When cats, as strict carnivores, catch their prey, they often eat them with skin, bones, etc. These tissues behave as “animal fibre”. The current methods to analyse fibre in a diet only detects fibre from plant origin and not from animal origin, mainly because the latter consists of protein. Therefore, the high protein intake in the wild may be incorrectly translated to petfood requirements, whereas the fibre requirement may be underestimated. Cats often have health problems similar to captive specimens of another feline, the cheetah. In captive cheetahs fed whole prey, less toxic metabolites are formed by protein fermentation than when fed highly digestible meat with no fibre sources. The aim of this study is to determine if animal-based fibrous food will also have a beneficial influence on the health of cats. This project will optimise a method to analyse all fibrous matter in diets. This method will be used to more accurately analyse the fibre content in cat diets, and will allow the reconstruction of the proportion of dietary fibrous matter in nature. These results will be a reference to create a cat diet with a natural content of dietary fibre; the hypothesis is that such diets may bring a long-sought solution for some of the inflammatory diseases occurring in domestic cats. The project will evaluate this hypothesis by comparing such a “natural fibre” diet with a standard commercial cat food on their effect on inflammation, renal health and overall digestion features.