Maryland is home to about 700 contract poultry farms, according to the U.S. Department of Agriculture. Pictured are chickens at a farm owned by Allen Family Foods in Cordova. (Baltimore Sun photo by Jed Kirschbaum / June 23, 2011)

Democratic Sen. Jon Tester of Montana, who is a farmer, offered amendments to strike both provisions from the funding bill, but Democratic leaders blocked them from receiving a vote.

Advocates acknowledge the language did not originate with Mikulski, but Etka said they have traditionally relied on Democratic leaders in the Senate to stop these types of controversial policy proposals from being slipped into spending bills.

Asked about the provision on genetically modified crops last month, Mikulski told The Baltimore Sun she did not support it but accepted it as part of a larger agreement to avoid a government shutdown.

Her response this past week on the poultry provisions was more muted. In a statement, she called for a "fair and balanced rule" that meets the needs of both the farmers and the companies.

"This is an important issue that should be addressed in the farm bill," she concluded, "not an appropriations bill."

An aide said Republican Rep. Andy Harris, who represents the Eastern Shore, supports maintaining the flexibility chicken companies have to set terms with farmers and intends to introduce language that would make the rollback of the regulations permanent.

The genesis of the regulations was the 2008 farm bill, legislation Congress passes periodically to fund agriculture and food assistance programs. The Agriculture Department drafted regulations based on that law to require the 90-day notice before suspending contracts and to prohibit companies from retaliating against farmers who speak publicly about their long standing concerns with industry practices.

Appropriations legislation generally affects agencies only through the end of a fiscal year. It is not clear what will happen to the poultry provisions when the new fiscal year begins Oct. 1.

The industry believes the regulations will remain rescinded permanently, Super said.