Discriminating spontaneous locomotor play of dairy calves using accelerometers

Abstract

Play behavior is a promising welfare indicator in dairy calves because it decreases in negative situations such as pain or hunger and increases in positive contexts such as in appropriate social environments. Directly measuring play is time consuming because it is performed in irregular bouts and can be inconsistent over days. To facilitate automatic recording of play, previous studies fitted triaxial accelerometers to the hind legs of calves and measured the velocity of movements in large arenas; high correlations were reported between vertical axis peak duration and the duration of locomotor play. The current study aimed to validate accelerometers for recording spontaneous locomotor play in calves' home pens over longer periods. Data were collected from 48 Holstein Friesian calves, housed in groups of 3 in pens of 10 m 2 , at either 4 or 8 wk of age. Acceleration at the vertical axis of the hind leg was recorded at a rate of 1 Hz. One active time period for each calf was randomly selected (mean duration ± standard deviation = 34 ± 9 min). From video of the corresponding time period, the frequency of locomotor play events, consisting of run, turn, and buck/buck-kick, was recorded using behavior sampling. Combined counts of play events were highly correlated (Pearson r = 0.91) with counts of acceleration peaks. However, for calves with higher levels of locomotor play, this method underestimated the extent of play. Alternatively, run, turn, and buck events obtained from video were transformed by creating intervals of 10 s and then classifying each 10-s interval as comprising events of play ("play") or not comprising events of play ("no play"). The corresponding accelerometer data for all 10-s periods, equaling 10 consecutive readings each, were classified into play or no play by using quadratic discriminant analysis; 79% of periods with locomotor play were correctly classified. Counts of observed play intervals correlated with the counts of play periods from accelerometers (r = 0.87), but the discriminant analysis consistently overestimated play. In conclusion, accelerometer measurements at 1 Hz (in 1-s intervals) and at the vertical axis cannot be used alone to exactly quantify absolute levels of locomotor play in the home pen. However, counts of peak accelerations can provide a rough estimate of inter-individual differences in play events, and discriminant analysis can be used as a proxy for one-zero sampling of inter-individual differences in locomotor play.

Use of a Tri-Axial Accelerometer Can Reliably Detect Play Behaviour in Newborn Calves

“…Rather, the number of sampling intervals in which the MI exceeded a defined cut point could be calculated in a method analogous to one-zero sampling (using visual observations) where the number of sampling intervals in which a defined behaviour is observed (in this, case play) is calculated [ 14 ]. One-zero sampling produces a single score for the required recording session that is expressed as a proportion of the total number of sample intervals during which the defined behaviour was observed and has previously been used by authors recording play, as it can capture sporadic, short-duration behaviours and is suited to capturing patterns of behaviour that are clustered [ 14 , 42 , 64 ]. Short sampling intervals are optimal when one-zero sampling is used, and this was reflected in our findings that the sensitivity and specificity of 1 min sampling intervals was more accurately repeatable than the sensitivity and specificity of 15 min sampling intervals.…”

“…Accelerometer technology has been utilised to monitor different behaviours in a wide variety of wild and domestic species including cattle [19,[25][26][27][28][29]. Accelerometers have been evaluated as tools for identifying many different types of bovine behaviour including lying behaviours [30][31][32][33][34][35], locomotion [34,36,37], feeding/drinking behaviours [35,[38][39][40] and play behaviour [41,42]. Whilst accelerometer generated data have shown good correlation with visual observations for standing and lying behaviours in adult cows [21,32,35,43,44] and lying behaviours in calves [30,45], the reported correlation between accelerometer measurements and locomotor activity in calves is inconsistent.…”

“…For example, Luu et al [41] reported a good correlation between the number of acceleration peaks and the duration of time engaged in running, jumping/kicking and walking (r = 0.96, 0.86 and 0.75, respectively), whereas Trénel et al [33] reported a low sensitivity (raw data sensitivity = 0.15; filtered data sensitivity = 0.22) for identifying movement in calves. Some studies have evaluated the use of accelerometers to identify play behaviours in calves [41,42,46,47], but these evaluate behaviour in calves aged four weeks or older [41,42,46], evaluate play behaviour in arena tests [41,46,47] or apply data manipulation methods to the raw accelerometer data [41]. No studies have evaluated the use of accelerometers to identify play behaviour in neonatal calves aged up to 48 h old in their home pen using the raw accelerometer data that would be available to farmers, welfare auditors and veterinarians.…”

“…Play behaviour is not considered to be essential for survival, and animals typically do not expend energy expressing play behaviour when resources are limited or welfare is compromised [48]; play is therefore considered to be a "luxury behaviour" that is exhibited when animals are in a positive welfare state [51]. Play is also thought to be an indicator of positive emotions in animals [50,52]; however, play behaviour can be time consuming and laborious to assess as it occurs spontaneously, infrequently and over short durations [42]. Play cannot be predicted, and long periods of observation are required to accurately determine the duration and number of play bouts, making the assessment of play behaviour impractical for inclusion into on-farm welfare assessments.…”

“…Accelerometer technology can potentially mitigate these limitations, and, as such, the use of accelerometers to identify play behaviour for the purposes of the assessment of positive states is of interest. Größbacher et al [42] assessed locomotor play in group-housed calves aged four and eight weeks old and found that the Hobo Pendant G Acceleration Data Logger (Onset Computer Corporation, Bourne, MA, USA) correctly identified 79% of the sampling periods in which play occurred but consistently overestimated play behaviour, and a correction factor had to be applied to enable the accelerometer derived data to reflect visual one-zero sampling. They concluded that, although this accelerometer provided a good approximation of spontaneous locomotor behaviour in calves, the sensor did not have a high enough recording frequency (1 Hz) for the accurate measurement of play behaviour [42].…”