Assessing leg health in chickens using a force plate and gait scoring: how many birds is enough?

Meat chickens from experimental flocks were tested repeatedly from three to six weeks of age using gait score (GS) and force plate (FP) techniques, and the findings were related to postmortem results for leg health. This initial study indicated that five weeks was the optimal age to test birds using the FP to indicate abnormalities and pathologies. Birds (n=492) with a range of walking styles were then selected at five weeks of age from three commercial flocks, gait scored and tested using a FP. A subsample of these birds (n=191) was examined postmortem, and relationships between leg abnormalities and pathologies, GS and FP results were investigated. Models of leg abnormalities and pathologies with GS or FP measurements as covariates left much variation unexplained; hence, the number of birds that would need to be tested using these methods to assess the flock prevalence of leg abnormalities or pathologies is high.