Ear Postures Research Articles

Evaluation of Sheep Anticipatory Response to a Food Reward by Means of Functional Near-Infrared Spectroscopy.

Simple SummaryAnticipatory behaviour to an oncoming food reward can be triggered via classical conditioning, implies the activation of neural networks, and may serve to study the emotional state of animals. This work aimed to investigate how the anticipatory response affects cerebral cortex activity in sheep. Eight ewes were conditioned to associate a neutral auditory stimulus (water bubble) to a food reward (maize grains). Then, sheep were trained to wait 15 s before accessing the food (anticipatory phase). Behavioural reaction and changes in cortical oxy-haemoglobin ([ΔO2Hb]) and deoxy-haemoglobin ([ΔHHb]) concentration were recorded by functional near infrared spectroscopy (fNIRS). During the anticipatory phase, sheep increased their active behaviour together with a cortical activation (increase of [ΔO2Hb] and a decrease of [ΔHHb]) compared to baseline. Sheep showed a greater response of the right hemisphere compared to the left hemisphere, possibly indicating frustration. Behavioural and cortical changes observed during anticipation of a food reward reflect a learnt association and an increased arousal, but no clear emotional valence of the sheep subjective experience.Anticipatory behaviour to an oncoming food reward can be triggered via classical conditioning, implies the activation of neural networks, and may serve to study the emotional state of animals. The aim of this study was to investigate how the anticipatory response to a food reward affects the cerebral cortex activity in sheep. Eight ewes from the same flock were trained to associate a neutral auditory stimulus (water bubble) to the presence of a food reward (maize grains). Once conditioned, sheep were trained to wait 15 s behind a gate before accessing a bucket with food (anticipation phase). For 6 days, sheep were submitted to two sessions of six consecutive trials each. Behavioural reaction was filmed and changes in cortical oxy- and deoxy-hemoglobin concentration ([ΔO2Hb] and [ΔHHb] respectively) following neuronal activation were recorded by functional near infrared spectroscopy (fNIRS). Compared to baseline, during the anticipation phase sheep increased their active behaviour, kept the head oriented to the gate (Wilcoxon’s signed rank test; p ≤ 0.001), and showed more asymmetric ear posture (Wilcoxon’s signed rank test; p ≤ 0.01), most likely reflecting a learnt association and an increased arousal. Results of trial-averaged [ΔO2Hb] and [ΔHHb] within individual sheep showed in almost every sheep a cortical activation during the anticipation phase (Student T-test; p ≤ 0.05). The sheep showed a greater response of the right hemisphere compared to the left hemisphere, possibly indicating a negative affective state, such as frustration. Behavioural and cortical changes observed during anticipation of a food reward reflect a learnt association and an increased arousal, but no clear emotional valence of the sheep subjective experience. Future work should take into consideration possible factors affecting the accurateness of measures, such as probe’s location and scalp vascularization.

Positive and negative emotions in dairy cows: Can ear postures be used as a measure?

Applying objective measures to assess the emotional states of animals is an important area of research and essential for improving animal welfare. In this study, we have built upon previous research to test whether ear postures can be used as an indicator of emotional states in dairy cows.By using a positive and negative contrast paradigm, we elicited the emotional states of excitement and frustration in 22 dairy cows. Each cow was first conditioned to expect the delivery of standard feed when a bell was rung. Once they were familiar with the experimental set-up and the delivery of the feed, they were then given concentrates feed instead. As concentrates are highly desired, this was considered to elicit the emotional state of excitement. This was then repeated five times. On the following trial, the cows were given inedible woodchip, and the cows’ unfulfilled expectations were considered to elicit a state of frustration.We observed the cows’ ear postures and mean heart rate (beats per minute) during 15-minute focal observations, each comprised of 5 min of pre-feeding (baseline), 5 min of feeding, and 5 min of post-feeding. Both the woodchip treatment and the concentrates elicited significantly higher mean heart rates compared with the standard feed, indicating that both treatments elicited a high arousal emotional state. The woodchip and concentrates treatments were also significantly associated with the increased performance of different ear postures, indicating that cows do perform certain ear postures in relation to both positive and negative high arousal emotional states.Our results complement previous research performed with both cows and sheep, and indicate that with training and contextual knowledge, ear postures may be suitable as a reliable measure of emotional state in dairy cows.

