Facial expressions in horses are non-verbal cues that involve the movement of facial muscles and structures, such as the eyes, ears, nostrils, and mouth. These expressions can convey information about a horse's emotional state, intentions, or responses to external stimuli. The study of equine facial expressions involves analyzing specific movements and configurations, such as ear positioning or nostril flaring, to interpret behavioral and emotional contexts. Researchers utilize various methodologies, including observational studies and facial action coding systems, to systematically document and understand these expressions. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, interpretation, and implications of facial expressions in equine behavior and welfare.
Maloney B, Jung MS, Kearns G, Bowe C.Equestrian-related activities inherently involve the risk of serious injury. There are few reports of maxillofacial injury patterns and management arising from equestrian activities in the literature. Objective: To investigate maxillofacial fracture presentations at a tertiary trauma centre to identify injury profiles of patients who have sustained equine-based injuries over 5 years. Methods: This work involved a retrospective review of all trauma presentations to our unit over 5 years. The data collected included patient demographics, injury mechanisms and patterns, and management of fractu...
Portier K, Schiesari C, Gauthier L, Yeng LT, Tabacchi Fantoni D, Formenton MR.Myofascial trigger points (MTrPs) are localized, hypersensitive areas in muscles that can cause pain and reduced performance. This study aimed to compare the prevalence and location of MTrPs in show-jumping and dressage horses. A secondary objective was to evaluate the potential of thermography, pressure algometry, and facial expression scoring in characterizing MTrPs in horses. Fourteen horses (seven dressage, seven show-jumping) were examined. Muscle palpation was used to identify MTrPs. Thermography was used to compare the skin surface temperature of MTrPs with adjacent control areas. Addit...
Jardat P, Yamamoto S, Ringhofer M, Tanguy-Guillo N, Parias C, Reigner F, Calandreau L, Lansade L.Emotional contagion, the emotional state-matching of two individuals, has been documented in various species. Recent findings suggest emotional contagion could also take place between humans and domestic mammals. However, the range of targeted animal species and human emotions that have been studied is still limited, and the methodology to investigate emotional contagion in this context is not fully established. This study examined emotional contagion of fear and joy from humans to horses by measuring physiological (heart rate, infrared thermography) and behavioral responses (posture, laterali...
da Fé VCS, Dos Santos VMO, de Lima ACB, Hernandes MSP, Caldara FR, Gomes MNB.This study aimed to evaluate the effect of auditory stimuli on mares and geldings during social isolation and movement restriction, and their ability to promote the reduction of stress responses. The research was conducted with eight Pantaneiro horses, divided into Experiment I (4 mares) and Experiment II (4 geldings), both experiments were executed equally using a 4x4 Latin square design with experimental (classical, country and new age) and control (no music) treatments. Physiological parameters (heart rate, heart rate variability, respiratory rate, ocular temperature by infrared thermograph...
Phelipon R, Bertrand L, Jardat P, Reigner F, Lewis K, Micheletta J, Lansade L.The welfare of an animal is closely linked to their emotional experiences, making it essential to identify reliable indicators of these emotions. This study aimed to identify behaviours and facial movements in horses experiencing contrasting emotional valence, triggered by the anticipation of a positive condition (going to pasture) or a negative condition (going alone to a novel environment). Twenty horses were daily trained to wait in a starting box before being exposed to these two conditions. After one week of positive training or negative training, we analysed horses' behaviours, cortisol ...
Van den Branden E, Salamone M, Broothaers K, Peere S, Polfliet E, Dewulf M, Van Steenkiste G, van Loon G, Smits K, Govaere J.The use of transvaginal ultrasound-guided follicle aspiration (TVA) for oocyte collection has become a widely used procedure in horses for embryo production (IVEP). The TVA procedure is characterized by various manipulations, which are physical restraint, perineal preparation, transrectal palpation, insertion of an intravaginal device, and needle punctures. These repeated transvaginal and transovarian punctures have raised concerns about their potential effects on mare welfare. Our study aimed to investigate the effects of TVA manipulations, and especially puncturing, on pain and stress in ma...
