* October cattle fall through key chart support
* Cattle report keeps traders on edge
* Hogs slide with cattle, cash prices
By Theopolis Waters
CHICAGO, Aug 17 U.S. cattle futures fell more than 2 percent on Wednesday on fund selling and expectations a government on Friday will show a large increase in the number of cattle placed in feedlots in July.
Moving of October positions into the December, called rolling, also weighed on the nearby contract, traders said. That action pushed October through technical support levels, including its 117.55 cents 100-day moving average.
Analysts and traders polled by Reuters, on average, expect the U.S. Department of Agriculture report to peg the number of cattle at feedlots on August 1 at 107.3 percent of a year ago.
They expect placements in July at 117.3 percent and marketings in July at 96.5 percent.
Chicago Mercantile Exchange hog futures fell as traders took their cue from live cattle's losses. In addition, talk that cash hog and pork prices may be waning as the U.S. September 5th Labor Day holiday nears added pressure.
CME cattle contracts retreated from the outset as August traders bailed out of some positions before the contract's Aug. 31 expiration.
Most-actively traded October lost ground after funds sold it and bought December on spreads. The move caused October to fall through several technical support floors including its 117.55 cents 100-day moving average.
"August is pretty much done as the spot month which makes October look high compared to cash last week. The board's plunge today doesn't bode well for this week's cash," a CME cattle trader said.
Cash cattle in the Plains so far were offered at $118 to $120 per cwt, bolstered by still rising wholesale beef prices. Futures traders have now built in a $116 cash trade, which would be about steady with last week.
USDA Wednesday morning reported average choice wholesale beef price was up $1.73 at $186.05 per cwt. That gains was likely, spurred by the recent break from extreme heat, which had consumers firing up outdoor grills.
Some contend beef sales could subside as grocers curtail buying fresh product once Labor Day holiday needs are filled.
August cattle 2LCQ1 closed 2.050 cents per lb lower, 1.74 percent, at 115.850 cents. Actively traded October 2LCV1 fell 2.775 cents, or 2.31 percent, to 117.400. It was October's biggest one-day percentage drop since May 23.
Feeder cattle ended lower on live cattle's retreat, fund selling and sell stops.
August feeder cattle 2FCQ1 closed down 1.075 cents, 0.79 percent, at 134.500 and September 2FCU1 down 1.950 cents, or 1.42 percent, at 135.425 cents.
CATTLE, PORK WEIGH ON HOGS
CME hogs succumbed to live cattle pressure along with ideas retailers may be close to wrapping up significant pork purchases for the fast-approaching September three-day holiday weekend.
Also, the recent cooler temperatures are expected to help hogs gain weight and lead to increased marketings which should weaken cash values.
USDA showed average hog weights in Iowa/southern Minnesota for last week at 261.0 pounds, compared with 260.8 the previous week and 265.6 a year ago.
Cash hog prices in Midwest on Wednesday traded steady to $1 per cwt lower, according to hog dealers.
Wednesday's average wholesale pork price was unchanged at $107.45 per cwt, after dropping $2 on Tuesday, according to USDA.
October hogs 2LHV1 closed down 2.000 cents per lb., or 2.24 percent, at 87.400 cents. December ended 1.450 cents lower, or 1.69 percent, at 84.225 cents.
(Reporting by Theopolis Waters)