Image: Eastern wild turkeys
Maslowski  /  National Wild Turkey Federation
Eastern wild turkeys have that classic gobbler look, but domesticated turkeys are generally bred with breasts so big that they can't mate naturally.
Inside Science News Service
updated 11/23/2011 7:37:52 PM ET 2011-11-24T00:37:52

The great majority of today's domesticated turkeys may not be able to fly, but their ancestors sure got around. The quintessential New World bird, Meleagris gallopavo, was already an Old World favorite by the time colonists in North America first celebrated any Thanksgiving feasts. Today's turkey researchers are investigating the big bird's genetic heritage and biology as part of an effort to improve several aspects of its cultivation.

In 2010, a team of researchers from numerous labs in the United States announced the sequencing of more than 90 percent of the turkey genome. This represented a big step in turkey research, but efforts continue.

"Once you identify genes, the next step is to figure out what they do," said Rami Dalloul, a poultry and immunology researcher at Virginia Polytechnic Institute and State University in Blacksburg.

"What we've been doing for the past almost year is building upon that sequence and trying to figure out, are there traits in the original [wild] bird that might be useful for today's bird?" said Julie Long, a poultry researcher at the research arm of the U.S. Department of Agriculture in Beltsville, Md.

The researchers have been working with the genetic material from the most popular domesticated commercial breed, the broad breasted white turkey. It is descended from turkeys domesticated in modern Mexico by predecessors of the Aztecs. The birds were well-established as a food source by the time the Conquistadors arrived. The Spanish took the birds back to Europe, and they quickly spread across the continent.

"Very quickly the domesticated turkey became, as far as I could tell, the real first New World food to be adopted in Europe," said Andrew F. Smith, a food historian and the author of "The Turkey: An American Story."

"When the Pilgrims and when the Jamestown colonists arrived, they had already eaten turkey," Smith said.

Smith said that by the 1550s, turkeys were already popular at Christmas dinners in England. When colonists came to the New World, they found large populations of wild birds that provided a reliable food source.

Colonists eventually began raising turkeys, but did not domesticate the wild birds.

"The commercial birds that we eat today were actually developed in the United States," said Long. "But they were developed on stocks that came from Europe that originally came from Mexico."

A whole different breed
After hundreds of years of breeding, today's commercial turkeys are far removed genetically from the wild turkeys from Mexico, which were already isolated from any of the five subspecies of wild turkeys found in the United States today.

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The genetic sequence of the domestic turkey differs from its wild turkey relatives, and can be used to illustrate differences between the animals.

"Once you have the baseline, which is the domestic turkey, then you have a good reference genome to come back to and then make a valid comparison," said Dalloul.

Wild turkeys have a gene that makes them resistant to a type of toxic fungus sometimes found in corn and soybeans. This toxin can be deadly on its own or lower a turkey's resistance to other infections and cause death that way.

The domestic breed no longer carries that resistant genetic trait.

"If you can bring back that gene into the domestic population, then you can have these birds again more resistant to [the toxin]," said Dalloul.

No natural mating
Even the intended consequences of commercial turkey breeds have introduced complications. Breeders developed birds with more white meat. The resulting turkeys, such as the broad breasted white, grow muscle quickly, and, as the name suggests, that muscle is concentrated in the breast area.

"[The breast] protrudes quite a bit and physically gets in the way when the birds need to reproduce," said Long. "In the commercial turkey industry there are no birds that naturally mate."

The great majority of turkey farmers must therefore depend upon artificial insemination, said Long. She suggested that there may be rare exceptions among small farms raising older breeds of turkeys, called heritage breeds, which may reproduce naturally. Artificial insemination is a laborious job in turkey facilities, as the sperm from male toms must be collected and female hens inseminated weekly.

"The amazing thing about the turkey hen is she's capable of keeping viable sperm cells for up to ten weeks after a single insemination," said Long. "The best we can do and still maintain high levels of fertility is about six hours."

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If turkey researchers could find a way to increase the amount of time that they can store sperm for later use, it might make the process of artificial insemination easier and less time-consuming. This is a primary area of research for Long, who hopes that further study of molecular DNA may help explain other reproductive issues as well, including why some hens lay more eggs than others.

More Thanksgiving science:

Chris Gorski is a writer and editor for Inside Science News Service. This report was originally published as "The Globe-Trotting Turkey" on the website.

