Analysis of Walking Activity as a Non-Invasive Measure of Turkey Well-Being
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Animal behavior observation is a widely used method of detecting when animals are ill or injured, but there are limitations to using behavioral observations. Behavioral observations can be labor-intensive, subjective and unreliable. The development of technologies such as accelerometers, which record acceleration and activity-based data in 3D space, enables faster, more accurate and quantitative methods of detecting changes in animal behavior. Previous research has demonstrated the utility of using accelerometers to detect changes in animals’ health and well-being. However, limited information is available on the use of accelerometers to detect changes in behavior due to heat stress, which is a major poultry welfare concern, or to detect changes in activity levels of turkeys. The overall objective of this study was to determine whether micro-acceleration data loggers (accelerometers) can be used to detect changes in turkeys’ activity levels and to identify changes in turkey behavior that are indicative of changes in turkey well-being. Two trials were conducted. Specific objectives for Trial 1 were to: 1) determine the effects of accelerometers and habituation to accelerometers on turkey gait and welfare, 2) determine age-related changes in gait and welfare, and 3) evaluate the validity of the accelerometers. Thirty-six male commercial turkeys were randomly assigned to one of five groups: accelerometer and habituation period (AH), accelerometer and no habituation (AN), VetRap bandage (no accelerometer) and habituation (VH), bandage (no accelerometer) and no habituation (VN), and nothing on either leg (C). Welfare was assessed prior to video-recording birds as they walked across a Tekscan® pressure pad at 8, 12 and 16 wk to determine effects of treatment on number of steps, cadence, gait time, gait distance, gait velocity, impulse, gait cycle time, maximum force, peak vertical pressure, single support time, contact time, step length, step time, step velocity, stride length, total double support time, and duty factor. Accelerometer validity and reliability were determined by comparing the number of steps detected with the accelerometer to the number of steps determined from video recordings. Several age-related changes in turkey gait were found regardless of habituation, including a slower cadence at 16 wk, shorter gait distance at 8 wk, and slower gait velocity at 16wk. Habituation to the accelerometer and bandage had limited effects on turkey gait: non-habituated turkeys (VN and AN) spent more time standing on two feet (total double support time) compared to C birds, but did not differ from habituated (VH and AH) birds. Accelerometer validity and reliability were affected by both age and treatment. Validity and reliability were lowest for non-habituated birds (AN). Precision and sensitivity of accelerometers decreased with age but were unaffected by treatment. False discovery rate increased, and accuracy and specificity decreased with age. Results demonstrated that micro-data loggers do not adversely affect turkey welfare, but habituation to wearing accelerometers affects accelerometer reliability and validity. Accelerometer validity and turkey gait are also greatly affected by the age of the turkeys.
The second experiment used the validated accelerometers to assess changes in walking activity when turkeys were under an immune challenge or mild heat stress. Another objective of Experiment 2 was to identify changes in welfare and behavior associated with mild heat stress and a mild immune challenge. A total of 92 tom turkeys (trial 1: 51 turkeys; trial 2: 41 turkeys) were assigned to 3 different treatments in a crossover design: control (C; no heat stress or immune challenge), heat stress (HS), and immune challenge (IC). HS treatment was induced by slowly heating rooms to a peak temperature before slowly returning the rooms to normal temperatures. IC treatment was induced by a live-virus hemorrhagic enteritis vaccine which was added to the drinking water. Video (walking, sitting, standing, eating, drinking, preening, feather pecking, aggression and heat-stress related behavior) and accelerometer (steps/hr) data were recorded for 5 days at 10, 12, and 14 wk of age in order to gather behavior and walking activity data pre and post treatment, which occurred on day 3 of the 5 day period. Steps/hr decreased with age, treatments HS and IC had lower step counts compared to control groups, and each day proved to have a different step count regardless of whether a treatment was imposed. On the day of the imposed treatments, steps/hr were lower for both HS and IC turkeys. Welfare analysis indicated that tail and wing feather condition was worse at 14 wk compared to 10 and 12 wk. Behaviorally, the amount of time spent sitting increased as birds aged. Treatment also affected behavior: HS and IC turkeys performed less standing and walking compared to C birds on the day of the imposed treatment. Turkeys under a heat stress treatment performed more aggressive interactions and were observed performing heat-stress related behavior, including panting and sitting with their wings spread apart.
Results from both trials indicated that accelerometers can be useful tools to assess walking activity of turkeys and that accelerometers have the potential to detect changes in behavior that may be associated with conditions that negatively impact turkey welfare. The process of wearing an accelerometer on the leg did not adversely affect turkey welfare, but habituation is important to ensure that accelerometers are accurately and reliably recording turkeys’ steps. In addition, it was determined that changes in behavior, such as decreased walking and standing, can be indicative of potential welfare issues, such as heat stress and an immune challenge in turkeys. Further research is needed to explore the best step threshold for particular turkey ages in order to get the most accurate data in future analysis of walking activity. Furthermore, sex differences were not a factor in these studies as only male turkeys were used which may differ from females in terms of gait and behavior under heat stress and an immune challenge. It may also be beneficial to further explore turkey gait as there were discrepancies in the literature and this study concerning age related differences in gait (duty factor). Future research should focus on the early detection potential accelerometers can provide to the turkey industry for welfare concerns. As shown by our results, walking activity decreases under both a mild heat stress and immune challenge, so future studies should now determine if this decrease in activity level is detectable before overt visual behavioral signs. If accelerometers can detect signs of stress more objectively, accurately, and quicker than visual inspection, then both farmers and researchers could benefit from utilizing these devices to improve animal welfare in the future.