Are Dogs Carnivores or Omnivores?

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Most of the controversy over carbohydrates comes from discussions over whether dogs should eat grains or not. Beliefs about grains for dogs (for or against) usually stem from beliefs about food allergies and/or whether dogs are carnivores. So, let’s take time to look at these beliefs here.

Are Dogs Carnivores?

The answer to this question depends on who you ask and what day of the week it is. Ask a raw feeder and they will usually tell you that, yes, of course, dogs are carnivores. Ask many veterinarians and they will often tell you that they were taught in vet school that dogs are omnivores (though this can depend on the university). Ask a dog food company and it can depend on their philosophy, marketing, and the foods they sell.

With cats the answer is much more clear-cut. Cats are obligate carnivores and absolutely must eat meat in their diet. Some of the nutrients they require only come from meat sources. Dogs are not obligate carnivores – that much is clear. They do not have that same absolute nutritional requirement for meat that cats have. Biologically, dogs have the sharp, tearing teeth, grinding molars, and shorter gastrointestinal tract associated with a carnivorous predatory animal. In this regard they are similar to cats and to their own close relative, the wolf. However, this is where things take a turn for dogs. Dogs have been domesticated for at least 12,000 years and possibly much longer in some parts of the world, if the fossil record is to be believed. For all these thousands of years dogs have not only lived with humans, but, to a great extent, shared our diet. Their domestication seems to pre-date the invention of agriculture, but dogs managed to adapt and they have been consuming leftovers, breads, grains, and other foods during these thousands of years, along with our meaty foods. We can say that dogs are carnivores – they certainly enjoy meat – but they are also scavengers and they have some characteristics of omnivores.

(Honestly, if you leave your dog unattended in the kitchen, is there anything he won’t taste? Can you leave food sitting out on the counter or table? Has your dog never gotten into the trash? My dogs will eat almost anything – animal, vegetable, or mineral.)

Recent research has shown that dogs have evolved an ability to digest starches that their wolf relatives do not possess. They have at least 10 genes for digesting starches and breaking down fats that wolves don’t have. They still don’t have enzymes in their saliva to break down starches, as humans do, but they more than make up for this by having plenty of amylase to break down starches in their gut.

This research does not mean that your dog needs to eat a starchy diet or live on nothing but cereal. But it does suggest that some of the dislike of carbohydrates in general, and grains in particular, has been misplaced. It helps explain how dogs were able to survive on scraps of bread and kitchen trimmings when they lived as farm dogs. It also means that dog food companies that tell you that dogs are like wolves and need to eat a carnivore’s diet that is mostly meat are taking advantage of people.

Carbs and food allergies

Most dog lovers are probably aware that food allergies occur when the dog’s immune system has an over-reaction to proteins in something they eat, which triggers an allergic reaction. So, the allergic response doesn’t actually occur in response to the entire ingredient or food. It’s the protein that leads to the reaction.

Dogs can have an allergic reaction to the proteins in grains such as corn or wheat, but these are not the most common food allergens for dogs. The most common food allergens for dogs are, in order: beef, dairy products, chicken, lamb, fish, chicken eggs, corn, wheat, and soy. Your dog is more likely to be allergic to some of these meat proteins than to grains though some dogs can have multiple food allergies.

Common allergens can change over time. In the 1980s, lamb was considered to be a novel protein and dog owners who had dogs with food allergies and skin problems were often advised to cook lamb and rice for their dogs – since this was before lamb dog foods were available. There were no grain free dog foods at that time and no holistic dog foods. Seeing a niche, dog food companies began making lamb and rice dog foods. These foods have become so common in the last two decades that some dogs have developed allergies to lamb. It’s no longer a novel protein but almost as common as chicken in dog food.

Grain free dog foods came about in much the same way. People who had dogs with skin and allergy problems were making food for their dogs, often on veterinary advice. Again seeing a niche, some dog food companies began making grain free foods for dogs that needed them. They probably never imagined that grain free dog foods would become so widely popular or that so many people would believe that their dogs needed them. Today many people believe that grain free foods are healthier for dogs but this depends on many factors. Many grain free dog foods are not lower in carbohydrates. They use other kinds of carbohydrates instead. More on this subject when we discuss grain free foods later.

Suffice to say that grains like corn and wheat are often incorrectly blamed for dog food allergies when other foods are to blame. In some cases a dog can have skin problems for reasons that are completely unrelated to his food.

