The dog’s physiology matches the wolf and is so close to the wolf ( Canis Lupus) that the Smithsonian reclassified the dog in 1939 to Canis Lupus Familiarise. 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 (; 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 carnivores, and wild domestic dog / dingo hybrids of Australia are strict carnivores.
Biology doesn’t lie and though dogs come in different shapes and sizes, their basic physiology hasn’t changed. Regardless on whether the breed is a chihuahua or a Rottweiler, all dogs are carnivores. Descendants of the wolf, designed to eat raw meat and bones.
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. This does not occur in carnivores e.g. dog and cat. The food is held in the mouth for a very short time before it is swallowed.
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.
Figure 1: The Skull of an adult dog showing permanent dentition*
Incisor :Fine nibbling and cutting meat: often used for delicate grooming
Canines:Holding prey firmly in the mouth
Premolars: Shearing flesh off the bone using scissor like action: flattened surface helps to chomp up the flesh to facilitate swallowing and digestion
Molars: Shearing and chomping meat
Carnassials Very powerful teeth sited close to the angle of the lips: this type is only found in carnivores
Stomach
“…….The dog has a simple, very acidic gut, typical of a carnivore, designed to process large quantities of meat and bone. At it’s most acidic (during digestion) the dog’s gut can reach below Ph1.0, equivalent to car battery acid, a level it can remain at for 5 hours (Itoh et al. 1980, Sagawa et al., 2009). Youngberg et al. (1985) found the average gastric pH of dogs ranges from pH1.5 ranging to pH2.1 a couple of hours after consuming a meal, when gastric juices would be in full flow. At this sort of acidity a meat and bone is rapidly broken down, often reduced to chyme within an hour (Lonsdale, 2001). Furthermore this acidic environment is inhospitable to all but the most specialized of microbiology, protecting healthy scavenging dogs from common meat-borne pathogens such as Salmonella and E. coli. Great quantities of mucous protect the dog from doing itself damage. Post-digestion the stomach will abruptly change to neutral, presumably to neutralise the corrosive acid before it hits the duodenum and intestines that are less equipped to withstand the corrosive power of a pH1 acid broth.
Length of GI Tract
The digestive system of the carnivore is described as mono-gastric. The tract is relatively short, as meat is easy to digest 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
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.