New York (CNN Business) America's biggest retailers are pushing back against this country's largest meat processors. The future of the nation's food chain is on the line.

Walmart last week opened a meatpacking plant in south Georgia that will cut, package and label its own brand of steaks and roasts to deliver to meat cases at 500 stores in the region. It is Walmart's first meatpacking plant. Costco has also developed its own farm-to-store poultry production operation in Nebraska to control some of its chicken production

Although Walmart's plant is a step toward a farm-to-shelf meat production, Walmart doesn't actually operate the facility, nor does it own any cows or butcher the meat. An outside processor will operate the plant in Thomasville , Georgia, 20 miles from the Florida border and a little bigger than the size of a Walmart supercenter.

The plant's opening is the latest move in top US retailers' attempts to muscle into the food supply chain, an area traditionally dominated by food processors. Four companies control around 85% of the US cattle market , according to the Department of Agriculture.buys its beef fromand Cargill, and it's Tyson's largest customer.

"I think the broader implications are more big retailers exploring expanding into processing themselves versus buying the product from a current packer or processor," said David Anderson, agricultural economist at Texas A&M University.

Pushing into beef and milk

Walmart is trying to break big processors' stranglehold over the beef industry, drive down costs and sell a higher-end line of beef at some stores.

Bob McClaren , a Texas rancher who is helping lead Walmart's effort to source its cattle, said in an interview that the new supply chain will be able to "pull some of those costs out of all these other middlemen along the way," allowing the more than 600 ranchers Walmart has partnered with so far to receive a premium on their cattle.

"One of the things that has always hindered the cattle industry is the multiple, multiple hands that are involved in the supply chain," McClaren said. "We're reducing some of that work."

Walmart's new meatpacking plant in Thomasville, Georgia, 20 miles from the Florida border and a little bigger than the size of a supercenter.

Walmart is also trying to gain an upper hand on its current suppliers. Working directly with ranchers to produce some of its beef supply may put Walmart in a stronger position when it negotiates contracts with processors in this consolidated market.

"There are two key players out there that we do business with," former Walmart US CEO Greg Foran said in June. "I think we all know the market dynamics of what happens when you generally operate in a duopoly. It's not all that good for the customer."

Additionally, Walmart leaders say moving into the beef chain will help it attract customers with its own brand of premium steaks.

"Meat is center of the plate" and "drives the customer to the store," Scott Neal, Walmart's senior vice president of meat, said in a CNN Business interview last year. Walmart has not announced a name for the brand yet.

Walmart also entered the milk supply chain recently. The company built a milk processing plant in Indiana to supply milk to 500 stores.

"What drives a decision like that is if we start to see a consolidation in supply," former Walmart leader Foran said in June of Walmart's move into diary.

Walmart's milk suppliers' prices had gone up, leading the company to explore other options. Walmart does not want to supply all of its more than 4,700 US stores with its own milk brand. But "it gives us some leverage" when negotiating contracts with its distributors, he added.

Bob McClaren, CEO of 44 Farms in Texas, is helping lead Walmart's effort to source its cattle for its new beef supply chain.

Costco's rotisserie chickens

Other retailers are seizing control of segments of their food supply chains to drive down costs and produce their own food as well.

Costco in October opened a $450 million chicken plant in Nebraska that will soon produce roughly 100 million rotisserie chickens a year— 40% of its annual chicken needs-— to sell at the retailer's food courts and poultry aisles.

Costco was having trouble finding the size of birds it needs for its rotisserie chickens. So the retailer decided to integrate the production process from farm to store, making key decisions down to the grain the chickens eat and the type of eggs hatched. Costco hopes that bringing poultry production in house will reduce its costs by 10 to 35 cents per bird.

Will Sawyer, animal protein economist at agricultural lender CoBank, said that the Walmart plant will only represent a small fraction of the company's overall beef business. He views Walmart's entrance into the beef industry as a small-scale test to asses whether it can grow profit by pushing deeper into the supply chain.

"Their ownership level is very different than Costco's," Sawyer said. "It's not like Costco where Costco is owning these chickens from egg to grocery stores."

But despite key differences between Walmart's beef and Costco's chicken operations, agricultural experts predict the trend of retailers playing a larger role in supplying food for their own stores to expand.

Farmers under pressure

Local and state officials are pleased about the Walmart plant because it will deliver hundreds of jobs and investment in the area. Georgia Governor Brian Kemp was on hand for a ribbon-cutting ceremony last week.

"The Thomasville community is very excited," Mayor Greg Hobbs said in an interview.

However, Walmart and other retailers gaining more power in the food industry troubles some farmers and ranchers' advocates.

Dean Foods DFODQ Walmart's decision to enter the dairy market pressuredand was one of a range of factors that led the company into bankruptcy . Dean missed out on the sale of 55 million gallons of milk in the latter half of 2018 because of the lost Walmart business, it said.

A spokesperson for Walmart said its new cattle program is a "win-win situation" for farmers and will create steady demand for its supply chain partners.

But opponents believe Walmart's new chain denies most ranchers the opportunity to participate and "does nothing to relieve the pressure on America's family farmer," said Joe Maxwell, the former Missouri lieutenant governor and policy director for the Organization for Competitive Markets, an advocacy group for farmers and ranchers that opposes corporate consolidation and is critical of Walmart.

"It only keeps them locked in to a supply chain run by the world's largest company," he said. "The farmer is still just trapped."

Jess Peterson, senior policy adviser at the US Cattleman's Association, a lobbying group for ranchers, said his group is in a "wait-and-see process" with the Walmart supply chain.

He fears a "singular, vertically-integrated system" that limits access for independent ranchers and reduces competition.

"It does give us pause for concern that we might be moving toward vertical integration," he said. "Walmart is assuring us that it's not."