422 The use of 3D kinematics for improved gait assessment in broilers

Abstract Genetic selection for high growth rates in broiler chickens has resulted in larger broilers and changes in broiler gait. Traditionally, broiler gait is assessed using visual observation which is subjective and labor intensive. In contrast, newer technologies are available which can be adapted to objectively score changes in broiler gait, thereby, increasing the validity and reliability of gait scoring with less labor required. The objective of this study was to compare the use of 3D kinematics versus visual scoring to assess broiler gait. Second, to determine how strain and age affect 3D kinematic gait metrics in broilers. Four strains of broiler chickens were used; two heritage strains: 1957 (H57; n = 52) and 1977 (H77; n = 51); and two commercially available strains: Cobb (n = 50) and Ross (n = 53). All broilers were weighed weekly throughout the study. Kinematic markers were placed along the spine and bony landmarks of each leg. Commercial strains had kinematic recordings and body weights (BW) recorded every week for 4 wk while Heritage strains had measurements recorded every week for 6 wk. Visual gait scoring was completed using a 5-point scale each week by two trained observers. Data were analyzed using the correlation procedure in SAS to determine the relationship between visual gait score and kinematic metrics as well as the GLIMMIX procedure to determine the effects of strain, age, and strain x age on all gait parameters. There was a weak positive correlation (r < 0.2) between visual gait score and all kinematic metrics. Cobb were the heaviest strain (1,292.6 ± 14.71 g P < 0.001) while H57 broilers were the lightest (326.4 ± 9.99 g P < 0.001). Each week, the BW of all strains increased significantly. Total Stride Time differed significantly by strain (P < 0.001; Cobb: 26.3 ± 0.47 cs, Ross: 23.1 ± 0.39 cs, H77: 23.7 ± 0.28 cs, H57: 21.5 ± 0.26 cs) and Age (P < 0.01; Commercial: wk 3: 21.8 ± 0.54 cs, wk 6: 28.1 ± 0.68 cs and Heritage: wk 3: 19.7 ± 0.42 cs, wk 8: 25.4 ± 0.52 cs). Total stride length (SL) also significantly differed by strain. Cobb had the longest SL of the two commercial strains (P < 0.001; 88.6 ± 1.94 mm) while H77 had the longest stride of the heritage strains (97.9 ± 1.51 mm). Total SL also increased with age resulting in longer stride times. Heavier birds, such as Cobb, had longer stride Times and SL compared with lighter birds such as the H57 strain. In conclusion, visual gait score and kinematic metrics were not found to be measuring the same things. However, kinematics can be a used as an informative and objective tool for assessing gait metrics associated with broiler lameness such as changes in stride length and stride time.