USDA pig researchers have more insight into porcine stress syndrome after mapping the stress disorder to a genetic mutation located in the dystrophin gene—the largest known gene in the mammalian genome. Porcine stress syndrome is associated with poor response to stressors like transport and with poor-quality pork. 

It has been eliminated from commercial herds in the United States, but stress-related issues, most often associated with transportation, continue to cause substantial losses—an estimated $50 million per year—to the U.S. swine industry.

Scientists at the Agricultural Research Service’s Roman L. Hruska U.S. Meat Animal Research Center (USMARC) in Clay Center, Neb., have identified a previously undetected genetic stress syndrome that is most likely affecting the pig industry. They are mapping the defect in pigs to get to the root of the problem.

Research into this rare, life-threatening condition, which causes a fast rise in body temperature, severe muscle contractions, and sometimes death, was limited until the discovery of a similar disorder in pigs, referred to as porcine stress syndrome.

Piglets underwent general anesthesia, and their heart rates and electrocardiographs (ECG) were monitored. Pigs identified as having the stress syndrome had abnormal ECG readings and sometimes died, whereas the heart rate of unaffected pigs remained steady. In some cases, piglets that did not undergo the anesthesia challenge were identified as having the stress syndrome when they had a stress response or died during typical procedures, such as weighing.

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Researchers found that creatine phosphokinase was about three times higher in pigs suspected of having the disorder.

The discovery of the defect may provide a unique biomedical model for cardiomyopathy—a heart muscle condition—associated with muscular dystrophy in humans. Scientists at USMARC and Iowa State University are investigating the possibilities.

In the meantime, scientists are using next-generation sequencing technology, which produces millions of DNA sequences simultaneously, to completely sequence the chromosomal region in affected and normal animals and to identify all the DNA variation in dystrophin. 

The main goals are to identify the mutation, test as many commercial pigs as possible, find out how prevalent the new stress syndrome is, and develop strategies in cooperation with the pork industry to eliminate it from the U.S. pig population.