As a veterinarian who carries pet food in his Northern California clinic, Dr. Paul Palmatier doesn’t need to make runs to the market to keep his dog in kibble. So when he visited a local feed store recently, he was stunned.

“I was overwhelmed both by the number of food choices and also their cost,” Palmatier said.

The visit gave the 26-year practitioner a sharp appreciation for the choices his clients face. Palmatier said he thinks “constantly” about pet food these days, in part because clients come to him with questions or admit to alternative diets for their pets — raw or homemade food, for example — that the mainstream veterinary community typically doesn’t advise.

Just as consumers are thinking more critically about where their food comes from and what’s in it, many are applying the same scrutiny to what they feed their animal companions. Palmatier believes the movement gained momentum from the melamine scandal of 2007, in which unscrupulous suppliers added an industrial chemical to pet food, killing and sickening thousands of animals and spurring a giant product recall involving leading manufacturers.

Speaking to consumers’ growing concern about safety and health, some pet-food makers are using a variety of labels that they hope will convey superiority — “all-natural,” for example, “holistic” and even “human grade.”

That last one prompted Palmatier last month to post a query on a Veterinary Information Network discussion board. Just what does that term mean? he wanted to know. Does it have an official definition, or is it just marketing?

The answer, it turns out, is both.

“Human grade” has no formal legal definition. But the U.S. Food and Drug Administration (FDA) Center for Veterinary Medicine has taken the position that if every ingredient in a product is edible, meaning that it was processed according to rules of sanitation required of food sold to people, then the product may be labeled “human grade,” said Dr. William Burkholder, a veterinary medical officer and the agency’s resident pet nutrition expert.

The fact that the FDA doesn’t frown upon the term doesn’t mean that the claim always is used appropriately.

“We see a lot of ‘this ingredient is human grade’ claims but our position is that an edible ingredient becomes inedible when you add it to other inedible ingredients,” Burkholder said.

One pet food maker that says it meets FDA’s strict definition of the term was refused permission to sell its food in Ohio by that state’s Department of Agriculture, on the grounds that the label was misleading. (States and the FDA, together, have a hand in regulating animal feed.) The company, The Honest Kitchen of San Diego, Calif., took the state to court in 2007. It won on the basis of free speech.

The Honest Kitchen, founded in 2002, produces dehydrated raw food for dogs and cats. Owner Lucy Postins said the company originated from her desire to make food for her own puppy. Then she discovered that other pet owners shared her concerns about what goes into conventional kibble.

“When you’re feeding these homogenous brown chunks, it’s difficult to determine what’s in there,” Postins said.

The ingredients The Honest Kitchen uses not only are edible for humans, they are eaten by humans, she said.

“We actually physically eat the raw ingredients that are going into our food. As part of our QC (quality control), we taste every batch of food ... They actually taste pretty good,” she said, comparing the aroma of the finished product to soup or stuffing mix.

The meat, she added, is sampled after it’s dehydrated.

Although Postins feels strongly about her company’s right to call its food “human grade,” she said she’s aware of other manufacturers that use the term inaccurately.

Because of its misuse, many players in the industry decry the label. “It is essentially a made-up term used by marketing interests to describe and promote products in light of anthropomorphic responses people have to their pets,” David Syverson, chair of the Association of American Feed Control Officials’ Pet Food Committee wrote in an e-mail response to questions.

AAFCO is an advisory body of state and federal feed regulators that develops nutrient standards and ingredient definitions for animals, whether livestock or pets.

Regardless whether a pet-food product meets the standard for human-edible food, people tend to misunderstand the term, Syverson said. He suspects consumers believe it applies to various body parts — intestines versus muscle, for instance — but it does not.

Whether a food is edible for humans “has little to do with the nature of the product. It has everything to do with how the product is handled,” he said. He offered this example:

“We have two steaks that came out of a USDA meat processing plant. One is edible and can be sold for human consumption because it has been handled continuously under process controls established by law/rule to assure that the product is not exposed to anything that would make the product unfit for human consumption.

