There is some confusion with the nutritional needs of the dog, so it is essential to go back to the origin of the dog to understand the nutritional needs of this specie.
The evidence of genetic proximity between wolves and dogs is found. In a study conducted at the Smithsonian Institute on the molecular evolution of the family of dog is showed that dogs and wolves share 99.8% of mitochondrial DNA. Due to the close genetic relatedness existing between these two species, domestic dogs have been reclassified taxonomically, becoming Canis Familiaris to Canis Lupus Familiaris.
Despite the continuous attempts of humanization of the dogs have been subjected for years by man, the domestic dog has anatomical, physiological and behavioral similarities of their ancestors; the Wolves.
Like wolves, dogs belong to the group of carnivores. Irrefutable proof of this is the adaptation of all its anatomy and digestive physiology to a meat diet; so first of all, the dog is a meat and organs eater.
To understand the nutritional needs of the dog, it is useful to highlight a number of pre particular anatomical features of their digestive tract, which also serve to distinguish the group of omnivores and herbivores.
Dogs lack amylase in saliva, which is a digestive enzyme necessary for degradation of complex of carbohydrates. When this enzyme is not present when dogs are fed by high carbohydrate diets it produces the exacerbation of pancreatic function which needs to produce amylase in sufficient quantity to degrade starch into glucose molecules so they can assimilate. It is in the pancreas where dogs exclusively produce amylase.
Another digestive anatomical characteristic of dogs that gives clarity on their nutritional needs is the fact of present a large, muscular and elastic stomach designed to contain large amounts of food. If we recall the origins of their ancestors, wild animals as predators are eating the most, because they do not know when the opportunity will arise again. Therefore, the dog's stomach is adapted to eat large amount of food in a short time. Furthermore, the stomach of dogs and carnivores maintains a pH between 1-2 because they possess a high concentration of hydrochloric acid. This acid environment facilitates the degradation of proteins and destroys bacteria from the putrefaction of meat, it must be remembered that in addition to carnivores, dogs are opportunistic scavenger’s animals; hence the explanation that some dogs bury food scraps.
As for the intestine, the dogs have a short and simple intestine adapted to rapid digestion of meat. Their gut is ready to give a quick pass to bacteria without giving time to be colonized. The animal fed with high processed feed by carbohydrate, because of not having a prior digestion of starch in the mouth results to the lack of amylase, animals suffer bacterial overgrowth in the gut due to the high availability of sugars that arrive undigested. This bacterial proliferation triggers digestive system in dogs.
So if the dogs are carnivores and their digestive system is adapted to it, why the most commercial foods include high amounts of carbohydrates in its composition?
The big brands of dog food and most pet food manufacturers put on a first place the economic gains, without addressing the nutritional needs of the animal. Thus the inclusion explained in the feed formula of raw materials from processed grains and cereals are low cost and in addition with high-carbohydrate composition.
The natural diet of a dog should be as similar as possible to the wolf. As carnivorous species that requires a diet where the major component is consist of protein of animal origin, otherwise if act against this their particular digestive anatomophysiology, the dog will present difficulty to digest foods rich with carbohydrates complex as rice, cereals and vegetables. The absence of salivary amylase makes these carbohydrates escape a pre-digestion process that takes place in the mouth, so they take longer to be digested and it is not until they reach the pancreas when they are degraded. Consequently they suffer with overstress and that could lead to future diabetes. Therefore, if the composition of the diet of our pet abound sugars we are forcing its digestive system to work more and that is where digestive problems, endocrine, dermatological and allergy sufferers and others appear. It is important to have this nutritional aspect very present, since not all dogs have the same level of carbohydrate tolerance contained in commercial feeds. The solution of this problem would be feed the pet with food 100% natural, guarantee highly protein composition or administer in feed an enzyme supplement to compensate the lack of digestive enzyme.