Short communication: An observational study investigating inter-observer agreement for variation over time of body...

Body condition score (BCS) is strongly correlated with energy reserves. The ease, rapidity of scoring, and high intra- and inter-observer repeatability make it a widely used herd management tool in bovine practice and in scientific studies. Loss or gain of BCS, rather than a single BCS measurement, is frequently used to monitor energy balance in dairy cows. It is unknown if the difference between 2 BCS measures taken at different moments (ΔBCS) would demonstrate inter-observer agreement similar to that of a single BCS measurement. The objective of this study was to compare inter-observer agreement of BCS and ΔBCS in dairy cows when multiple observers perform data collection. An observational study was conducted between April and September 2015; 3 observers independently assessed BCS of 73 Holstein cows from 1 commercial dairy herd. Body condition score assessments of the animals were performed between 1 and 20 d in milk (early lactation; exam 1) and again between 41 and 60 d in milk (peak of milk production; exam 2). Quadratic weighted kappa (κ_w) was computed to quantify agreement between observers for single BCS measurements and ΔBCS. For single BCS measurements, κ_w of 0.79 (95% CI: 0.69, 0.85) and 0.84 (95% CI: 0.77, 0.89) were obtained for exam 1 and exam 2, respectively. Such values would be interpreted as strong agreement and are consistent with the available literature on BCS repeatability. When computing agreement for ΔBCS, a κ_w value of 0.49 (95% CI: 0.32, 0.63) was obtained, suggesting moderate agreement between observers. These findings suggest that studies investigating single BCS measures could use many observers with a high degree of accuracy in the results. When ΔBCS is the parameter of interest, more reliable results would be obtained if one observer conducts all assessments.