Franzen V, Reisbeck D, Leibl Y, Schoster A, May A.While there is agreement that horses experience pain during the actual headshaking attacks, there is still a lack of research about the time between the individual episodes in this species. Objective: To evaluate the signs of pain in horses with TMHS at rest in the absence of common triggering factors. Methods: Twenty TMHS horses (not head shaking at the time of pain assessment), 20 horses with colic, and 20 clinically healthy horses. Methods: Descriptive study assessing pain in TMHS horses during the absence of clinical signs using the Horse Grimace scale (HGS). To grade the pain shown with T...
Mota-Rojas D, Whittaker AL, Bienboire-Frosini C, Buenhombre J, Mora-Medina P, Domínguez-Oliva A, Martínez-Burnes J, Hernández-Avalos I....Recognizing that nonhuman animals are sentient beings has increased interest in studying their emotional state. Similar to humans, research has shown that some nonhuman mammals can modify facial expressions by contraction/relaxation of facial muscles according to their affective state. From a neurophysiological perspective, emotions are processed in several brain structures, mainly from the limbic system, such as the hypothalamus, hypophysis, hippocampus, prefrontal cortex, and amygdala. The converged pathways between the amygdala, the motor cortex, and its projections to the facial nerve cont...
Mota-Rojas D, Whittaker AL, Coria-Avila GA, Martínez-Burnes J, Mora-Medina P, Domínguez-Oliva A, Hernández-Avalos I, Olmos-Hernández A....The growing interest in managing and recognizing pain in animals has led to the search for more sensitive methods to evaluate it, especially because some species conceal any visible changes associated with pain or are not easily assessed. Research has shown that an animal's facial expression changes when exposed to painful stimuli. Thus, developing several pain scales (grimace scales) in species such as horses, cattle, pigs, sheep, donkeys, rabbits, rats, mice, and cats has helped to improve the study of pain in veterinary medicine. The possibility of using facial expression as an indicator of...
Lundblad J, Rhodin M, Hernlund E, Bjarnestig H, Hidén Rudander S, Haubro Andersen P.Facial expressions in prey animals such as equines can convey information regarding their internal state and are therefore often used as cues for welfare and pain evaluation. The state of pain is commonly compared to a neutral state with little consideration given to other experiences that could affect the animal, although this situation is rare outside of experimental contexts. To evaluate the effect of managerial contexts on facial expressions from a nociceptive input, conspecific isolation and sedation with known physiological effects were compared to compound states of nociception. Using a...
Feighelstein M, Ricci-Bonot C, Hasan H, Weinberg H, Rettig T, Segal M, Distelfeld T, Shimshoni I, Mills DS, Zamansky A.[This corrects the article DOI: 10.1371/journal.pone.0302893.].
Clayton HM, Murray R, Williams JM, Walker V, Fisher M, Fisher D, Nixon J, Mackechnie-Guire R.Noseband adjustment should avoid discomfort and allow some jaw movement. Objective: To determine pressure beneath a cavesson noseband at five tightness levels during standing and chewing. It was hypothesised that increased noseband tightness is associated with increases in nasal and mandibular pressures while standing and chewing, accompanied by increases in eye temperature and blink rate. Methods: Experimental. Methods: Eight highly-trained dressage horses wore a snaffle bridle with their own bit. Pressure mats over the nasal bones and beneath the mandibular rami recorded sub-noseband pressur...
Sidwell AE, Duz M, Hill B, Freeman S, Hole SL.Dental disease is a common but often under-recognised condition in horses, possibly due to an inability to recognise clinical signs of oral discomfort. Some dental disorders are reportedly more painful than others, but there is no current metric by which dental pain can be objectively assessed. This study aimed to determine whether a facial expression-based pain scale offered an objective and reliable method for assessing dental pain in horses. It was hypothesised that dental disorders affecting the periodontium would produce high pain scores. Twelve horses with dental disease were evaluated f...
Zimmermann B, Castro ANC, Lendez PA, Carrica Illia M, Carrica Illia MP, Teyseyre AR, Toloza JM, Ghezzi MD, Mota-Rojas D.An emotion is defined as the affective response to a stimulus that leads to specific bodily changes, enabling individuals to react to positive or negative environmental conditions. In the absence of speech, emotions in animals are primarily studied by observing expressive components, such as facial expressions. This review aims to analyze the available literature on the influence of environmental stimuli on measurable behaviors in horses, describing the anatomical components involved in perception at the central nervous system level and the efferent pathways that trigger facial muscle contract...
