Validation of Body Condition Scoring as a Screening Test for Low Body Condition and Obesity in Common Marmosets ( Callithrix jacchus )

Assessing body weight is common practice for monitoring health in common marmosets ( Callithrix jacchus ). Body composition analysis via quantitative magnetic resonance (QMR) is a more in-depth assessment allowing measurements of lean and fat mass, but it is expensive and remains unavailable to most. Alternatively, body condition scoring (BCS) is an instrument-free method for visually inspecting and palpating lean and fat tissue. Animals are rated for lean and fat mass abundance, using an ordinal scale with species-specific descriptions as reference. However, modified BCS systems developed for other species are being used, because no BCS system has been fully validated for marmosets. The accuracy of BCS in identifying marmosets with poor body condition or obesity remains unknown. We assessed an adapted BCS for marmosets (n=68, 2–16 years). Objectives were to 1) determine whether BCS predicts body weight and body composition, and 2) evaluate the performance of BCS as a screening test for low body condition and obesity in marmosets, in comparison to QMR body composition analysis. BCS predicted body weight and body composition ( F (15, 166)=7.51, Wilks’ Λ=0.240, p <0.001), and was better at predicting low lean mass and obesity, than at predicting low adiposity. Marmosets with low BCS had higher odds of low lean mass ( B =3.37, (95% CI, 0.95-5.78), OR=29.0, p =0.006). Marmosets with excessively high BCS had higher odds of obesity ( B =2.72, (95% CI, 1.07-4.38), OR=15.23, p =0.001). The accuracy of BCS suggests it can serve as an instrument-free method to screen for low body condition (79.4%-91.2%) and obesity (77.9%) in marmosets.