Sheep genetics: Researchers make progress in mapping sheep genomeWritten by Christy Martinez
Such research could prove beneficial in Wyoming’s project to identify a gene or a group of genes responsible for feed efficiency in sheep.
Cockett is the U.S. representative on the international genome sequencing project, which is coordinated by the International Sheep Genomics Consortium (ISGC), a partnership with scientists and funding from Australia, Austria, Brazil, China, Finland, France, Germany, Greece, India, Iran, Israel, Italy, Kenya, New Zealand, Norway, Spain, Switzerland, Turkey, United Kingdom and the U.S. The project formally began in 2002, with a goal to help researchers find genes associated with production, quality and disease traits in sheep.
According to the American Sheep Industry Association (ASI), within a few months of the submission of the USDA grant request, the Beijing Genome Institute (BGI) announced a project to sequence the genomes of 1,000 species, including sheep. The ISGC invited BGI to become a player in the international project to sequence the sheep genome, and the BGI work accelerated the project and resulted in the public release of a draft sequence for the sheep genome in Spring 2011. The draft sequence includes data from a Texel male collected by the ISGC and data from a Texel female, collected by the BGI.
The inclusion of sequence from two animals has allowed the identification of additional genetic markers that can be used in mapping traits in sheep.
“The downside is it made the assembly of the sequence more difficult in complexity, but the upside is it gave us more SNPs,” Cockett told ASI of the recent advance.
SNPs are small genetic differences that can be used to separate a productive or disease resistant animal from the rest of the flock.
“New technology allows us to generate the sequence very quickly. We now have 2,569,509,652 bases of sequence and we’ve identified five million SNPs, which translates to five million differences between the male and female Texel animals,” explained Cockett, adding that the technology currently has a 92 percent accuracy rate.
According to ASI, another step for the project is to continue to generate SNP chips. Cockett estimated that more than 10,000 animals have been tested with the existing SNP chip, and these data are now being analyzed for specific genes within the sheep. To do this, researchers will compare the sheep sequence to the sequence of a genome done to high quality, such as the human or cattle sequence, allowing the detection of well-defined genes, says ASI.
For example, in the case of parasite resistance, researchers can compare results in and use those genes that similarly affect parasite resistance in sheep.
In addition, now that the sequence has been completed it opens up possibilities to sequence specific breeds of sheep.
“They are doing that in cattle and have sequences for about 15 breeds now,” said Cockett.
Although the commercial use of genomics is not yet common in the sheep industry, Wyoming Wool Growers Association Executive Vice President Bryce Reece says that, as researchers improve the techniques, it will have a lot of applications in the sheep industry.
“Wyoming will be well-positioned to take advantage of the technology, because we’re one of the few states left with a sheep program,” he says, mentioning preliminary research in Laramie using the GrowSafe system that is laying the foundation for finding whether or not a gene for feed efficiency exists.
“It appears it’s fairly heritable, but we’re still trying to determine the exact heritability. Because it is heritable, that indicates there’s a genetic control,” says Reece. “The difficulty comes with whether it’s a single gene or multiple. If it’s a single gene, that will make it much simpler to find where that gene is, but some of these traits are controlled by multiple genes.”
Reece says that, based on what’s been seen in terms of how rams on test with the GrowSafe system are turning out with feed efficiency, the inefficient rams cost the industry millions, if not billions, because of the difference between highly efficient and less efficient rams.
“It will have as much application to the sheep industry as it has to the beef industry,” says Reece. “Almost everything is controlled by genetics, from milk production to twinning to wool production.”
Looking beyond those specific traits, Reece also notes that there is controversy with “genetic engineering,” but he comments that sheep and cattle breeders have manipulated genetics for hundred of years.
“To meet the future needs of agriculture and food production, these kinds of tools are the only way we’ll feed the number of people we expect to be on the planet. We can’t make the kind of genetic progress that we need to by using only the tools we have available today,” he says. “Mapping the sheep genome will not only be positive for the industry, but for society.”