The Truth about Grain, By-products, and other Pet Food Myths

For those of you who have read my other blogs regarding pet nutrition you should now be aware that as an integrative veterinarian, who often advocates for feeding whole foods to my patients, I believe in having honest discussions with my clients when it comes to the best foods to feed their pets.   I am reluctant to simply buy into the most recent trends in pet food without any scientific substantiation, clinical or even empirical evidence to support some of the claims made by various pet food retailers and other pet enthusiasts including some of my fellow “holistic” veterinarians.

Let me give you an example.  Recently I saw a client whose dog likely has a severe protein losing intestinal disease called “lymphangectasia”.   Dogs with this disease cannot handle even normal levels of fat in their diet.  She came to me seeking an integrative approach for treating her dog.  After reviewing the excellent work-up performed at another veterinary clinic, including medications and prescribed veterinary diet, I performed my own physical exam as well as a more detailed history to better understand the relationship between this dog’s individual constitution, environment and current medical condition.  I then developed an integrative treatment plan including a combination of appropriate pharmaceutical medication, Chinese herbal medicine, nutritional supplements and dietary recommendations.

This particular dog will require a significantly fat-restricted diet for the rest of its life.  Having contacted her breeder the owner had already started to feed some home cooked tilapia combined with sweet potato.  “So far,so good”, I told her, explaining that this is a good choice for two low fat ingredients.  The initial veterinarian had prescribed a specific canned veterinary diet – Royal Canin Gastro-intestinal Low Fat.

The veterinary diet prescribed is uniquely designed for dogs with chronic pancreatitis or lymphangectasia that will require a fat-restricted diet long term. The main ingredients read as follows: Pork By-Products, Corn Grits, Rice Flour etc. and the Guaranteed Analysis: Crude Protein min 6%, Crude Fat min 1%, Moisture max 77%.

However, my client had been advised by a (no doubt well meaning) “pet nutritional advisor” that she needed to avoid by-products and grains amongst other things in this dog’s diet.  So taking this advice to heart she proceeded to buy a good quality canned diet from the pet store – Natural Balance Limited Ingredient – Fish and Sweet Potato.

The main ingredients include: Fish Broth, Ocean White Fish, Sweet Potatoes, Salmon, Potatoes, Salmon Meal, Canola Oil, Salmon Oil etc. and the Guaranteed Analysis: Crude Protein min 7.0% , Crude Fat min 4.0% minimum, Moisture max 78%.

So let’s do an important comparison between these two diets, with a particular focus on the fat content that is key to managing this dog’s medical condition. Since we know the canned foods contain 77% and 78% water respectively we can approximate the amount of fat in each on a dry matter basis by dividing the % fat by the % dry matter and then multiplying by 100.   Starting with the veterinary diet we have 1% Fat (as fed) divided by 23% dry matter thus giving us approx 4% Fat on a dry matter basis while the Natural Balanced canned diet provides 4% Fat (as fed) divided by 23% dry matter equals at least 18% Fat on a dry matter basis.

The above example provides a reasonable approximation of the actual fat content on a dry matter basis.  While veterinary pet food manufacturers provide precise calculations on both a dry matter and metabolizable energy basis of all their key nutrients this information is just not available for most retail foods.  According to information provided by Royal Canin, the veterinary canned diet we are referring to actually contains 7% Fat on a dry matter basis.   Regardless it is plain to see that the canned food chosen by this owner has close to 3 times or more the amount of Fat in it than the canned diet recommended by the veterinarian.   In fact it is not likely possible to find a comparable fat-restricted diet through any retail source other than a veterinarian.  While the intentions of the pet owner were excellent, the pet store diet would be detrimental for her dog, probably resulting in additional medical care and costs.  This left me and my client with just one of two options for this dog.  She either needs to feed the recommended canned veterinary diet or a properly balanced home-made, fat-restricted diet to her dog for the rest of his life.

What about the by-products and corn grits contained in the veterinary diet – aren’t those “undesirable” ingredients?

Advising pet owner’s to reject any by-products shows a lack of understanding of the nutritional merits of various parts of animal food products.  By-product is no more than a word used to describe any part of an animal other than the muscle meat.  Pet food manufacturers who follow AAFCO guidelines (particularly if they sell products into the United States) are required to list any animal based food ingredient that is not muscle meat as by-product.   No carnivore in the wild eats just muscle meat!  Skin along with visceral organs and their contents provide wild carnivores with a rich variety of nutrients not found in muscle meat alone.  So I called Royal Canin and asked them specifically what part of the pig is included in their “pork by-products”.  By definition pork by-product consists of meats from healthy, veterinary inspected pigs and can contain organ meats as well as bone and joint tissue but does not include any inedible material such as hair or hooves.   Pork by-products are an excellent source of nutrients including protein (essential amino acids including taurine), fat (energy), minerals (such as iron) vitamins (such as B12 and Vitamin A), and functional nutrients such as glucosamine, chondroitin and L-carnitine.

I also explained to this client that there is no scientific or empirical evidence to support that it is ill-advised (in general) to feed grains to pets.  Almost all grain free diets contain some form of carbohydrate, such as potato.  The argument that wild carnivores do not eat grains just does not hold when compared to the unlikely image of a wild wolf digging up potatos!  In fact a published study of the foraging and feeding habits of the Gray Wolf demonstrated in the summer months, when it is hard to catch prey, that 75% of the scat contained plant material.  In addition, modern wolves that prey on farm animals are likely to ingest the stomach and intestinal contents of these animals that are often raised on grains.  Refined grains have been shown to be significantly more digestible for dogs and cats than whole grains and particular fractions of grain such as the wheat gluten provide a highly digestible and well balanced source of protein, not just a “cheap filler”!

So what is all the fuss about grains?  It is true that some dogs and cats develop food allergies or intolerance to certain grains.  Chicken, beef, corn and wheat appear to be among the most common food allergens.  This may have some relation to being among the most common ingredients found in many commercial pet foods.  Does that mean we should stop feeding Chicken and Beef to our pets?  For animals with suspected allergies or intolerance to certain grains or meats we need to feed a diet that is devoid of that particular ingredient.

It is also true that feeding diets too high in refined carbohydrates can play a role in promoting obesity, diabetes, chronic inflammation and other metabolic conditions.  Highly refined carbohydrates (whether from potato starch or corn starch) can result in spikes in blood glucose levels that potentiate inflammation.  Pets with chronic inflammatory disorders, diabetes and certain other metabolic conditions will likely do better on diets that exclude or at least are lower in the more refined carbohydrates.  So understanding the ratio of Protein, Fat, Carbohydrate and Moisture can be essential to choosing an appropriate diet for these pets.  From our discussion at the beginning of this blog you can see just how difficult this can be by comparing labels alone.  It is also important to know what part of the plant is being used and how it has been processed.  Corn gluten and wheat gluten for example are highly digestible proteins not carbohydrates.  Gluten sensitivity (similar to Celiac disease in humans) is a very rare condition in animals that only seems to affect certain predisposed breeds such as some Irish Setters.  However, wheat gluten can be allergenic in some select pets.

In the end my client decided to feed the canned fat-restricted veterinary diet in combination with a properly balanced home-made diet that can include tilapia and sweet potato.  More on how to ensure a home-made diet is properly balanced in a future blog.


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