(AP Photo/Darren Calabrese)

The last time I ate a hamburger, the meat didn't taste as good.

That's because rattling around in my head was a fact that should have been obvious but hadn't dawned on me until recently: that meat patties aren't just made from the muscle tissue of a single animal, but from the fibers of as many as a hundred cows, or even more. We mix different kinds of cow tissue like one combines colors on a palette, potentially putting animals that once grazed next to each other into tightly packed beef discs.

It shouldn't matter how many cows go into a burger, but the number is a vivid and maybe even repulsive reminder that eating meat exposes us to a process where animals are slaughtered and mixed together for our eating pleasure. And while that may not change anyone's opinion about the morality of it all—it hasn't changed mine-—it still exposes us to a lingering pang of doubt about whether any of it is ethical.

"If you have a negative reaction to it, it’s probably because it makes you realize how much of an industrialized process animal production is," said Peter Singer, a professor of bioethics at Princeton University, and acclaimed moral philosopher. "You might still have this ideal that there’s a farmer with cows, and every now and again he has to kill one. If that's the case, you might not have a good grasp of how modern meat production works."

But the thing is that I do. My job is to think about the food industry, which means that I think about meat production ad nauseam. And that makes my reaction all the more telling. 

Hamburgers are the ultimate embodiment of modern day meat production. They are both one of the most ubiquitous forms of processed meat—they're on menus practically everywhere—and one of the least considered. Unlike a cut of steak, which necessarily come from the meat of a single cow, hamburgers are almost always a mishmash of many animals. The ground beef we buy at the supermarket is made of an unknown collection of muscle tissues. 

I tried to figure out how many cows are in a single hamburger. And it was really hard.

It is possible to eat a hamburger made from the meat of a single cow. Restaurants that grind their beef in house, mixing the cuts of only one animal at once, serve them. Those who raise their own cattle, and then slaughter them for food, can have them too. But the single cow burger is a rarity.

Last year, McDonald's confirmed that its beef patties can contain the meat of more than 100 different cows. But it isn't just the world's largest purveyor of hamburgers that has trouble keeping track of the animals in its meat.

I called the fresh meat department at a local Costco, where a butcher who asked not to be named said that there is no way to tell how many cows contribute to a single packet of ground beef. Costco grinds the beef in house, but does it by bulk. "Sorry I cannot tell you how many cows, because I don't know," he said. "But it's more than a few."

I reached out to the butcher department at Giant, and they didn't know the answer. The stores don't grind or pack their own hamburger meat—an outside distributor does. So I called National Beef, one of the country's largest providers of packaged beef, to figure out whether they had a clear understanding of what exactly was in their ground product. They told me Keith Welty, the company's spokesperson, would get back to me shortly. He hasn't. That was last Friday.

I also posed the question to Mark Pastore, the president of Pat LaFrieda Meat Purveyors, a high end distributor used by some of New York City's best regarded chefs. He told me that ideally they would be able pack hamburgers made from the meat of a single cow, but that it would be hard and expensive. Pastore estimates that Pat LaFrieda patties contain the meat of roughly four animals, mainly because they grind about four times as much beef as any one cow can offer at a time, but said that it can be a misleading metric.

"Single sourcing is the best way to do things, it's the handmade way, but it would increase the cost," he said. "More isn't worse. I would probably just worry about the cheaper end bulk grinders, the ones that make the meat for McDonald's and Wendy's and other fast food joints. That's where price plays too big of a role."

But here's the contradiction. It's actually unclear what exactly there is to worry about. Our reactions, however visceral they might be, are also arguably illogical.

From an efficiency standpoint, hamburgers might, in fact, be one of the more ethical uses of meat there is. After all, they make use of disparate scraps, many of which would otherwise be discarded. At the very least, eating a hamburger, which might contain the remnants of more than a hundred animals, should arguably be seen as no less ethical than eating a steak, which, necessarily, involves only one.

"There is something strange about thinking about how there are all these separate animals that get mixed up," said Singer, "But I don't think ethically it ought to make much of a difference. Whether one person eats a substantial part of one animal or a small part of a dozen or even hundred, in the end they're all getting consumed."

There are many reasons to be skeptical of the hamburgers that McDonald's serves, but the number of animals packed into each is among the least of them. In 2002, PBS ran a short documentary called 'Modern Meat,' which explored the contours of the American meat industry through the lens of its favorite child: the commercial hamburger. The confinement of thousands of cows on single farms, the film argued, was compromising the safety of American beef.

As Singer alluded, the reason that people feel so uncomfortable when they think about hamburgers being comprised of hundreds of animals is pretty simple: We are thoroughly detached from the process that allows everyone to eat meat.