We all know dogs aren’t herbivores! Just a small whiff of a sausage or burger at a barbecue can turn your peaceful puppy into a delighted doggy. Bounding up to you and your friends, pleading for a taste; it’s enough to ruin even the most low-key social event. But just because they eat meat, does that make them a carnivore? Or could they be omnivores? This has become a key topic discussion as more and more pet owners want to explore a vegetarian lifestyle for their pets. But is a vegetarian diet enough for your best friend?
Carnivores and Omnivores
I’m no scientist, so if you are anything like me a small refresher on the exact differences between carnivores, omnivores and herbivores might be helpful. Although it might seem obvious, there are some contentious issues that make some animals difficult to place.
- Herbivores are animals who eat only plant matter. Think of bunnies chewing on carrots, horses munching on hay and cows grazing on grass.
- Carnivores eat animal matter. In the wild, this conjures up pictures of a lion preying on a gazelle or a pack of wolves devouring a deer together. But the reality can be more complex. Cats, for examples, are carnivores who need protein to survive, but some cats also occasionally enjoy certain grains and vegetables.
- Omnivores need a varied diet of both animal and vegetable matter. We humans are omnivores and, although it is an unflattering comparison, so are pigs. Historically, dogs have been put into this category.
Why Is There Some Disagreement?
Unsurprisingly, there is a lot of crossover between pet owners and vegetarians, as both are often animal lovers. As vegetarianism and veganism grows, more people are considering ways they can further cut animal products out of their lives. Lowering your household meat intake can help the environment, as well as promote the ethical treatment of animals. But your pets often have different biological needs from humans and going fully animal-product-free might not be feasible.
Cats, for example, are carnivores who need a protein-rich diet, regardless of additional grains and vegetables they can consume. Dogs, however, have traditionally been seen as omnivores. This suggests you could cut out meat and other animal products quite easily. But the truth might be a little more complex. Lots of people have really strong opinions on both sides of this debate and the online message boards on the topic are full of capital letters and exclamation marks. So what are the arguments for either side, and what do we suggest?
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Being an Omnivore
Historically, dogs have been seen as omnivores. This isn’t just because they can eat some grains and vegetables. After all, cats can do that too. There are some genuine physiological signs that dogs are designed for the consumption of plant products.
- Their ancestors occasionally eat grains and berries
Dogs are descended from wolves and, while they might be carnivores, their diets can be as complex as cats. In the wild, they clearly mostly hunt and eat animals, but it has been suggested that they can eat grains and some berries. There are even reports of wolves in captivity eating vegetable matter found in the stomach’s of their prey. Scientists disagree about whether this is normal behaviour in the wild, but it indicates that wolves may have the capability and occasional hunger for non-animal-products.
- They’ve further adapted to better handle grains
While wolves simply occasionally eat grains, recent studies have compared the genes of the two species and found that dogs have crucial genetic differences that make them better able to digest the starch and glucose found in grains. A similar comparison has been made between the genetics of hunter-gatherer humans, who had meat-rich diets, and pastoral, farming communities, who switched to consuming the grains they were growing. Specifically, dogs have more of a gene called AMY2B, which helps break down food by producing amylase, and they have another gene which facilitates breaking down maltose into glucose.
- They don’t have the intestines of a carnivore
An easy physiological way to tell the difference between omnivores and carnivores is intestine size. The complexity of plant matter compared to animal matter means that plant matter needs more time to digest. Therefore, carnivores have shorter intestine and herbivores have longer intestines. Omnivores similarly will have fairly long intestines to process plant matter. Dogs tend to have longer intestines, suggesting that they have evolved away from their carnivore ancestors to become omnivores.
Being a Carnivore
It is easy to see why dogs have traditionally been classified as omnivores when you compare them to wolves. Their ancestral history, their genetics and their biology all suggest elements of plant matter consumption. However, not all scientists agree and it is worth considering the other side of the debate to see why dogs could be considered carnivores.
- Evidence of wolves eating grains might be a myth
There is a lot of controversy surrounding the recorded observations of wolves. For example, that famous study of alphas, betas and omega roles in a pack has since been thrown out and even the very scientist who first suggested it has since rescinded his findings. Similarly, it is possible that only wolves in captivity consume grains and vegetation. In an attempt to settle the controversy, one researcher called Dr Hendriks did a literature review to find the source of the rumour that wolves have eaten the stomach contents of their prey, and couldn’t find anything. This suggests it is a myth, and that the more common observation of wolves throwing out the contents of their prey’s stomachs is a more reliable hypothesis.