Inducing positive emotions: Behavioural and cardiac responses to human and brushing in ewes selected for high vs low social reactivity

Welfare concerns not only the absence of negative emotional experiences but also the presence of positive experiences. However, scientific investigation on positive emotions in farm animals has been long neglected. This study aimed to investigate the perception of sheep to positive stimuli and whether emotional reactivity influences such perception, through behavioural and cardiac indicators. Therefore, 38 Romane ewes belonging to two divergent lines, high (R+) or low (R−) reactive, were submitted to the presence of a familiar experimenter (HUM) or brushing by a familiar experimenter (BRU). The procedure was divided in three phases: before (2.5 min), during (3.0 min) and after (2.5 min) HUM or BRU. Body postures, head orientation, ear changes and postures, closed and half-closed eyes, tail wagging and feeding behaviour were analyzed, and heart rate variability parameters (RMSSD, RMSSD/SDNN and LF/HF ratios) were estimated. Data were analyzed using linear models with different correlation structures. The models considered treatment, genetic line and phase as fixed effects, including their interactions. Brushed ewes showed fewer body posture, head orientation and ear posture changes and a higher proportion of closed and half-closed eyes, tail wagging and rumination during the procedure, when compared to ewes submitted to the human presence (P < 0.05). Both BRU and HUM ewes had lower HR during and after the procedures and higher RMSSD/SDNN rate during the procedures, reflecting the activation of the parasympathetic nervous system in response to both treatments (P < 0.05). Behavioural and cardiac results suggest that both treatments induced a relaxing state in sheep, more pronounced for the brushing treatment. Interestingly, an anticipatory agitation before the treatment was observed mainly in BRU sheep. Highly reactive ewes expressed less head orientation changes and a higher proportion of horizontal ear postures and feeding behaviour in response to brushing than when submitted to human presence (P < 0.05), indicating that brushing might have elicited a more relaxing effect on R+ animals. Differences between R+ and R− ewes suggest that reactivity might modulate sheep responses to assumed positive stimuli.

Valence and Intensity of Video Stimuli of Dogs and Conspecifics in Sheep: Approach-Avoidance, Operant Response, and Attention.

Simple SummaryAnimals’ judgement of stimuli’s negativity or positivity cannot always be assumed. To assess the valence and intensity of video stimuli (dogs as negative vs. conspecifics as positive stimuli) in sheep, we used three experimental approaches: (1) an approach-avoidance paradigm; (2) operant conditioning using the videos as reinforcers; and (3) an attention test. We measured sheep’s behavioral and physiological reactions. Sheep generally reacted to the videos presented. Nevertheless, we found no support with the approach–avoidance paradigm, and the attention test for dog videos were more negative than sheep videos. However, the operant conditioning indicated that sheep were more prone to avoid videos of moving dogs. Overall, we found that standard video images may not be ideal to represent valence characteristics of stimuli to sheep.Stimuli are often presumed to be either negative or positive. However, animals’ judgement of their negativity or positivity cannot generally be assumed. A possibility to assess emotional states in animals elicited by stimuli is to investigate animal preferences and their motivation to gain access to these stimuli. This study’s aim was to assess the valence of social stimuli in sheep. We used silent videos of varying intensity of dogs as negative versus conspecifics as positive stimuli in three approaches: (1) an approach–avoidance paradigm; (2) operant conditioning using the video stimuli as reinforcers; and (3) an attention test. In the latter, we assessed differential attention of sheep to simultaneous projections by automatically tracking sheep head and ear postures and recording brain activity. With these approaches, it was difficult to support that the sheep’s reactions varied according to the stimuli’s presumed valence and intensity. The approach–avoidance paradigm and attention test did not support the assumption that dog videos were more negative than sheep videos, though sheep reacted to the stimuli presented. Results from the operant conditioning indicated that sheep were more prone to avoid videos of moving dogs. Overall, we found that standard video images may not be ideal to represent valence characteristics of stimuli to sheep.

