Clinical interpretation of body language and behavioral modifications to recognize pain in domestic mammals

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TYPE Review PUBLISHED 15 October 2025 DOI 10.3389/fvets.2025.1679966 Clinical interpretation of body OPEN ACCESS language and behavioral modifications to recognize pain EDITED BY Melissa Bain, University of California, Davis, United States REVIEWED BY Teddy Lazebnik, in domestic mammals University of Haifa, Israel Lorenzo Alvarez, National Autonomous University of Mexico, Daniel Mota-Rojas 1*, Alexandra L. Whittaker 2, Lydia Lanzoni 3, Mexico Cécile Bienboire-Frosini 4, Adriana Domínguez-Oliva 1, *CORRESPONDENCE Alfonso Chay-Canul 5, Vivian Fischer 6, Temple Grandin cheryl.miller@colostate.edu Ismael Hernández-Avalos 7, Andrea Bragaglio 8,9, Daniel Mota-Rojas dmota100@yahoo.com.mx Eleonora Nannoni 10, Adriana Olmos-Hernández 11, RECEIVED 05 August 2025 Arthur Fernandes Bettencourt 12, Patricia Mora-Medina 7, ACCEPTED 26 September 2025 Julio Martínez-Burnes 13, Alejandro Casas-Alvarado 1 and PUBLISHED 15 October 2025 CITATION Temple Grandin 14* ​Mota-Rojas D, Whittaker AL, Lanzoni L, ​ 1 Neurophysiology, Behavior and Animal Welfare Assessment, DPAA, Universidad Autónoma Bienboire-Frosini C, ​Domínguez-Oliva A, ​ Metropolitana (UAM), Mexico City, Mexico, 2 School of Animal and Veterinary Sciences, Roseworthy Chay-Canul A, Fischer V, ​Hernández-Avalos I, Campus, University of Adelaide, Roseworthy, SA, Australia, 3 Animal Production and Health Division, Bragaglio A, Nannoni E, ​Olmos-Hernández A, Food and Agriculture Organization (FAO), Rome, Italy, 4 EPLFPA-Avignon, Avignon, France, 5 División Fernandes Bettencourt A, ​Mora-Medina P, ​ Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco, Villahermosa, Martínez-Burnes J, ​Casas-Alvarado A and Mexico, 6 Department of Animal Science, Federal University of Rio Grande do

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utónoma de Tabasco, Villahermosa, Martínez-Burnes J, ​Casas-Alvarado A and Mexico, 6 Department of Animal Science, Federal University of Rio Grande do Sul, Porto Alegre, Brazil, Grandin T (2025) Clinical interpretation of 7 Facultad de Estudios Superiores Cuautitlán, FESC, Universidad Nacional Autónoma de México body language and behavioral modifications (UNAM), Cuautitlán Izcalli, Mexico, 8 CREA Research Centre for Engineering and Agro-Food to recognize pain in domestic mammals. Processing, Consiglio per la Ricerca in Agricoltura el’Analisi dell’Economia Agraria, Treviglio, Italy, 9 Exo Front. Vet. Sci. 12:1679966. Research Organization, Potenza, Italy, 10 Department of Veterinary Medical Sciences, DIMEVET, doi: 10.3389/fvets.2025.1679966 University of Bologna, Bologna, Italy, 11 Division of Biotechnology-Bioterio and Experimental Surgery, COPYRIGHT Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra (INR-LGII), Mexico City, Mexico, © 2025 Mota-Rojas, Whittaker, Lanzoni, 12 Department of Animal Science, Federal University of Santa Maria, Santa Maria, Brazil, 13 Instituto de Bienboire-Frosini, Domínguez-Oliva, Ecología Aplicada, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Chay-Canul, Fischer, Hernández-Avalos, Tamaulipas, Victoria, Mexico, 14 Department of Animal Science, Colorado State University, Fort Collins, Bragaglio, Nannoni, Olmos-Hernández, CO, United States Fernandes Bettencourt, Mora-Medina, Martínez-Burnes, Casas-Alvarado and Grandin. This is an open-access article Nonhuman animals use nonverbal cues to communicate their mental state about distributed under the terms of the Creative positive and negative events, including pain. Pain is a multidimensional process Commons Attribution License (CC BY).

