Why is your cat such a picky eater? Scientists reveal clues.

Cats may experience some bitter compounds differently than humans, new research suggests.

Melanie Stetson Freeman/The Christian Science Monitor
A Maine Coon cat lies in her cage during a cat show, on January 25, 2014 in Dover, New Hampshire.

With names like Fancy Feast and Pedigree, it seems that, when it comes to feeding our feline friends, only the finest foods will do. But even if you open a can of Solid Gold, sometimes your cat will turn up her nose. Feeling defeated, you look around, can of meat-like substance in hand, wondering what went wrong.

Cats are notoriously picky eaters, and veterinarians, nutritionists, and pet food makers are just a few of those interested in unraveling Felix’s fickle taste.

Scientists have conducted extensive research on human responses to different tastes, but less is known about how felines experience flavor.

But this may be changing. Researchers from AFB International and Integral Molecular studied the behavior of cats’ bitter taste receptors, and published their findings this week in the British medical journal BMC Neuroscience.

Instead of directly using cats, who are not known for being cooperative research subjects, the scientists sampled gene sequences from cats, which they used to engineer new taste receptor cells. They then exposed these cells to different chemical compounds, observing each cell's reaction.

If a reaction did occur, calcium levels inside the cell would increase and a fluorescent dye attached to the cell would illuminate in relation to the strength of the reaction, allowing the research team to observe the responses in real time.

The researchers found that cats have a different response than humans to two chemical compounds known for having a bitter taste: PTC and PROP.

“We know that bitter taste from a human perspective is really well studied, and we know a lot about the human response to PTC and PROP and so for humans, the response is that if a human receptor will respond to PTC, you’ll respond to PROP. With cats, this was not the case. The receptor only responded to PTC and not PROP. This was a very different response than was seen before in any other species studied to date.” says Michelle Sandau, lead author of this study and researcher at AFB International, a primary sponsor of the study. 

In fact, cats’ responses to PTC and PROP differ from all other animals studied to date, Dr. Sandau added.

“To us that was a very surprising and unexpected piece of data,” says Sandau.

AFB International and Integral Molecular are the two private enterprises involved in this study. AFB International focuses on “pet food palatability” and is based in St. Charles, Missouri. Integral Molecular is a research and biotechnology company based in Philadelphia.

For all animals, the sense of taste is a product of evolution, and “there’s a pretty good relationship between bitter things and toxins,” says Paul Breslin of Rutgers University Department of Nutritional Sciences and Monell Chemical Senses Center.

The two receptors that the scientists studied were the TAS2R43 and TAS2R38 human receptors and their feline equivalents. The human TAS2R38 receptor was found to be 10 times more sensitive to bitter compounds than the cat’s equivalent receptor, but the human TAS2R43 receptor was less sensitive to denatonium than the cat receptor (Tas2r43).

“We’re finding that some of these genetic sequences have lost their functionality,” says Mike Montague from The Genome Institute, Washington University School of Medicine who recently published his own work analyzing behavioral aspects of the cat genome.

“I think it brings into question that we shouldn’t assume that the basic taste quality should be the same for cats. They are a mammal, but they are a meat-eating carnivore. It’s not safe to assume that the cats’ taste of bitter qualities will be the same as other animals and this is just a demonstration of that.” says Sandau.

“It’s sort of a basic finding, but also very significant in terms of the scientists that are trying to understand how bitter taste evolved among the species,” says Nancy Rawson, another member of the research team involved with the study.

“It does really inform the evolution and comparative aspects of different animals,” says Dr. Montague.

“The greatest story that we want to understand is who we are, why we are, and where we come from and evolution is part of that question,” says Dr. Breslin. “Evolution keeps surprising us with new things that it’s capable of doing.”

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