Abstract
Accelerometry is an accepted means of quantifying human physical activity. Quantitative physical activity tracking could be beneficial for studies into equine health and disease prevention, for example in relation to obesity management. Validate accelerometer use in grazing horses, determine between-day repeatability, and assess the effects of pasture size on time budget (i.e. duration in each activity category). Proof of concept. Accelerometers (ActiGraph) were positioned at the poll. Horses underwent 5min of observed activity in three categories: standing, grazing and ambulating. Receiver-operating characteristic curve analysis, used on ten second data epochs, calculated cut points between the activities. A 20-day study was then undertaken on 6 horses at pasture. Time in each category (per day) was deduced; a Mann Whitney U test was performed to compare standard vs. small paddock and day vs. night turn out. Cut-off values with the optimum sensitivity (94.7-97.7%) and specificity (94.7-96.8%) were found to be <127.6 counts for standing, 127.6-702.7 counts for grazing and >702.7 counts for ambulating. Repeatability was analysed descriptively: Median (IQR) of the between-day difference in minutes standing, grazing and ambulating were 46.9 (21.3-87.9), 77.3 (40.2-124.5) and 15.6 (6.8-40.2) respectively. Median times standing and ambulating were significantly different between standard and small paddocks: standing: 8.7 vs. 10.3h (P<0.001); ambulating: 55.7 vs. 39.6min (P=0.002). There was no significant difference in the median time spent grazing. There were significant differences between day and night: standing: 32.95% vs. 50.97% (P=0.001), grazing: 60.81% vs. 46.77% (P<0.001) and ambulating: 4.57% vs. 2.40% (P<0.001). Small sample size and lack of cross-validation of cut-off points on independent, 'unseen' data. Accelerometry can differentiate standing, grazing and ambulating in horses. Our proof-of-concept study demonstrates modifying pasture size influences activity budgets; opening avenues into studying obesity management.
Highlights
Accelerometry is recognised as a reliable means of quantifying human physical activity [1,2,3] and it has been proposed that quantitative physical activity tracking could be a valuable tool for equine veterinary research [4]
Cut off point establishment Using the same data, receiver-operating characteristic (ROC) curve analyses were performed to determine the accelerometer cut points that defined each of the physical activity categories (Table 2)
In line with our hypothesis, horses in a small paddock showed significantly increased amount of time spent standing compared with a standard grazing system, time spent grazing was not significantly altered
Summary
Accelerometry is recognised as a reliable means of quantifying human physical activity [1,2,3] and it has been proposed that quantitative physical activity tracking could be a valuable tool for equine veterinary research [4]. Accelerometry has proven to be a valid, reliable and practical means of measuring physical activity [15,16,17]. It is suggested that a lack of physical activity is a contributing factor in equine obesity, the exact effects are as yet unknown [24]. Harnessing this technology for use in horses would be valuable for future studies into the effect of physical inactivity on equine health. We hypothesised that, when compared to day-time, during the night horses would spend proportionally more time standing and less time ambulating
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