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under the terms of the Creative positive and negative events, including pain. Pain is a multidimensional process Commons Attribution License (CC BY). The use, distribution or reproduction in other that elicits behavioral changes aimed at preventing further damage and promoting forums is permitted, provided the original healing. These changes include restrictions on movement and/or activity, as well author(s) and the copyright owner(s) are as adopting body postures to relieve pain. Additionally, changes in the ear and tail credited and that the original publication in this journal is cited, in accordance with position have been associated with pain perception and are considered a sign of accepted academic practice. No use, pain in several domestic species. Thus, this review aims to critically analyze and distribution or reproduction is permitted discuss the behavioral modifications and body language expressions associated which does not comply with these terms. with pain in domestic animals, with a particular emphasis on changes in tail position, ear posture, and overall postural dynamics. This review also aims to highlight the essential role of veterinarians and animal scientists in recognizing these subtle non-verbal indicators during clinical evaluation, thereby fostering early detection and effective pain management through more precise observational assessment. KEYWORDS back arching, ear flattening, tucked tail, companion animals, farm animals Frontiers in Veterinary Science 01 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 1 Introduction association between pain processing and both behavioral and body posture changes, these aspects have been integrated into pain Pain assessment in veterinary medicine requires a multimodal assessment scales for

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body posture changes, these aspects have been integrated into pain Pain assessment in veterinary medicine requires a multimodal assessment scales for domestic mammals, which categorize pain by its approach that considers parameters beyond physiological and intensity and duration (24–26). Additionally, characterization of pain endocrine biomarkers due to its subjective and multidimensional requires consideration of the medical condition (e.g., surgical, nature (1–4). Some animals, such as horses and rodents, conceal signs traumatic, pathological, physiological) and the anatomical region (e.g., of pain due to their prey nature, which forces them not to appear lumbar, abdominal, limbs) to objectively associate certain behaviors vulnerable to other individuals (5–9). Moreover, non-human animals with pain (27). cannot self-report the presence or intensity of pain (1). Thus, Regardless of the differences between species, in animals such as considering the animal’s nonverbal communication cues are essential dogs, cats, horses, pigs, cattle, sheep, and goats, the modification of the to accurately evaluate pain (10). Nonverbal communication includes position of the ears or tail is considered one of the main changes in behavioral changes and modifications in body language (8, 11). body language related to the perception of pain (28–30). However, due Behavior refers to the movements and actions performed to respond to the variability in the expression of pain-associated responses in to stimuli (e.g., withdrawal response, guarding the affected area, or domestic mammals, assessment using pain scales requires training in vocalizing) (12). On the other hand, body language refers to changes the specific behavioral repertoire to detect alterations (31, 32). The in the

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in vocalizing) (12). On the other hand, body language refers to changes the specific behavioral repertoire to detect alterations (31, 32). The in the animal’s body posture, as well as limb movements, gestures, and complexity of recognizing behaviors and postures associated with pain facial expressions (13, 14). Changes in behavior and body language are in animals highlights the role that veterinarians have in promptly species-specific and have been recorded in animals exposed to noxious detecting pain and educating owners to detect it at home (33). stimuli (15–17). Through the recognition of the anatomical regions involved in According to the neurobiology of pain, the activation of peripheral pain processing and how pain manifests as changes in posture and nociceptors (nerve fibers specialized in detecting noxious stimuli) and behavior, a clinical and non-invasive evaluation of pain can their projection to the brain results in the conscious perception of pain be obtained. Thus, this review aims to critically analyze and discuss by the somatosensory cortex (Figure 1), also known as the affective the behavioral modifications and body language expressions component of pain (18–21). Pain demands attentiveness from animals. associated with pain in domestic animals, with particular emphasis on In consequence, this triggers several active or passive, defensive or changes in tail position, ear posture, and overall postural dynamics. reactive behavioral and body posture changes to prevent further This review also aims to underscore the essential role of the damage and promote recovery (6, 22, 23). Due to the neurobiological veterinarian in recognizing these subtle non-verbal indicators during FIGURE 1 Pain pathway and its association with behavioral responses. Frontiers

