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Cloned Gene May Benefit Cattle Feeders, Plastics Manufacturers

By Ben Hardin
March 28, 1997

More lactic acid is good news for some, bad news for others.

Companies that manufacture lactic acid for food and industrial uses would like to find a way to make greater amounts of the acid while cutting production costs. But cattle feedlot managers would like to find a way to reduce the lactic acid that’s naturally produced in cattle’s stomachs, because it means big headaches for them--and big stomachaches for the cattle.

Scientists with USDA’s Agricultural Research Service may be able to help both groups with a single discovery.

Lactic acid is produced naturally by the bacterium Streptococcus bovis with help from an enzyme called lactate dehydrogenase. The ARS scientists have isolated the gene that’s responsible for production of the crucial enzyme. Armed with that information, the scientists could someday genetically manipulate S. bovis to produce less lactic acid in cattle.

When cattle switch from a high-forage diet to a grain-rich finishing ration, millions of S. bovis in the cattle’s rumen--a stomach compartment--gobble up more glucose from the grain than they need and, in turn, spew out an abundance of lactic acid. The animals can develop lactic acidosis--a giant stomachache.

Sometimes life-threatening, lactic acidosis inhibits animals’ weight gain and can lead to liver abscesses and other abnormalities. The result: Losses of up to $100 million annually for the U.S. cattle feeding industry.

At the other end of the spectrum, commercial manufacturers of lactic acid also could benefit from manipulation of the lactate hydrogenase gene.

To produce more lactic acid where it’s wanted--for the manufacture of industrial products such as biodegradable plastic--the ARS scientists hope to transform microbial species other than S. bovis to make more lactic acid. They’ve already genetically engineered multiple working copies of the lactate dehydrogenase gene into the bacterium Escherichiacoli.

Scientific contact: Michael A. Cotta, USDA-ARS, National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6273, e-mail