3/16/98

Contacts:
Douglas Cook, Animal Science, 515/294-2286
Susan Thompson, Agriculture Information, 515/294-0705

ISU STUDY FINDS SOYBEAN COMPONENT BUILDS SWINE MUSCLES

DES MOINES, Iowa -- Feeding compounds present in soybeans increased swine carcass muscle percentage in a research project conducted at Iowa State University. Isoflavones are found in several plant foods, with soybeans being a major source. Since soybean meal is a common ingredient in swine feed rations, researchers wanted to determine if isoflavones found in soybeans impact muscle growth.

Douglas Cook, an assistant research scientist in the ISU animal science department, led the project. "Some research on muscle cell cultures in the lab has shown one isoflavone in particular that inhibits muscle growth, so our objective was to determine if this would also occur in swine," he says. "But we were surprised to find an increase in muscle growth."

Cook presented the research results at the Midwest meetings of the American Society of Animal Science and American Dairy Science Association Mar. 16-18 in Des Moines.

Fifteen sets of two littermate gilts were used. Within each litter, pigs were divided into groups that received no supplemental isoflavones or received a soybean extract that contained a mixture of three isoflavones, which is typical of soybean meal. The pigs' weights and feed consumption were recorded every four days.

Cook says pigs fed diets with isoflavones showed increased average daily weight gains (579 vs. 595 g), but no increase in feed intake. These pigs also had increased percentages of carcass muscle (59.1 vs. 60.1) and higher estimated muscle gain per day (234 vs. 245 g).

With such positive results, producers may think they want to start adding isoflavones to their hog feed rations. But Cook says it's too early for that.

"We aren't making a specific recommendation to add isoflavones to swine rations because there isn't a production facility that can provide these compounds to producers on a cost-effective basis yet," he says. "Some plants are being built, but whether their production capacity will be large enough, and their cost low enough, isn't clear."

Cook also says the initial study used a mixture of three soybean isoflavones, so it's now important to determine which isoflavone is having the positive effect before swine ration recommendations can be developed.

Isoflavones have been shown to alleviate some symptoms of menopause and are thought to prevent some forms of cancer, which is fueling the human market for isoflavones. Cook says this may limit the cost-effectiveness of isoflavones as a feed ingredient for pigs.

Cook says several more ISU studies are underway using isoflavones in livestock rations to learn more about how these compounds impact muscle development in animals.

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