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l veterinarian in recognizing these subtle non-verbal indicators during FIGURE 1 Pain pathway and its association with behavioral responses. Frontiers in Veterinary Science 02 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 clinical evaluation, thereby fostering early detection and effective pain highlight the importance of pain-related behaviors in dogs by management through more precise observational assessment. developing a behavior-based scale to assess pain. In this scale, Moreover, this review also provides practical information that restlessness, vocalization, and reluctance to rise or sit are present in veterinary practitioners can use to assess pain in different domestic animals with severe surgical pain after ovariohysterectomy (OVH) or mammals. Figure 2 schematizes the overall structure of the review. castration. Similarly, in Reid et al.’s (44) study, groaning or screaming, growling, and snapping in response to touch, as well as anxiety, fearfulness, or non-responsiveness to stimulation, are considered signs 2 Behavioral responses associated of severe pain during the postsurgical period. These results align with with pain studies reporting that, after OVH and castrations, the response to palpation, reduced movement, and increased frequency of Evaluating the behavioral responses of animals when experiencing vocalizations are signs of pain regardless of the analgesic pain is considered one of the main noninvasive methods to assess its treatment (46). affective component (34). As previously mentioned, pain-related When dogs perceive musculoskeletal pain, particularly in the behaviors in domestic mammals comprise a wide range of activities joints (hip, stifle) or fore/hindlimbs, which represent very common to reduce the discomfort caused by pain,

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mmals comprise a wide range of activities joints (hip, stifle) or fore/hindlimbs, which represent very common to reduce the discomfort caused by pain, such as protecting the injured (29–71%) sources of pain (47), main behavioral modifications are area (35). As mentioned by Camps et al. (36), both losing the reduced general activity and resistance/stiffness to walking (48, 49). presentation of normal behaviors and developing abnormal ones are These changes may be accompanied by pain-related aggression, as considered signs of pain. Among the main reported signs in animals observed in dogs (66.7%) with hip dysplasia (36). Stevens et al. (50) experiencing pain are reluctance to move, depression, sleep mention that scales scoring appendicular joint pain (in mani, carpi, disturbances, loss of appetite, restlessness, frequent vocalization, elbows, shoulders, pes, tarsi, stifles, hips) consider aggression or licking, biting, scratching, self-mutilation, anxiety, irritability, and intention to bite when trying to manipulate the injured area a sign of aggressiveness (Figure 3) (25, 26, 37–43). severe pain. The behavioral response and the change intensity depend on the Additionally, this type of pain is also related to unwillingness to species and the painful condition. For example, behavioral changes in learn or participate in training sessions, house-soiling issues, and domestic species such as dogs and cats are the basis for evaluating clinginess to the owner (47). An example is Dodd et al.’s (51) study acute pain (as observed in their respective pain assessment scales) (25, focusing on military working dogs with lumbosacral stenosis. 44). Firth and Haldane (45) were among the first researchers to Twenty-one dogs (32.8%) presented behavioral alterations such as FIGURE 2

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al stenosis. 44). Firth and Haldane (45) were among the first researchers to Twenty-one dogs (32.8%) presented behavioral alterations such as FIGURE 2 Overall structure of the review, where behavioral responses and body language will be discussed as methods to assess pain. Frontiers in Veterinary Science 03 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 3 Behavioral responses to pain in different species. unwillingness or reluctance to jump (38%), self-mutilation in the to palpation, decreased appetite, growling, groaning, and decreased affected area (25%), anxiety (25%), anorexia (25%), and reluctance to grooming (61). sit (25%). Figure 4 illustrates some examples of behavioral changes in According to Brondani et al. (62), a cat with severe surgical pain companion dogs and how these can change according to the etiology licks/bites the surgical wound, reacts aggressively when touching the of pain (e.g., pancreatitis, nasal transmissible venereal tumor, wound, vocalizes (growls, howls, hisses), shows restlessness and gastroenteritis, and postsurgical pain) (47, 52–56). reluctance to move. Similarly, Marangoni et al. (27) mention In dogs, gastrointestinal pain is associated with compulsive-type descriptors such as the level of exploratory behavior, restlessness, behaviors such as star gazing, excessive licking of surfaces, and pica grooming, stretching, attention to the wound, growling/hissing, and (47). Bécuwe-Bonnet et al. (57) observed copious licking of surfaces no interest in food. In the case of chronic pain, a reduction in the (floors, walls, carpets, and furniture) in 59% of dogs diagnosed with animal’s activity is observed, as well as loss of appetite, a tendency to eosinophilic and/or lymphoplasmacytic infiltration in the hide or avoid

