NEW YORK (CNNMoney.com) -- Warren Buffett continued to pare his investments in energy companies during the fourth quarter, while boosting his stake in a waste management provider, a regulatory filing showed Tuesday.
Buffett's Omaha, Neb.-based holding company, Berkshire Hathaway, sold 19.6 million shares of ConocoPhillips (COP, Fortune 500) and cut its already diminished holdings of Exxon Mobil (XOM, Fortune 500) by about half, according to documents filed with the Securities and Exchange Commission.
Meanwhile, the widely respected investor bought 4.6 million shares of Republic Services, Inc., (RSG) a Phoenix-based waste management company, bringing his stake to nearly 8.3 million shares.
Buffett, the world's second richest man, also bought 300,000 shares of medical device maker Becton Dickinson. In the third quarter, he bought 1.2 million shares of BD (BDX, Fortune 500) stock.
However, he trimmed his holdings of Johnson & Johnson (JNJ, Fortune 500) and Procter & Gamble (PNG).
Buffett increased his stake in Wal-Mart (WMT, Fortune 500) by 1.2 million shares to about 39 million, and bought nearly 700,000 shares of Wells Fargo (WFC, Fortune 500).
As part of the company's $26 billion takeover of Burlington Northern Santa Fe, Berkshire sold its holdings in rival railroad companies Norfolk Southern Corp. (NSC, Fortune 500) and Union Pacific Corp. (UNP, Fortune 500)
All told, Buffett's portfolio increased in value during the fourth quarter to more than $57.9 billion from $56.5 billion in the previous quarter.
Berkshire Hathaway joined the S&P 500 index last week after shareholders approved a 50-for-1 split of Class B common stock last month. The newly issued Class B shares (BRK.B) rose more than 1% to close at $76.05 on Tuesday. 
| Index | Last | Change | % Change |
|---|---|---|---|
| Dow | 32,627.97 | -234.33 | -0.71% |
| Nasdaq | 13,215.24 | 99.07 | 0.76% |
| S&P 500 | 3,913.10 | -2.36 | -0.06% |
| Treasuries | 1.73 | 0.00 | 0.12% |
| Company | Price | Change | % Change |
|---|---|---|---|
| Ford Motor Co | 8.29 | 0.05 | 0.61% |
| Advanced Micro Devic... | 54.59 | 0.70 | 1.30% |
| Cisco Systems Inc | 47.49 | -2.44 | -4.89% |
| General Electric Co | 13.00 | -0.16 | -1.22% |
| Kraft Heinz Co | 27.84 | -2.20 | -7.32% |
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