Abstract

Affective states are key determinants of animal welfare. Assessing such states under field conditions is thus an important goal in animal welfare science. The rapid Defence Cascade (DC) response (startle, freeze) to sudden unexpected stimuli is a potential indicator of animal affect; humans and rodents in negative affective states often show potentiated startle magnitude and freeze duration. To be a practical field welfare indicator, quick and easy measurement is necessary. Here we evaluate whether DC responses can be quantified in pigs using computer vision. 280 video clips of induced DC responses made by 12 pigs were analysed by eye to provide ‘ground truth’ measures of startle magnitude and freeze duration which were also estimated by (i) sparse feature tracking computer vision image analysis of 200 Hz video, (ii) load platform, (iii) Kinect depth camera, and (iv) Kinematic data. Image analysis data strongly predicted ground truth measures and were strongly positively correlated with these and all other estimates of DC responses. Characteristics of the DC-inducing stimulus, pig orientation relative to it, and ‘relaxed-tense’ pig behaviour prior to it moderated DC responses. Computer vision image analysis thus offers a practical approach to measuring pig DC responses, and potentially pig affect and welfare, under field conditions.

Highlights

  • Affective states are key determinants of animal welfare

  • Components of the Defence Cascade (DC) response are modulated by affective state in humans and rodents, making them potentially valuable indicators of these states

  • The ground truth Observer Startle Magnitude measure was significantly positively correlated with all automated measures of startle magnitude (Table 2)

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Summary

Introduction

Affective states are key determinants of animal welfare. Assessing such states under field conditions is an important goal in animal welfare science. The rapid Defence Cascade (DC) response (startle, freeze) to sudden unexpected stimuli is a potential indicator of animal affect; humans and rodents in negative affective states often show potentiated startle magnitude and freeze duration. Computer vision image analysis offers a practical approach to measuring pig DC responses, and potentially pig affect and welfare, under field conditions. Because concerns about animal welfare are, for many, based on an assumption that non-human animals can experience negative affective (emotional) states and suffer[8,9,10,11], there is a particular need to develop validated indicators of animal affect that can be implemented quickly and To this end, a variety of behavioural measures have been developed for use under farm conditions (e.g. human approach tests, novelty tests, Qualitative Behavioural Assessment[12,13,14,15]). Startle-potentiating effects of aversive conditioned stimuli are observed in monkeys[40]

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