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with animal’s activity is observed, as well as loss of appetite, a tendency to eosinophilic and/or lymphoplasmacytic infiltration in the hide or avoid social interaction, and excessive licking of the affected gastrointestinal tract, reduced gastric emptying, irritable bowel area, decreasing normal grooming (43, 63). syndrome, pancreatitis, and giardiasis. Excessive licking might also Likewise, some authors refer to key behaviors that help distinguish progress to self-mutilation in cases of acral dermatitis (58). The overall between painful and nonpainful cats, as reported in kittens subjected reduction in activity and mobility observed in animals experiencing to OVH (64). When comparing kittens receiving opioid-free all types of pain is related to the protective nature of pain, i.e., its multimodal analgesia with those that did not receive analgesic drugs, function to prevent further damage, avoid activities that might delay animals in pain showed less interest in their surroundings (5 vs. 0%) healing, and decrease the inflammatory response that frequently and played less (7 vs. 35%). Temperament changes are also often escalates to hyperactivation of peripheral receptors, sensitization, and reported in cats (91%), as mentioned by Bennett and Morton (65) in chronic pain (23). adult animals diagnosed with musculoskeletal pain, with reported In the case of cats, contrary to dogs, pain evaluation and avoidance of conspecifics and owners. In a case study, aggression due recognition of pain-related behaviors are challenging due to their to fearfulness due to arthritic pain in the thoracolumbar spine was tendency to hide any sign of discomfort unless severe (59). Due to this reported in a cat presenting house-soiling issues, posturing, and aspect, the behavioral

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o hide any sign of discomfort unless severe (59). Due to this reported in a cat presenting house-soiling issues, posturing, and aspect, the behavioral modifications observed in dogs might not vocalization (47). always be present in cats (or be less evident). For example, Monteiro In companion animals, these behavioral changes help and Steagall (60) mention that mobility changes are less common in veterinarians rate the degree of pain. However, studies have shown domestic felines due to their species-specific behavioral repertoire and that dog owners can identify pain through behavioral alterations. inclination to withdraw and hide when threatened. However, among For example, 52.6% of owners reported that behavioral signs were the main behavioral changes related to abdominal pain are a reaction very useful to assess pain, and 48.8% of owners reported that Frontiers in Veterinary Science 04 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 4 Behavioral changes observed in dogs during hospitalization. (A) A patient recovering from pancreatitis. This pathology is associated with restlessness and increased difficulty in adopting a comfortable position to rest. Slower reflexes, body stiffness, changes in appetite, and vocalization can also be observed if the pain is severe. (B) A dog diagnosed with a nasal transmissible venereal tumor. This clinical presentation is associated with nasal discharge, sneezing, nosebleeds, respiratory difficulty, and nasal deformity, which can lead to postural changes in patients due to perceived pain. (C) A patient with gastroenteritis. Among the behavioral alterations, lethargy, apathy, difficulty in standing, and walking are frequently observed. In addition, dogs may refuse abdominal palpation. Postural changes may include

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y, apathy, difficulty in standing, and walking are frequently observed. In addition, dogs may refuse abdominal palpation. Postural changes may include back arching and an orthopneic neck position. (D) A patient with excessive salivation is observed after elective OVH. Dogs experiencing postoperative pain may show rapid or abdominal breathing, reluctance to move, abnormal postures when sitting or lying down (e.g., hunched posture with a tense abdomen), and decreased appetite. Photos taken by the authors in a private clinic. identifying these changes was very useful in determining whether (higher sensitivity to thermal stimulus) compared with healthy they should consult a veterinarian (66). Similarly, in cats, 90% of cows, which is observed as a fast foot-lift response at lower owners consider it helpful to resort to behavioral evaluations to temperatures (e.g., 50.9 °C). determine the animal’s degree of pain, and 86% find it helpful to seek Fogsgaard et al. (75) reported that cows suffering from mastitis veterinary care (67). spent less time lying during the initial phase of the inflammatory In the case of farm species, several instances might cause pain disease (720 min/day), and had a higher frequency of kicking (more (30, 68). For example, pathological pain due to mastitis or laminitis than 0.70 kicks/min/milking). In addition, Siivonen et al. (76) found in ruminants and horses or surgical pain due to castration in piglets that cows spend less time lying on the side with the inflamed udder and dehorning or disbudding in ruminants, respectively, are (control quarter: 40.94 ± 4.60 min; affected quarter: 33.76 ± 2.32 min) accompanied by behavioral modifications that, as seen with dogs, and stepped more after an animal model of induced mastitis (up to aim to

