Genomic Research Unravels Livestock Origins04 May 2012
GLOBAL - Modern cattle are descended from a small herd domesticated in the Middle East about 10,500 years ago, according to recent genetics research.
Researchers extracted DNA from domestic cattle bones found at archaeologically sites. By examining the DNA of ancient and modern cattle, they traced taurine cattle to about 80 female aurochs. Taurine cattle include beef breeds like Herefords and Angus, and dairy breeds like Holsteins, writes Lisa Guenther on Livestock Blog, a companion site to Genome Alberta’s Bovine Genome Sequencing Project.
The study, published in the Journal of Molecular Biology and Evolution, states that the low number of domesticated aurochs indicates “initial domestication took place in a restricted area and suggests the process was constrained by the difficulty of sustained managing and breeding of the wild progenitors of domestic cattle.”
In other words, domesticating wild aurochs took a heavy dose of bravery. Goats, sheep, and pigs were domesticated in the same area, making the region a cradle of livestock development.
Soon people began selecting for specific traits, such as docility and production, shaping the animals into breeds suited to specific human needs. Today, genomic technology is both speeding up and refining trait selection. For example, researchers are working on techniques to select pigs less susceptible to diseases such as PRRS and to choose cattle with traits related to growth performance, grade and yield. Australian scientists are pinning down traits linked to drought tolerance in sheep.
Yet as agriculture becomes more global, some are worried that heritage breed genetics will be lost. The issue is highlighted by the bizarre story of a sheep flock theft in Ontario, according to Livestock Blog. The Canadian Food Inspection Agency had planned to slaughter the Shropshire flock because it was linked to scrapie. The flock’s owner protested on the grounds that the Shropshire is a rare heritage breed. Then a group, calling themselves the Farmers’ Peace Corp, took the sheep “into protective custody,” leaving only a note in the barn.
Sheep-napping aside, governments and other organisations around the world are working to preserve heritage and livestock breeds. In Denmark, researchers and farmers are using frozen semen collected more than 15 years ago to rebuild the Danish ‘Bacon Pig’. The Kenyan government is spending US$3.6 million to establish a gene bank. The gene bank will store semen, ova, embryos, frozen tissue and genes from indigenous livestock, such as Zebu cattle.
While some may wonder why we should preserve rare livestock breeds, there are compelling reasons. Some consumers seek out heritage meat, and livestock producers can profit from meeting consumer demand. Heritage breeds can offer desirable traits such as meat flavour and general hardiness. Local breeds may also be well-adapted to local conditions.
Heritage breeds are also a genetic resource to draw on to improve other breeds. Researchers are crossing Nguni cattle, which are tick-resistant, to tick-susceptible breeds like Angus. By locating genes that confer tick-resistance, the scientists hope to eventually transfer specific genes into other breeds. Researchers are also working on transferring desirable carcass traits into the Nguni cattle, and documenting the unique genomic profile of the Nguni to preserve the breed.
The livestock industry has come a long way since people began domesticating the now-extinct aurochs, concludes Livestock Blog. As researchers and producers improve the breeds, hopefully they continue to preserve the genetic material of rare breeds.
|-||You can view the scientific paper published in Journal of Molecular Biology and Evolution by clicking here.|
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