More people are giving their dogs and cats pet food branded as natural, and while there are plenty of people who support the movement toward healthier fare, there are some who remain skeptical.

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In 2013, pet owners spent about $4.6 billion on natural pet foods, a nearly 12 percent increase from 2012, according to research by GfK, a company that studies pet food trends.

Donna Cheetham is a store manager for Concord Pets, a chain of pet stores with four locations in New Jersey. She said because dogs and cats have a much shorter intestinal tract more natural and protein-dense foods break down quicker in their system.

"There is more available ingredients, more available nutrients for the pet," Cheetham added.

What about the trend toward feeding dogs and cats foods that are grain-free?

According to Cheetham, for a lot of pets, grain-free is better.

For cats, grain-free is almost a must because they are obligate carnivores. "Their digestive tracts are not actually set up to process grains. They are hunters. They need meat in their diet," Cheetham said.

In general, Cheetham advised pet owners to make sure the pet food they purchase is free of artificial flavors, colors and preservatives.

One New Jersey veterinarian, however, isn't completely sold on the trend toward natural pet food.

"There is no nutritional definition for 'natural.' That's a marketing term," said Peter Falk, a veterinarian at the Ocean County Veterinary Hospital.

According to Falk, dogs get their nutrition from proteins and fats mostly, and there are no carbohydrates or grain requirements. But they often do get some.

"Eight percent of the dog's calories and nutrition probably should come from meat or fats, and they don't necessarily have to be grain-free. Dogs can digest that pretty well regardless," Falk said.

He said for the most part, major pet food manufacturers do a good job of producing pet food that is not only good for animals, but enjoyable as well.  "A happy, healthy pet is good business for them."

Regardless as to whether pet owners choose a more natural diet or not, all owners need to make sure their pet is getting what they need, nutritionally.  How can pet owners know if that's happening?  Cheetham recommended watching for certain conditions.

"The condition of the skin, is the skin flaky, are there red areas? Is the pet losing hair anywhere? Is the pet chewing on their feet? Do they get a lot of ear infections? Those are all signs that you may want to first try switching the pet's food," Cheetham said.