Carl Icahn is expanding his animal-welfare campaign to Kroger, after first targeting McDonald's
Kroger said it first heard from Icahn on Friday. The grocer said that during the discussion, the billionaire investor "voiced his concerns regarding animal welfare and the use of gestation crates in pork production."

Icahn has submitted a plan to nominate two candidates to Kroger's board, the Cincinnati-based company said in a release Tuesday .

Carl Icahn is expanding his animal-welfare campaign to the nation's largest supermarket chain, Kroger , after the famed activist investor initially targeted McDonald's .

In a letter to Kroger CEO Rodney McMullen, Icahn also took aim at what he called the "egregious wage gaps" between McMullen and other employees at the company.

"The wage gap between the CEO and median worker at Kroger is unconscionable," Icahn wrote in the letter, which was obtained by CNBC. "Our candidates will take our concerns about deplorable animal suffering and these wage gaps (and other governance problems) at Kroger seriously and add proper oversight."

Kroger's announcement Tuesday comes a little more than a month after Icahn launched a proxy fight with McDonald's focused on the treatment of pigs. In an interview last Tuesday, Icahn addressed his involvement with the fast-food giant.

"I'm not doing that to make money," Icahn told CNBC's Scott Wapner on "Closing Bell: Overtime."

Instead, Icahn described his efforts as a response to his feelings on animal rights. "Emotionally, when you read about what they do to these animals, the unnecessary torture and cruelty, it really bothers me. Whenever I can do something about it, I try," Icahn said.

Kroger said it will review Icahn's proposed board nominees, Alexis C. Fox and Margarita Palau-Hernandez, as part of its standard governance policies. The company also addressed Icahn's issues with animal treatment.

"While Kroger is not directly involved in raising or the processing of any animals, we are committed to helping protect the welfare of animals in our supply chain," the press release said. "Kroger has an established Responsible Sourcing Framework to clearly define our policies, requirements and practices, including our Animal Welfare Policy, which articulates our expectation that all suppliers will have transitioned away from gestation crates by 2025."

McDonald's also has defended its animal rights policies in the face of Icahn's campaign. The company said last month that by year-end, it expects between 85% and 90% of its U.S. pork volumes will be sourced from sows who do not live in gestation crates during their pregnancy. McDonald's said it expects that percentage to increase to 100% by the end of 2024.

Icahn's stake in Kroger is small, as is his position in McDonald's. Icahn told Kroger he owns 100 shares of the company, according to a person familiar with the matter. The grocer has about 746.8 million fully diluted shares outstanding, according to FactSet.

Kroger shares closed down 1% Tuesday at $56.39. The stock has gained about 25% year to date, bringing its market value to $41.46 billion.

In his letter to McMullen, Icahn said his goal was not to profit from this proxy campaign, but to make a difference in the "glaring injustices" at Kroger. Icahn criticized the company's board for what he called a lack of oversight on supply chain policies and compensation. McMullen is chair of the board, in addition to serving as CEO since 2014.

Icahn, specifically blasted McMullen's compensation increase in 2020, while noting the company removed a $2 per-hour raise for store and warehouse workers it offered for a few months during the early days of the Covid pandemic.

"What has happened at Kroger with the issues of animal welfare and employee wages is an affront to the basic fibers of our society — that of decency and dignity," Icahn wrote. "Your Board of Directors has created an unnecessary situation, placing your company at risk, by rubber stamping unethical policies as well as breaking promises they made to frontline workers during the pandemic."

Kroger defended its employee compensation record. A spokesperson told CNBC the grocer has "been investing more than ever before in wages," both prior to the Covid pandemic and during it.

"Kroger invested an incremental $1.2 billion in associate wages and training over the last four years," the spokesperson said. "This has increased our national average hourly rate of pay from $13.66 to nearly $17, reflecting an increase of more than $3 per hour, or a 25% increase. When benefits like health care and pensions are factored in, our average hourly rate is now over $22."

— CNBC's Scott Wapner contributed to this report.