A guest shot lasting 42 minutes and 30 seconds on the most popular television talk show in the country changed Howard Lyman's life forever.

Oprah Winfrey will never be the same, either.Lyman, a former Montana cattle rancher and now-vegan activist, told the queen of daytime TV in April 1996 that a common practice of feeding ground-up animal parts to cattle could lead to the spread of the so-called "mad cow" disease to humans in the United States.

When Winfrey, called one of the most influential Americans, responded, "That stops me cold. I'll never eat another burger," ranchers said the bottom dropped out of the meat market.

After the show, Lyman approached Winfrey. "Give me 10 more minutes, and I'll get you off chicken," he said to the former journalist who is as famous for her diets as her film roles.

"Only one animal a day," Winfrey responded.

As a result of the show, Lyman, Winfrey and her company, Harpo Productions Inc., were sued for $11 million by a dozen Texas cattlemen under a 1995 state law that protects agricultural products from slander.

The federal lawsuit, which ended with a not-guilty verdict after six grueling weeks, tested the newly enacted "veggie libel" laws. Thirteen states have passed laws against falsely disparaging perishable products since a 1989 "60 Minutes" report on chemically enhanced apples sent the market into a downward spiral.

"I would not have gone on that show and told people something I didn't think to be true," Lyman said at the Utah Valley Health and Nutrition Conference Saturday at Brigham Young University.

Lyman and Winfrey maintained a right to hold public debate on issues that affect the public. To defense attorneys, it was a public-health and First Amendment fight worth fighting.

"I don't know much about law. But what I do know is this," Lyman said. "Never sue anyone who has nothing. That was me. And never sue anyone who talks to 20 million people a day. That was Oprah."

Mad cow disease, or bovine spongiform encephalopathy, is a brain-destroying disease that has ravaged cattle in Britain since the late 1980s. At least 20 people overseas have been killed by meat tainted with the disease.

Feeding cattle the processed animal parts is now mostly banned in the United States. But Lyman said ranchers and farmers also inject growth hormones and steroids into animals that will eventually have an adverse affect on humans.

He claims some farmers sprinkle arsenic in feed given in chicken coops to stimulate growth. Weak birds, which won't fetch a good price, are killed, ground up and fed back to the other chickens.

"Have you ever really thought about how chickens are raised?" he said. "It gives new meaning to the words `finger licking good.' "

Lyman, who wrote a pro-vegetarian book titled "The Mad Cowboy," said fish also should be suspect. Although studies have shown pollutants dumped into rivers and lakes have contaminated waters with dangerous toxins, people continue to eat fish, he said.

"Let's get serious. We are herbivores. Our digestive system is designed for a herbivore and not a heavy meat eater," he said. "I have learned you can't go out on the street and shake your finger and tell people they need to be vegetarians. . . . If you talk about being a vegan, you can hear their ears slam shut."