Sen. Bernie Sanders, known for railing against giant corporations and the nation's richest billionaires, took aim at the U.S. agricultural industry during a three-day campaign swing through Iowa over the weekend.

The independent senator from Vermont stuck to his 2016 presidential campaign themes of increasing the federal minimum wage to $15, creating a free college tuition program and making the Medicare program available to all. But his 2020 campaign stump speech sought to highlight the plight of Iowa's rural communities, which have suffered decades of population loss.

Now, Sanders connected his longstanding disdain of corporate America with the state of Iowa's agricultural industry, a major force in rural communities from the Missouri River to the Mississippi River.

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At rallies in Council Bluffs, Iowa City and Des Moines, he chided the CEO of Smithfield Food's parent company for reportedly earning $291 million in 2017. While executives get rich, he said, the livestock farmers who lease animals and equipment from giant agribusiness firms earn "an inadequate wage for doing extraordinarily hard work."

Sanders said federal regulators haven't been tough enough with anti-trust enforcement; specifically criticizing the $66 billion Monsanto-Bayer merger for concentrating the seed corn market.

The senator said Iowa's independent pork producers have been put out of business, and slaughterhouse employees have suffered through three decades of stagnant wages.

"Meanwhile, instead of protecting family-owned farms, federal support of agriculture is skewed toward large factory farming," he said. "The top 10 percent of farms currently get 77 percent of all subsidies."

Sanders criticized Congress for not doing enough to help rural America. He lamented waves of school and church closures that have hurt small communities across the country.

"I pledge to you to do everything I can to restore the well being of rural communities all across this country," he told a crowd of more than 1,500 in Iowa City on Friday evening.