The relationship between trailer motion and carcass bruising in market cows during transport
Increased trailer motion, coupled with large accelerations and decelerations, have been associated with decreased carcass quality and increased stress indicators in cattle, sheep and hogs. However, motion of livestock trailers has not been measured in North-American cattle semi-trailers over long distances (>1000 km). The objective of this study was to describe the acceleration within each of the 5 compartments of a cattle semi-trailer and to determine the relationship between trailer acceleration and bruising severity. The root mean square (rms) of acceleration was measured at a sampling rate of 200 Hz in 3 orthogonal axes; x (vertical, positive upward), y (front-to-rear, positive forward) and z (lateral, positive leftward as viewed from rear) by rigidly clamping an accelerometer to the cross beam below each of the five compartments of 8 trailers transporting 331 animals from assembly yard to a processing facility. Journeys ranged in duration from 780 min to 942 min. A bruise severity score was obtained prior to trimming for n=291 carcasses using the number of bruises weighted by the size of bruise on a 3-point scale (1≤6.5 cm; 2=6.5 to 12 cm and 3≥12 cm). Due to limitations in the battery capacity of the sensors, the acceleration was only measured for the first half of the journey for all but 2 journeys. The percent difference in rms between the entire journey and the first half of those 2 journeys ranged from 7.22% to 14.54%. The mean rms of acceleration for all trailers (34 accelerometers) was 1.43 ± 0.42 m/s2, 1.32 ± 0.53 m/s2 and 1.67 ± 0.50 m/s2 for x, y and z axes, respectively. Mean bruise number and severity per carcass were 4.52 ± 2.43 and 5.31 ± 2.84 respectively. When measured by trailer a quadratic relationship was observed between acc (rms) and bruise severity in the z-axis (r = 0.69, P = 0.09) however, no relationship was observed between either the x or y axes and bruise severity. Acceleration varied slightly between trailer compartments in the z (P = 0.10) and y-axes (P = 0.10) but not in the x-axis. Bruising also varied slightly by trailer compartment (P = 0.11). Results indicate that reductions in side to side trailer movements could decrease bruising thereby improving carcass quality and animal welfare. Extension and replication of this research is required to further understand the relationships between trailer motion, carcass bruising and overall animal welfare.
Keywords: cattle transport acceleration