Measuring body composition in dogs using bioelectrical impedance spectroscopy

Assessment of body composition is an essential aspect of veterinary canine care, particularly as prevalence of overweight and obesity in dogs is increasing. Few quantitative objective methods for body composition measurement are available for routine clinical use. Bioelectrical impedance analysis is widely used in human medicine and nutritional assessment and although it has shown promise in production animals it has not yet been adopted for companion animals. The present study validated bioimpedance spectroscopy (BIS) against the reference method of dual-energy X-ray absorptiometry. Resistivity coefficients for use in BIS were determined: ρe = 444.8 and ρi = 1477.8 ohm.cm and used to predict fat-free mass (FFM) in a cohort of 35 mixed breed dogs. Overall, FFM was predicted to within 3.5% of reference values. At an individual level, FFM was predicted within 2 standard deviations (95% confidence) of 10%. BIS provides an objective quantitative alternative to the widely used semi-quantitative body condition scoring. In addition, BIS provides estimates of body water volumes (total, extra-and intracellular), information that can be useful in fluid management. BIS is inexpensive, and simple to perform but does require brief (<5 min) sedation of the animal.