Vitamins and Minerals

Many dog food companies add vitamins and minerals to their foods to make up for the nutrients that are lost during cooking at high temperatures. If companies use lower cooking temps or take other special measures, it is sometimes possible to only use the vitamins and minerals that are naturally included with the food ingredients.

For companies that add vitamins and minerals you will sometimes notice that they use chelated, “proteinated” minerals, or amino acid complexes. These minerals have been bonded to amino acids so your dog can digest them more easily when they eat the food. At one time these chelated minerals were mostly used for foods that contained larger amounts of grain because grains contain phytic acid – an antinutrient that can interfere with the absorption of minerals such as zinc, magnesium, and calcium. Today you often find chelated minerals in foods that contain lots of legumes for the same reason. Legumes are also high in phytic acid. The chelated minerals ensure that your dog is able to digest the appropriate amount of each mineral.

Other Ingredients

There are lots of other ingredients added to dog foods today besides these basic nutrients. Many of them are added to help with the dog’s digestion. You can usually recognize these ingredients because many of them are labeled as fermentation products or have Latin/scientific names such as “Enterococcus faecium.” Enterococcus faecium is a common probiotic used in many dog foods. It’s destination is the dog’s gut where its organisms are supposed to grow and help digest the dog food. Some dog foods add lots of probiotics and prebiotics to their food in the form of enzymes. Other foods add ingredients that are supposed to supply probiotics or prebiotics to the food. Chicory and beet pulp are common prebiotics that appear in dog foods in whole form. Some foods don’t bother. Probiotics, prebiotics and other enzymes appear regularly on many dog food labels, especially some of the more expensive foods. However, many dog lovers and critics question how effective these additives are. Many of these ingredients, especially probiotics, depend on delivering live organisms to the dog’s gut. This means the organisms have to survive the dog food manufacturing process, bagging, shipping, being stored in distribution centers, and sometimes sitting on store shelves for months. With many dog foods you do have to wonder how many beneficial organisms in the food are still alive by the time they are poured into your dog’s dish.

There are some companies that claim to use special processes to avoid these problems. They claim they have found ways to make sure the organisms they add to the food are still alive when your dog eats the food. When comparing dog foods, especially foods that make claims about adding enzymes and other probiotics, this is something that you should consider. You could be better off adding your own probiotics to your dog’s food whether you buy a probiotic made for dogs or use something like whole yogurt with live cultures.

Many dog foods also add supplements such as taurine for heart health and glucosamine and chondroitin for the joints. Taurine has long been recognized as a necessary additive for cats. Cats have a very limited ability to make taurine in their own bodies. As early as the 1970s it was noticed that cats without enough taurine in their diet could develop blindness and tooth decay and other health problems. It was not clear that some dogs might require taurine in their diets until much later. Some breeds with heart problems were shown to benefit from added taurine. Taurine deficiency in dogs was also linked to dogs that ate lamb and rice diets; high fiber diets, low protein diets (lamb dog food is often lower in protein than other dog foods, among other things), and vegetarian diets. Adding taurine to dog food is widespread today and seems to be good for heart health, even for dogs that don’t appear to have heart problems. There is also some suggestion that taurine can help with seizures and some other health issues.

Adding glucosamine and/or chondroitin to dog food is a little more complicated. These supplements are not regulated by the U.S. Food and Drug Administration (FDA) since they are not drugs. (However, the FDA can be quick to contact dog food manufacturers if they feel they are making claims of curing diseases such as arthritis with these supplements. ) There is contradictory evidence that glucosamine or chondroitin successfully help humans with joint and mobility problems. However, many people feel that they are beneficial – both for themselves and for pets. A further difficulty comes with the amounts of the supplements that is said to be required to help a dog with a joint problem. According to both veterinarians and investigative reporters, if you want to give your dog an effective dose of glucosamine and chondroitin found in dog food, you would probably have to stuff your dog with more food than he could possibly eat in 24 hours. You are probably better off buying these supplements from your local drugstore or a trusted online source to give to your dog yourself. However, you need to be careful and make sure you are buying from a company with a good reputation. Not every nutriceutical company can be trusted.

There are plenty of other additives in some dog foods but they tend to be tailored for a dog’s age, size, and other special circumstances, such as adding DHA (docosahexaenoic acid) to puppy food for brain development. We’ll discuss some of these ingredients as we come to them when we talk about lifestages.

