(Reuters) - Chesapeake Energy Corp (>> Chesapeake Energy Corporation) on Wednesday raised its oil and gas production forecast for the year, even as the second largest U.S. producer of natural gas reported a quarterly loss due to lower commodity prices.

Chesapeake now expects oil and gas output of 640,000 to 650,000 barrels oil equivalent per day (boed). Previously, it forecast output of 635,000 to 645,000 boepd. In the first quarter, output rose a better-than-expected 14 percent.

Chesapeake, like other shale producers including Devon Energy Corp (>> Devon Energy Corp), has slashed budgets as crude oil prices collapsed, but a focus on making the drilling process more efficient and lower costs are enabling the companies to pump more oil.

Chesapeake said it is able to squeeze more oil and natural gas from its wells in places like the Eagle Ford in South Texas by drilling longer horizontal well sections and using more sand in hydraulic fracturing.

Chesapeake reported a first-quarter net loss of $3.78 billion, or $5.72 per share, compared with a year-earlier profit of $374 million, or 54 cents per share.

Excluding one-time items that reduced the company's net income by $3.8 billion, profit was 11 cents per share. Analysts, on average, expected a profit of 4 cents per share, according to Thomson Reuters I/B/E/S.

Fadel Gheit, oil company analyst at Oppenheimer & Co, said trading in all shale companies is jittery after influential hedge fund manager David Einhorn said on Monday that crude oil frackers drill "lots and lots of holes" and burn through plenty of cash.

"You have this guy Einhorn saying these stocks are overvalued so you are going to see a knee-jerk reaction to the news."

Chesapeake shares fell 5 percent to $15.05.

Chesapeake was not specifically mentioned in Einhorn's presentation, but Pioneer Natural Resources Co (>> Pioneer Natural Resources) was.

Tim Dove, Pioneer's president, said on an earning call on Wednesday that Pioneer has "identified several areas where our view and Mr. Einhorn's view regarding the assumptions and analysis and conclusions regarding our business differ materially."

Pioneer shares dropped 1.9 percent to $160.

(Reporting by Anna Driver; Editing by Franklin Paul and Jeffrey Benkoe)