“The Protein Requirement of Adult Cats for Maintenance”, 1984-03 ():
The cat has traditionally been regarded as having a higher protein requirement than other mammals, but research has been hampered by a lack of knowledge of amino acid needs.
This investigation assessed the protein requirement of adult cats through the use of a nitrogen balance technique and the feeding of a semi-purified diet with amino acid levels adjusted to those which have been recently reported to be adequate for kitten growth [Table 1: 0.10% taurine].
Regression analysis of test diets containing ~17%, 13% and 10% protein (in a diet with a caloric density of 5 kcal/g) indicated a level around 12.5% as the requirement, and this protein concentration was then fed to cats for 32 weeks. Nitrogen balance and bodyweights were maintained, and no health problems were observed.
Although lower than previously reported values, this figure is still higher than other mammals’ requirements, and the results provide further evidence that the cat is unable to adapt to a low protein intake.
…The remarkable similarity of the urinary nitrogen outputs for the 3 diets in Phase 1 is a good indication of the cat’s inability to regulate its protein breakdown rate when faced with a low-protein diet. It is this peculiarity which is thought to be mainly responsible for the cat’s relatively high protein requirement.10
In this investigation we had the advantage of being able to adjust dietary amino acid levels to values which are known to be adequate for kitten growth and, therefore, to be more than satisfactory for adult cats. Would it be possible to formulate a commercial diet to 12.5% protein using commonly available raw materials and still achieve a satisfactory amino acid profile? At present, it would certainly be difficult, but it begs the additional question of what is a satisfactory amino acid profile. This aspect of adult cat nutrition has yet to be studied in any detail; but when the information is available, it will be possible to match dietary amino acid levels more precisely to the cat’s requirements. This in turn should make it feasible to formulate diets with crude protein levels at or even below 12.5% which support bodyweight and nitrogen balance in adult cats.