PESCADERO, Calif. — When Tom Steyer first learned that his wife, Kat Taylor, wanted to sell beef from the cattle herd on their ranch here, he rolled his eyes.

Mr. Steyer is the founder of Farallon Capital, one of the largest hedge funds in the world with some $20 billion under management for universities, foundations and some of the country’s wealthiest people — and he was sure beef was a lousy business investment, particularly on a small scale.

“Practically every year since 1865 has been a bad year for beef,” he said, only somewhat in jest. “And Kathryn” — virtually everyone else calls her Kat — “knew nothing about selling beef.”

Mr. Steyer may have made billions of dollars for his investors before retiring this year, but he would have lost money betting against Ms. Taylor and Leftcoast Grassfed, the brand name of the Steyer-Taylor beef.