There are also lots of ingredients you should try to avoid, if possible, such as unnamed or vague ingredients, meat by-products and digests, added sweeteners, artificial colors, and artificial preservatives. We’ll discuss more about them later, too.

Many dog owners are happy to feed a food labeled “complete and balanced” and don’t give much more thought to their dog’s nutrition. With a little luck and regular vet care, these owners and their dogs will enjoy long, happy, healthy lives together. On the other hand, there are lots of dog lovers today who expect – even demand – top quality dog foods. They read labels, check ingredients, investigate companies, and compare percentages. “Complete and balanced” is not enough for these owners. They want better quality food for their dogs.

Some dog lovers will completely eliminate commercial dog food from their dog’s diet and feed a raw diet or a homemade diet instead. Sometimes people do this for health reasons but many people choose these feeding approaches because they dislike the idea of feeding commercial dog foods.

Whatever feeding method you choose, it’s important to know something about canine nutrition. You need to know what your dog really needs in his diet as opposed to some of the things that pet food companies sometimes add that your dog doesn’t need. If you are making your dog’s food yourself, with either a homemade or a raw diet, then understanding canine nutrition is even more important. Before we consider your dog’s nutrition, we can look at how he digests his food.

 Your dog’s digestion

Illustration of digestive system of the dog anatomy

Your dog’s digestion begins to prepare before he ever starts to eat. He has a sense of smell that is 10,000 times more powerful than a human’s. He can smell food long before you can. Most dogs have 42 teeth that include “canines” for tearing, teeth for cutting, and molars for grinding and crushing. Your dog can gnaw bones and crush plant material.

Your dog has considerably fewer taste buds than you do. They are said to have 1700 taste buds compared to some 10,000 taste buds for a human. Dogs don’t spend a lot of time tasting their food. The expression “wolfing” down food has its basis in reality. Most dogs eat quickly – before another predator can take the food away from them. It doesn’t matter if the other predator is a littermate or a wolf, dogs instinctively eat quickly. While dogs don’t have well-developed taste buds, they can taste different flavors such as salty, sweet, bitter, umami (savory/meaty) and sour, just as we do. (Poor cats only have about 470 taste buds so they are really at a taste disadvantage. They have also lost the gene to taste sweets.)

Dogs also have little amylase in their salivary glands. Humans use salivary amylase to start digesting carbohydrates before they reach our stomachs. Dogs can’t do very much of this pre-digestion. Your dog’s pancreas does produce amylase, however. He can break down starches/carbohydrates once they reach his stomach.

Your dog’s stomach is able to expand to help him when he eats large meals. In the wild, wolves have to eat prey when they kill it. They can gorge on the kill then rest for several days before they have to hunt again. Although we don’t try to feed our dogs on this schedule, dogs still have stomachs that can accommodate this kind of gorging. (We don’t recommend that you try it.) This does help explain how your dog can stuff himself at times and then sleep it off.

The stomach pH in your dog’s stomach is much more acidic than the acid in our stomachs. For example, your dog is able to digest bones. Dogs are also able to cope with harmful bacteria that would be dangerous to humans. Dog food recalls involving Salmonella, for example, are typically done because of concerns for human health since we handle the dog food. Unless your dog is elderly or has a weakened immune system, it is unlikely that Salmonella will bother him. You should not take any chances, however, and if you have pet food that has been recalled, return it to the store. Do not feed it to your dog.

Dogs also have a digestive track that is much shorter than the human digestive tract. They typically digest their food in 12-30 hours. It can take humans anywhere from 30 hours to five days to digest a meal.

The dog’s colon provides room for bacterial fermentation to break down material. The large intestine in a healthy dog has a wide array of microbial organisms at work.

From nose to tail, your dog digests his food and makes use of its nutrients.

What your dog really needs in his diet

There are several respected sources you can check to find canine nutritional requirements. The National Research Council (NRC) publishes nutrient profiles for dogs (and cats) for various life stages. You can find their nutrient profile tables on various sites but we like to use the tables from the Merck Veterinary Manual.

The Association of American Feed Control Officials (AAFCO) also publishes dog and cat nutrient profiles for adult maintenance and reproduction. You can also find these tables on the Merck Veterinary Manual site. We have provided these tables in an Appendix at the back of this book.