Do Different Emotional States Affect the Horse Grimace Scale Score? A Pilot Study

The Horse Grimace Scale (HGS) is a facial-expression–based pain coding system that incorporates six Facial Action Units, independently scored. The aim of this pilot study was to determine whether HGS score changed in response to emotional states other than pain. Seven riding school horses were exposed to different experimental conditions that are known to elicit different emotional states (new environment, grooming, anticipation of food reward, fear). As a control, videos were also recorded with the horse undisturbed in their home environment. Videos were recorded in each experimental condition and individual frames were captured from HD video files. Thirty-five pictures were scored using HGS by three experimental design blind observers. The results showed that the HGS score did not change in any of the experimental conditions when compared with control. In all the conditions but one (fear), the mean HGS score was low (≤2 on a maximum score of 12), but not zero; the scores of stiffly backward ears and prominent strained chewing muscles tended to be higher in fear than in other conditions. Although these are preliminary results as the number of tested horses is limited, HGS seems to be a specific tool to assess pain in horses. Changes in ear posture and tension in chewing muscles tend to be present in negative emotional states such as fear; therefore, a larger scale study is needed to collect data from the same horses in positive and negative situations, including pain.

Face-based perception of emotions in dairy goats

Faces of conspecifics convey information about identity, but also gaze, and attentional or emotional state. As a cognitive process, face-based emotion recognition can be subject to judgement bias. In this study we investigated whether dairy goats (n=32) would show different responses to 2-D images of faces of familiar conspecifics displaying positive or negative emotional states. We also examined the possible use of images of faces as stimuli in cognitive bias studies. The faces of four subjects were photographed in a positive and a negative situation. Three types of images of ambiguous facial expressions were then created using morphing software (75% positive, 50% positive, and 25% positive). In a test-pen, each goat was exposed for 3s to each type of image, obtained from the same goat. All goats were shown non-morphed faces first, before being shown the three types of morphed faces, balanced for order. Finally, the first non-morphed face was shown again. Spontaneous behavioural reactions including ear postures (forward, backward and asymmetrical) and interactions with the screen (time spent looking or touching) were recorded during the 3s. Results were analysed using REML with repeated measurements. Goats spent more time with their ears forward when the negative was shown compared to the positive(F4,121.3=2.51, P=0.018), indicating greater interest in negative faces. Identity of the photographed goat influenced the time spent with the ears forward (F2,57.4=7.01, P=0.002). We conclude that goats react differently to images of faces displaying different emotional states and that they seem to perceive the emotional valence expressed in these images. Response to morphed faces was not necessarily intermediate to response to negative and positive faces, and not on a continuum. Further study is thus needed to clarify the potential use of faces in cognitive bias studies.

Behavior and body surface temperature as welfare indicators in selected sheep regularly brushed by a familiar observer

Research on emotions in farm animals has increasingly contributed to their welfare. We aimed to study behavioral and body temperature responses of dorper and white dorper sheep regularly brushed on their ventral neck, lateral chest, and withers. We performed 3-minute assessments in prebrushing, brushing, and postbrushing phases. Vocalization, ear postures and changes, half-closed eyes, and tail wagging were assessed. We also recorded withers (Tw), anal (Ta), and nasal (Tn) temperatures with an infrared thermometer. Vocalization was infrequent throughout the phases. We identified 3 ear postures frequently performed by the animals: raised up (R), horizontal (H), and backward (B). We noted a longer duration of R rather than H posture before brushing than during brushing. By comparing B and H, we observed that dorper sheep performed the B posture for longer, mainly during than postbrushing. When B and R were compared, sheep expressed the B posture for longer during brushing than both prebrushing and postbrushing phases; dorpers and male sheep also performed the B posture for longer. The results suggest higher performance of B and H postures during the stimulus and that their expression might be associated with a positive, relaxing state of the animals. No significant result was found for ear changes. Sheep showed half-closed eyes mainly in brushing and postbrushing phases, in comparison with the prebrushing phase, indicating that brushing might have elicited a relaxing state in the animals, which might have persisted after the stimulus. Only 4 male sheep wagged their tails, mostly when brushed. We also noted attention-seeking behaviors, including following the observer, leaning against the brush with the head or neck, and stretching the neck when brushed. The results on body temperatures indicated higher variance for Tw in relation to Tn and Ta, which had similar variances. Pairwise comparisons indicated that Tw was higher in postbrushing than in the prebrushing phase; Tn was also higher in the postbrushing phase than in both prebrushing and brushing phases, suggesting an increase in Tw and Tn temperatures after the stimulus. No significant differences were reported for Ta. Brushing might have elicited a positive state in sheep. Ear postures and half-closed eyes may be useful tools for assessing emotions in sheep, as well as withers and nasal temperatures. Furthermore, breed may be a highly significant effect on the expression of ear postures in sheep.