Werner LC, de Oliveira GM, Daros RR, Costa ED, Michelotto PV.The use of grimace scales enables the clinical identification of changes in the facial expressions of animals caused by pain. The Horse Grimace Scale (HGS) is one such tool, comprising a pain coding system based on facial expressions and assessing six Facial Action Units (FAUs). Each FAU is accompanied by descriptions and anatomical details to assist the evaluator. However, the morphological descriptions for certain FAUs in the HGS are not sufficiently detailed, potentially hindering accurate interpretation. This study is an analytical investigation aimed at enhancing the morphoanatomical deta...
Wolschrijn CF, Smit IH, Schouten J, Moller Te NCR.Facial expressions are important in pain recognition in horses, but current observation-based pain scales remain subjective. A promising technique to quantitatively measure subtle changes in expression patterns, including changes invisible to the human eye, is surface electromyography (sEMG). To achieve high-quality and reliable sEMG signals, unilateral placement of bipolar electrodes is required in relation to the motor endplates (MEP). We aimed to localize the nerve entry points (NEPs; where the nerve branch first pierced the muscle belly) and the direction of the terminal nerve endings to e...
Feighelstein M, Riccie-Bonot C, Hasan H, Weinberg H, Rettig T, Segal M, Distelfeld T, Shimshoni I, Mills DS, Zamansky A.Animal affective computing is an emerging new field, which has so far mainly focused on pain, while other emotional states remain uncharted territories, especially in horses. This study is the first to develop AI models to automatically recognize horse emotional states from facial expressions using data collected in a controlled experiment. We explore two types of pipelines: a deep learning one which takes as input video footage, and a machine learning one which takes as input EquiFACS annotations. The former outperforms the latter, with 76% accuracy in separating between four emotional states...
Torres Borda L, Kelemen Z, Auer U, Jenner F.Equine social behaviour studies face challenges stemming from the absence of a comprehensive ethogram with unequivocal standardised definitions and the resulting limits to data comparison across studies. To address these constraints, this ethogram offers researchers a standardised framework, defining thirty-seven distinct equine social behaviours supplemented by video examples for enhanced clarity. These definitions amalgamate insights from existing ethograms and are fine-tuned through meticulous video observations, encompassing contextual cues such as distinguishing between aggressive and pla...
Kloock T, Hellige M, Kloock A, Feige K, Niebuhr T.Horses with trigeminal-mediated headshaking (TMHS) exhibit different headshaking patterns (HSPs), electric shock-like jerking, signs of nasal irritation, and painful facial expressions. The History Rest and Exercise Score (HRE-S) was developed to objectively clarify the severity of the condition in affected horses. This score considers the history and severity of clinical signs at rest and exercise. This study aimed to assess the frequency of different clinical signs and their individual associations with diagnosis, treatment, and outcome in horses diagnosed with TMHS.The clinical records of h...
Nannarone S, Ortolani F, Scilimati N, Gialletti R, Menchetti L.This study addresses the refinement and revalidation of a composite pain scale that focuses on equine facial expressions and behavioural indicators as exhibitions of ophthalmic pain. This scale included only Behavioural and Facial and Ocular expression indicators and, compared to the first version of Equine Ophthalmic Pain Scale (EOPS), item descriptors and related ratings were changed. Thirteen horses with ocular diseases that required medical or surgical treatment were enrolled (group P). In each animal, the refined EOPS (R-EOPS) was applied prior to any treatment (T0) and one week later (T7...
Eichler F, Ehrle A, Machnik M, Jensen KC, Wagner S, Baudisch N, Bolk J, Pötzsch M, Thevis M, Bäumer W, Lischer C, Wiegard M.As a remedy against stress and anxiety, cannabidiol (CBD) products are of increasing interest in veterinary medicine. Limited data is available describing the actual effectiveness of CBD in horses. The aim of this study (part 2 of 2) was to analyze stress parameters via behavioral observation, heart rate monitoring and assessment of blood and saliva cortisol levels in healthy horses treated repeatedly with a CBD containing paste. Twelve horses were randomly assigned to a treatment or a control group. Two pastes were orally administered in a double-blinded study design, one paste containing CBD...
