It ultimately offered a total $550 million guarantee in order to speed the return of billions in cash and collateral.
"The exchange has a broken wing now because it has not yet healed from the MF Global thing. So, it's a bad time to be throwing another curve at its members," said Joseph Ocrant, president of Oak Investment Group, who has traded cattle for 42 years.
The exchange said it would release details of the new rules and timelines for the roll-out early in 2012. The transition to the new rules will occur in March and April, subject to review by the U.S. Commodity Futures Trading Commission.
"Nobody's happy about this," said Maurie Schneider, an independent livestock trader whose career spans more than 60 years dating back to the old egg and butter futures contracts. "It would soon kill the floor because there would be no reason for it (the pit) to be there."
Some traders said they had been amazed that the floor-based settlement mechanism had persisted so long. With more and more volume being transacted on the "screen" rather than the "floor", the roar from the pits in the final minute of the trading day appeared increasingly anachronistic.
Most of the rest of CME's contracts are already settled using electronic prices.
"I'm really surprised it's taken this long to include data from electronic trade," said Sterling Smith, market analyst for Country Hedging, St. Paul, Minnesota. "I do think this is for the best and I do support this. Pit traders are understandably upset and like any wounded animal it fights back."
The shift toward electronic trading in agricultural contracts has gathered pace this year. In the first 11 months, total open outcry trading in commodity and alternative investment products -- including New York oil and metals contracts -- fell 18 percent, while electronic trading rose nearly 38 percent, CME data shows.
In all, "pit" trade was just over a quarter of the total volume, down from almost half in 2010. But it accounts for the vast majority of trading in the last minute of the day.
"The basic approach of the new methodologies will be to include additional information in the settlement calculation by incorporating both floor and Globex activity in the determination of settlement prices," CME Group said in a statement. (Additional reporting by Sam Nelson and Theopolis Waters; Editing by David Gregorio and Dale Hudson)