Coding and quantification of a facial expression for pain in lambs

Facial expressions are routinely used to assess pain in humans, particularly those who are non-verbal. Recently, there has been an interest in developing coding systems for facial grimacing in non-human animals, such as rodents, rabbits, horses and sheep. The aims of this preliminary study were to: 1. Qualitatively identify facial feature changes in lambs experiencing pain as a result of tail-docking and compile these changes to create a Lamb Grimace Scale (LGS); 2. Determine whether human observers can use the LGS to differentiate tail-docked lambs from control lambs and differentiate lambs before and after docking; 3. Determine whether changes in facial action units of the LGS can be objectively quantified in lambs before and after docking; 4. Evaluate effects of restraint of lambs on observers’ perceptions of pain using the LGS and on quantitative measures of facial action units. By comparing images of lambs before (no pain) and after (pain) tail-docking, the LGS was devised in consultation with scientists experienced in assessing facial expression in other species. The LGS consists of five facial action units: Orbital Tightening, Mouth Features, Nose Features, Cheek Flattening and Ear Posture. The aims of the study were addressed in two experiments. In Experiment I, still images of the faces of restrained lambs were taken from video footage before and after tail-docking (n=4) or sham tail-docking (n=3). These images were scored by a group of five naïve human observers using the LGS. Because lambs were restrained for the duration of the experiment, Ear Posture was not scored. The scores for the images were averaged to provide one value per feature per period and then scores for the four LGS action units were averaged to give one LGS score per lamb per period. In Experiment II, still images of the faces nine lambs were taken before and after tail-docking. Stills were taken when lambs were restrained and unrestrained in each period. A different group of five human observers scored the images from Experiment II. Changes in facial action units were also quantified objectively by a researcher using image measurement software. In both experiments LGS scores were analyzed using a linear MIXED model to evaluate the effects of tail docking on observers’ perception of facial expression changes. Kendall’s Index of Concordance was used to measure reliability among observers. In Experiment I, human observers were able to use the LGS to differentiate docked lambs from control lambs. LGS scores significantly increased from before to after treatment in docked lambs but not control lambs. In Experiment II there was a significant increase in LGS scores after docking. This was coupled with changes in other validated indicators of pain after docking in the form of pain-related behaviour. Only two components, Mouth Features and Orbital Tightening, showed significant quantitative changes after docking. The direction of these changes agree with the description of these facial action units in the LGS. Restraint affected people’s perceptions of pain as well as quantitative measures of LGS components. Freely moving lambs were scored lower using the LGS over both periods and had a significantly smaller eye aperture and smaller nose and ear angles than when they were held. Agreement among observers for LGS scores were fair overall (Experiment I: W=0.60; Experiment II: W=0.66). This preliminary study demonstrates changes in lamb facial expression associated with pain. The results of these experiments should be interpreted with caution due to low lamb numbers.

Lambs show changes in ear posture when experiencing pain

AbstractEar posture, or the frequency of postural changes, may reflect various emotional states of animals. In adult sheep (Ovis aries), the ‘forward’ ear posture has been associated with negative experiences whereas the ‘plane’ posture has been associated with positive ones. This study aimed to see whether ear postures related to the experience of pain in lambs. The ear behaviour of four to eight week-old lambs (n = 44) was measured before and after tail-docking using a rubber ring. Each lamb was docked and its behaviour recorded while in the company of an observer lamb of similar age; each acted once as focal (docked) lamb and once as observer within the same pair. Lambs were docked in one of two rounds, so that half were docked in their first exposure to the test environment and half in their second exposure. Tail-docking was associated with an increase in the proportion of time spent with ears backward and decreases in the proportion of time spent with ears plane and forward (mean [± SEM]: Backward: pre 0.12 [± 0.04], post 0.56 [± 0.04]; Plane: pre 0.55 [± 0.05], post 0.19 [± 0.05]; Forward: pre 0.27 [± 0.04], post 0.18 [± 0.04]). There was also a significant increase in the number of changes between ear postures after docking (pre 5.63 [± 0.66], post 9.11 [± 0.66]). Over both periods, female lambs held their ears asymmetrically for longer than males (mean of ranks [± SEM] [raw proportion of time]: Females 52.14 [± 3.44] [0.09 (± 0.01)], males 37.54 [± 3.40] [0.05 (± 0.01)]). This is the first study to demonstrate changes in the ear posture of lambs associated with the negative experience of pain. Ear posture is a non-invasive indicator of physical pain in lambs and may be useful for evaluating potential welfare compromise.