Ask K, Rhodin M, Rashid-Engström M, Hernlund E, Andersen PH.A number of facial expressions are associated with pain in horses, however, the entire display of facial activities during orthopedic pain have yet to be described. The aim of the present study was to exhaustively map changes in facial activities in eight resting horses during a progression from sound to mild and moderate degree of orthopedic pain, induced by lipopolysaccharides (LPS) administered in the tarsocrural joint. Lameness progression and regression was measured by objective gait analysis during movement, and facial activities were described by EquiFACS in video sequences (n = 348...
Eichler F, Ehrle A, Jensen KC, Baudisch N, Petersen H, Bäumer W, Lischer C, Wiegard M.Cannabidiol (CBD) products have been proposed to exert stress- and anxiety-relieving effects in animals. Despite the increasing popularity of CBD for veterinary use, the available research detailing the effects of CBD in horses is limited. The aim of this study (part 1 of 2) was to analyze stress parameters via behavioral observations and heart rate monitoring in healthy horses following single oral administration of a CBD containing paste in different doses. Study products were two pastes for oral administration, one containing CBD and one containing no active ingredient. Pastes were applied ...
Jardat P, Liehrmann O, Reigner F, Parias C, Calandreau L, Lansade L.Communication of emotions plays a key role in intraspecific social interactions and likely in interspecific interactions. Several studies have shown that animals perceive human joy and anger, but few studies have examined other human emotions, such as sadness. In this study, we conducted a cross-modal experiment, in which we showed 28 horses two soundless videos simultaneously, one showing a sad, and one a joyful human face. These were accompanied by either a sad or joyful voice. The number of horses whose first look to the video that was incongruent with the voice was longer than their first ...
Carmo LG, Werner LC, Michelotto PV, Daros RR.Food rewards are believed to have a positive valence in horses. The aim of this study was to assess the effect of food rewards on horse behavior before entering a horse chute, and behavior and facial movements while restrained in it. Thirteen female adult horses were brought once daily to an animal handling facility for three weeks. In week 1, baseline period, no reinforcement was applied. In weeks 2 and 3, experimental phase, half of the horses received positive reinforcement treatment after entering and remaining in the chute; the remaining horses were considered as controls (no positive rei...
Tomberg C, Petagna M, de Selliers de Moranville LA.Facial micro-expressions are facial expressions expressed briefly (less than 500 ms) and involuntarily. Described only in humans, we investigated whether micro-expressions could also be expressed by non-human animal species. Using the Equine Facial action coding system (EquiFACS), an objective tool based on facial muscles actions, we demonstrated that a non-human species, Equus caballus, is expressing facial micro-expressions in a social context. The AU17, AD38 and AD1 were selectively modulated as micro-expression-but not as standard facial expression (all durations included)-in presence of ...
Anderson KA, Morrice-West AV, Wong ASM, Walmsley EA, Fisher AD, Whitton RC, Hitchens PL.Musculoskeletal injuries in racehorses are difficult to detect prior to catastrophic breakdown. Lameness is commonly attributed to orthopaedic pain in horses, therefore, subtle lameness may be a pre-clinical sign of injury and, if identified early, could allow for preventative intervention. Our objective was to determine if facial expressions could be used to detect mild lameness as an indicator of orthopaedic pain in 'fit to race' horses. The Horse Grimace Scale (HGS) and the facial expressions in ridden horses (FEReq), were used to score images (n = 380) of mildly lame (n = 21) and non-lame ...
Kim SM, Cho GJ.This study aimed to prove that deep learning can be effectively used for identifying various equine facial expressions as welfare indicators. In this study, a total of 749 horses (healthy: 586 and experiencing pain: 163) were investigated. Moreover, a model for recognizing facial expressions based on images and their classification into four categories, i.e., resting horses (RH), horses with pain (HP), horses immediately after exercise (HE), and horseshoeing horses (HH), was developed. The normalization of equine facial posture revealed that the profile (99.45%) had higher accuracy than the fr...
