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Topic:Facial Expressions

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.
Sex and Age Don’t Matter, but Breed Type Does-Factors Influencing Eye Wrinkle Expression in Horses.
Frontiers in veterinary science    May 29, 2019   Volume 6 154 doi: 10.3389/fvets.2019.00154
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...
Facial expression and oxytocin as possible markers of positive emotions in horses.
Scientific reports    October 2, 2018   Volume 8, Issue 1 14680 doi: 10.1038/s41598-018-32993-z
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...
Can grimace scales estimate the pain status in horses and mice? A statistical approach to identify a classifier.
PloS one    August 1, 2018   Volume 13, Issue 8 e0200339 doi: 10.1371/journal.pone.0200339
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...
Corrigendum to: “Directional asymmetry of facial and limb traits in horses and ponies” [Vet. J. 198 (2013) e46-51].
Veterinary journal (London, England : 1997)    December 18, 2017   Volume 232 15 doi: 10.1016/j.tvjl.2017.12.001
Leśniak K.No abstract available
Management of combat-related facial injuries.
La Tunisie medicale    October 11, 2017   Volume 94, Issue 12 856 
Mardassi A, Turki S, Mbarek H, Hachicha A, Chebbi G, Benzarti S, Abouda M.Combat-related facial injuries involve various lesions of the mouth, the eye sockets and the facial bones. The goal of this study is to precise the particularities of these affections and their therapeutic management. Methods: A retrospective study was performed about 56 cases of combat-related facial injuries over a period of 5 years (2010 - 2014). Results: Our study included 56 male patients with an average age of 29 years (20-37). The trauma occurred during a real security intervention in all the cases. It was isolated in 18 cases and associated to other lesions in 38 cases. Clinical examin...
Horses discriminate between facial expressions of conspecifics.
Scientific reports    December 20, 2016   Volume 6 38322 doi: 10.1038/srep38322
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...
Are Eyes a Mirror of the Soul? What Eye Wrinkles Reveal about a Horse’s Emotional State.
PloS one    October 12, 2016   Volume 11, Issue 10 e0164017 doi: 10.1371/journal.pone.0164017
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...
Horses give functionally relevant responses to human facial expressions of emotion: a response to Schmoll (2016).
Biology letters    September 15, 2016   Volume 12, Issue 9 20160549 doi: 10.1098/rsbl.2016.0549
Smith AV, Proops L, Grounds K, Wathan J, McComb K.No abstract available
Influence of transvaginal ultrasound-guided follicular punctures in the mare on heart rate, respiratory rate, facial expression changes, and salivary cortisol as pain scoring.
Theriogenology    June 6, 2016   Volume 86, Issue 7 1757-1763 doi: 10.1016/j.theriogenology.2016.05.040
Diego R, Douet C, Reigner F, Blard T, Cognié J, Deleuze S, Goudet G.Transvaginal ultrasound-guided follicular punctures are widely used in the mare for diagnosis, research, and commercial applications. The objective of our study was to determine their influence on pain, stress, and well-being in the mare, by evaluating heart rate, breath rate, facial expression changes, and salivary cortisol before, during, and after puncture. For this experiment, 21 pony mares were used. Transvaginal ultrasound-guided aspirations were performed on 11 mares. After injections for sedation, analgesia, and antispasmodia, the follicles from both ovaries were aspirated with a needl...
Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus).
Biology letters    February 13, 2016   Volume 12, Issue 2 20150907 doi: 10.1098/rsbl.2015.0907
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...
Correction: EquiFACS: The Equine Facial Action Coding System.
PloS one    September 3, 2015   Volume 10, Issue 9 e0137818 doi: 10.1371/journal.pone.0137818
Wathan J, Burrows AM, Waller BM, McComb K.No abstract available
EquiFACS: The Equine Facial Action Coding System.
PloS one    August 5, 2015   Volume 10, Issue 8 e0131738 doi: 10.1371/journal.pone.0131738
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...
The eyes and ears are visual indicators of attention in domestic horses.
Current biology : CB    August 6, 2014   Volume 24, Issue 15 R677-R679 doi: 10.1016/j.cub.2014.06.023
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...
An equine pain face.