Reactions of sheep towards three sets of emotional stimuli: (In)Consistency in respect to stimulus valence and sheep identity

There is an increasing interest in affective states in applied animal behaviour science, because these states are thought to reflect welfare from the perspective of the animals. Also, it can be expected that individuals differ in how they consistently react to emotional challenges. Recently, we conducted three experiments in which the same sheep were repeatedly confronted with either physical, social or thermal stimuli that presumably varied in their valence. These sheep had been housed in either unpredictable, stimulus-poor or predictable, stimulus-rich housing conditions in order to manipulate their long-term mood. When the sheep were exposed to the stimuli, we measured general activity, ear movements, ear postures and frontal cortical haemodynamic changes as indicator variables for their emotional reaction. In the meta-analysis presented here, we searched for effects of the presumed valence and mood state on the indicator variables. Furthermore, we investigated the unexplained between- versus within-subject variability as an indicator of personality. Deoxy- [HHb] and oxy-haemoglobin concentrations [O2Hb] as well as general activity showed weak linear relationships with presumed valence. Sheep from the unpredictable, stimulus-poor housing conditions were generally more active and showed more ear movements, higher absolute [HHb], more transverse ears and less left-forward ears than sheep from the predictable, stimulus-rich housing conditions. However, these differences were small. The ratio of between- to within-individual variability was very low indicating little consistency in individual reactions. In conclusion, we found only weak evidence that presumed valence had a consistent effect on the indicator variables for emotional reactions in a given sheep, and these reactions were not modulated by presumed mood. Also, there was little indication that the sheep reacted in a way reflecting an individualised personality.

Correlates between ear postures and emotional reactivity in a wild type mouse species

Facial expressions have been extensively used to assess emotions in humans and thus could be extended to other species that also display facial movements. In mice both painful and fearful situations have been associated with particular shifts in facial expressions. Like other species, mice frequently show a great inter-individual variability when exposed to emotional situations, but so far no study has been conducted to investigate if facial expressions are related to these differences. The aim of this study is to explore if mice of wild origin (Mus spicilegus) express different facial expressions when confronted to novelty and to relate these mimics to their emotional reactivity profile. We used individual exploration scores in a novel odour test and in the elevated plus maze test as proxy measures of individual emotional reactivity. Our results showed that exploration scores in both tests were positively correlated, and both were related to the ear postures expressed by the individuals during their first exploration of the novel odour. This single component of facial expression was in fact a good indicator of inter-individual differences expressed in these two different tests suggesting a strong link between this marker and the individual emotional reactivity. These results highlight the great potential of facial expressions to assess emotional states in animals.

Quantitative Method to Assess Acute Stress Related Behavior in Dogs by Using Motion Capture Technology

Animal therapy is a form of healthcare intervention conducted with the aid of therapy animals, most commonly dogs. For a therapy dog to play an active role in animal therapy, an animal therapist must design a therapy program, which does not place the dog under stress. Generally, a dogs stress can be evaluated by observing its behavior. However, existing ethological evaluation indices of stress behavior are subjective and obscure, and discrimination between dogs stress behaviors is difficult for observers with insufficient experience. Thus, we propose to quantitatively evaluate behaviors associated with acute stress in dogs. We quantified dog behavior by using a motion capture system. Specifically, body and ear postures such as the opening degree of left and right ears, anteroposterior tilt of left and right ears, height of the vertex above the floor, height of the center of gravity above the floor, and angle between the lateral axis of the body and the floor were recorded using nine motion capture markers. During the experiments, a canine subject was acutely stressed using a tail clamp, and the dogs posture while under stress was quantitatively distinguished from non-stress postures via quadratic discrimination analysis (QDA). From the results, we distinguished the dogs body and ears postures while under acute stress from those under non-stressed conditions with 81% sensitivity and 93% specificity, and a quantitative evaluation of the dogs acute stress behavior was carried out.

