The Influence of Predictability and Controllability on Stress Responses to the Aversive Component of a Virtual Fence

Abstract

To ensure animal welfare is not compromised, virtual fencing must be predictable and controllable, and this is achieved through associative learning. To assess the influence of predictability and controllability on physiological and behavioral responses to the aversive component of a virtual fence, two methods of training animals were compared. In the first method, positive punishment training involved sheep learning that after an audio stimulus, an electrical stimulus would follow only when they did not respond by stopping or turning at the virtual fence (predictable controllability). In the second method, classical conditioning was used to associate an audio stimulus with an electrical stimulus on all occasions (predictable uncontrollability). Eighty Merino ewes received one of the following treatments: control (no training and no stimuli in testing); positive punishment training with an audio stimulus in testing (PP); classical conditioning training with only an audio stimulus in testing (CC1); and classical conditioning training with an audio stimulus followed by electrical stimulus in testing (CC2). The stimuli were applied manually with an electronic collar. Training occurred on 4 consecutive days with one session per sheep per day. Sheep were then assessed for stress responses to the cues by measuring plasma cortisol, body temperature and behaviors. Predictable controllability (PP) sheep showed no differences in behavioral and physiological responses compared with the control treatment (P < 0.05). Predictable uncontrollability of receiving the aversive stimulus (CC2) induced a higher cortisol and body temperature response compared to the control but was not different to CC1 and PP treatments. CC2 treatment sheep showed a higher number of turning behaviors (P < 0.001), and more time spent running (P < 0.001) than the control and PP treatment groups, indicating that predictability without controllability was stressful. The behavior results also indicate that predicting the event without receiving it (CC1) was less stressful than predicting the event then receiving it (CC2), suggesting that there is a cost to confirmation of uncontrollability. These results demonstrate that a situation of predictability and controllability such as experienced when an animal successfully learns to avoid the aversive component of a virtual fence, induces a comparatively minimal stress response and does not compromise animal welfare.

A Multi-Disciplinary Approach to Assess the Welfare Impacts of a New Virtual Fencing Technology

“…To demonstrate this, plasma cortisol and β-endorphin concentrations were assessed in beef cattle receiving an electrical pulse compared with a range of common husbandry procedures and this showed that the stress response to an electrical pulse was not different to being restrained in a crush ( 17 ). In a similar comparison study with sheep, a mild cortisol response to an electrical pulse was shown and this was similar to hearing a barking dog ( 18 ) and sheep did not differ in their cortisol responses to the audio cue once they had successfully learnt the virtual fence ( 24 ). Overall, these results indicate that while the electrical pulse is aversive, it is not more stressful than common handling procedures in both sheep and cattle.…”

“…Indeed, cattle learn rapidly after an average of 2.5 interactions with the virtual fence before responding to the audio cue alone ( 6 ). This hypothesis was tested Kearton et al ( 24 ) in a study that assessed the influence of controllability on stress responses to virtual fencing stimuli. Sheep that had learned to predict and control receiving the electrical pulse through their behavioral responses, did not differ in their cortisol, core body temperature and behavioral responses compared with a control treatment that did not receive any cues.…”

The Relationship Between Perceived Control and Hypothalamic–Pituitary–Adrenal Axis Reactivity to the Trier Social Stress Test in Healthy Young Adults

“…The result indicated that subjective uncontrollability was associated with stress-induced HPA axis activation. Many animal studies have found that objective uncontrollability could affect neurobiology after stress, manifested as elevated cortisol levels (e.g., Davis et al, 1977;Dess et al, 1983;Kearton et al, 2020). However, other studies found that control is not correlated with HPA axis responses when manipulating actual control over a stressor in rodents (e.g., Maier et al, 1986;Weinberg et al, 2010).…”

“…Controllability is one factor that may influence the HPA axis response to stress (Dickerson and Kemeny, 2004). Many animal studies demonstrated that lack or loss of actual control was associated with HPA axis stress response (e.g., Davis et al, 1977;Dess et al, 1983;Kearton et al, 2020). For example, sheep receiving predictable but uncontrollable aversive stimulus had a higher cortisol compared to the control group (Kearton et al, 2020).…”

“…Many animal studies demonstrated that lack or loss of actual control was associated with HPA axis stress response (e.g., Davis et al, 1977;Dess et al, 1983;Kearton et al, 2020). For example, sheep receiving predictable but uncontrollable aversive stimulus had a higher cortisol compared to the control group (Kearton et al, 2020). In rodents, inescapable shock leads to a prolonged steroid elevation (Davis et al, 1977).…”