Explainer: Seven courses of science for Thanksgiving

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    A familiar Thanksgiving routine goes something like this: Eat a big meal centered on a deliciously stuffed turkey, retire to the couch, flip on the TV and promptly fall asleep. No doubt the holiday festivities can be exhausting, but scientists say it's a fallacy to blame the post-meal nap on the bird. True, turkey contains tryptophan, an amino acid that produces the brain chemical serotonin, known to induce calm and sleepiness. But the amount of tryptophan in turkey is minuscule, and other amino acids in the Thanksgiving meal actually block tryptophan's entry to the brain. The nap, scientists say, probably has more to do with missing out on sleep, consuming alcohol and working hard to digest the typical carb-loaded Thanksgiving meal, shown here. Click the "Next" arrow above for six more bites of Thanksgiving science to chew on.

  • How science built a 'better' turkey

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    "White meat or dark meat?" the turkey carver asks. Most Americans reply white. To meet the demand for white meat, industry put science to work to create the big-breasted birds at the center of most holiday feasts today. Only big-breasted birds are bred, which passes on the desired genetic trait to offspring. The chicks are then fed a diet engineered to promote breast growth. Today's farmed turkeys have breasts so big that it's hard for the birds to stand up straight, and sex is no longer possible. Instead, females are artificially inseminated. Turned-off consumers are turning to heritage, free-range and organic turkeys, which are gobbling up market share.

  • How science built a better balloon

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    As the turkey cooks in the oven, millions of Americans will tune in to the annual Macy's Thanksgiving Day Parade to see the Energizer Bunny and other larger-than-life characters soar above the streets of New York City. According to John Piper, head parade designer, a scientific process guides the balloons' journey from the initial sketches and models made of steel and clay to the construction and test flights. Each balloon is a series of chambers engineered to hold the desired form. The individual characters contain 10,000 to 16,000 square feet of helium, a gas lighter than air that allows the balloons to float. About 50 people hold on to lines to keep the balloons tethered to the ground along the parade route.

  • Knowing the turkey is done

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    When's the turkey done? Millions of cooks will wait for a little red thermometer to pop up, a triumphant sign the bird is ready to eat. How does this work, and should it be trusted? The science of the pop-up thermometer is fairly straightforward. A drop of solder holds a spring-loaded plunger in the down position. When the turkey heats up to 185 degrees Fahrenheit, the solder melts and the plunger pops up. The apparatus is encased in plastic to keep the metal from contaminating the bird. But to prevent an undercooked bird from contaminating you, the U.S. Department of Agriculture recommends also taking the turkey's temperature with a standard food thermometer in several places, including the innermost part of the thigh. At a minimum, the agency says a turkey should be cooked to 165 degrees F.

  • Return of the wild turkeys

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    National Wild Turkey Federation

    Each year, hunters bag nearly 1 million wild turkeys, according to figures from the National Wild Turkey Federation. In the 1930s, such a harvest would have spelled the wild bird's extinction: They numbered just 30,000 back then, due to decades of habitat destruction and unregulated hunting. A coordinated conservation program, started in 1937, has led to a stunning reversal that continues to this day. For example, wildlife agencies trap wild turkeys where populations are abundant and transfer them to regions with suitable habitat but few birds. The wild turkey population currently stands at about 7 million.

  • Turkeys smarter than they appear

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    Being called a turkey is almost always an insult, even on Thanksgiving. The birds, after all, have a reputation for stupidity. While scientists say flightless farmed turkeys like these lack the survival skills of their wild cousins, they aren't as dumb as they appear. For example, the oft-told story that turkeys will cock their head skyward and stare at falling rain until they drown stems from a misunderstanding, according to Thomas Savage, an animal scientist at Oregon State University. His research shows that some turkeys have a genetically caused nervous disorder that causes them to cock their heads and hold the position for a minute or two. "I've always viewed turkeys as smart animals with personality and character and keen awareness of their surroundings," he said in a media statement. "The dumb tag simply doesn't fit."

  • Saying 'thanks' is good for your health

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    Thanksgiving compels many of us to express gratitude for our family and friends, a place to live, and food to eat. According to Robert Emmons, a psychology professor at the University of California at Davis, saying thanks every day, not just on Thanksgiving, is good for our health. His research shows that grateful people have more energy, sleep better, exercise more, have lower blood pressure and are better-liked by others. A good habit, he says, is to write down five things for which you're grateful before bed each night. In this file image, an appreciated U.S. soldier dressed as a pilgrim enjoys a Thanksgiving meal in Baghdad, Iraq.


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