Carnivore and not an Omnivore (proven by science and not anecdotal)

The dog’s physiology matches the wolf and is so close to the wolf ( Canis Lupis) that the Smithsonian reclassified the dog in 1939 to Canis Lupis Familiaris. Extensive genetic analyses of the dog and other wolf-like canids clearly show that the dog is derived from gray wolves only, rather than jackals, coyotes, or Ethiopian wolves (Fig. 1C; Wayne et al. 1987a,b; Vila et al. 1997, 2005; Leonard et al. 2002; Savolainen et al. 2002). Consequently, the immense phenotypic diversity in the dog owes its origin to primarily the standing genetic variation existing in the ancestral population of gray wolves and any subsequent mutations that occurred during the brief history of domestication. All 37 of the other wolf descendants are absolute carnivores, and wild domestic dog / dingo hybrids of Australia are strict carnivores.

Because the dog is able to survive on plant-based foods and garbage scraps the erroneous assumption that dogs are omnivores has been propagated by pet food companies and councils sponsored by them. Dogs are facultative carnivores – occurring optionally in response to circumstances rather than by nature. The evidence is available to the eye, without even have to read reams and reams of opinion and conjecture.

Gastrointestinal System:

Lack of salivary amylase in carnivores. Amylase is a digestive enzyme  that the body needs to convert plant based starches into sugars. Amylase is found in the saliva of herbivores and omnivores to begin the breakdown of starches  as soon as the plant matter enters the mouth.

Dentition:

The teeth of the Carnivore  are adapted shearing and tearing the flesh off their prey. to rip and tear meat from the bone and then gulp it down for further digestion in the stomach. The canine teeth are long, pointed and sharp to allow deep penetration into the prey.  The mandibles articulate with the temporal bones of the skull forming the temporo-mandible joint. In carnivores the action of the joint is scissor-like to shear flesh off the bones of their prey. The teeth also have a tight inter-digitation to lock in place to allow the carnivore to rip the flesh away from the prey. There is little to no grinding – the meat is mechanically broken down by only two or three chomps of the molars before the food is swallowed. 

Herbivores such as horses and cattle, have long, large, wide molars with flat surfaces to allow for proper grinding of their high fiber plant source diets. This grinding breaks down plant material into smaller, more usable matter.

Figure 1: Skull of an adult dog showing the permanent dentition*

* Introduction to Veterinary Anatomny and Physiology

Length of GI Tract

In omnivores and herbivores digestion of the carbohydrates beging in the mouth with the secretion of salivary enzymes. This does not occur carnivores e.g. dog and cat. The food is held in the mouth for a very short time before it is swallowed

Herbivores have the longest GI tracts, at about 100 feet in length. Their GI tract includes areas for the fermentation of cellulose, which is difficult to break down. Even after the mechanical breakdown of grasses by the grinding teeth and salivary amylase, and the further breakdown by the stomach acid and its digestive enzymes, the cellulose may still need to be fermented in the rumen or the cecum.

Omnivores such as humans have medium length GI tracts of about 20 to 40 feet. The appendix is actually the remnant of a fermentation system in the large intestine.

The digestive system of the carnivore is described as monogastric. The tract is relatively short, as meat is easy to digeste and the stomach is simple.  Cats have the shortest GI tracts of all the species, at 12 to 15 inches. This is because carnivores typically eat easily digestible food such as meats. The canine GI tract is also quite short, at about two feet. This is drastically shorter than the herbivore but also much shorter than the omnivore. Neither the cat nor the dog has an area of the GI tract where the fermentation of cellulose can take place. A carnivore wouldn’t need it. Gray wolf, dingo and domestic dog have a gut length 3.5 -4.2 times body length – absolute carnivores