Frontal Brain Activity and Behavioral Indicators of Affective States are Weakly Affected by Thermal Stimuli in Sheep Living in Different Housing Conditions.

Many stimuli evoke short-term emotional reactions. These reactions may play an important role in assessing how a subject perceives a stimulus. Additionally, long-term mood may modulate the emotional reactions but it is still unclear in what way. The question seems to be important in terms of animal welfare, as a negative mood may taint emotional reactions. In the present study with sheep, we investigated the effects of thermal stimuli on emotional reactions and the potential modulating effect of mood induced by manipulations of the housing conditions. We assume that unpredictable, stimulus-poor conditions lead to a negative and predictable, stimulus-rich conditions to a positive mood state. The thermal stimuli were applied to the upper breast during warm ambient temperatures: hot (as presumably negative), intermediate, and cold (as presumably positive). We recorded cortical activity by functional near-infrared spectroscopy, restlessness behavior (e.g., locomotor activity, aversive behaviors), and ear postures as indicators of emotional reactions. The strongest hemodynamic reaction was found during a stimulus of intermediate valence independent of the animal’s housing conditions, whereas locomotor activity, ear movements, and aversive behaviors were seen most in sheep from the unpredictable, stimulus-poor housing conditions, independent of stimulus valence. We conclude that, sheep perceived the thermal stimuli and differentiated between some of them. An adequate interpretation of the neuronal activity pattern remains difficult, though. The effects of housing conditions were small indicating that the induction of mood was only modestly efficacious. Therefore, a modulating effect of mood on the emotional reaction was not found.

Do lambs perceive regular human stroking as pleasant? Behavior and heart rate variability analyses.

Stroking by humans is beneficial to the human-animal relationship and improves welfare in many species that express intraspecific allogrooming, but very few studies have looked at species like sheep that do not express such contact except around parturition. This study investigated the way lambs perceive regular human tactile contact using behavioral and physiological responses. Twenty-four lambs were reared and bucket-fed in groups of four. All were stroked daily by their familiar caregiver. At 8 weeks of age, the lambs were individually tested in their home pen but in a 1×1m open-barred pen after a 15h period of habituation to physical separation from peers while remaining in visual and auditory contact. Half of the lambs received stroking by their caregiver for 8min and half were exposed to their caregiver’s immobile presence. Heart rate and heart rate variability were recorded and analyzed by 2-min slots over the same interval based on three measures: mean heart rate value (HR), root mean square of successive differences (RMSSD) and standard deviation of all intervals measured between consecutive sinus beats (SDNN). Behavioral responses (ear postures of the lamb and time spent in contact with the familiar caregiver, on the knees of the familiar caregiver, and moving) were recorded throughout the test. Lamb HR decreased continuously while in the presence of their caregiver. Lambs being stroked showed slower HR and higher RMSSD which reflected positive emotional states compared to lambs left unstroked. All behavioral variables were highly correlated with the main component axis of the PCA analyses: the more the animals stayed in contact with their caregiver, the less they moved and the more their ears were hanging. This first component clearly differentiates lambs being stroked or not. Behavioral and physiological observations support the hypothesis that gentle physical contact with the caregiver is perceived positively by lambs.

Can ear postures reliably measure the positive emotional state of cows?