As with any animal, dogs will require different nutrient amounts at different life stages. Calorie requirements for dogs will differ depending on the dog’s size, how active he is, whether he is neutered, his age, and other factors. However, there are certain basic nutrients that your dog needs to survive: amino acids from proteins, fatty acids and carbohydrates, vitamins, minerals, and water. Before you say that dogs don’t need carbohydrates, keep reading. Technically speaking, humans don’t need them either, but they play a role in our nutrition.

Protein

Protein is essential to your dog’s diet and they cannot survive without it. There are 22 natural amino acids that make up various proteins. “Essential” amino acids are amino acids that cannot be made by the body. For dogs there are 10 amino acids that they cannot make in their own bodies. (Humans have nine essential amino acids – we can make one more than dogs can in our bodies.) These essential amino acids have to be supplied in the diet, through the proteins that are consumed. They provide some of the building blocks to make proteins and important compounds in the body. They can also contribute to making glucose for the body’s energy. Good quality proteins typically have a balance of the essential amino acids. Dogs will often avoid food that lacks an amino acid and they will choose foods that have higher protein. Studies have shown that they will choose foods that contain the 10 essential amino acids though it’s not known if this is due to the taste of the food or an instinct to fill their biological needs.

Protein in your dog’s diet is important for basic body functions such as cellular regeneration, hormone and enzyme production, tissue maintenance, as well as promoting healthy energy. However, not all proteins are the same. Protein varies in quality and bioavailability. (Bioavailability refers to the ease with which any nutrient can make its way from the food you eat into your body.)

Several factors can affect how your dog uses various proteins:

  • Protein source: Meat-based proteins, sometimes called animal proteins, normally have an amino acid profile that is considered a “complete” protein for dogs. By contrast, plant proteins have incomplete amino acid profiles and do not meet a dog’s protein requirements. This means that while dogs can obtain some protein from plant-based sources, most of their protein needs to come from animal-based proteins. Some dog food brands use a lot of plant-based protein in their foods in the form of corn, wheat, and soy, as well as other legumes (think peas) and lentils. These plant-based sources of protein are less expensive ingredients for dog food companies than meat-based proteins. Many companies, including highly respected brands, have greatly increased the amount of plant protein in their foods. Most dog owners think only cheap dog food uses plant-based protein such as corn, wheat, and soy, but many dog lovers are paying a lot of money for expensive dog foods that use plenty of plant protein. It may not be corn, wheat, or soy but peas and lentils are plant sources of protein that reduce the amount of meat protein in your dog’s food.
  • Protein digestibility: Compared to a human, your dog has a very short digestive tract. While it can take food up to five days to pass through your gastrointestinal system, most food will exist a dog’s system between 12 and 30 hours after ingestion. Herbivores (cattle, horses) also have longer digestive tracts. It takes longer to digest plant material than meat. Your dog has strong stomach acids – and an expandable stomach – to help him digest large amounts of meat and bone efficiently. But he is not able to digest plant-based protein as efficiently or to take as much nutrition from it without a lot of additives from pet food companies. With the increase in peas and lentils in dog food, there has been a corresponding increase in enzymes/fermentation products and other supplements in many dog foods to help dogs better digest plant materials that are naturally harder for them to digest. By contrast, protein from animal meat is easier for dogs to digest and doesn’t normally require such additives.

Some animal proteins are harder for dogs to digest than others. Eggs are considered to have the most bioavailable protein and rate at 100 percent digestibility. Muscle meats such as beef, chicken and lamb are also fairly easy for dogs to digest. These are followed by organ meats such as liver, kidney, and heart in terms of digestibility. Fish is moderately easy for dogs to digest. Plant sources of protein such as corn, wheat, oats, rice, and soy are less digestible and have a protein digestibility between 54 and 75 percent. What this means is that even when two dog foods appear to have the same percentage of protein, one food might have protein from a source that is easier for your dog to digest and more available to your dog. That food can provide your dog with better nutrition.

Fats and Fatty Acids

Fats in your dog’s diet come from ingredients such as animal fat and oils from plant seeds such as flaxseed oil and canola oil (from the rapeseed plant). While humans often try to avoid fat in their diet, good sources of fat are important for your dog’s health. They provide a concentrated source of energy that your dog’s body will use before it uses carbohydrates or protein for energy. They can provide over twice as much energy as protein and carbohydrates.

