Surprise in Drug Experiment : Pigs That ‘Pig Out’ Turn Leaner

An experimental drug that erodes a pig’s natural defense against “pigging out” may be the key to producing leaner pork, a U.S. Department of Agriculture scientist says.

“Ordinarily, pigs know when they are full and don’t really pig out,” said Jerome C. Pekas, an animal physiologist at the U.S. Meat Animal Research Center in Clay Center.

Pigs’ aversion to stuffing their snouts is due to a naturally produced hormone that tells them when to lay off the feed, he said in a telephone interview from Las Vegas, where he was attending the 72nd annual meeting of the Federation of American Societies for Experimental Biology.

An initial study found pigs ate more but put on leaner tissue when injected with a compound that immunizes them against the hormone cholecystokinin, or CCK.

“The pigs ‘thought’ they were hungry so they ate more,” Pekas said.

A pig’s immune system treats the compound--a harmless decoy--as a foreign invader by developing antibodies to it, he said.

Pekas conducted the study in Nebraska with animal physiologists Bruce D. Schanbacher and William E. Trout. Pekas said he has researched appetite regulation and feeding of swine since 1981. The latest study began in the fall of 1986.

“This is pretty brand-spanking new stuff we are talking about here. This is the first public disclosure,” Pekas said.

The 12 leaner pigs in the test group consumed an average of 22.5 pounds more feed and gained 11 pounds more during the 82-day treatment period compared to the 12 control pigs, he said.

The scientists injected the pigs first at 11 weeks and later gave three booster shots, but Pekas believes only one booster may eventually be used.

“Pigs that got the special injection continue to use feed efficiently, digest extra feed and go to the feed trough more often than pigs in the control group,” he said.

Pekas said researchers were somewhat surprised and don’t really understand why the meat on pigs receiving the compound was leaner. He added that more research was needed to determine if the drug was the cause.

“I was impressed myself that the meat grows leaner. I’d be almost inclined to say that was unexpected. I would have been content to have observed that the animals were eating more feed and gaining more weight,” he said.

Physiologists first recognized CCK as a hormone that causes the gall bladder in humans and animals to contract, Pekas said. Its possible effect on appetite regulation became known within the last 10 years. He said technology for using the new compound could be available within a year, but the USDA would have to clear its use.

Pekas said he envisions the hormone being further studied in human medicine to treat problems caused by low appetite such as anorexia nervosa or insatiable appetite such as obesity.