You’re dutifully reading the ingredients on the back of the dog food label, just like your veterinarian told you you should, and what do you spy but the dreaded three-syllables you’re always at a loss to completely comprehend? I mean, what is a by-product anyway?

by-prod·uct, \bi-,prä-(ˌ)dəkt\, noun

1 : something produced in a usually industrial or biological process in addition to the principal product
2 : a secondary and sometimes unexpected or unintended result

That’s Merriam-Webster’s take, anyway. And while it’s not exactly wrong, it doesn’t help us any, either. What we really want to know is:

1. What does "by-product" mean when it's in my pet's food?

2. Does it really mean there are beaks, hooves, feathers and feet in it?

3. If so, is there something so wrong with beaks, hooves, feathers, and feet that I shouldn’t buy the food, or can they be OK in small quantities?

4. Is all by-product created equal, or are some by-products better than others?

5. Will it make my pet sick to eat food with by-products in it?

That’s what I was trying to figure out over the last weekend. One of my clients had pointedly asked me these five seemingly innocuous questions, and somehow, I felt like a veterinary impostor. I had a good hunch, but I wasn’t completely sure of my answers. Which is why I did what all good, honest people do. I hedged:

A by-product is a part of the animal normally not intended for human consumption," I explained. "But while chicken feet are considered edible in the Orient (for example), they tend to be labeled as meat by-product in the U.S. So it is that a batch of by-product will differ according to what’s available, what’s seasonal, and what’s most prized. The by-product will be the rest of the animal that’s not used.

That’s what I offered, hoping to throw off my questioner for long enough to regroup and recruit some serious help. The definition for meat by-products by the Association of American Feed Control Officials (AAFCO) is:

The non-rendered, clean parts, other than meat, derived from slaughtered mammals. It includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth and hoofs. It shall be suitable for use in animal food. If it bears name descriptive of its kind, it must correspond thereto.

So, by extension, it seemed to me that poultry by-product would be similar, though I wasn’t too sure about the feathers, so I found an AAFCO reference to poultry by-product meal (which is basically the same thing as poultry by-product with the fat and the water removed):

[Poultry by-product meal] consists of the dry, ground, rendered, clean parts of the carcass of slaughtered chicken, such as necks, feet, undeveloped eggs, and intestines — exclusive of feathers except in such amounts as might occur unavoidably in good processing practices.


But I had to know: How bad is this anyway? After all, one man’s by-product is another’s beloved chitlins or exalted haggis. (Blood sausage, tripe soup, or kidney pie, anyone?) Which is why I had to seek more refined assistance, this time from the loftier sources at the FDA’s Center for Veterinary Medicine (CVM). Here’s an excerpt from their bulletin titled, "Pet Food: The Low-Down on Labels":

Some people prefer to pass up animal by-products, which are proteins that have not been heat processed (unrendered) and may contain heads, feet, viscera and other animal parts not particularly appetizing. But protein quality of by-products sometimes is better than that from muscle meat, says Burkholder (CVM's pet food specialist, William Burkholder, D.V.M., Ph.D.).

Does this FDA veterinarian’s opinion make you feel better? Hmmmm … for me not so much.

Sure, I can get behind the concept that by-products can be super nutritious. After all, I personally LOVE cooking with organ meats and will happily feed my dogs raw chicken hearts, for example (a by-product if ever there was one).

Problem is, saying that the protein quality is "sometimes" higher in by-products doesn’t actually tell us whether the by-products we’re actually buying are high quality or not. We simply can’t know whether they’re the crappy by-products or the good stuff. Which is why I can safely offer you my opinion on this one:

While it's highly unlikely that any by-product will make your pet sick, given the choice between the by-products behind door number one, and the animal muscle between door number two, I think I’ll always choose the known quantity. How about you?

OK, so now it's time to check out what that bag in the pantry says you're feeding your pet.


Dr. Patty Khuly

P.S. Like this post? Stay tuned for tomorrow's post on "fillers" in your pets' food.

Art of the day: "Rrrr" by Hotash