Short Takes: November 2015

Why They’re ‘Picky’ Eaters: It May Be in Their Genes

Cats have long endured the reputation for being fussy eaters. We’ve known for a decade that, with some exceptions, most cats lack the taste receptor gene for sweets. Now a study suggests that they may have a legitimate reason for avoiding another flavor.

Researchers at AFB International, a pet food palatability company, and Integral Molecular, a biotechnology company, used cell-based experiments to compare two different bitter taste receptors in cats with human versions of the receptors. Their findings, reported in the journal BMC Neuroscience: Cats’ taste receptors respond differently, sometimes less sensitively, to bitterness. They simply don’t like it.

For instance, humans have the taste receptor TAS2R38 that causes a strong sensitivity to bitter compounds such as broccoli and Brussels sprouts. Compared with the human TAS2R38 receptor, the cat receptor was 10 times less sensitive to a key bitter compound called phenylthiocarbamide (PTC). A study reported in Clinical Genetics explains that the ability to taste PTC is “a classic inherited trait in humans,” the subject of genetic and anthropological studies, which has been shown to correlate with dietary preferences.

The recent study of taste receptors is the first glimpse into how domestic cats perceive bitterness in food at a molecular level, says Joseph Rucker, Ph.D., at Integral Molecular.

Although cats are carnivores, one theory about the perception of bitter chemicals holds that it’s evolutionary — it developed to avoid toxic compounds in plants. Today, pet cats may encounter bitter flavors in food and medicines.

Researchers hope their study will have an impact in both areas and other studies will follow. “We confront the challenge of ‘finicky cats’ every day,” says study co-author Nancy Rawson at the pet food flavor company. “It is exciting to find an unexpected receptor response to bitter compounds that has never been described in the literature 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.”

Their Scratching Preference

If you’ve ever wondered why cats like to scratch certain objects — not the scratching tree but your custom-made silk curtains — John McGlone, Ph.D., has the answer. He’s a professor of animal welfare and behavior in the Department of Animal and Food Sciences at Texas Tech University College of Agricultural Sciences & Natural Resources.

Dr. McGlone and a team of researchers studied kittens’ scratching various objects and theorized that cats may favor an object more because of pheromones — chemical scent signals — that were left from another cat. They presented their findings at a joint meeting of the American Dairy Science Association and American Society of Animal Science in Orlando.

The researchers used several types of scratchers — flat, rope and hemp — and made their own of cardboard, carpet and bubble wrap. Dried catnip applied to the scratchers didn’t change the rate of scratching. We know when a cat grooms himself, he licks the hair all over the body, paws included, Dr. McGlone says. “We know a cat is continually applying scent, and cat hair is a much more potent stimulator of scratching than is catnip. That cat hair contains pheromones.”