Validation of a Three-Point Gait-Scoring System for Field Assessment of Walking Ability of Commercial Broilers

Abstract

ABSTRACT A 3-point gait-scoring system used to evaluate broiler walking ability in welfare audits of commercial flocks in the United States was compared with the 6-point Kestin system. In 2 university trials, market-age broilers of 2 commercial varieties were gait-scored by 2 observers for each scoring system. Subsamples of birds were rescored and evaluated in latency-to-lie (LTL) tests. Too few birds had significant walking difficulties in these trials to allow for a good comparison of the 2 scoring systems across all the gait score categories, but the data were encouraging despite sampling limitations. There was a significant association between the 2 systems, and both had substantial between-observer agreement. Both scoring systems had significant correlations with LTL, but the variation of LTL was too high to give gait score or LTL much predictive value for each other. In the field observations, 2 teams of observers scored broilers 47 to 61 d of age on 5 commercial farms each. Two pairs of observers on each team scored the same birds, each pair using the 3-point system or the Kestin system. Broilers with walking problems were oversampled to obtain an adequate number in each gait score category. Weighted κ statistics showed substantial between-observer agreement in each system but more so in the 3-point system, suggesting that the application of the 3-point system was more consistent between observers. Spearman correlations between 3-point and Kestin scores for individual birds indicated good correspondence between the 2 systems. The simplicity of the 3-point gait-scoring system appears to facilitate between-observer agreement, making it preferable to more complex systems for use in commercial animal welfare audits. The correspondence between the gait-scoring systems validates the 3-point system in light of the 6-point Kestin system.