So, what can we learn from analyzing BerkshireHathaway's (NYSE:BRK.A) (NYSE:BRK.B) portfolio? Well, the legendary investors are quietly tweaking their holdings... and perhaps nursing their wounds from Coca-Cola's (NYSE:KO) recent weakness.

In its most recent filing with the Securities and Exchange Commission, Berkshire provided an update of its holdings at the end of the third quarter of 2004. As reported by Bill Mann in August, the only two new holdings in the portfolio are Comcast (NASDAQ:CMCSA) and ServiceMaster (NYSE:SVM).

ServiceMaster -- a lawn care, maid service, and pest control company -- is also a selection of the Motley Fool Income Investor due to its rock-solid business and its 3.4% dividend yield. Since the filing in late August that disclosed holdings of 3.7 million shares of ServiceMaster, Berkshire has continued to add to its position in the stock, bringing its total holdings as of September 30 to 5.6 million shares, worth approximately $72 million.

Berkshire also made a number of small adjustments to some of its existing stocks. It continued selling shares it sold off last quarter, including all of its remaining holdings of Zenith National Insurance (NYSE:ZNT). After cutting 20% of its stake in Mueller Industries (NYSE:MLI) last quarter, it sold off another 567,900 shares in the company, bringing its total to 1.3 million shares or just under $60 million.

Like last quarter, the largest cut in absolute dollar terms was due to the sale of shares of HCA (NYSE:HCA). After selling off 910,000 shares of the health care company last quarter, Berkshire sold off another 1 million shares worth approximately $40 million in the most recent quarter. Finally, Berkshire slightly increased its position in insurance provider Torchmark, bringing its holdings to just over $100 million.

Overall, it was a quiet quarter of trading for Berkshire. It added net shares worth about $150 million -- driven primarily by the addition of $140 million of Comcast shares and ServiceMaster shares worth $72 million. These additions were offset by reductions in its holdings in HCA, Zenith, and Mueller.

Keep in mind that these transactions are merely a drop in the bucket in the company's $33 billion equity portfolio. Over the third quarter, the value of the portfolio dropped 6% or about $2 billion, as prices of some key holdings fell. Most notably, the value of Berkshire's 200 million shares in Coca-Cola fell from just over $10 billion at the end of June to just over $8 billion at the end of September -- a loss of $2 billion in three months. That sort of loss will require something a wee bit stronger than the bubbly brown liquid to lift up spirits in Omaha.

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Fool contributor Salim Haji lives in Denver, Colo. He owns shares in Berkshire Hathaway, but not in any of the other companies mentioned.