Vegetarianism in dogs is a controversial subject, as many believe that our largely carnivorous canine friends should be fed a species appropriate diet that contains a generous proportion of ingredients derived from animal sources, and lower or minimal levels of those derived from plants. It is widely considered that although dogs are not obligate carnivores (unlike cats) who can survive on a vegetarian or vegan diet, it is not as biologically appropriate for them as a meat or fish (or even egg) based diet. The main reason being, that meat, fish and eggs have a higher nutritional value to the dog; meaning that these ingredients supply nutrients that are more effectively digested, absorbed and ultimately assimilated within the canine body.
Despite its controversial status with many dog owners, there are however some cases when a vegetarian or vegan diet could legitimately be required. These may include households where family members are unable to handle animal based products due to very strict ethical reasons, or handle certain meats due to religious reasons. Some dog owners disapprove, but as dogs can and do fare well on (properly formulated) vegetarian or vegan diets, it should remain a viable option and an owner’s ethical and religious stances respected. Another situation where a vegetarian or vegan diet could be necessary is when a dog suffers from multiple allergies to meat proteins. This is actually becoming more of a problem, because with so many owners choosing to feed such a variety of different meat sources, including exotic options simply by preference rather than by necessity, it can make it very difficult to find a suitable exclusion diet containing a novel protein source that the dog has never eaten before should dietary allergies arise. This is where vegetable based prescription diets may benefit the dog’s health. One other case where a vegetarian diet could be beneficial is in a dog with a very severe proliferation of urate crystals. Dogs suffering from this condition require a diet which is low in purine rich ingredients. Most meats and fish have a moderate purine content and may be acceptable for a dog with a milder proliferation, but egg is the only truly low purine animal based protein source which can limit options.
The Vegetarian Society defines a vegan as “a strict vegetarian who does not eat any dairy products, eggs or honey.” Nutritional guidelines for vegans are essentially similar to those for vegetarians. However, vegetarians gain certain nutrients from dairy products and eggs. Vegans need to ensure their diets contain plant food sources of these nutrients. A vegan diet can thus be described as one which excludes meat, fish, eggs, dairy products, and any other ingredient derived from animal sources or foods that have been processed using animal products.
There are only a few commercial pet food manufacturers who produce vegetarian dog food and even less who produce vegan dog food. These products tend to rely on a larger proportion of whole grains (which include the protein fraction) and protein-rich legumes such as soya beans. It is generally important that these diets provide several different protein sources to ensure that the amino acid profile is correct for the canine species. Dogs require 23 different amino acids, and whilst they can manufacture 13 of them, 10 need to be provided by the diet. These are: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. If just one amino acid is missing, the entire protein manufacturing process fails which illustrates just how important it is to supply every single one at the correct level. This is why home-prepared vegetarian or vegan diets for dogs require special expertise to formulate, and for the average pet owner it is better to purchase a commercial feed which can guarantee nutrient values at the correct parameters. Protein from animal sources does supply a more favourable amino acid content, but it is still possible to provide the correct levels via a carefully considered combination of vegetable proteins.
The primary fat source in the vegetarian or vegan dog food is usually soybean oil, which is rich in Omega-3 fatty acids. However, this is in the form of inactive alpha-linolenic acid (ALA) which needs to be converted to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to be of nutritional benefit. Therefore, animal based oils such as salmon oil or krill would represent a higher nutritional value as they supply a more easily utilised source of EPA and DHA. While plant based oils and fats may be considered the “poor relation”, dogs can digest and derive energy from plant, seed and nut oil.