The idea for the product came after General Nutrition Centers customers stopping by the store for supplements started asking about products for their pets, too.

Maybe it was some garlic to improve their bloodhound's blood circulation, brewer's yeast to regulate their border collie's blood sugar or perhaps glucosamine to soothe arthritic joints in greyhounds.

Now Pittsburgh-based GNC and Phoenix-based PetSmart are teaming up to join the growing market for dietary supplements for dogs and cats. The product line, called GNC Pets, will be available this fall at both chains.

If the dogs and cats take to them, the companies hope to expand to supplement offerings for pet rodents, reptiles, birds and fish.

"Customers are always looking for natural options to help keep fleas off their pets, relax their pets and keep their digestion system healthy," said GNC Executive Vice President Tom Dowd. "Overall, general health and shedding are also top areas of concern that drives customers to look for supplements."

The products may come in a variety of forms: pills, soft chews, liquids, powders. "We have every delivery system out there," he said. The exact formula will be proprietary, but "nobody out there in the market is putting together this kind of formula for pets."

Point Breeze veterinarian Lawrence Gerson called the initiative "an interesting idea. I think there are some pets that would benefit from a good supplement."

Still, he pointed out that major pet food brands such as Purina already sell a wide range of products, including food and supplements for specific ailments of the kidney or liver or for pets with diabetes.

"Animals really should eat a meat-based diet rather than a carbohydrate-based diet. We tell people to buy the most expensive food they can afford," said Dr. Gerson. "Most of the higher end foods are excellent products that have 100 percent balanced and complete nutrition, so I'm not quite sure what a supplement is going to do."

It is more common for veterinarians to see overnourished rather than malnourished pets, he said. "I'm not sure a chubby pet needs a supplement, other than some fiber."

He recommended pet owners ask their veterinarian about their pet's needs and if a supplement would help.

When the new GNC/PetSmart line hits the shelves, Mr. Dowd said the store setup will differ in the two chains, reflecting the differences in the clientele. Where PetSmart will devote an 8-foot section for dog supplements and a 4-foot section for cats, GNC plans to have a gondola-type display in its stores.

All PetSmart stores will carry the supplements but only select GNC stores, including all area mall stores and larger strip mall stores, will have the line. Still, the GNC locations may be more convenient locally, as the chain has 200 stores in southwestern Pennsylvania compared with 10 PetSmart locations. GNC has not set a price range for the products yet.

Mr. Dowd said GNC also is still working on the all-important taste testing, since the major challenge with dietary supplements for pets is getting the supplements to their final destination. Humans might be willing to swallow a bitter pill; good luck getting a fussy cat or dog to do it.

"As great as you think the product is," noted Mr. Dowd, "it's not going to do any good if the animal doesn't eat it."

But if animals do like it, capturing even a small slice of the pet food/supplement market could be a nice financial supplement for GNC and PetSmart.

According to a recent survey, Americans own about 77.5 million dogs and 93.6 million cats, representing more than one-third of all U.S. households.

The animal supplement market has grown and is now a $1.3 billion business, with about half of that spent on dogs and cats, according to the National Animal Supplement Council, based in California.

"We saw this as a huge opportunity to step into this category," said Mr. Dowd. "Everyone's really excited about it."

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