Chipotle has made a very big deal out of its commitment to using only "naturally raised beef" from cows that aren't pumped full of antibiotics. The move hasn't hurt business—sales have more than doubled to $2.73 billion in 2012, and the chain is becoming an increasingly ubiquitous fast food presence across the country. There's just one problem; as Chipotle spokesman Chris Arnold put it, "We're growing faster than the supply of natural beef."

Chipotle announced today that it will probably have to supplement its natural beef supply with cows treated with antibiotics. "Every year we need 20 to 25 percent more of everything than we did the year before, and the beef supply isn't keeping up as well," Arnold tells Bloomberg News. Part of the problem is that U.S. beef production is the lowest since 1973, due to record-high grain costs resulting from last year's drought.

Only 80 percent to 85 percent of beef sold at Chipotle's 1,500 stores so far this year was naturally raised, compared with nearly 100 percent in 2012. The company will now use a small percentage of meat from cattle treated with antibiotics because of an illness, but it still won't use beef from animals given antibiotics for other reasons, like promoting weight gain.

"Many experts, including some of our ranchers, believe that animals should be allowed to be treated if they are ill and remain in the herd," said Chipotle founder Steve Ells. "We are certainly willing to consider this change, but we are continuing to evaluate what's best for our customers, our suppliers and the animals." We're probably just crazy or ignorant, but we're thinking the best thing for the animals would be not getting slaughtered.