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Let's talk cat nutrition and pet food ingredients. There have been a lot of buzz words and phrases thrown around without a lot of education as to the meaning. "Grain-free" and "by-product meal" are a couple of examples that I see on television all the time. Each commercial pet food has their own niche and advertising objectives that are important to note.

Let's start by defining some of these words and phrases:

  • Cat Eating Pet FoodGrain — the seeds of plants (such as wheat, corn, and rice) that are used for food.
  • Gluten — the protein-containing portion of the plant extracted.
  • Meat by-product —a usable product other than flesh obtained from slaughter animals including edible organ meats and various inedible products (such as hair and bone).
  • Meat by-product meal — those by-products dehydrated and ground into a powder. FYI – this still has a very high-protein, low-fat and low-carb content.
  • Meat meal — Meat/animal flesh dehydrated and ground into powder.

Do cats NEED grains? No. Do cats NEED by-products? Some (such as heart, kidney and liver), yes. A grain-containing cat food is not necessarily harmful to a cat unless they have a sensitivity or the amount of grain in the food far outweighs the meat.

Pet Food Meat and Bone MealAs a cat-only veterinarian I see cats every day on a variety of diets so I can offer my observations on health and diet. Most cats that I see as a new diabetic are on a diet high in high-glycemic index carbohydrates, not just grains. That means a diet high in starchy ingredients that creates fast blood sugar spikes like white potato, white rice, corn meal (remember meal means concentrated – dehydrated product ground into powder), and brewers rice (a by-product of rice production for humans that lacks nutrients of the whole grain rice). This does not mean that if these products are in the food at all your cat will get diabetes

My observation with my own patients is that foods with these products high on the list of ingredients (remember they are arranged by weight of product contained in the food on the ingredient list) means they are getting way too many high-glycemic index carbohydrates creating fast glucose spikes. These spikes tax the pancreas to secrete a large amount of insulin. Over several years of taxing the pancreas, it starts to get tired and shut down. Let's take a look at a couple ingredient lists and analyze them.

Ground yellow corn, corn gluten meal, poultry by-product meal, soybean meal

Royal Canin's Nutritional Value of By-Products ListThis list means that the ingredient making up the highest WEIGHT of the food is ground yellow corn and the second is corn gluten meal. When a product is dehydrated and made into a meal, it take up less weight but occupies more space because it is now a waterless powder. Now to the poultry. The by-products of chicken include everything BUT the flesh (skin and muscle), ground into a waterless powder (meal).

One problem with any pet food ingredient list is that we don't know the ratio of ingredients. Does it look like this: 50% ground yellow corn, 10% corn gluten meal, 9% poultry by-product meal, 8% soybean meal and 23% the rest? Or how about this: 99% ground yellow corn, 0.25% corn gluten meal, 0.25% poultry by-product meal, 0.25% soybean meal and 0.25% the rest?

Let's try another one.

Boneless chicken, chicken meal, chicken liver, whole herring

What do you notice in comparison to the previous list? Zero carbohydrates in the first four ingredients. One thing to note – when regular meat is listed it contains water, which weighs a lot. Don't be afraid of a food if the first ingredient is meat meal – that simply means that it was dehydrated and ground into a powder for a more concentrated meat protein. So a thought that may have crossed your mind is "well, if the water is removed from these meat ingredients listed would they weigh less than the other ingredients? The simple answer is "probably," but here are more of the ingredients in the same food, in order of weight:

boneless turkey, turkey meal, turkey liver, whole eggs, boneless walleye, whole salmon, chicken heart, chicken cartilage, herring meal, salmon meal, chicken liver oil, chicken fat, red lentils, green peas, green lentils, sun-cured alfalfa, kelp, pumpkin, butternut squash, spinach greens, carrots, apples, pears, cranberries...

What do you notice about the carbohydrate sources? They are low on the weight list and whole, not by products of their processing like brewers rice. The glycemic index of lentils and peas are much lower meaning blood sugar spikes will be very small. The fruit and vegetables are not necessarily a staple in your carnivorous cat's diet however, given that most cats are now indoors, overweight and not very active, they could use a little fiber in their diets, not to mention antioxidants.

Next, let's examine those confusing percentages on the back of the bag.

Calories come from three sources and three sources only: protein, fat and carbohydrates. The first food list we explored shows a 31% protein. So... 31% of what is protein? It means 31% of the food BY WEIGHT is protein. We break it down as follows: this food reports 12% moisture, 31% protein and 11% fat. To find the dry matter basis of the food, subtract the moisture (100-12) and that leaves us 88% of the food by weight is protein, fat and carbs. Next we have to divide the caloric percentages by our new 88% to get the true dry matter basis percentages. If written out now in percentages we have 35% protein and 13% fat. That leaves us with a food with 52% carbohydrates {100-(35+13)=52}.

Now you try with the second food. The guaranteed analysis is 42% protein, 20% fat and 10% moisture. We then get 47% protein, 22% fat and 32% carbohydrates. Much better! Just for comparison's sake a high-quality canned food is 50% protein, 44% fat and 5% carbs. Even if the canned food had 47% protein, 22% fat and 32% carbohydrates, it would still be more beneficial for your cat than dry food because of the added water content. However, I know that dry kibble is convenient, cats like it and it isn't going anywhere, unfortunately, so let's make sure we are choosing one that is nutritious.

One take-home message from all of this information is that "grain-free" can be beneficial because some of the high-glycemic index carbohydrates are removed from your cat's food, but beware. Those grains may have been replaced by equally detrimental starches like white potatoes, by too much animal fat or by a high amount of other carbs that cats just simply do not need. Don't vilify all grains – pay attention to the carb sources!