Led by the actively traded February contract, lean hog prices hit a four-and-a-half-week low on pressure from its premium over cash hog prices.

Ample hog and pork supplies weighed on nearby futures contracts, while losses in deferred months were less severe as investors anticipated improved export demand from China, where the domestic hog herd has been hard hit by African swine fever. A new case of the disease was confirmed on Tuesday, bringing the total of affected farms to about 90.

The chief executive of major meat packer JBS SA said the outbreak may benefit exporters in the United States and Brazil. But China has thus far bought only modest amounts of US pork as tariffs enacted by Beijing in response to US duties on Chinese products remain in effect.

"All the African swine fever headlines have been traded. They're still a fantasy. We haven't seen the really big (export) numbers yet, just a few sales," said Craig VanDyke, analyst with Top Third Ag Marketing.

The most active CME February hog futures contract fell 1.175 cents to 62.650 cents per pound, breaking through chart support at its 100- and 200-day moving averages. The cash-settled contract remains at a large premium to the latest CME lean hog index of 55.13 cents.

"The hog market has carried a premium to cash for a while and with the December contract going off the board last week, we're just narrowing that spread," VanDyke said.

Positioning ahead of Thursday's US Department of Agriculture quarterly hogs and pigs report also weighed on futures. Analysts surveyed ahead of the report said, on average, that the US hog herd expanded by 2.7 percent in the September-December quarter.

Reported by Karl Plume