CHICAGO, July 20 (Reuters) - Chicago Mercantile Exchange live cattle futures rose to all-time highs on Thursday, with signs of strong export demand and good sales on the cash market supporting prices, traders said.

But cattle prices closed lower on a round of profit-taking as traders took money off the table ahead of key government supply reports on Friday.

"We have rallied basically the whole month," said Austin Schroeder, a commodity analyst with Nebraska-based Brugler Marketing. "We were overbought."

The U.S. Agriculture Department said on Thursday morning that export sales of beef rose to 20,900 metric tons in the week ended July 13, up from 9,900 metric tons the prior week.

Pork export sales fell to 19,200 metric tons from 24,500 metric tons a week earlier.

August live cattle futures dropped 1 cent to settle at 180.325 cents per pound after hitting a fresh contract high of 182.975 cents during the session. On a continuous basis, that was the highest price on record for the front-month live cattle contract.

Technical resistance for August cattle was noted at the high end of the contract's 20-day Bollinger range.

The most-active October live cattle contract fell 0.975 cent to end at 182.75 cents per pound after topping out at 185.75 cents, also a contract high.

August feeder cattle fell 1.7 cents to 245.1 cents per pound.

USDA will provide a supply update on Friday when it issues a bi-annual inventory report and separate monthly data about the number of cattle on feed. Analysts surveyed by Reuters estimated there were 2.3% fewer cattle on feed on July 1 compared to a year earlier.

August lean hogs gained 2.7 cents to 100.625 cents per pound.

In the wholesale market, prices for select cuts of boxed beef fell $1.25 to $274.71 per hundredweight (cwt), while prices for choice cuts were off $1.03 at $302.56 per hundredweight, USDA said. (Reporting by Mark Weinraub; Editing by Shounak Dasgupta)