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± 2.32 min) accompanied by behavioral modifications that, as seen with dogs, and stepped more after an animal model of induced mastitis (up to aim to decrease pain perception and promote recovery (69–71). In 1,413 8.6 steps). Another routine procedure on dairy farms that can the first instance, several studies have reported behavioral cause pain and discomfort is drying off, as the accumulation of milk alterations due to pathological conditions such as mastitis in cattle within the mammary gland increases intramammary pressure. Rajala- (72, 73). In this sense, Medrano-Galarza et al. (74) evaluated lying Schultz et al. (77) observed that cows subjected to gradual drying-off behavior and reactivity during milking (stepping, lifting, and spent more time lying down compared to those undergoing abrupt kicking) and its relation to the inflammatory process of the cessation. Similarly, Maynou et al. (78) reported that the use of mammary gland due to the presence of bacteria. The authors acidogenic boluses reduced milk production, which in turn decreased reported that animals in pain spent statistically significantly less intramammary pressure (55.0 vs. 61.9 kg/m/s2) and consequently time lying (707.5 min/24 h) than their healthy counterpart increased lying time. In particular, lying behavior responses in cows (742.5 min/24 h) and that the frequency of lifts and kicks was are relevant due to their high motivation to lie down (79). In this higher in cows with mastitis (0.70 and 0.10 per minute, respectively). sense, veterinarians and stockpeople could use lying time in cattle as Moreover, Peters et al. (73) evidenced that cows affected by a potential behavioral marker of pain, as lower lying times are subclinical and clinical mastitis had a lower thermal threshold primarily

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affected by a potential behavioral marker of pain, as lower lying times are subclinical and clinical mastitis had a lower thermal threshold primarily due to the pain and the inflammation of the udder (79, 80), Frontiers in Veterinary Science 05 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 which could help to promptly identify the painful condition and (102 ± 25.3 counts) and lower frequencies of tail wagging (0.3 ± 0.1) administer pharmacological treatment when necessary. compared to non-castrated animals. Some other behavioral changes Tail docking also induces behavioral alterations, as reported in were reported in lambs after castration, and similar to tail docking, the 21- to 42-day-old dairy heifers, tail banding without epidural method influences the behavioral response. For example, when anesthesia increased restlessness (up to three changes of comparing castration in lambs by cutting with a knife and rubber posture/15 min) (81). Similarly, in crossbred beef heifers, Kroll et al. rings, Lester et al. (95) concluded that behavioral alterations such as (82) compared the behavioral response of docked and undocked abnormal standing/walking and restlessness were predominantly animals immediately after the procedure. The authors found observed in knife-treated lambs within the first four hours after the significantly more steps (up to 200 counts/h), more rear foot stomping procedure. In contrast, Maslowska et al. (96) reported that rubber ring (87.2%), and less lying time (approximately 15 min/h) immediately castration increased the frequency of active pain behaviors (observable after tail docking than in the subsequent days. A decreased appetite actions when animals experience pain) (a frequency of 110.5) and was reported by Eicher et al. (83) in

