CHICAGO, Aug 4 (Reuters) - Chicago Mercantile Exchange live cattle futures firmed on Wednesday as cash trade firmed and wholesale beef prices march higher, traders said.

"We have some tighter market-ready cattle supplies right now. The outlook is for supplies to tighten further later in the year and into next year," said Doug Houghton, technical analyst with Brock Capital Management.

In Nebraska, cash cattle traded at $124-$125 per cwt, according to the U.S. Department of Agriculture, while the southern U.S. Plains continued to see $120 trade.

Benchmark CME October live cattle futures added 0.825 cent to 128.975 cents per pound. CME September feeder cattle futures added 0.350 cent to settle at 162.875 cents per pound.

Wholesale beef prices continued to strengthen, with Choice cuts gaining $3.50 to $289.34 per cwt, while select cuts firmed $3.66 to $271.15 per cwt, according to the U.S. Department of Agriculture.

Daily cattle slaughter eased to 122,000 head processed, above rates a week earlier and the same time last year, the USDA said.

Meanwhile, lean hog futures traded mixed, with the nearby contract firming to converge with the higher CME Lean Hog Index, while the more active October contract eased on expectations of increased production.

"We're going to get seasonal weakness in the cash market here at some point," Houghton said. "Overall the cash index has been steady."

The CME's lean hog index, a two-day weighted average of cash prices, dipped to $111.59 per hundredweight (cwt), though it has remained within a range since late June.

CME August lean hog futures added 0.400 cents to 109.475 cents per pound, though benchmark October hogs eased 1.250 cents to 90.125 cents per pound.

Hog slaughter fell on Wednesday to 472,000 head processed. The U.S. Department of Agriculture revised slaughter downward a second day, lowering Tuesday's slaughter by 6,000 head. (Reporting by Christopher Walljasper; Editing by Sandra Maler)