I found this insight into the petfood industry very interesting. In
case you didn't see this from the Sunday NY Times:

March 25, 2007
The Basics
For Cats and Dogs, Life Is a Bowl of ...

What exactly are pet owners getting when they buy their pet food —
some $16 billion worth each year in the United States?

That’s a question many asked last week after the deaths of at least 14
cats and dogs and the recall of 60 million containers of pet food by
Menu Foods of Canada.

The company produces 95 brands of pet food, including premium labels
like Iams and private labels for Wal-Mart and others. On Friday, the
New York State Department of Agriculture said it had found a toxic
chemical used as rat poison in food linked to the pet deaths, though
it did not explain how it got there.

The Week in Review asked Marion Nestle, a nutrition professor at New
York University and the author of “What to Eat” (North Point Press;
2006), for insight. Ms. Nestle and Malden Nesheim, a professor
emeritus of nutrition at Cornell University, are writing a book on the
pet food industry to be published next year.

Q. How much is known about an industry that does business with the
majority of 90 million cat owners and 74 million dog owners in this
country?

A. It’s an extremely secretive industry, more secretive than the food
industry, from our experience. A lot of that has to do with animal
research, and pressure from animal rights groups not to do research on
cats and dogs.

Q. What research is done by these companies? After reports last month
that its food was making pets ill, Menu Foods tested its product on
animals, nine of which died.

A. It’s usually taste preferences. A great deal of the industry’s
effort is making cats, for example, go for Product A instead of
Product B. You cook up flavor additives — a mixture of chemicals and
food ingredients — line up hungry cats, and that’s basically the
extent of the research. In addition to making sure the formulation
supports growth of kittens and puppies.

Q. What’s in pet food then? Is it regulated?

A. Pet food is regulated by the F.D.A. through the same state agencies
that regulate food for farm animals. But product excluded from animal
feed can go into pet food — meat and bone meal, nervous system tissue
— parts of animals not allowed for anything else. There were cases of
mad-cow disease in cats in England. The opportunity for cheap
byproducts is much greater in pet foods. The assumption is that better
brands don’t do that, but it’s not verified.

Q. If a few companies are making many of the brands, are pet foods all
the same then?

A. Nutritionally, they have to meet the same industry standards,
though they’re priced very differently. You read the labels and they
all look alike — corn is the first ingredient in a lot of dry food.

Q. Why are some brands more expensive?

A. The quality of the ingredients. Are you using human-grade food or
food that humans wouldn’t care to eat? It doesn’t matter to animals
but it matters to the people who own them.

Q. What about health claims?

A. When you see food claims on breakfast cereal — for instance, that
it lowers cholesterol — there has to be some scientific substantiation
behind them. Pet foods have claims on them, that they support a
healthy immune system, reduce risk of whatever, but they don’t have to
be supported by large amounts of science. They’re worded in such a way
that doesn’t violate the F.D.A.’s labeling rules. I think the F.D.A.
will have to take a much closer look at pet foods — this is the second
recall in a short time.

Q. What do cats and dogs enjoy eating?

A. Cats don’t have a taste for sugar; they don’t taste sweet things.
They have a particular taste for what is referred to in the industry
as “animal extract” — God knows what’s in it. Dogs can taste sweet,
but, dogs will eat anything. Cats are very fussy, as any cat owner
will tell you. The one thing that’s never been studied is to find out
how long it would take for a cat to eat something it doesn’t like —
owners never wait it out. People are very attached to their pets, and
it’s painful to watch a cat not eat.

Q. Should owners prepare their own food for pets or feed them table
scraps?

A. There’s evidence that dogs can be fed table scraps and do quite
well, provided they’re healthy table scraps — meat, dairy, vegetables,
fruit. The problem is a lot of humans don’t eat that way.