Chipotle founder said McDonald's chicken farm was the most disgusting thing he's ever seen

Chipotle once had a close relationship with McDonald's.

The Big Mac chain invested in Chipotle's business in 1998 when it had 14 locations. By 2005, McDonald's had a 90% stake - and Chipotle had 460 locations.

During that period, McDonald's executives invited Chipotle founder Steve Ells to one of the company's chicken farms and Ells was apparently shocked by what he saw there, Bloomberg reports.

"They [McDonald's] invited Steve to go to their chicken farm in Arkansas," Ells' father, Bob Ells, told Bloomberg. "He came back and said it was absolutely the most disgusting thing he'd ever seen in his life."

Steve Ells said the cultural differences between McDonald's and Chipotle were stark, even when McDonald's owned the burrito chain.

"What we found at the end of the day was that culturally we're very different," Ells told Bloomberg. "There are two big things that we do differently. One is the way we approach food, and the other is the way we approach our people culture. It's the combination of those things that I think make us successful."

For example, McDonald's wanted Chipotle to add drive-throughs to its restaurants and change its name to Chipotle Fresh Mexican Grill, according to the report.

The company also forced Chipotle to franchise some of its restaurants, which it did reluctantly.

"Bless their hearts, McDonald's had a lot of great suggestions, and we were always polite about it," Chipotle Chief Operations Officer Gretchen Selfridge told Bloomberg. "They really wanted us to do drive-throughs. They really wanted us to do breakfast. But we just really didn't do any of that."

McDonald's divested its stake in Chipotle in 2006.

We've reached out to McDonald's for comment and will update if we hear back.