The chicken industry has been remarkably effective in breeding efficient egg-layers and plump-breasted broilers, but a new study says that focus has created a chicken population that lacks genetic diversity, leaving the birds more vulnerable to diseases. The study found that industrial chickens have lost about half of the genetic variations once found in the wild chicken populations, and some have lost 90 percent of those genes.
This means most of the world’s chickens lack characteristics that evolved when they lived in the wild, and may be useful again to help them face stress and disease as livestock. Scientists want to breed DNA for traits such as disease resistance, or “animal well-being”, back into commercial birds without introducing undesirable traits at the same time [New Scientist]. Researchers say the biggest concern is that if commerical chickens are nearly identical genetically they’ll all be susceptible to the same infectious diseases, and an outbreak of of a ailment like avian flu could devastate the entire industry.
All white egg-laying chickens in the U.S. are derived from the white Leghorn breed, whereas all chickens grown for meat, known as broilers, derive from the British Cornish, or Indian, game breed. Winnowing the genetic code has allowed farmers to meet the current global demand of 61 metric tons of meat and more than 55 million metric tons of eggs—an increase in production of 436 percent since 1970 [Scientific American].
In the study, published in the Proceedings of the National Academy of Sciences [subscription required], lead researcher Bill Muir argues that what’s needed is an infusion of genetic material from chickens outside the industry, especially those bred by small farmers in the developing world. The standards of commercial farming won’t be easy to crack, but it’s necessary. “This will take much time and effort,” said Muir, “but it’s an insurance policy on the future” [Wired News]. But it will be a hard sell, as introducing breeds of slower-growing chickens would interfere with the fast profits of commercial farming.
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Image: flickr / Katie@!
May 1st, 2009 at 10:35 am
Not sure its necessary to go outside the US for needed genetics. “Heritage” chickens are currently enjoying a resurgence in the US: as pets, as “Slow Food” sources, and backyard egg producers. Some of these breeds have retained foraging instincts, broodiness, hardiness to climate & disease, etc.— all features missing in the “industrial” chicken.
For more info, see “Mad City Chickens” (a documentary about Madison, Wis. backyard poultry), and the American Livestock Breeds Conservancy (dedicated to preserving genetic diversity in all livestock, including poultry).