Nov. 25, 1999 For millions of Americans, Thanksgiving and Christmas dinner wouldn't seem right without turkey on the menu. Research by North Carolina State University scientists is helping make sure we always have a plentiful supply. A team of NC State researchers led by Dr. Vern Christensen, professor of poultry science, has found that adding a tiny amount of iodine to a female turkey's feed can boost the number of eggs that hatch successfully, and also promote healthier, faster growing young birds.
"This is natural growth, not synthetically induced or genetically engineered," Christensen says. "Iodine is a naturally occurring component of thyroid hormones. We've found that it plays a key role in helping organ systems mature faster than they would have normally, so a young poult's state of maturity at hatching is more advanced."
Christensen's team produced a 4.2 percent increase in hatching rates -- a tenfold improvement over old standards -- by adding just four parts per million of iodine to breeder hens' feed. The iodine-enriched diet also resulted in a 50 percent improvement in post-hatching survival rates and significantly faster growth after that, especially from the sixth day on.
In recent years, geneticists working to speed the growth of turkeys have focused their attention on devising ways to boost the growth of muscle mass, often to the detriment of the embryos' other developing organ systems. "When a turkey is genetically selected for increased muscle mass development, there's often a trade-off, because it gives up growth in other vital organ systems, like the heart or lungs," Christensen says. This means that although the embryo has the muscles to break through the shell, its life-sustaining organs are less mature than they should be, making it more likely to die or grow more slowly.
Feeding the breeder hen an iodine-enriched feed can help balance this inequity, he says.
The cost to producers of feeding breeder hens an iodine-enriched diet is negligible, just a few cents per ton of feed. Yet the financial payoff can be substantial, Christensen says. Based on USDA national production figures of between 300 million and 360 million young poults a year, growers could save $17 million a year in reduced mortalities. And that doesn't account for any increased profits they would see from reducing turnaround time -- the number of days it takes to raise turkeys to market size.
Christensen and his colleagues have published their findings in two peer-reviewed papers this year in the journal Poultry Science. He has been studying the role of thyroid hormones such as iodine in turkey health for more than 20 years.
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