Rising commodities prices led both Smithfield Foods Inc. (NYSE: SFD), the nation's largest pork producer and processor, and poultry producer Sanderson Farms Inc. (NASDAQ: SAFM) to report quarterly losses on Tuesday.

Smithfield Foods said it lost $12.6 million, or 9 cents per share, in its fiscal first quarter due in part to a $20.1 million write-down in the value of commodity contracts. The Smithfield, Va.-based company had reported a profit of $54.6 million, or 41 cents per share, a year ago.

Revenues rose 20% to $3.14 billion in the quarter. Analysts surveyed by Thomson Reuters had forecast a loss of 4 cents per share on $2.87 billion in sales.

In addition to hurting from high costs for such ingredients as grain and fuel, Smithfield also faces an oversupply of meat on the market, which is keeping prices for pork lower. To help push prices up, meat producers such as Smithfield have announced intentions to cut supply.

Shares of Smithfield fell 88 cents, or 3.7%, to $22.71 in morning trading. That's up from a 52-week low of $16.61 in early July, but shares have fallen about 21% since the beginning of the year.