This is the VOA Special English AGRICULTURE REPORT.
People often experience stress as a result of events in their lives. Stress is a physical condition that results from real or expected problems. People may experience stress when they lose a job or feel threatened. Common signs include increased heart rate, higher blood pressure and muscle tension.
American agriculture experts say farm animals also may experience stress. Animals may experience stress after giving birth or for other reasons. They say stress may affect meat quality, milk production and the health of farm animals.
Experts say stress in animals is more difficult to identify. Farmers can look for signs such as lower than expected body weight and increased risk of disease.
Ted Elsasser is a scientist at the United States Agricultural Research Service. He is studying a possible sign of stress in animals. He says changed proteins called nitrated proteins may serve as an early warning system for the problem.
Currently, farmers use antibiotics to treat stress in animals. However, repeated use of use antibiotics can lead to bacteria that resist the drugs.
Mister Elsasser is studying another method. He found that Vitamin E may protect farm animals against the harmful effects of stress. In an experiment, he gave Vitamin E to six young cows. Then he injected the animals with a harmful substance taken from the cell walls of bacteria. This toxin causes the defense system of the animals to react as if an infection were present. The scientist injected six other calves with only the toxin. Four other cows did not receive the toxin or the Vitamin E.
Then Mister Elsasser studied the animals. All of the animals that received the toxin had lower levels of a natural growth substance in their liver and blood, compared with the untreated calves. However, the calves that were given Vitamin E and the toxin had higher levels of the growth factor than those that received only the toxin. The calves given vitamin E also recovered more quickly from the effects of the harmful substance.
Mister Elsasser says using Vitamin E helps support growth rates and may prevent some infections. He says being able to prevent infections linked to stress could lead to lower medical costs and healthier farm animals.
This VOA Special English AGRICULTURE REPORT was written by George Grow.