Cats are obligate carnivores and need some essential nutrients only found in animal sources, therefore they cannot be fed a vegetarian or vegan diet. Dogs on the other hand, being omnivores can adapt to a well-balanced vegetarian or even vegan dog food diet. However, these types of diets might be deficient in many important nutrients, therefore you should always consult a vet or animal nutritionist if you're considering feeding your dog this kind of diet.
• Cats have high requirements for protein and amino acids which their bodies breakdown very rapidly. If resources run low, they are unable to reduce the rate of breakdown that makes them particularly sensitive to deficiencies.
• Taurine (an amino acid only found in animal-based proteins) is particularly important in cat nutrition as its deficiency can lead to blindness and/or heart failure. It's difficult for a cat's body to produce enough taurine to meet their needs, therefore they require a dietary supply which is found exclusively in animal tissue. Although synthetic supplements are available, these can vary in their effectiveness and any defficiency can be immediately deterimental to your pets' health.
• Arachidonic acid (an essential fatty acid) is another example of a nutrient required by cats which is only available from animal sources, along with preformed vitamin A (retinol), as cats cannot utilize sufficient quantities from the pro-vitamin A of vegetables.
• Cats also need to sustain good levels of vitamin B12, naturally found in meat.
Dogs are classified as omnivores, this means that dogs are able to obtain all of their nutritional needs from either meat or plant ingredients and can adapt to a well-balanced vegetarian diet for dogs. Both vegetarian and vegan dog food diets should be carefully checked by a vet or animal nutritionist, as they may be deficient in some amino acids, vitamins and minerals.