According to the USDA nutrient database:
A whole raw broiler chicken is 15.5% protein
Raw chicken liver is 15% protein
A whole raw turkey is 22% protein
A beef shank is 21% protein
Raw beef liver is 20% protein
Raw beef tripe is 12% protein
A whole raw egg is 12% protein
Keep in mind that the USDA nutrient database does not include the nutrients contained within the bone content because humans aren't generally eating bones.
As fed, meat is made up of mostly moisture. Think about it...the human body is made up of around 60% water. All mammals (which make up the majority of the components of a raw feeding diet) are similarly made up of a large percentage of water. This is also why cats and dogs eating a raw diet will drink much less water than their kibble fed counterparts.
Edible bones generally comprise 10% or more of a raw fed animals diet and contain little in the way of digestible protein. Bones contain 65 to 70% hydroxyapatite, which is a compound made of 10 parts calcium, 6 parts phosphorus, 26 parts oxygen and 2 parts hydrogen. Essentially...calcium and phosphorus (minerals).
The remaining one third of the bone is comprised of 95% collagen (a fibrous protein) which is poorly digested by cats and dogs. Besides being found in bone, collagen is also abundantly present in tendons, ligaments, skin, cartilage and stomach tissue (tripe). Whereas, there is high a digestibility of raw muscle meat (92%), organ meat (90%) and eggs (100%).
Raw Chicken Backs as Fed: Raw Chicken Backs on a Dry Matter Basis
Crude Protein (min) 10% Protein 19.6%
Crude Fat (min) 36% Fat 70.6%
Crude Fiber (max) 1% Fiber 1.9%
Moisture (max) 49% N/A
Raw Turkey Grind as Fed: Raw Turkey Grind on a Dry Matter Basis:
(meat, bone & organ)
Crude Protein (min) 14% Protein 51.8%
Crude Fat (min) 6% Fat 22.2%
Crude Fiber (max) 1% Fiber 3.7%
Moisture (max) 73% N/A
Ash (max) 4.6% Ash 17%
As you can see raw diets are certainly not "all protein" diets. Raw flesh, bone and organ is the time tested natural diet for for cats and dogs and the protein level is not harmful to the animal eating it. On the contrary it is required for optimal health.
This blog post was inspired by wrong information being proclaimed (where else) on the internet. It is very frustrating to see so much incorrect information flying around which is quite misleading to pet owners.