Valence of physical stimuli, not housing conditions, affects behaviour and frontal cortical brain activity in sheep

Abstract

Modulation of short-term emotions by long-term mood is little understood but relevant to understand the affective system and of importance in respect to animal welfare: a negative mood might taint experiences, whilst a positive mood might alleviate single negative events. To induce different mood states in sheep housing conditions were varied. Fourteen ewes were group-housed in an unpredictable, stimulus-poor and 15 ewes in a predictable, stimulus-rich environment. Sheep were tested individually for mood in a behavioural cognitive bias paradigm. Also, their reactions to three physical stimuli thought to differ in their perceived valence were observed (negative: pricking, intermediate: slight pressure, positive: kneading). General behaviour, activity, ear movements and positions, and haemodynamic changes in the cortical brain were recorded during stimulations. Generalised mixed-effects models and model probabilities based on the BIC (Bayesian information criterion) were used. Only weak evidence for mood difference was found. Sheep from the unpredictable, stimulus-poor housing condition had a somewhat more negative cognitive bias, showed slightly more aversive behaviour, were slightly more active and moved their ears somewhat more. Sheep most clearly differentiated the negative from the intermediate and positive stimulus in that they exhibited more aversive behaviour, less nibbling, were more active, showed more ear movements, more forward ear postures, fewer backward ear postures, and a stronger decrease in deoxyhaemoglobin when subjected to the negative stimulus. In conclusion, sheep reacted towards stimuli according to their presumed valence but their mood was not strongly influenced by housing conditions. Therefore, behavioural reactions and cortical brain activity towards the stimuli were hardly modulated by housing conditions. Modulation of short-term emotions by long-term mood is little understood but relevant to 34 understand the affective system and of importance in respect to animal welfare: a negative 35 mood might taint experiences, whilst a positive mood might alleviate single negative events. 36To induce different mood states in sheep housing conditions were varied. Fourteen ewes 37 were group-housed in an unpredictable, stimulus-poor and 15 ewes in a predictable, 38 stimulus-rich environment. Sheep were tested individually for mood in a behavioural 39 cognitive bias paradigm. Also, their reactions to three physical stimuli thought to differ in their 40 Only weak evidence for mood difference was found. Sheep from the unpredictable, stimulus-45 poor housing condition had a somewhat more negative cognitive bias, showed slightly more 46 aversive behaviour, were slightly more active and moved their ears somewhat more. Sheep 47 most clearly differentiated the negative from the intermediate and positive stimulus in that 48 they exhibited more aversive behaviour, less nibbling, were more active, showed more ear 49 movements, more forward ear postures, fewer backward ear postures, and a stronger 50...

Housing conditions influence cortical and behavioural reactions of sheep in response to videos showing social interactions of different valence

“…For the experiments, which took place between September and October 2012, 12 focal sheep of about 20 months of age from each of two housing groups were chosen to allow for full sets of all possible sequences of the presentation of three stimuli (6 possible sequences; see 2.4) and to reach a sample size (2 x 12) which provided sufficient power to detect such differences in previous studies [12,18]. These were the same focal sheep that had been tested in a previous experiment using physical stimuli [12].…”

“…We aimed at inducing different mood states by housing animals under two different housing conditions, namely a predictable, stimulus-rich and an unpredictable, stimulus-poor pen described in detail by Vögeli et al [12]. In short, the predictable, stimulus-rich housing…”

“…While humans can express their subjectively perceived emotions verbally, indicators are needed to assess emotional states in animals [9,10]. Locomotor activity [11], restlessness behaviour [12], and ear postures and movements [11][12][13][14][15] have been used as behavioural indicators of animal emotions in recent studies. These studies related increased locomotor activity and restlessness behaviour with negative stimuli.…”

“…To vary valence and at the same time as few other aspects of the stimuli, such as arousal, as possible, it seems useful to remain within one sensory channel in a given experiment (e.g. [12]). Emotional reactions investigated in previous studies include physical stimuli [12,18] and situations with ambiguous information [20] in sheep, feed and feed frustration in goats [19] as well as interactions with a human handler in dogs [21].…”

“…[12]). Emotional reactions investigated in previous studies include physical stimuli [12,18] and situations with ambiguous information [20] in sheep, feed and feed frustration in goats [19] as well as interactions with a human handler in dogs [21]. In all these studies an attempt has been made to vary valence of the stimuli to a certain extent.…”