By late 2016, many of the nation’s 25,000 chicken farmers said they had grown bitterly frustrated by the administration of President Barack Obama.

Under Obama, top officials had promised to help farmers by tightening regulations on meat processing companies, which for decades had been growing bigger and more powerful. The industry consolidation extended to beef, dairy and pork as well as poultry, but the Obama administration was particularly concerned about the effects on farmers who raise chickens on contract for giants such as Tyson Foods and Pilgrim’s Pride.

Farmers complained that they had been lured into the business with rosy profit projections only to discover that the processing companies — which they depend on for supplies of chicks and feed — could suddenly change their contract terms to impose additional costs or drop them for any reason.

By the time the Obama administration finally pushed through the rules meant to address these problems in December 2016, Donald Trump, a Republican, had won the White House, backed by many farmers who said they had been let down by Obama, a Democrat.