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an in the subsequent days. A decreased appetite actions when animals experience pain) (a frequency of 110.5) and was reported by Eicher et al. (83) in cows after tail docking, reducing 44.8% of lambs were more restless and painful than animals that were the time spent feeding from 17.8 to 13.3% and increasing the only handled. Thus, the variability of pain-related behaviors is closely frequency of kicking the ground (4%), due to the adoption of related to the pain source or the method (i.e., castration method), as alternative behaviors to scare away flies in docked animals. Thus, mentioned by Canozzi et al. (97). caudectomy in cattle could have behavioral repercussions because the In the case of goats undergoing elective surgical castration, tail is part of the body language of the species. Additionally, tail behavioral modifications such as lying down motionless, standing still, docking of dairy cows is declining and is banned in some countries and looking at the affected area were considered by Fonseca et al. (98) (84). In other species of ruminants, such as sheep, the method of tail to develop the Unesp-Botucatu acute pain scale for goats. Vocalizing docking highly influences the degree of pain perceived by the animals. and teeth grinding have also been reported in adult goats and goat In this sense, Grant et al. (85) compared tail docking in lambs by kids during husbandry practices, including castration, disbudding, rubber ring and hot iron for 90 min after the procedure. The authors and dehorning, and during pathological conditions such as lameness found that tail docking by rubber rings significantly increased the or mastitis (99). During disbudding, Kongara et al. (100) summarized frequency of pain-related behaviors such as vocalization (9.9 ± 3.0 that the main

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or mastitis (99). During disbudding, Kongara et al. (100) summarized frequency of pain-related behaviors such as vocalization (9.9 ± 3.0 that the main behavioral changes observed in kids were head and animals), number of times the animal changed their lying posture body shaking, head scratching, and tail shaking. Similar to these (62.1 ± 5.2%), tail wagging (14.6 ± 2.6 times), kicking/stomping findings, Hempstead et al. (101) compared the frequency of pain- (8.3 ± 1.3 times), and lick/bite the affected area (4.7 ± 0.6 times). related behaviors in disbudded goat kids with cautery iron with a In farm animals, vocalization and its acoustic characteristics sham group. The results showed an increased frequency of head during tail docking or castration are considered indicators of pain shaking (31.2 ± 3.11 vs. 17.5 ± 1.79), head scratching (15.8 ± 5.90 vs. (86–88), as mentioned by Cordeiro et al. (89), who evaluated the 2.2 ± 1.11), head rubbing (4.2 ± 0.77 vs. 0.8 ± 0.27), and body shaking maximum amplitude, pitch frequency, and intensity of vocalization in (6.1 ± 0.36 vs. 8.8 ± 0.49) in disbudded animals, which can be used as piglets undergoing castration and tail docking. After the procedure, signs associated with pain. Recognizing these signs is essential to the maximum amplitude, pitch frequency, and intensity increased by adopt adequate analgesic protocols. For example, Alvarez et al. (102) 0.78 Pa, 159 Hz, and 16.9 dB, respectively (89). Similarly, in piglets evaluated the effect of cornual nerve blocks on goat kids undergoing after hot tail docking, an increase in the frequency and duration of disbudding. The authors evaluated the total behavioral response vocalizations was found along with increases in cortisol and (including struggle/attempts to

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ding. The authors evaluated the total behavioral response vocalizations was found along with increases in cortisol and (including struggle/attempts to escape, vocalizations, and tail β-endorphin levels (90). Hansson et al. (91) reported that the movements). It was found that lidocaine administration did not administration of local anesthesia decreases the number and intensity decrease the mean number of said behaviors (control: 59.6 ± 6.8; of vocalizations in castrated piglets. lidocaine: 52 ± 6.8), suggesting that pain after disbudding should Another common practice on livestock farms is castration. be complemented with other analgesics, such as non-steroidal drugs Among the castration methods commonly applied to farm animals are or general sedation. Burdizzo (B), rubber ring (RR), and surgical castration (S), which are Dehorning in cattle has also been associated with pain-related frequently compared to a control group subjected only to scrotal behaviors such as head-shaking, ear flicking, and increased inactivity handling (H) (92, 93). According to Melches et al. (93), lambs (103, 104). This has been reported in Holstein calves (4–8 weeks old) castrated using B and S exhibited more frequent pain-related behaviors after iron-hot dehorning (104). When compared to a control group during the procedure compared to those in RR and H groups. without receiving analgesic drugs (ketoprofen), treated calves had a Moreover, lambs in the S group showed higher cortisol concentrations lower frequency of head shaking (0.74 ± 0.25 vs. 6.27 ± 2.57) and ear and a greater occurrence of abnormal postures on the day of flicking (0.56 ± 0.17 vs. 11.43 ± 3.07) after dehorning. Similarly, the castration, along with reduced feed intake and rumination during the application of

