Data_Sheet_1_The Influence of Predictability and Controllability on Stress Responses to the Aversive Component of a Virtual Fence.xlsx

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.

为保障动物福利不受损害，虚拟围栏（virtual fencing）需具备可预测性与可操控性，这一目标可通过联想学习实现。为评估可预测性与可操控性对动物面对虚拟围栏厌恶性刺激时的生理与行为反应的影响，本研究对比了两种动物训练方案。第一种方案为正惩罚训练（positive punishment training）：使绵羊学会，当听觉刺激（audio stimulus）出现后，若未在虚拟围栏前停下或转向以做出响应，则会随之受到电刺激（electrical stimulus），即该条件具备可预测性与可操控性。第二种方案为经典条件化训练（classical conditioning）：在所有场景下将听觉刺激与电刺激建立关联，即该条件具备可预测性但不可操控。80只美利奴母羊被随机分配至以下四组处理：对照组（测试阶段无训练且无刺激）、测试阶段伴随听觉刺激的正惩罚训练组（PP）、测试阶段仅呈现听觉刺激的经典条件化训练组（CC1），以及测试阶段先呈现听觉刺激后施加电刺激的经典条件化训练组（CC2）。刺激通过电子项圈手动施加。训练连续开展4天，每只绵羊每日接受一次训练单元。随后通过检测血浆皮质醇（plasma cortisol）浓度、体温及行为表现，评估绵羊对相关提示信号的应激反应。可预测且可操控组（PP）绵羊的行为与生理反应与对照组无显著差异（P < 0.05）。可预测但不可操控的厌恶性刺激接收场景（CC2组）会导致绵羊皮质醇水平与体温较对照组显著升高，但与CC1组及PP组无显著差异。相较于对照组与PP组，CC2组绵羊的转向行为次数更多（P < 0.001），奔跑时长也更长（P < 0.001），这表明仅具备可预测性但无操控性的场景会引发应激反应。行为结果还显示，仅预测到事件发生但未实际接收刺激的场景（CC1组）的应激程度低于先预测到事件再接收刺激的场景（CC2组），这表明确认刺激不可操控会带来应激代价。本研究结果表明，当动物成功学会规避虚拟围栏的厌恶性刺激时，其所经历的可预测且可操控的场景，仅会引发相对微弱的应激反应，且不会损害动物福利。