Falciform fat:femur length ratio provides a novel method for objective postmortem estimation of total body fat in overweight and obese cats

Determination of the nutritional condition, including estimation of amounts of total body fat (tBF), at routine postmortem examination of cats is typically based on subjective visual assessment. Subjective assessment may result in uncertainties regarding degree of overweight, and objective methods that provide a numerical value reflecting the tBF could be valuable to accurately judge excess body fat. We investigated if the falciform fat pad weight (FFPW) was correlated to tBF and could be used to detect overweight and obesity in cats. The FFPW and the femur length (FL) were recorded at postmortem examination in 54 cats and the FFPW:FL ratio (FFR) calculated. Each cat was additionally assigned to a fat category (FC) according to subjective assessment. Computed tomography was used to determine tBF as the body fat percentage (%BF), the body fat volume (BFV), and BFV normalized to animal size (nBFV) in 39 cats. There was strong correlation between the FFPW and the BFV (r = 0.888) and between the FFR and the nBFV (r = 0.897). The correlation between the nBFV and %BF was very strong (r = 0.974). Using a lower FFR cutoff value of 3.5 for obesity and 1.6 for overweight, there was a discrepancy in FC between using the FFR and subjective assessment in 6 of 54 cats (11%). We conclude that the FFPW increases proportionally with tBF and that the FFR provides a method for objective tBF estimation. We suggest introducing the FFR to feline postmortem examination protocols as an objective estimate of tBF.