Veterinary anaesthesia and analgesia    July 31, 2014   Volume 42, Issue 1 103-114 doi: 10.1111/vaa.12212
Gleerup KB, Forkman B, Lindegaard C, Andersen PH.The objective of this study was to investigate the existence of an equine pain face and to describe this in detail. Methods: Semi-randomized, controlled, crossover trial. Methods: Six adult horses. Methods: Pain was induced with two noxious stimuli, a tourniquet on the antebrachium and topical application of capsaicin. All horses participated in two control trials and received both noxious stimuli twice, once with and once without an observer present. During all sessions their pain state was scored. The horses were filmed and the close-up video recordings of the faces were analysed for alterat...
Development of the Horse Grimace Scale (HGS) as a pain assessment tool in horses undergoing routine castration.
PloS one    March 19, 2014   Volume 9, Issue 3 e92281 doi: 10.1371/journal.pone.0092281
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 ...
Equine-associated maxillofacial injuries: retrospective 5-year analysis.
The British journal of oral & maxillofacial surgery    October 26, 2013   Volume 52, Issue 2 124-127 doi: 10.1016/j.bjoms.2013.09.019
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...
Sucrose Bobs and Quinine Gapes: horse (Equus caballus) responses to taste support phylogenetic similarity in taste reactivity.
Behavioural brain research    August 21, 2013   Volume 256 284-290 doi: 10.1016/j.bbr.2013.08.024
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...
Investigation of a progressive facial deformity and stridor in an adult horse with a bone sequestrum and subsequent sinonasal abscess.
The Canadian veterinary journal = La revue veterinaire canadienne    December 4, 2012   Volume 53, Issue 6 653-658 
Marqués FJ, Sharma A, Wilson DG.Advanced diagnostic imaging and histopathological investigation were performed in an adult horse with chronic facial swelling due to a bone sequestrum and abscessation. In contrast to other cases, there were no draining tracts, difficulty eating, weight loss, head shaking, or fistula formation between the oral cavity and the maxillary sinus. Une investigation d’imagerie diagnostique avancée et un examen histopathologique ont été réalisés chez un cheval adulte présentant de l’enflure faciale chronique attribuable à un séquestre osseux et à une abcédation. Par contraste à d’aut...
Imaging diagnosis–nasofrontal suture exostosis in a horse. 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.
A case of facial deformity due to bilateral developmental maxillary cheek teeth displacement in an adult horse.
The Canadian veterinary journal = La revue veterinaire canadienne    January 5, 2011   Volume 51, Issue 10 1152-1156 
Robert MP, Gangl MC, Lepage OM.A 7-year-old mare presented with facial deformities associated with oral discomfort and weight loss was found to have bilateral, palatal, developmental displacements of the maxillary 08s, with secondary diastema. Following repulsion of both displaced teeth, the horse regained weight and resumed training. Bony deformities remained visible 9 mo after discharge. Une jument de 7 ans présentée avec des déformations faciales associées à de l’inconfort oral et à une perte de poids a montré, après examen, des déplacements développementaux, bilatéraux, du coté palatal des 4 prémolaires ...
Suture exostosis causing obstruction in the nasolacrimal duct in three horses.
New Zealand veterinary journal    August 4, 2009   Volume 57, Issue 4 229-234 doi: 10.1080/00480169.2009.36907
Carslake HB.Three horses were presented with facial swelling and epiphora. Results: All horses had facial swellings and radiographic findings consistent with exostosis at the lacrimomaxillary suture, and ipsilateral epiphora. Positive contrast dacryocystorhinography demonstrated that the site of obstruction of the nasolacrimal duct was located where the duct traverses the lacrimomaxillary suture. Methods: Lacrimomaxillary suture exostosis. Conclusions: Lacrimomaxillary suture exostosis should be considered as a differential diagnosis in cases of epiphora in horses. Dacryocystorhinography, preferably retro...
Pneumocephalus secondary to removal of an osteoma from the paranasal sinuses of a horse.
Journal of the American Veterinary Medical Association    July 16, 2009   Volume 235, Issue 2 184-188 doi: 10.2460/javma.235.2.184
Ragle CA, de Mira MC, Pearson LK, Coelho JC.A 2-year-old Quarter Horse was evaluated because of a progressive left-sided facial deformity and unilateral nasal and ocular discharge. Results: Physical examination revealed convexity of the left frontonasal region, left-sided nasal and ocular discharge, and decreased air flow through the left nares. Radiography and computed tomography revealed an extensively mineralized mass occupying most of the left paranasal sinuses. Results: The mass was surgically debulked, but complete removal was precluded because the mass was tightly adhered to the frontal and maxillary bones. Results of histologic ...