Fats are also the source of essential fatty acids that your dog can’t synthesize in his own body. Dogs have to obtain these essential fatty acids from their diet. The same way amino acids are the building blocks of protein, fatty acids are the building blocks of fats, along with glycerol. Your dog needs these fatty acids to carry necessary fat-soluble vitamins (A, D, E, and K) so the body can absorb them. (Other vitamins are water-soluble and your dog can absorb them without fatty acids.) Fatty acids also help develop the body’s cells, tissues, muscles, and nerves. They help the body produce prostaglandins – hormone-like substances that can reduce inflammation, regulate blood flow and blood clots, and labor during pregnancy. Fatty acids are polyunsaturated fats. The most well-known essential fatty acids for dogs are omega-3 and omega-6, though they can actually be broken down into more specific kinds of fatty acids such as Alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA) for Omega-3 fatty acid; and Linoleic acid (LA), Gamma linolenic acid (GLA), Dihomo-gamma-linolenic acid (DGLA), and Arachidonic acid (AA) for Omega-6 fatty acid.

It’s important that dogs have these essential fatty acids in the proper balance in their diet. Most dogs foods have much more Omega-6 fatty acid than Omega-3 fatty acid. At one time it was thought that the best ratio for dogs was about 15:1 (Omega-6 to Omega-3) but current research suggests that a ratio from 10:1 to 5:1 is preferred. The amount of EPA (Eicosapentaenoic acid) from Omega-3 fatty acid in dog foods is particularly important. Omega-3 fatty acids are often supplied by fish oils such as salmon and herring and by flaxseed. Omega-6 fatty acid can come from chicken or other poultry fats, pork fat, sunflower oil, and vegetable oils such as corn oil and soybean oil.

There is also an Omega-9 which is commonly found in animal fat and vegetable oil. It is not considered an essential fatty acid since dogs can make it in their bodies. Adding it to your dog’s food can actually decrease the amounts of Omega-3 and Omega-6 fatty acids in his body.

The fats used in dog foods are easily digestible and they help food taste and smell good to your dog. They keep your dog’s skin and coat supple, shiny and healthy. And they are necessary for reproduction. Dogs that don’t have enough good sources of fat in their diet can end up with itchy, dry skin and a dull coat. Their immune system can suffer and they can have other health problems.

As with proteins, not all fats are equal. When choosing a dog food you should look for named fat sources. A named fat source would be something like chicken fat. The more specific the source, the better. In some instances fat is included with the protein sources but most dog food companies add fat as a separate ingredient.

While dogs don’t usually have problems with high cholesterol, obesity has become a widespread problem among pets. Some dog foods have very high fat percentages. A dog food that provides 10 to 15 percent fat for a normal, healthy dog is considered to be a good range. If you have an active working dog, a lactating mother dog, or a growing puppy, it’s not unusual to feed a dog food that contains 20 percent fat. Many dogs are overweight or obese not necessarily because of the fat percentage of their dog food but because of overfeeding compared to the amount of exercise they get.

Carbohydrates

Carbohydrates seem to cause lots of controversy among dog lovers but they are a healthy part of the dog’s diet. Your dog uses energy that comes from three major dietary components: carbs, protein, and fats. Dogs require energy for normal daily activities. Growing puppies require more energy. Pregnant and nursing dogs need more. And dogs under stress or doing any kind of heavy work need more energy. Most people probably think that energy comes from the calories in fat – and some of it does. However, some energy also comes from the sugars, starches and dietary fiber found in carbohydrates.

In dog foods you can find carbs in the form of cereals/grains, legumes, and other plant material, including added vegetable matter. Some carbohydrates (absorbable carbohydrates) in the form of glucose and fructose can be absorbed by the dog’s body directly and don’t have to be digested by enzymes. Digestible carbohydrates can be easily broken down by the enzymes in the dog’s gastrointestinal tract. Some starches and dietary fibers, called fermentable carbohydrates, pass through the small intestine to the colon where micro-organisms help ferment them into short-chain fatty acids. Results from some studies suggest that fibers from these fermentable carbohydrates may improve the body’s immune function and help regulate blood glucose concentrations. There are also nonfermentable fibers among carbohydrates, such as cellulose, that don’t provide much nutrition or energy but they can lower the calories eaten by overweight dogs when they are included in dog foods. They act as desirable filler, helping the dog feel full.

Knowing the basic nutrients that all dogs need should help you choose a good diet for your dog. When you factor in his lifestage, size, breed or type, and overall health, you should be able to make good decisions for him. We’ll discuss those factors next.

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