Actors wearing chicken suits were on the streets of the capital a few weeks ago, arguing that Tyson Foods Inc. and Pilgrim's Pride Corp., the two biggest processors in the $58 billion-a-year U.S. chicken market, shouldn't be able to call their birds 100 percent natural. That's because up to 15 percent of their weight is an injected solution of ingredients such as salt, broth and seaweed extract.

The publicity stunt, by a coalition of smaller processors, is another example of recent pressures on government to pay more attention to truth-in-labeling, additives and food-safety issues.

"This is about the USDA not managing the use of the natural label properly," said Lampkin Butts, president of Sanderson Farms Inc. in Laurel, Mississippi, one of the challengers. "Seaweed extract is in the ocean, not in chickens." His company is the nation's third-biggest publicly traded U.S. poultry processor.