BACKGROUND: Keratinised tissues, such as nails and claws, accumulate hormones over time
the claws' hormone concentrations are being explored as potential biomarkers. Timelines for hormone deposition can be established if claw growth rates are known. Hormone concentration within cat claws has been recently evaluated, yet the growth rates of cat claws remain unknown. HYPOTHESIS/OBJECTIVES: To estimate the growth rate of adult cats' claws, we hypothesised that front claw growth rates would differ from those of rear claws. ANIMALS: Seventeen client-owned, indoor, neutered, adult cats. MATERIALS AND METHODS: Cats' claws were clipped and then measured lengthwise. Claws were repeatedly measured over time with repeat claw trims after approximately 1 month, followed by repeat measurements. Average claw growth rates were calculated for three digit groups: forelimb digit 1, forelimb digits 2-5 (front) and hind limb (rear). Growth rates of the front compared to the rear and digit 1 were compared through linear mixed effects regression modelling. RESULTS: The daily mean claw growth rates were 0.13 mm for front and digit 1, and 0.08 mm for rear. The growth rate of rear claws was significantly lower (p <
0.001) than for front claws
rear claws grew, on average, 0.04 mm less per day than front claws. CONCLUSIONS AND CLINICAL RELEVANCE: Our study provides the first measurement of claw growth rates in cats. The significantly slower growth rate of rear claws compared to front claws should be considered when evaluating metabolites within cat claws.