Cats are finicky eaters, and new research shows the reason why this is the case. The animals respond to bitter tastes in a manner that is different from the way humans experience the sensation.
Bitter tastes may have evolved in humans as a means of avoiding toxins in plants. However, cats rarely eat plants, providing little use for that sense of taste.
A bitter taste receptor in humans known as Tas2r38 helps people taste bitter chemicals. However, for some "supertasters," the taste can be overwhelming, leading to strong aversions to certain foods such as Brussels sprouts and cabbage. The new study shows that cats lie on the complete opposite end of the spectrum from such supertasters. Cats showed only 10 percent of the response of typical human tasters to a bitter chemical known as Ptc, and another bitter chemical, Prop, had no effect at all on the cats.
Another receptor, Tas2r43, was found to have differing effects in cats, depending on the substance used in testing. Felines were even more sensitive than humans to denatonium, the world's most bitter substance which is used to sour the taste of antifreeze to prevent poisoning. However, cats were less sensitive than people to the bitterness of aloin, a chemical present in aloe plants. The animals were also not sensitive at all to saccharin, a sweetener which often leaves a bitter aftertaste in the mouths of humans.
"We confront the challenge of 'finicky cats' every day. As such, it is exciting to find an unexpected receptor response to bitter compounds that has never been described in the literature to date for any other species. These insights and future discoveries will be invaluable in formulating appealing food for cats, as well as enhancing the acceptability of their medications," said Nancy Rawson from pet food flavor company AFB International.
This is the first major study to examine how felines respond to bitter tastes on a molecular level.
The team also found that probenecid, a chemical known to reduce bitter tastes in humans, also carries out the same function in cats.
A study published in 2005 found that domestic cats lack a receptor to recognize sweet tastes. This could be another reason why the furry pets are so fussy about what they eat. With no sweetness in foods, and hit-or-miss sensations of bitterness, cats may be left with meats and other proteins as the sole foods which provide the animals with a pleasant taste.
Cat food and medicines could be made more palatable following this research. This also could make it easier for people to provide needed drugs to their pets.
Analysis of how house cats perceive tastes was profiled in the journal BMC Neuroscience.
Photo: D. Coetzee | Flickr
