Millions of years of evolution have designed the ideal hunters, dogs and cats, with bodies designed to catch, kill and derive all their nutritional needs from prey, let's look at some of those features.
These fabulous carnivores have a strong jaw with impressive crushing power filled with various teeth, each with a distinct function. The large canines, distinctive in their long shape, are great for holding their prey firmly, behind them sit large premolars and molars great for ripping flesh off bone and breaking chunks down into manageable sizes. The small incisors to the front are perfect for nibbling little morsels of meat off the bone[1].
Fig 1: Skull of an adult dog showing permanent teeth[2].
Like people, dogs and cats are monogastric meaning they have just one stomach. This acts like a super stretchy holding tank for the prey eaten while cells on the stomach wall release hydrochloric acid and enzyme precursors to create a great acidic gastric mix to digest the animal protein and destroy any bacteria[3].
From the stomach, this lovely acidic gastric mix makes its way to the small intestine where enzymes tailored to breaking down animal protein get to work, they break down the food into small enough molecules to be absorbed with other organs acting in support of this process with more enzymes joining the mix.
Fig 2: Digestive system of the dog.[4]
The small intestine does not contain any enzymes capable of digesting cellulose, the cell wall surrounding all plant matter. Their digestive system is 100% geared toward eating live prey. The only plant matter that cats and dogs can digest and obtain nutrients from, is that which already has the cell walls split open or digested, for example when they eat the partially digested gut contents of their prey. Intact plant matter simply moves through to the large intestine undigested with the rest of the waste. Great if your dog is on a diet, not so great if they’re relying on the plant matter for their nutritional requirements[1].
The large intestine is where any excess liquid is absorbed leaving just the waste to be expelled from the body. For those eating a diet of meat, bones and organs the digestive system is very efficient at digesting and absorbing all the nutrients with very little waste to be expelled, it’s always easy to spot (and smell) those not on a species appropriate diet by what they leave behind[3].
Sources
[1] Billinghurst, I. (1993). Give your dog a bone. Australia: Warrigal publishing. [2] Smith, R. N. (1991). Anatomy and Physiology II, The digestive system. In Lane, Jones's Animal Nursing, 5th edn,. Pergamon press, Great Britain. [3] Syme, B. (2011). Scientific Guide to Natural Nutrition. Soutbank, Australia: Vets all natural Pty Ltd. [4] Newman, S. (2018). Manipulation / Retouching. Retrieved from The Illumination Sorceress: https://www.illuminationsorceress.com/galleryGD.html
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