Animal welfare science is increasingly concerned with the promotion of positive emotions in animals, yet little is known about how to measure them. We examined whether ear postures in dairy cows were reliable indicators of a low arousal, positive emotional state. We conducted a total of 381, 15min focal observations, across a group of 13 cows, using stroking as a positive stimulus. Each focal observation was comprised of three, 5min segments; pre-stroking (baseline), stroking (stimulus), and post-stroking (post-stimulus). Throughout the focal observation, one researcher filmed the focal cow's ear on the side which was to be stroked, and a second researcher recorded the focal cow's behaviour. During the stroking segment the third researcher, who was present in the cow pen throughout, stroked the habituated cow on certain regions of their head, neck and withers for 5min. Following this, the stroker left and the filming and behavioural observations continued for another 5min (post-stroking segment). To eliminate extraneous variables we controlled for activity levels and other behaviours thought to be positive such as feeding.Prior to video analysis we identified four ear postures; an upright posture (EP1), a forward ear posture (EP2), a backward ear posture (EP3), and a hanging ear posture, where the ear fell loosely, perpendicular to the head (EP4). We then analysed the video footage to determine the duration of time spent in each of the four ear postures, and the number of ear posture changes performed during each segment. We performed One-Way ANOVA analyses, taking account of repeated measures, and found that EP1 and EP2 were performed for longer during the pre-stroking and post-stroking segments, than during the stroking segment (EP1; F(1.87, 671.09)=241.22, p<0.001; EP2; F(1.86, 668.87)=39.09, p<0.001). The opposite was found for EP3 and EP4, which were performed for longer during stroking than during either the pre-stroking or post-stroking segments (EP3; F(1.95, 698.27)=81.20, p<0.001, EP4; F(1.65, 591.02)=169.98, p<0.001). Furthermore, EP1 was performed for less time in the post-stroking segment compared with the pre-stroking segment, and EP3 was performed for longer during post-stroking compared with the pre-stroking segment (EP1; p<0.001, EP2; p<0.001). The number of ear posture changes increased during the stroking segment, compared with during both the pre-stroking and post-stroking segments (F(2, 718)=17.89, p<0.001).These results suggest that relaxed ear postures are indicative of what is suggested to be a positive, low arousal emotional state in dairy cows and could therefore be a useful, non-invasive measure of emotional state when used by trained observers. The results need further validation with other stimuli and arousal levels, but they have the potential to be incorporated into on-farm welfare assessments.

Investigating the motivation to play in lambs

The aim of this study was to identify behaviours and ear postures linked to the appetitive, consummatory and post-consummatory motivational phases of play in male lambs, and to evaluate how cortisol was affected by play. Ten pairs of male lambs, Ovis aries were observed in a play arena three times a week for 4 weeks. They were kept in a holding pen for 5min (appetitive phase) where they could look into the play arena (containing a ball, two chains and a tunnel) and thereafter released into the play arena for 20min (consummatory phase). They returned to their home pen where they were observed for 6min (post-consummatory phase). Direct observations were made in each location and behaviours were recorded as frequencies per min. Ear postures were recorded instantaneously every 15s for 3min per location. Saliva samples were taken in the 4th week for analysis of cortisol. Behaviours were analysed with a generalized linear model and cortisol with paired t-test. In the holding pen, the most common behaviours were walking, sniffing pen, standing facing play arena, standing facing alley, butting and pawing. Walking (P<0.001) and standing facing play arena (P<0.001) were higher during the 1st min whereas butting (P<0.001) was lower during the 1st min compared to the other 4min. In the play arena, social play was more frequent than locomotor and object play (median: 1.85, 0.97, and 1.14 events per min, respectively). Total play and locomotor play decreased across the 20min, whereas social play remained high until the 8th min. Total play (P<0.001) and social play (P<0.01) were most frequent during the 2nd week. Walking and standing were performed immediately after returning to the home pen but after the 1st min, lambs spent most of their time feeding. Raised and backward ear postures were common in the holding pen and play arena whereas plane ear postures were more common in the home pen. Salivary cortisol tended to increase after play (P=0.08). In conclusion, lambs showed different active behaviours together with raised and backward ear postures during the appetitive phase, high amounts of play together with backward and raised ear postures during the consummatory phase and mainly feeding together with plane ear postures during the post-consummatory phase.

