Updated from Wednesday, April 8

Warren Buffett's Berkshire Hathaway ( BRK-A) and several subsidiaries were downgraded late Wednesday by Moody's Investors Service, which cited hits to "key businesses" amid the recession.

Moody's downgraded Omaha, Neb.-based Berkshire's long-term issuer rating to Aa2 from Aaa, as well as the insurance financial strength rating of National Indemnity Co. and other major insurance subsidiaries to Aa1 from Aaa.The rating agency said the outlook for all the entities is stable.

Falling stock prices have hit the companies' investment portfolios and their capital cushions, said Bruce Ballentine, Moody's lead analyst for Berkshire. Berkshire's portfolio includes pressured financial companies like American Express ( AXP), Wells Fargo ( WFC) and US Bancorp ( USB), consumer staples makers like Procter & Gamble ( PG), Coca-Cola ( KO) and Kraft ( KFT), and Moody's Investors Service ( MCO) itself.

"These extraordinary market pressures have reduced the excess cushion available from National Indemnity and the other affected operations to support potential funding needs of the parent company," Ballentine said in a press release.

Moody's action came almost a month after Fitch Ratings cut Berkshire's triple-A issuer default rating, but affirmed its triple-A insurer financial strength ratings on the company's insurance and reinsurance subsidiaries, with a negative outlook. Standard & Poor's two weeks ago revised its rating outlook for Berkshire, to negative from stable.

National Indemnity's regulatory capital fell by 22% during 2008 to $27.6 billion as of year-end and by a significant additional amount through early March, Moody's said. The rating agency said National Indemnity still has a robust capital base, but remained exposed to further stock market downturns.

Berkshire Hathaway Assurance Corp., Columbia Insurance Co., General Reinsurance Corp. and Government Employees Insurance Company (GEICO) were other insurance companies affected by the downgrade.

In his annual letter to investors from late February, Buffett acknowledged Berkshire's $7.5 billion investment and derivative losses, but said the U.S. still had its best days ahead of it.

"Though the path has not been smooth, our economic system has worked extraordinarily well over time," Buffett wrote. "It has unleashed human potential as no other system has, and it will continue to do so.

Moody's said it could further downgrade Berkshire if it took on more risk, experienced continued losses in insurance underwriting, investments or derivatives that cause a 20% in shareholder equity or a "material decline" in operating cash flow.
Gannon joined TheStreet.com in March 2007, after spending more than six years as a reporter and editor for The Journal News in Westchester County, N.Y., most recently as an assistant metro editor. He earlier covered several political and government beats as a reporter, including the city of Yonkers. Earlier in his career, he covered venture capital, private equity and the IPO market for Thomson Financial�s Venture Capital Journal and advertising for Sales-Fax, a small, independent trade weekly. He earned a B.A. in history from the College of the Holy Cross and an M.S. in journalism from Northwestern University�s Medill School.