Scientists Study Early Warning Stress Indicator in Animals

By Sharon Durham
January 15, 2002

Although an animal's life processes--such as giving birth and weaning--are natural, they can be stressful, and that stress can impair the animal’s normal biological functions. But how do you know how stressed an animal is? Agricultural Research Service scientist Ted H. Elsasser is close to answering that question.

Elsasser, based at the ARS Growth Biology Laboratory in Beltsville, Md., is investigating nitrated protein measurement as a biomarker of stress. Nitrated proteins, naturally present in the body, may serve as an early warning system for identifying an animal that may need help recovering from an illness, or that could yield unsafe meat or milk.

In response to high levels of infectious stress or injury, or when immune system hormones are secreted inside the animal, certain protein components, called tyrosines, can alter the function--and the shape--of the proteins. When this happens, the protein is said to be “nitrated.” Proteins are like jigsaw puzzle pieces that are designed to fit together to perform a specific function. When proteins are altered, they no longer fit and become ineffective.

Stress causes several undesirable effects, including slow animal growth and lowered immune response. Currently, farmers often use antibiotics to avert these effects. But sustained doses of antibiotics can accelerate the development of antibiotic-resistant bacteria that may later infect humans.

To slow the formation of nitrated--and thus ineffective--proteins, Elsasser is investigating vitamin E, a standard antioxidant supplement. Using vitamin E as a preconditioner allowed researchers to maintain animal growth rates better under stress and perhaps prevent the occurrence of secondary infections. Being able to prevent infections due to stress could lead to lower disease-management costs, less antibiotic use, and healthier animals.

A more detailed story appears in the January issue of Agricultural Research magazine.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.