Resting hogs before slaughter may eliminate serious stresses that reduce pork quality, according to a University of Missouri (MU) researcher.

“High preslaughter stress is the single biggest factor responsible for reductions in pork quality,” says David Newman, a meat science graduate student. “However, it appears that suboptimal transportation and too short of resting periods at the plant can worsen the negative effects of high stress.”

Newman studied stress factors during an internship at the Nutreco Swine Research Center in the Netherlands. About 400 hogs were divided into different treatment groups to measure variations in conditions for transport, preslaughter holding times and preslaughter stress levels. After slaughter, researchers measured lean meat quality attributes including fresh pork color, meat pH, and electrical conductivity. Stress hormones including plasma lactate and cortisol were evaluated from blood samples.

Stressed pigs experienced increases in body temperature, blood pressure and hormone levels, says Eric Berg, MU meat scientist and Newman’s faculty adviser. “When the lights go out, all that heat and energy are trapped in the muscle. The result is PSE (pale, soft, exudative) pork, which tends to be tougher, drier and less appetizing to the consumer,” he says.

PSE pork costs the industry hundreds of millions of dollars in lost quality and sales. “It can’t be sold as whole, boneless cuts; it can’t be sold to export markets,” says Berg. “That’s lost value.”

To retain pork quality, Newman advises producers do everything possible to reduce stress during production, even selecting a truck driver certified in quality assurance.

For their part, packers should give hogs a chance to rest when they come off the truck at the plant. Also, ensure all employees practice proper handling procedures to reduce stress before slaughter.