(Reuters) - Pilgrim's Pride Corp (>> Pilgrim's Pride Corporation) on Tuesday offered to buy Hillshire Brands Co (>> Hillshire Brands Co) in an all-cash deal valued at $6.4 billion, as the world's second-largest chicken processor seeks to expand its protein footprint with Hillshire's sausages and lunch meats.

Shares in Hillshire soared almost 23 percent on word of the bid, which landed two weeks after the maker of Hillshire lunch meats and Jimmy Dean Sausages offered to buy Pinnacle Foods Inc (>> Pinnacle Foods Inc), known for its Birds Eye frozen vegetables, in a $4.3 billion deal.

Pilgrim's competing overture, which requires Hillshire to drop its Pinnacle bid, also signaled an aggressive return to deal making by Brazilian meatpacking giant JBS SA (>> JBS SA), which owns about 75 percent of Pilgrim's and recently cut its debt.

A buying spree launched in 2005 transformed JBS into the world's biggest beef producer with more than 14 major acquisitions in six years, including U.S. rivals Swift, Smithfield Beef and Pilgrim's Pride.

Growing global appetite for meat also has fueled other big protein deals, including last year's roughly $5 billion acquisition of pork giant Smithfield Foods by China's WH Group Ltd, previously known as Shuanghui International Holdings.

Investors were cool on a Hillshire-Pinnacle marriage and sent shares down roughly 6 percent in intraday trading when the proposal came on May 12.

Under that deal, Hillshire would suspend share buybacks, take on debt of $2.3 billion and expand into areas that are out of synch with U.S. consumers' appetite for fresher food.

J.P. Morgan analyst Ken Goldman in a client note called Pilgrim's offer both strategically and financially superior to the Pinnacle deal.

"That's more like it," Goldman said. "Joining two protein companies makes a lot more sense than marrying a meat company with one that has a focus on frozen vegetables."

Pilgrim's Chief Executive William Lovette said in a letter to Hillshire that "our proposal will no longer exist if the proposed acquisition of Pinnacle is consummated."

Hillshire said in a statement that it continued to "strongly believe in the strategic merits and value creation potential" of the Pinnacle merger, but that it would thoroughly review the Pilgrim's Pride proposal.

Pilgrim's offer of $45 per share represents a premium of about 22 percent to Hillshire's closing share price on Friday.

Pilgrim's also would pay a termination fee of $163 million to Pinnacle and assume Hillshire's long-term debt of about $840 million.

Pilgrim's, which sells fresh chicken under brands such as Pilgrim's and Country Pride, said it expects the Hillshire deal to close in the third quarter and to be immediately accretive to earnings per share. It expects to fund for the deal with existing cash and third party financing.

U.S. antitrust regulators would determine if the Pilgrim's-Hillshire deal means that American lunches and dinners could become more expensive because there are too few competitors to prevent large firms from unfairly raising prices. Sometimes firms sell assets to win deal approval.    One antitrust expert urged regulators to take a hard line.

"The evidence is quite clear that these deals lead to less for the farmer and higher food prices," said David Balto, a veteran of the Federal Trade Commission now in private practice.

(Additional reporting by Brad Haynes in Sao Paulo and Diane Bartz in Washington; Editing by Saumyadeb Chakrabarty and Andrew Hay)

By Lisa Baertlein and Devika Krishna Kumar