Carvalho JRG, Trindade PHE, Conde G, Antonioli ML, Funnicelli MIG, Dias PP, Canola PA, Chinelatto MA, Ferraz GC.Facial-expression-based analysis has been widely applied as a pain coding system in horses. Herein, we aimed to identify pain in horses undergoing subcutaneously polylactide-based polymer implantation. The sham group was submitted only to surgical incision. The horses were filmed before and 24 and 48 h after implantation. Five statistical methods for evaluating their facial expressions (FEs) were tested. Primarily, three levels of scores (0, 1, and 2) were applied to the seven FEs (ear movements, eyebrow tension, orbicularis tension, dilated nostrils, eye opening, muzzle tension, and masticato...
Dalla Costa E, Minero M, Lebelt D, Stucke D, Canali E, Leach MC.The assessment of pain is critical for the welfare of horses, in particular when pain is induced by common management procedures such as castration. Existing pain assessment methods have several limitations, which reduce the applicability in everyday life. Assessment of facial expression changes, as a novel means of pain scoring, may offer numerous advantages and overcome some of these limitations. The objective of this study was to develop and validate a standardised pain scale based on facial expressions in horses (Horse Grimace Scale [HGS]). Results: Forty stallions were assigned to one of ...
Smith AV, Proops L, Grounds K, Wathan J, McComb K.Whether non-human animals can recognize human signals, including emotions, has both scientific and applied importance, and is particularly relevant for domesticated species. This study presents the first evidence of horses' abilities to spontaneously discriminate between positive (happy) and negative (angry) human facial expressions in photographs. Our results showed that the angry faces induced responses indicative of a functional understanding of the stimuli: horses displayed a left-gaze bias (a lateralization generally associated with stimuli perceived as negative) and a quicker increase in...
Wathan J, Burrows AM, Waller BM, McComb K.Although previous studies of horses have investigated their facial expressions in specific contexts, e.g. pain, until now there has been no methodology available that documents all the possible facial movements of the horse and provides a way to record all potential facial configurations. This is essential for an objective description of horse facial expressions across a range of contexts that reflect different emotional states. Facial Action Coding Systems (FACS) provide a systematic methodology of identifying and coding facial expressions on the basis of underlying facial musculature and mus...
Wathan J, Proops L, Grounds K, McComb K.In humans, facial expressions are rich sources of social information and have an important role in regulating social interactions. However, the extent to which this is true in non-human animals, and particularly in non-primates, remains largely unknown. Therefore we tested whether domestic horses (Equus caballus) could discriminate between facial expressions of their conspecifics captured in different contexts, and whether viewing these expressions elicited functionally relevant reactions. Horses were more likely to approach photographic stimuli displaying facial expressions associated with po...
Dalla Costa E, Pascuzzo R, Leach MC, Dai F, Lebelt D, Vantini S, Minero M.Pain recognition is fundamental for safeguarding animal welfare. Facial expressions have been investigated in several species and grimace scales have been developed as pain assessment tool in many species including horses (HGS) and mice (MGS). This study is intended to progress the validation of grimace scales, by proposing a statistical approach to identify a classifier that can estimate the pain status of the animal based on Facial Action Units (FAUs) included in HGS and MGS. To achieve this aim, through a validity study, the relation between FAUs included in HGS and MGS and the real pain co...
Wathan J, McComb K.Sensitivity to the attentional states of others has adaptive advantages, and in social animals, attending to others is important for predator detection, as well as a pre-requisite for normal social functioning and more complex socio-cognitive abilities. Despite widespread interest in how social species perceive attention in others, studies of non-human animals have been inconclusive about the detailed cues involved. Previous work has focused on head and eye direction, overlooking the fact that many mammals have obvious and mobile ears that could act as a visual cue to attention. Here we report...
Waller BM, Julle-Daniere E, Micheletta J.Darwin observed that form, and in his view, meaning, of facial behaviour (observable changes in the appearance of the face, often termed facial 'expression') is similar between a wide range of species and concluded that this must be due to a shared ancestral origin. Yet, as with all social behaviours, exactly how to define similarity and determine homology is debated. Facial behaviour is linked to specific facial muscle movements, so one important factor in determining homology is the anatomical basis of facial behaviours that appear similar in both appearance and social function. The Facial A...
