UPDATE 1-Thomas & Betts 1st quarter profit up slightly

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NEW YORK, April 30 (Reuters) - Thomas & Betts Corp (TNB.N: Quote, Profile, Research), a maker of electrical components used in industrial and commercial markets, reported a slight rise in quarterly profits on Wednesday, helped by acquisitions.

The results missed the average forecast of analysts and the company's shares sagged 7 percent.

First-quarter net profit was $38.3 million, or 66 cents per share, compared with $37.1 million, or 63 cents per share, in the year-ago quarter.

Analysts surveyed by Reuters Estimates had expected the company to post quarterly profit of 77 cents per share.

Sales rose almost 26 percent to $595.5 million, helped by acquisitions. Still, the company said underlying sales volumes declined year over year as the continued slowdown in U.S. residential construction hurts demand.

Looking ahead, Thomas & Betts expects full-year sales to increase by about 25 percent, with acquisitions contributing about 20 percent.

"Price increases taken recently in response to sharply higher commodity costs will play a more significant role than previously anticipated in sales growth in the second half of the year," Chief Executive Officer Dominic Pileggi, said in a statement.

Thomas & Betts shares were down $3.06, or 7.5 percent, at $37.53 in afternoon trading on the New York Stock Exchange. The stock has slid 23 percent so far this year.

The company is selling for 9.1 times next year's expected earnings, compared with an average 13.7 times for companies in the Dow Jones U.S. industrials index .DJUSIN. (Reporting by Chelsea Emery; Editing by Andre Grenon)