Reliability of body condition scoring using the Rabbit Size-O-Meter in companion rabbits (Oryctolagus cuniculus)

Background: Body condition scoring systems are commonly used to monitor adiposity in companion animals, but their reliability in rabbits remains unvalidated. This study assessed the inter- and intra-rater reliability of the five-point Rabbit Size-O-Meter (RSOM) scale in a diverse rabbit population by raters of varying experience.
Methods: Using the RSOM, 205 rabbits were scored by veterinary professionals (n = 3), master's students (n = 2) and laypersons (n = 2). Inter-rater reliability was analysed using Krippendorff's alpha, and intra-rater reliability was analysed using Cohen's kappa. A linear mixed-effects model was used to evaluate the effects of age, sex and breed on rated body condition.
Results: Overall inter-rater reliability was poor (α = 0.58). Agreement among veterinary professionals was moderate (α = 0.72) but decreased for students or laypersons. Intra-rater reliability ranged from substantial to almost perfect (κ = 0.69‒0.90). Body condition score decreased with age (p = 0.043) and was affected by breed (p = 0.012).
Limitations: Intra-rater reliability was assessed in 10 rabbits. The RSOM was not validated against objective measures of adiposity.
Conclusions: Intra-rater reliability of the RSOM was high but inter-rater reliability was limited. Modifying the body scoring system and validating the RSOM against objective measures of adiposity are recommended.