WASHINGTON — With a little more than a month left in the Obama administration, the Agriculture Department on Wednesday announced new rules aimed at protecting the rights of livestock and poultry producers who do business with larger companies.

A years-long fight over the regulations has pitted small farmers and ranchers against some of the nation’s biggest meat companies. The administration first proposed similar rules in 2010, but Congress blocked funds for them. Congress lifted that ban in a spending bill last year.

USDA announced three rules Wednesday. A rule that is effective immediately would make it easier for farmers to sue the companies they contract with over unfair practices. Two proposed rules would aim to protect the legal rights of growers and help poultry producers who say they are being unfairly targeted.

“All too often, processors and packers wield the power, and farmers carry the risk,” said Agriculture Secretary Tom Vilsack. “Today, USDA is taking a big step toward providing the protections that farmers deserve and need.”

USDA says the four largest poultry processors control more than half of the market, giving chicken or turkey producers limited options for local processors to contract with. The department says that means processors can suppress how much the producers are paid or pit them against each other, among other unfair practices.

The rule that is effective immediately, called an interim final rule, would clarify that a farmer doesn’t have to prove that an unfair practice is damaging to the entire industry to sue. The two proposed rules would lay out certain criteria that USDA views as clear violations of the law.