NC State University Press Releases
Nov. 11, 1999
FOR IMMEDIATE RELEASE
For millions of Americans, Thanksgiving and Christmas dinner wouldnít 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. Weíve found that it plays a key role in helping organ systems mature faster than they would have normally, so a young poultís state of maturity at hatching is more advanced." Christensenís 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 hensí 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 embryosí other developing organ systems. "When a turkey is genetically selected for increased muscle mass development, thereís 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.
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 doesnít 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.
NOTE TO EDITORS: Christensenís journal abstracts follow. For full texts, contact him at (919) 515- 5534 or firstname.lastname@example.org or Tim Lucas at (919) 515-3470 or email@example.com
"Effects of Genetics and Maternal Dietary Iodide Supplementation on Turkey Embryonic Growth"published in 1999 Poultry Science 78:883-889by V.L. Christensen and W.E. Donaldson of NC State University; K.E. Nestor of Ohio State University; and J.P. McMurtry of USDA, ARS, Livestock and Poultry Science Institute
ABSTRACT: Embryonic growth of a turkey lines selected for 16-wk BW (F) or 180-d egg production (E) was measured and compared to randombred controls (RBC2 or RBC1). Egg weight at setting relative to poult weight at hatching indicated increased growth in F as well as E embryos compared to randombred controls. Eggs from F weighed 10 g more than those of RBC2 (P is less than or equal to 0.0001) but the poults at hatching were only 8 g heavier (P is less than or equal to 0.0001). Water vapor loss during incubation indicated that only 0.9% of the difference could be accounted for by water vapor loss. Selection for increased 16- wk BW resulted in decreased embryo growth rates relative to hatchling mass (P is less than or equal to 0.0001) beginning at Day 16 of incubation compared to that of RBC2. Eggs from E weighed 15 less than RBC1 (P is less than or equal to 0.0001) but produced poults weighing only 7 g less (P is less than or equal to 0.0001). Incubation water vapor loss was depressed in E compared to RBC1 (P is less than or equal to 0.0001) but accounted for only 1.4% of the difference between hatchling weights. Selection for egg production increased embryo growth rates (relative to hatchling mass) measured at 4-d intervals compared to those of the RBC1 line (P is less than or equal to 0.05). Iodide supplementation of the maternal diet depressed (P is less than or equal to 0.05) glycogen in F embryos but interacted with line to generally increase glycogen in E embryos. Increased glycogen was related to increased growth rates in F but not E line embryos. It may be concluded that iodide supplementation of the maternal diet and genetics are determinants of embryonic growth in turkeys.
"Effect of Genetics and Maternal Dietary Iodide Supplementation on Glycogen Content of Organs Within Embryonic Turkeys"published in 1999 Poultry Science 78:890-898 by V.L. Christensen and W.E. Donaldson, NC State University; K.E. Nestor, Ohio State University; and J.P. McMurtry, USDA, ARS, Livestock and Poultry Science Institute.
ABSTRACT: In prior studies it was shown that the growth of turkey embryos was dependent upon maternal dietary iodide as well as genetic selection. The current study posed the question of which organ systems respond to these variables. Embryos from lines selected for 16-wk BW grew at the same rate as unselected embryos from the randombred population serving as the initial source of the selected line until approximately 21 d of incubation (selected = F; randombred control = RBC2). Line differences in growth of F embryos could be accounted for increased liver and heart growth at the expense of muscle growth. Muscle growth increased in the growth-selected line prior to pipping. Muscle growth was affected less when dams were selected for egg production (selected = E; randombred control = RBC1). Muscle growth was slowed in E line embryos compared to that of RBC1, and liver and heart growth were slowed at internal and external pipping stages in E embryos compared to RBC1. Early muscle growth was augmented when F dams were fed supplemental iodide. A similar response was observed in E line embryos but occurred at a later stage of development. Measurements indicated decreased tissue glycogen in liver, heart and muscle of selected lines may be one possible mechanisms by which growth or organ function may come in conflict.