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ing (0.56 ± 0.17 vs. 11.43 ± 3.07) after dehorning. Similarly, the castration, along with reduced feed intake and rumination during the application of lidocaine reduced the frequency of head moving first 6 days post-castration relative to the other groups. Similarly, (2.9 ± 0.6 vs. 5.3 ± 1.5), head shaking (1.3 ± 0.6 vs. 27.4 ± 5.9), tail Molony et al. (92) observed in calves that castration using RR was wagging (1.5 ± 0.5 vs. 3.5 ± 0.5), and rearing (0.4 ± 0.2 vs. 1.9 ± 0.5) associated with more severe acute and chronic pain, with behavioral when compared to a control group of calves dehorned without indicators of discomfort persisting for up to 42 days. In contrast, analgesic (105). Head shaking, ear flicking, and head scratching were castration using S, B, or the combination of B + RR elicited also reported in calves dehorned with two methods: cream and hot comparatively lower behavioral and physiological stress responses, iron (103). Additionally, in the same animals, a decrease in lying time particularly during the chronic phase. was observed in comparison with the pre-dehorning period (from A study by Yun et al. (94) found that piglet castration without approximately 110 min to 75 min), together with decreased playing analgesics increased the observation of standing or sitting inactively behavior (from approximately 180 min to 60 min). Frontiers in Veterinary Science 06 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 Although the discussed pain-related behavioral responses in of pain and correctly classifies between pain-free and painful cats in domestic mammals can differ according to the species and, 95% of cases. Additionally, Merola and Mills (142) mention that in particularly, to the pain source, these reactions arise to avoid further

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ecies and, 95% of cases. Additionally, Merola and Mills (142) mention that in particularly, to the pain source, these reactions arise to avoid further cases of pain due to orthopedic conditions, cancer, urinary tract injury, increase survival chance, and promote healing (32). They are diseases, or dental issues, flattened ears are frequently observed when rapid responses of passive or active defense against pain. Therefore, perceiving high levels of pain, although it may also be a sign of fear. veterinarians and animal handlers should receive training to recognize In the case of laboratory rodents, Mittal et al. (143) determined subtle changes in behavior, as behavioral modifications are one the association between pain in sickle mice and changes in the ear method of communicating pain in animals and may serve as an position (and other facial indicators). The authors found that exposure indicator of their welfare. to 4 °C caused the ears to move parallel to the neckline, suggesting cold hypersensitivity and pain (scores of up to 1.5). In the same species, evaluations post-vasectomy with and without analgesics 3 Body language as a tool to assess found that animals in pain frequently showed ears rotated outwards, pain: anatomical structures related to and their assessment had an excellent (0.75) reliability score (144). For pain perception rabbits, Benato et al. (138) reported that the position and movement of the ears are accurate descriptors of pain. In this sense, flattened ears 3.1 Ear posture and lack/diminished ear movement were observed in rabbits after OVH and orchiectomy. Ear position has been used as an indicator of an animal’s affective In farm animals, Tallet et al. (145) determined the effect that tail state, including pain (106–108). The changes in ear

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ator of an animal’s affective In farm animals, Tallet et al. (145) determined the effect that tail state, including pain (106–108). The changes in ear posture are related docking has on piglets’ behavior and body posture. In particular, the to the neurobiological processing of emotions eliciting different facial authors found that immediately after cautery iron docking, piglets expressions according to the context (40, 109). Ear posture depends held their ears perpendicular to the head-tail axis (70% of animals) on motor control from the primary motor cortex and the subnuclei of and showed more ear posture changes (70%) than non-docked piglets the facial nerve (VII) (110–113). Although each nervous region has (30 and 20%, respectively). This is similar to what was observed in specific functional delimitations, the excitability of the motor cortex Danish Holstein dairy cattle during castration, mastitis, or laminitis. leads to positive feedback from the facial nerve, resulting in the In these animals, acute pain was observed as caudal rotation of the contraction or relaxation of the muscles that control ear movement ears, along with other changes such as keeping the head below the (20, 40). These changes are controlled by the ventral auricular, dorsal horizontal axis of the animal, piloerection, arching of the back, and an auricular, rostral auricular, and caudal auricular muscles (114, 115). increased reactivity (146). Additionally, ear posture can also suggest However, changes in ear posture alone should not be considered an the emotional state of animals, as mentioned by Lambert and Carder indicator of pain and must be considered among the several signs that (109), who evaluated the ear position of Holstein dairy cows under animals show when perceiving pain.