- You can’t just look at intestines
Intestine length is too simple as a measure of digestion. You should also take into account the girth of the intestine to create a more accurate measurement of digestive surface area. The best measure is the coefficient of fermentation. This takes into account the animal’s ability to extract nutrition through fermentation. Herbivores have a high coefficient of fermentation, while carnivores have a low coefficient. Ultimately, both the total surface area of intestines and the coefficient of fermentation in cats and dogs is similar and suggests they are both carnivores.
- Dogs still have many more carnivorous physiological traits than omnivorous
While genetic and physiological differences from their carnivorous ancestors cannot be denied, there are still many more carnivorous traits that remain in dogs than omnivorous or herbivorous. These include:
- Their metabolisms. Wolves and dogs are both designed to have long breaks between meals. Considering they have to hunt their food, this makes sense. As some weeks a pack might only successfully hunt a couple of animals, there is no way they could sustain hunting two or three meals a day like we humans do. Dogs can similarly survive up to five days without eating, although this doesn’t mean it is okay for you to forget to feed your best friend! It is also important to note that although dogs produce amylase for breaking down grains like other omnivores do, it is not in the same location. Instead of being produced in the mouth as saliva, the amylase is added in the pancreas, suggesting a secondary function and importance.
- Their teeth. Dogs still have teeth designed for tearing at meat and crushing bones. While humans can have pointy canine teeth, they are small and underdeveloped. Dogs continue to have the powerful jaws and sharp teeth of a carnivore, which suggests that is exactly what they are. Similarly, their jaws chop up and down, and not side to side. This is because they need to tear chunks of meat, rather than mush and grind grains.
- Their behaviour. Digging, biting, and pouncing are typical examples of persisting carnivorous behaviour in dogs. These behaviors are innate to their carnivorous ancestry as wolves and pack animals who hunt. Wolves dig to bury food for later, and biting and pouncing are obviously essential for hunting. Even when your pup nips at your toes, this is typical carnivore behaviour. You won’t often see a cow playfully nibble someone’s fingers.
Ultimately, scientists like Dr Hendriks believe that dogs have inherited an adaptive digestive system and metabolism from their wolf ancestors. The same systems that allow wolves to survive days without food and digest grains and berries in times of need, has allowed dogs to adapt to domestication. But, this doesn’t change their biological carnivorous traits.
The Case Against Vegan or Vegetarian Doggy Diets
It is clear that this is a confusing and contentious issue with no absolute clear answer. Therefore, it might be safer to keep animal products in your dog’s diet, as it has been for thousands of years. It is certain that dogs are not herbivores, even if they might be omnivores. Both omnivores and carnivores generally eat some meat, even if they don’t need it in every meal.
Dogs really need the vitamins and amino acids that come from meat. Collagen, keratin and elastin are just some of the vital building blocks for healthy joints, skin and muscles. Similarly, their digestive system does process animal matter better than plant matter. This suggests that meat is necessary for your dog to get the right amount of nutrients. Cutting anything out means you have to carefully consider how to replace it.
It is worth also noting, however, that lots of fatty meats, like sausages and chicken, is also very unhealthy for your pet. Wolves may have eaten fatty animals, but they also had to hunt those animals and would feast on them before potentially surviving many days without any food. Being domesticated means dogs have a certain lifestyle of regular feedings and daily, gentle exercise that should inform their diet.
Therefore, the easiest and simplest way of feeding your dog is to offer them a balanced diet of grains and not-too-fatty-meats. Fruits, vegetables, meats and grains all offer specific minerals, vitamins and amino acids that your dog needs. Finding replacements for any of these is a challenge. It is more important that you know what foods are poisonous to your dog within each food group so you can avoid them.
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Be Careful And Ask Your Vet
We don’t want to condemn any owner who does try a vegetarian or vegan doggy diet. It can be a ethical and healthy option under the right circumstances. Even if dogs are not naturally herbivores, they might be able to successfully eat, digest and enjoy a plant-based diet. Some dogs have lived on vegan or vegetarian diets and survived for many years.
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One notable example is Bramble, the border collie who turned 27 in 2002 after years of living on lentils, organic vegetables and rice. This doesn’t mean it will necessarily be the perfect option for your dog, so if you are very passionate about trying a vegetarian diet, consult with your vet. Be prepared to take their advice and don’t expect to be able to change everything overnight. You might have to settle on simply lowering their meat intake to improve your households ecological footprint.
If you do decide to try and change something, do it carefully. Start gradually and watch their behaviour and health closely. If you see any gastrointestinal issues or skin problems, seek help as soon as possible. You might also want to consider vitamins and supplements. There are important amino acids and vitamins that are in protein sources that you might need to replace, including:
- Vitamin D