.
The results reveal a lot about "the essence of bovinity," says Harris Lewin, director of the Institute for Genomic Biology at the University of Illinois at Urbana-Champaign.
DNA Of Cows And Humans Similar
Only a handful of species — including humans, dogs and rodents — have had their genomes fully decoded. A comparison of the bovine genome with those known sequences found lots of similarities, says Lewin, the author of one of several papers on the project that appear in the journal Science. And it turns out cows are genetically closer to humans, than humans are to mice.
But Lewin ways there were some important differences between cows and other species.
"For cattle we have found some extraordinary duplications and expansions of specific genes that are related to milk production, disease resistance and reproduction," he says. These regions, he says, "differentiate the genomes of cattle from all other genomes studied to date."
The genetic additions probably explain how cattle can produce so much milk and resist diseases that attack herd animals, Lewin says.
But sometimes less is more when it comes to genes, says Kim Worley of the Human Genome Sequencing Center at Baylor College of Medicine in Houston, which coordinated the bovine genome project.
For example, Worley says, cattle can digest things humans can't, even though they lack some of the digestive genes found in people. This may be possible because cattle have outsourced a lot of their digestive work over the past 100 million years, she says.
Instead, the work is done by a huge number of bacteria that live in the rumen, one of the four chambers of the bovine stomach. Cattle may have eliminated some digestive genes because "bacteria have taken up that function," Worley says.
Cows aren't the only creatures that need to convert stuff like prairie grass into fuel. It's something people have been trying to master in the search for new ways to power cars and produce electricity.
The bovine genome project should make that easier, Lewin says. "Knowing how the bugs in the cow's stomach do it is going to help us to learn how to release that energy from those plants for creating renewable energy," he says.
But Lewin says in the short term the bovine genome will be most useful to the beef and dairy industries.
Improving Genetic Traits
So far, these industries have relied primarily on old-fashioned breeding techniques to do things like choose a bull that will produce female offspring that make a lot of milk, he says.
"Now you can select that individual directly based on his genotype," Lewin says, rather than waiting years to see how his female offspring perform.
People have been selectively breeding cattle for thousands of years, which has raised concerns among scientists. Too much inbreeding can reduce genetic diversity and leave animals vulnerable to diseases.
But research from the bovine genome project, which sampled DNA from a number of breeds, suggests that's not a problem for cattle — at least not yet.
"Domestication has not driven down the diversity to such an alarming level that we should worry that the diversity is not present to allow us to do yet more selective breeding," says Richard Gibbs, who supervised the bovine genome project and directs the Human Genome Sequencing Center at Baylor.
As for L1 Dominette 01449, she continues to be the star bovine of Montana. She turned 8 a couple of weeks ago and is expecting her fifth calf this fall.