"The second came from the same slaughter plant, same animal and same production line, but slipped off the belt and hit the floor. This one is inedible.”

Furthermore, what is acceptable for one species to eat may be harmful for another, he said: “Humans can eat chocolate, for instance; however, if it is fed to a dog, it (can be) toxic.”

At the same time, some ingredients regularly found in pet food but considered less-than-desirable in the standard American diet (meat byproducts, for example) may be just fine for either to eat, he and others said. In fact, some people do eat them, noted Dr. Jennifer Larsen, an assistant professor of clinical nutrition at the University of California-Davis School of Veterinary Medicine.

“I have some good friends here from Spain and they’re really frustrated by what’s in the market,” Larsen said. “There’s no brains, there’s no kidneys. They think it’s really interesting that we even devein shrimp. It’s a cultural thing. There’s nothing wrong with byproducts; they’re quite safe. It’s just, Americans think they’re icky.”

Mark Heyward, owner of Timberwolf Organics pet food, said pet owners should judge pet food not on what they’d like to eat themselves, but on what constitutes good quality for those species.

“If you were to let a live chicken out in the back yard and your dog ate it, it would eat everything,” Heyward said.

Dr. Avi Deshmukh, scientific communications manager for pet-food maker Royal Canin USA, agreed. “When carnivores kill, the first thing they are likely to eat are the internal organs,” he said. “They know that’s where the gusto is. For example, liver and kidney contain vitamins. The intestines contain excellent protein. So a lot of these things provide a very good nutrition to the animals. They will go to the steak later.”

And to those people who say they don’t eat meat byproducts, Deshmukh responds with a chuckle, “Yes, you do. What do you think is (in) a hot dog?”

What, then, is the difference between people food and pet food? From the government’s point of view, the key distinction rests in rules governing the handling of food products, which are aimed chiefly at sanitation. “For animal feeds, of which pet foods are a subset, there are currently no ‘good manufacturing practices’ in regulation,” the FDA’s Burkholder said.

Ancillary parts of an animal, such as the beaks, feet and combs of a chicken, for example, could end up as components of a pet-food ingredient.

“I don’t know of any ingredient that is just feet and beak,” Burkholder added. “Feet would contribute protein and minerals to a product. Beaks are probably arguably filler, if it was just beaks. They’re sort of a chitin-keratin-composed substance. They tend to be components of poultry byproduct meal, which has a lot of other things in it.”

Similarly, meat and bone meal, which is a combination of “whatever is left over (from processing of meat for human consumption) -- bones, and meat portion attached to it,” Deshmukh said, may be used as an ingredient in pet food.

One category of meat source known as 4D, for “dead, dying, diseased or disabled,” is prohibited for use in human food, but allowed in animal feed, provided it was processed properly with heat to kill pathogens, AAFCO's Syverson said.

4D meats could include road kill. Syverson said he believes critics of conventional pet foods put undue focus on this fact. “People don’t go out of their way to find road kill to put in pet food,” he said. “...Somebody would have to physically collect it and bring it to the plant. I’m not saying it never happens; however, I have never seen it, and it’s unlikely.”

Just because something is permitted in pet food doesn’t mean it’s present, of course. “There’s a difference between good companies and mediocre companies,” Deshmukh said. “Responsible and reputable companies will use only meat or poultry from healthy animals.”

He acknowledged that pet owners have no way of knowing the quality of ingredients specified by a given manufacturer. “You have to go on the reputation of the company,” he said.

Palmatier, the veterinarian in Santa Rosa, said many in the veterinary community have close, mutually beneficial relationships with major pet-food companies, some of which fund continuing-education programs at professional conferences. For that reason, he said, practitioners have a responsibility to know what is in the food they promote.

“Veterinarians are aligned with major food manufacturers to some degree, so criticisms of the major food companies are, to some degree, a criticism of standard veterinary medicine, too,” he said. “So we should really know the products that either fund our CE programs or are sold ... from our offices.”