Walmart’s decision to add Choice beef to the meat cases in all 3,800 of its U.S. stores is big news for American cattlemen, and it’s likely to make many other retail grocers nervous.

Walmart has traditionally sold only Select grade beef, which fits with the giant retailer’s low-price mantra. But Walmart has been buying Choice beef for the past three months, and that strategic shift has created an impact on the wholesale beef market.

Walmart’s revelation about its buying habits in recent weeks also provides insight into the historically wide Choice-Select spread, which closed Friday at $17.38. In short, Choice beef is more expensive relative to Select beef.