Lansade L, Nowak R, Lainé AL, Leterrier C, Bonneau C, Parias C, Bertin A.Behavioural and physiological markers of discrete positive emotions remain little investigated in animals. To characterise new markers in horses, we used tactile stimulations to induce emotional situation of contrasting valence. In the Gentle grooming group (G, N = 13) horses were gently groomed during 11 sessions on the body areas they appreciated the most. Horses in the Standard grooming group (S, N = 14) were groomed using a fixed procedure, reported to induce avoidance reactions in some horses. At session 11, G horses expressed significantly more contact-seeking behaviours than S h...
Stone SM.The human-horse relationship has a long evolutionary history. Horses continue to play a pivotal role in the lives of humans and it is common for humans to think their horses recognize them by face. If a horse can distinguish his/her human companion from other humans, then evolution has supplied the horse with a very adaptive cognitive ability. The current study used operant conditioning trials to examine whether horses could discriminate photographed human faces and transfer this facial recognition ability a novel setting. The results indicated the horses (a) learned to discriminate photograph...
Lencioni GC, de Sousa RV, de Souza Sardinha EJ, Corrêa RR, Zanella AJ.The aim of this study was to develop and evaluate a machine vision algorithm to assess the pain level in horses, using an automatic computational classifier based on the Horse Grimace Scale (HGS) and trained by machine learning method. The use of the Horse Grimace Scale is dependent on a human observer, who most of the time does not have availability to evaluate the animal for long periods and must also be well trained in order to apply the evaluation system correctly. In addition, even with adequate training, the presence of an unknown person near an animal in pain can result in behavioral ch...
Trösch M, Pellon S, Cuzol F, Parias C, Nowak R, Calandreau L, Lansade L.Animals can indirectly gather meaningful information about other individuals by eavesdropping on their third-party interactions. In particular, eavesdropping can be used to indirectly attribute a negative or positive valence to an individual and to adjust one's future behavior towards that individual. Few studies have focused on this ability in nonhuman animals, especially in nonprimate species. Here, we investigated this ability for the first time in domestic horses (Equus caballus) by projecting videos of positive and negative interactions between an unknown human experimenter (a "positive" ...
Hintze S, Smith S, Patt A, Bachmann I, Würbel H.Finding valid indicators of emotional states is one of the biggest challenges in animal welfare science. Here, we investigated in horses whether variation in the expression of eye wrinkles caused by contraction of the inner eyebrow raiser reflects emotional valence. By confronting horses with positive and negative conditions, we aimed to induce positive and negative emotional states, hypothesising that positive emotions would reduce whereas negative emotions would increase eye wrinkle expression. Sixteen horses were individually exposed in a balanced order to two positive (grooming, food antic...
Lansade L, Colson V, Parias C, Trösch M, Reigner F, Calandreau L.Horses are capable of identifying individual conspecifics based on olfactory, auditory or visual cues. However, this raises the questions of their ability to recognize human beings and on the basis of what cues. This study investigated whether horses could differentiate between a familiar and unfamiliar human from photographs of faces. Eleven horses were trained on a discrimination task using a computer-controlled screen, on which two photographs were presented simultaneously (32 trials/session): touching one was rewarded (S+) and the other not (S-). In the training phase, the S+ faces were of...
Rashid M, Silventoinen A, Gleerup KB, Andersen PH.During the last decade, a number of pain assessment tools based on facial expressions have been developed for horses. While all tools focus on moveable facial muscles related to the ears, eyes, nostrils, lips, and chin, results are difficult to compare due to differences in the research conditions, descriptions and methodologies. We used a Facial Action Coding System (FACS) modified for horses (EquiFACS) to code and analyse video recordings of acute short-term experimental pain (n = 6) and clinical cases expected to be in pain or without pain (n = 21). Statistical methods for analyses were a f...
Dai F, Leach M, MacRae AM, Minero M, Costa ED.The Horse Grimace Scale (HGS) is a facial-expression-based pain coding system that enables a range of acute painful conditions in horses to be effectively identified. Using valid assessment methods to identify pain in horses is of a clear importance; however, the reliability of the assessment is highly dependent on the assessors' ability to use it. Training of new assessors plays a critical role in underpinning reliability. The aim of the study was to evaluate whether a 30-minute standardised training program on HGS is effective at improving the agreement between observers with no horse experi...
