CHICAGO (Dow Jones)--U.S. livestock futures faced a stiff selloff Thursday as a government report surprised investors and brokers, showing larger-than-expected grain supplies and increased corn plantings.

July contracts for lean hogs fell 0.82 cent, or 0.9%, to 94.4 cents a pound in trading at the Chicago Mercantile Exchange. CME August contracts for hogs fell 1.5c, or 1.6%, to 91.67 cents a pound. October contracts, which had recently risen on forecasts for higher feed costs later this year, fell 1.7% to 86.22 cents a pound.

Contracts for corn in July fell 69 cents, or 9.89%, to $6.29 a bushel in trading at the Chicago Board of Trade. September corn contracts fell by their one-day limit of 30 cents and closed down 4.4% to $6.48 a bushel.

The U.S. Department of Agriculture released data Thursday that projected planted acreage of corn at 92.3 million acres, well above expectations. The report also showed stockpiles of grains at higher levels than many analysts expected.

A fall in corn prices often drives down prices in hogs futures since producers have lower feed costs to pass on to packers. Lower feed costs can also encourage herd growth, which can increase supplies.

"The big story coming into [Thursday's] trade is the bearish quarterly grain stocks and acreage report released by the USDA," said Troy Vetterkind, president of Vetterkind Cattle Brokerage, in a note to clients.

Cash hog prices were reported steady to lower on slow buying interest by pork processors ahead of the Independence Day holiday weekend. Few hogs are being offered for sale since producers are current, or up to date, on shipments.

Saturday's slaughter is projected to be only around 2,000 head. All pork-processing plants are scheduled to be closed Monday for the Independence Day holiday.

The latest Dow Jones Newswires pork packer margin index was minus $11.42 per head, compared with minus $8.88 the previous day.

The USDA's pork carcass composite value, a measure of wholesale prices, on Wednesday fell 33 cents a hundred pounds to $97.04 a hundred pounds.

The terminal markets traded mostly steady to up $1 a hundred pounds with top prices from $66 to $70 a hundred pounds on a live basis.