Welfare by the ear: comparing relative durations and frequencies of ear postures by using an automated tracking system in sheep

AbstractGiven the increased interest in animal emotional reactions for assessing welfare, indicators for such reactions are sought. Ear postures and movements have been found to be promising indicators of emotional states in sheep and other animals. The manual recording of ear postures, however, is very time consuming and possibly prone to a degree of inaccuracy due to the subtle and fast nature of ear movements that have to be identified. Therefore, a number of previous studies have analysed the frequency of certain ear postures relative to all ear posture changes rather than measuring the relative duration spent with different ear postures. Here, we present an automated, continuous tracking system that keeps track of small and lightweight marker balls attached to the head and ears of sheep. We measured ear postures and movements when the animals were confronted with three physical stimuli thought to differ in valence (from negative to intermediate to positive). We then compared new ear-posture definitions reflecting the real time spent with certain ear postures during stimulation with previous definitions used for video-based analyses that assessed ear-posture changes in relation to the total number of observed ear postures. In the analysis, we correlated new and previous measures both between and within experimental stimuli using residuals from mixed-effects models. We found that the new and previous definitions of ear postures and movements correlated highly. Given these high correlations and the discussed theoretical and practical advantages of the automated tracking, the new recording system can be recommended highly for assessing reactions in animals that may indicate emotional states.

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

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.

Opioid control of behaviour in sheep: Effects of morphine and naloxone on food intake, activity and the affective state

The affective states of animals are important determinants of welfare, yet they are poorly understood. Here we investigate opioid involvement in the regulation of behaviours that may be indicative of the arousal and valence components of affective states in sheep. Ewes treated with sterile water (C), a low or high dose of the opioid agonist morphine (M1, M2) or opioid antagonist naloxone (N1, N2; n=8 per treatment) were exposed to a range of different situations, including availability of concentrate feed, grazing in a paddock, novel object test and isolation box test; behavioural indicators, activity and ear postures were assessed. Morphine treated ewes crossed more zones (78.1±5.4 for M1, P=0.025 and 99.3±5.4 for M2, P=0.01) compared to C ewes (37.3±5.4) and vocalized more (49.9±6.5 for M1, P<0.001 and 43.2±6.5 for M2, P=0.005) compared to C ewes (9.7±6.5) during the novel object test. Morphine treated ewes also attempted to escape more often (3.7±0.6 for M1, P=0.01 and 4.3±0.6 for M2, P<0.001) compared to C ewes (0.7±0.6) and showed a higher duration of the backward ear posture (14.9±2.0s for M1, P=0.02) compared to C ewes (6.1±2.0s) during the novel object test. While grazing, morphine treated ewes (M1, P=0.025 and M2, P<0.001) also walked more compared to compared to C ewes. Opioid treatment did not affect agitation during the isolation test. Concentrate feed intake (square-rootg) was slightly reduced in the N2 ewes (3.6±0.9, P=0.02) compared to the C ewes (6.6±0.9) at 1.5h after injection, while morphine had no effect on intake. In conclusion, morphine had a major impact on activity suggesting that the opioid system may be involved in regulating the arousal component of affective states in sheep. Morphine may have reduced the negative experience in the novel object test as indicated by the higher duration of the backward ear posture; however, further investigation is needed to determine the impact of opioid administration on emotional valence.

Housing induced mood modulates reactions to emotional stimuli in sheep

The assessment of positive and negative short-term affective states (emotions) in animals and their modulation by long-term affective states (mood) is an on-going challenge. This study investigated the use of behavioural and physiological measures to assess emotions and their modulation by mood in sheep. To induce a more Positive and more Negative mood, two groups of sheep ( n = 10 and 9) were kept under different housing conditions for 3 weeks. The Positive mood group was placed in a predictable environment rich in stimuli and with a calm human–animal interaction whereas sheep in the Negative mood group experienced a relatively barren and unpredictable environment with a harsher human–animal interaction. In the subsequent test week, 15 (8 and 7) experimental animals were exposed to four situations intended to elicit emotional reactions: separation from group members (negative valence), sham-grooming (low intensity negative), non-grooming (neutral), and grooming (positive valence). Data were tested for interactions between mood group and valence of the test situation using linear mixed models. More frequent ear-posture changes, a higher proportion of asymmetric ears, shorter inter-heartbeat intervals and higher respiration rates were observed during separation than during the other situations. Interactions between mood group and test situation showed that sheep in the Negative mood group reacted more negatively to the negative and more positively to the positive situation (proportion of asymmetric ears, inter-heartbeat interval, respiration rate). In conclusion, our findings suggest that sheep in a Positive mood reacted more weakly to an emotional situation independent of its valence, thus buffering negative events but also degrading positive events. In addition, this investigation showed the potential of using observations of ear postures and cardio-respiratory measures in sheep to assess the valence of short-term emotional states and their modulation by mood states.