Ask K, Rhodin M, Tamminen LM, Hernlund E, Haubro Andersen P.Equine orthopedic pain scales are targeted towards horses with moderate to severe orthopedic pain. Improved assessment of pain behavior and pain-related facial expressions at rest may refine orthopedic pain detection for mild lameness grades. Therefore, this study explored pain-related behaviors and facial expressions and sought to identify frequently occurring combinations. Orthopedic pain was induced by intra-articular LPS in eight horses, and objective movement asymmetry analyses were performed before and after induction together with pain assessments at rest. Three observers independently ...
Andersen PH, Broomé S, Rashid M, Lundblad J, Ask K, Li Z, Hernlund E, Rhodin M, Kjellström H.Automated recognition of human facial expressions of pain and emotions is to a certain degree a solved problem, using approaches based on computer vision and machine learning. However, the application of such methods to horses has proven difficult. Major barriers are the lack of sufficiently large, annotated databases for horses and difficulties in obtaining correct classifications of pain because horses are non-verbal. This review describes our work to overcome these barriers, using two different approaches. One involves the use of a manual, but relatively objective, classification system for...
Evangelista MC, Monteiro BP, Steagall PV.Facial expressions of pain have been identified in several animal species. The aim of this systematic review was to provide evidence on the measurement properties of grimace scales for pain assessment. The protocol was registered (SyRF#21-November-2019), and the study is reported according to the PRISMA guidelines. Studies reporting the development, validation, and the assessment of measurement properties of grimace scales were included. Data extraction and assessment were performed by 2 investigators, following the COnsensus-based Standards for the Selection of Health Measurement INstruments ...
Schanz L, Krueger K, Hintze S.Identifying valid indicators to assess animals' emotional states is a critical objective of animal welfare science. In horses, eye wrinkles above the eyeball have been shown to be affected by pain and other emotional states. From other species we know that individual characteristics, e.g., age in humans, affect facial wrinkles, but it has not yet been investigated whether eye wrinkle expression in horses is systematically affected by such characteristics. Therefore, the aim of this study was to assess how age, sex, breed type, body condition, and coat colour affect the expression and/or the as...
de Oliveira AR, Gozalo-Marcilla M, Ringer SK, Schauvliege S, Fonseca MW, Esteves Trindade PH, Prospero Puoli Filho JN, Luna SPL.Although facial characteristics are used to estimate horse sedation, there are no studies measuring their reliability and validity. This randomised controlled, prospective, horizontal study aimed to validate a facial sedation scale for horses (FaceSed). Seven horses received detomidine infusion i.v. in low or high doses/rates alone (DL 2.5 μg/kg+6.25 μg/kg/h; DH 5 μg/kg+12.5 μg/kg/h) or combined with methadone (DLM and DHM, 0.2 mg/kg+0.05 mg/kg/h) for 120 min, or acepromazine boli i.v. in low (ACPL 0.02 mg/kg) or high doses (ACPH 0.09 mg/kg). Horses' faces were photographed at i) baseline,...
Maglieri V, Bigozzi F, Riccobono MG, Palagi E.Social play is a window on cognitive and communicative abilities of species. Inter-specific play, in particular, is a fertile venue to explore the capacity to correctly perceive and interpret signals emitted by partners. Up to now, most studies have focussed on dog-human play due to the important implications such studies have in understanding the peculiar relationship we establish with our pets. Here, we focussed on social play between dogs and horses. By using a set of specific keywords (dog, horse, play, friend) we selected 20 videos of dog-horse social play (with each session lasting >3...
van Loon JPAM, Macri L.The objective assessment of chronic pain is of utmost importance for improving welfare and quality of life in horses. Freedom from disease and pain is one of the 'five freedoms' that are necessary for animal welfare. The aim of this study was to develop a pain scale for the assessment of chronic pain in horses (Horse Chronic Pain Scale; HCPS), which is based on behavioural and facial expressions. The scale was used to assess 53 horses (26 horses diagnosed with chronic painful conditions by means of clinical examination and additional diagnostic procedures (consisting of osteoarthritis, chronic...
