Research note: top-view walking features as proxy for walking ability in broilers and their potential use in breeding

Impaired walking ability is a welfare concern that affects many broilers. Walking ability can potentially be improved through genetic selection, but this requires objective data on large numbers of broilers in the breeding program. Here, it was studied whether top-view video recordings of broilers in a walkway can provide insight into walking ability. Five walking features were analysed from the videos for 595 female, pure-line broilers: 1) lateral body oscillation (LBO), 2) number of steps taken (STEP), 3) mean overall speed (MEAN_SPEED), 4) maximum forward moving speed (MAX_SPEED), and 5) maximum forward acceleration (MAX_ACC). Birds' gait scores (GS) were furthermore manually assessed (n = 153 with GS1; n = 344 with GS2; n = 87 with GS3 and n = 11 with GS4) and the heritabilities of the manual GS and the top-view derived walking features were estimated. The walking features all differed between GS groups, with a higher level of LBO in GS2 birds than in all other GS groups and a decrease in MEAN_SPEED and MAX_SPEED with increasing GS from GS1 to GS3. MEAN_ACC was lower for GS3 than GS1 birds. An interaction effect between body weight and GS was furthermore observed, in which - within the different body weight levels - higher GS levels were associated with more steps taken. Moreover, LBO, STEP, MEAN_SPEED and manual GS were found to be low to moderately heritable in broilers. Overall, the results of this study indicate that top-view derived features can provide insight into broiler walking ability and these outcomes can contribute to breeding for improved walking ability in broilers.