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Chronic stress causes genetic changes in chickens

TAGS: Poultry
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Methyl groups bind to DNA in red blood cells entirely differently in stressed birds versus control chickens.

Researchers from Uppsala University in Sweden and elsewhere have found epigenetic biomarkers that could be used to detect long-term exposure to stress in commercially raised chickens, which, in time, may lead to improved animal rearing conditions. The study was published in the journal Frontiers in Genetics.

When subjected to chronic stress, animals show deterioration in their general state of health and a weakened immune system, which has an effect on animal protection, Uppsala University said in an announcement.

For commercial animal production, this means that animal products are lower quality, so a larger quantity of meat has to be discarded, adversely affecting farmers’ finances and consumer food quality, the university said. Nonetheless, there are currently no reliable ways of measuring long-term stress in animals.

Researchers from Sweden and Brazil recently conducted chicken studies to look for signs of how chronic stress can affect the genes of red blood cells, causing “epigenetic changes.” In brief, this means that specific molecule types (“methyl groups”) attach themselves to different parts of the DNA strand (“methylation”), depending on how the animal has lived, the researchers explained. This may exert long-term effects on gene expression, as genes can, for example, be turned on or off (activated or deactivated).

For the study, males of the popular White Leghorn breed of laying chickens were divided into two groups. One group was raised in a normal commercial environment, housed with other chickens and with good access to food and water. In the other group, the birds were exposed to factors known to induce stress and were periodically isolated from one another, with limited access to food and water. The same experiment was performed in both Sweden and Brazil.

“We took blood samples from the chickens in both the control group and the stress group after the stress treatment ended. We analyzed the methylation of red blood cells and compared methylation patterns in the two groups,” said Fábio Pértille of the University of São Paulo, the first author of the study.

What the researchers saw was that in the stressed birds, the way the methyl groups had bound to the DNA of the red blood cells was entirely different from how this occurred in the control chickens, the announcement said. Although the scientists were unable to see how long these changes persisted, they were, nonetheless, an indication that the chickens had been exposed to prolonged stress.

Carlos Guerrero-Bosagna, a researcher in environmental toxicology at Uppsala University, said, “It’s early days, but the results from this study are a step towards being able to identify specific epigenetic biomarkers that are evidence of the stress imposed on commercially raised animals in their living environment. It would be highly useful to have a diagnostic tool for tracking recurrent stress in production animals. That could bring about, for example, improved health and protection for farmed animals, meat and dairy products of higher quality and reduced use of antibiotics.”

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