Manso-Díaz G, Taeymans O.A 14-year-old Quarter Horse had chronic facial swelling and a more recent history of progressive bilateral epiphora. Radiographic findings were compatible with exostosis of the nasofrontal suture. Computed tomography (CT) of the head, including CT dacryorhinocystography, confirmed the diagnosis and allowed presurgical planning of resection of the exostosis, which resulted in resolution of the clinical signs.
Dalla Costa E, Dai F, Lecchi C, Ambrogi F, Lebelt D, Stucke D, Ravasio G, Ceciliani F, Minero M.Pain in horses is an emergent welfare concern, and its assessment represents a challenge for equine clinicians. This study aimed at improving pain assessment in horses through a convergent validation of existing tools: we investigated whether an effective analgesic treatment influences the horse grimace scale (HGS) and the concentration of specific circulating microRNAs (miRNAs). Eleven stallions underwent routine surgical castration under general anaesthesia. They were divided into two analgesic treatment groups: castration with the administration of preoperative flunixin and castration with ...
Jankunis ES, Whishaw IQ.Evidence suggests that behavioural affective reactions to sweet and bitter substances are homologous in humans, nonhuman primates, and rodents. The sweet taste of sucrose elicits facial responses that include rhythmic tongue protrusions whereas the bitter taste of quinine elicits facial responses that include gapes, featuring an opening of the mouth and protrusion of the tongue. The present study using the horse (Equus caballus) was undertaken for three reasons: (1) there is debate about the presence of a sweet receptor gene in the horse, (2) there is a need to expand the examination of facial...
Tomberg C, Petagna M, de Selliers de Moranville LA.Facial micro-expressions are facial expressions expressed briefly (less than 500 ms) and involuntarily. Described only in humans, we investigated whether micro-expressions could also be expressed by non-human animal species. Using the Equine Facial action coding system (EquiFACS), an objective tool based on facial muscles actions, we demonstrated that a non-human species, Equus caballus, is expressing facial micro-expressions in a social context. The AU17, AD38 and AD1 were selectively modulated as micro-expression-but not as standard facial expression (all durations included)-in presence of ...
Dalla Costa E, Dai F, Lecchi C, Ambrogi F, Lebelt D, Stucke D, Ravasio G, Ceciliani F, Minero M.Pain in horses is an emergent welfare concern, and its assessment represents a challenge for equine clinicians. This study aimed at improving pain assessment in horses through a convergent validation of existing tools: we investigated whether an effective analgesic treatment influences the horse grimace scale (HGS) and the concentration of specific circulating microRNAs (miRNAs). Eleven stallions underwent routine surgical castration under general anaesthesia. They were divided into two analgesic treatment groups: castration with the administration of preoperative flunixin and castration with ...
de Camp NV, Ladwig-Wiegard M, Geitner CIE, Bergeler J, Thöne-Reineke C.As has been hypothesized more than 20 years ago, data derived from Electroencephalography (EEG) measurements can be used to distinguish between behavioral states associated with animal welfare. In our current study we found a high degree of correlation between the modulation index of phase related amplitude changes in the EEG of horses ( = 6 measurements with three different horses, mare and gelding) and their facial expression, measured by the use of the horse grimace scale. Furthermore, the pattern of phase amplitude coupling (PAC) was significantly different between a rest condition and a s...
Islam S, Gupta B, Taylor CJ, Chow J, Hoffman GR.We explored the relation between the causes of facial injuries in equestrians and the presence or absence of associated injuries. Over a 5-year period we retrospectively reviewed all patients who presented to the John Hunter Hospital, New South Wales, with facial injuries that had resulted from activity with horses. We analysed the rates of hard and soft tissue injuries, and of associated injuries by sex and mechanism. A total of 85 patients were included (50 female and 35 male) with an age range of 2-88 years. There was a significant difference in the rate of maxillofacial and associated inju...
Murphy J, Arkins S.Several species demonstrate obvious motor laterality (sidedness, handedness) in their motor function. Motor laterality in the horse affects locomotion and subsequently equine performance during training and may have inherent safety implications for equitation. Some of the most commonly used identification features in the horse are hair whorls (trichoglyphs), since their specific location and character vary to some degree in every horse. We investigated the relationship between the hair flow of single facial hair whorls and the incidence of lateralised motor bias in 219 horses when under saddle...
