Research conducted at Purdue on hog growth has found that chronic disease can slow the rate of growth by as much as 40 percent to 60 percent.
Animal scientist Allan Schinckel theorizes that chronic disease causes a genetic shift, which causes the animals to divert resources from growth to fighting disease.
"This genetic shift may be due to changes in gene transcription and gene expression," Schinckel says. "It may be that if the body is chronically fighting disease, that at some point it doesn't make RNA for a certain gene, that it activates a genetic switch, and goes into a survival mode where it puts energy into fighting disease instead of into growth." RNA is the biochemical messenger that tells cells to produce new protein.
Schinckel is in the middle of an experimental trial that will look at the RNA/DNA ratios in hogs. If the RNA levels are reduced in chronically diseased animals, it will lend support to his theory. "Already, we're seeing that differences in potential become smaller as the animal matures. In other words, chronic disease affects the growth of the animal less as it gets older." The study is a multidisciplinary trial that involves animal scientists, veterinarians, immuno-biologists and growth physiologists.
Although hogs are quite different from humans, they do provide a mammalian model for studying growth, according to Schinckel. "This gene switch may be why humans of generations past were shorter and smaller than people are today," he says. "This difference is normally attributed to better nutrition, but the smaller stature may have had as much to do with chronic disease as it did with differences in nutrition.
"We're at the 10 percent understanding point of how this works, so we've got to find the other 90 percent of this iceberg. It may take us three years, or it might take us 30."
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NOTE TO JOURNALISTS: This story could be used as a sidebar to the story "Hog vaccines protect bottom line and herd health, experts say." A black-and-white photo of Schinckel working with hogs is available from Purdue News Service or download here.
Allan Schinckel, professor of animal science at Purdue, is leading a multidisciplinary study on hogs to determine if chronic disease causes a "genetic shift" that slows growth. The findings may apply to other mammals, including humans, and help explain why people today are bigger than people who lived 100 years ago. (Purdue Agricultural Communication photo by Michael Gibson.)
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