Human facial discrimination in horses: can they tell us apart?
Animal cognition    June 17, 2009   Volume 13, Issue 1 51-61 doi: 10.1007/s10071-009-0244-x
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...
Facial hair whorls (trichoglyphs) and the incidence of motor laterality in the horse.
Behavioural processes    April 11, 2008   Volume 79, Issue 1 7-12 doi: 10.1016/j.beproc.2008.03.006
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...
Dentoalveolar and mandibular body fractures caused by a horse kick: report of a case.
The journal of contemporary dental practice    May 1, 2006   Volume 7, Issue 2 137-144 
Martins WD, Fávaro DM, Ribas Mde O, Martins G.A rare case of multiple mandibular fractures and severe facial laceration is presented. The cause was a horse hoof kick to an unmounted equestrian. The pertinent literature is reviewed and the maxillofacial injuries associated with animal interaction are discussed.
Use of distraction osteogenesis for the correction of deviated nasal septum and premaxilla in a horse.
Journal of the American Veterinary Medical Association    April 13, 2004   Volume 224, Issue 7 1147-1112 doi: 10.2460/javma.2004.224.1147
Puchol JL, Herrán R, Durall I, López J, Díaz-Bertrana C.A 13-month-old female Andalusian was evaluated because of a congenital left deviation of the maxilla and nasal septum, which had resulted in a gross malocclusion of the maxillary incisor teeth. Surgical correction of a deviated nasal septum and premaxilla in a horse was first reported in 1978 and involved a pre-maxilla osteotomy and use of an autogenous rib graft, with a nasal septum osteotomy performed in a second surgery; to the authors' knowledge, no alternative surgical treatments have since been described. In this horse, a new surgical treatment by distraction osteogenesis without nasal s...
Displacement of maxillary premolar teeth in a filly.
Journal of veterinary dentistry    January 7, 2004   Volume 20, Issue 3 143-145 doi: 10.1177/089875640302000302
Capik I, Ledecky V, Mihály M.Abnormalities of dental development such as hypoplasia of cementum, oligodontia, polydontia, enamel hypoplasia, brachygnathia, and prognathia are quite common in the horse. Abnormalities of eruption are less common and often associated with trauma. This case report describes the diagnosis and therapy for pre-eruption displacement of the maxillary left third and fourth premolar teeth resulting from previous facial trauma in a 1.5-year-old filly.
Electrically induced blink reflex in horses.
The Veterinary record    December 21, 1996   Volume 139, Issue 25 621-624 
Añor S, Espadaler JM, Monreal L, Mayhew IG.The electrically induced blink reflex was studied electromyographically in 21 healthy adult, detomidine-sedated horses. Using surface electrodes, the supraorbital nerve was electrically stimulated at the supraorbital foramen. The responses were recorded from the ipsilateral and contralateral orbicularis oculi muscles with concentric needle electrodes inserted in the lateral aspect of the ventral eyelids. Ipsilateral and contralateral recordings were made on successive stimulations of the same side of the face, maintaining a constant stimulus intensity. The electromyographically recorded respon...
The surgical correction of a deviated anterior maxilla in a horse.
Australian veterinary journal    March 1, 1993   Volume 70, Issue 3 112-114 doi: 10.1111/j.1751-0813.1993.tb03291.x
McKellar GM, Collins AP.The surgical correction of facial deformities of the horse have rarely been undertaken. The surgical and medical management of submucous clefting of the anterior maxilla in a young colt is described.
Horner’s syndrome in ten horses.
The Canadian veterinary journal = La revue veterinaire canadienne    May 1, 1992   Volume 33, Issue 5 330-333 
Green SL, Cochrane SM, Smith-Maxie L.Ten cases of equine Horner's syndrome were reviewed. None of the clinical signs in this series were transient (<48 hours). Sweating and ptosis were consistently observed by the attending clinician in over half of the affected horses. Enophthalmos and prolapse of the third eyelid were not reported consistently. The average duration of the clinical signs was 4.94 months and ranged from 14 days to 15 months. Eight of the ten horses developed associated complications, some of which affected performance. Airway obstruction and impedance of passage of a fiberoptic endoscope due to nasal mucosal e...