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must be considered among the several signs that (109), who evaluated the ear position of Holstein dairy cows under animals show when perceiving pain. two different contexts (frustration and excitement). The authors found The importance of ear posture as an indicator of pain in animals that cow ears had more changes in ear position during the frustration is reflected in the current scales that consider it as one of the most event (from 14.15 to 16.59 changes/15 min). noticeable changes when animals are exposed to a noxious stimulus. In small ruminants such as goats, Weeder et al. (124) analyzed the These scales have been adapted to cats (116), mice (117), rats (114, facial response of goats to induced lameness. Results showed that 118), rabbits (119), pigs (120, 121), sheep (122, 123), goats (124), animals with obvious changes due to pain were characterized by both horses (9), donkeys (125), and cows (126) (Table 1). Although the ears pulled backwards, along with behavioral modifications (e.g., change and position depend on the species and distinct anatomy, increased lying time). Ear posture changes were also reported by several similarities have been found (125, 127–129). When animals Hussein and Hidayet (147) in goat kids (10–14-day-old) undergoing experience pain, stimulation of the auricular muscles causes flattening ear tagging. After the routine procedure, a significant increase in ears or retraction of the ears in all species (129–131). For example, a cat backward (from 0.7 ± 0.2 to 11.6 ± 1.7 s), number of posture changes with severe pain shows ears that are markedly rotated outwards (132). (from 3.3 ± 0.4 to 9.8 ± 0.6), and a decrease in ears plane (e.g., Rats and mice in pain show ears that are curled, pointed, and/or perpendicular to the head-rump

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0.4 to 9.8 ± 0.6), and a decrease in ears plane (e.g., Rats and mice in pain show ears that are curled, pointed, and/or perpendicular to the head-rump axis) (from 25.3 ± 1.5 to 11.8 ± 2.1 s) angled forward or outward (118, 133). For rabbits, ears tightly folded was observed. against the neck, pulled back, and flattened are present when the Gleerup et al. (148) characterized the changes in ear position of animal is perceiving severe pain (134). Similarly, in farm species such adult horses exposed to experimental acute pain (a tourniquet to the as piglets and goats, severe pain is characterized by the ears drawn forearm and the topical application of capsaicin). Both stimuli back from the forward position and hanging (124, 135, 136), which increased the time the horses maintained asymmetrical ears and in a has also been reported in horses, donkeys, and cows (9) (Figure 5) low position (between 54 ± 0.5 and 51 ± 23%), which coincided with (109, 118, 132–134, 137, 138). the significant increase in the pain assessment scale score. Similarly, Clinical examples of pain identification through changes in ear Ask et al. (149) evaluated changes in ear position in horses that were posture and other facial indicators have shown an accuracy of 87% in administered lipopolysaccharide in the tarsal-crural joint to generate cats (139). Particularly, as Watanabe et al. (140) mention, ear posture acute pain, highlighting ear flattening and lateral rotation. has a good inter-rater reliability score (0.55–0.78) as it is one of the Additionally, in horses undergoing routine castration under general changes caregivers easily observe in cats that underwent procedures anesthesia, Dalla Costa et al. (144) found that stiffly backwards ears such as dental extractions. Holden et al. (141)

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cats that underwent procedures anesthesia, Dalla Costa et al. (144) found that stiffly backwards ears such as dental extractions. Holden et al. (141) found that the distance are associated with pain, with an excellent reliability coefficient of from the midpoint of the two ears is an indicator of pain, where a 0.96. Figure 6 shows the ear changes that can be observed in an equine greater distance between the tips of the ears is considered indicative patient with colic syndrome due to pain (150). This figure also shows Frontiers in Veterinary Science 07 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 TABLE 1 Description of ear changes in the currently available Grimace Scales in domestic mammals. Name Specie Ear change Reference Calf Grimace Cattle Both ears are backwards, or one ear is directed caudally. The ear pinna cannot be seen, and the angle between Farghal et al. (221) Scale (Bos taurus) the eye commissure, the base of the ear and the tilt of the ears is wider than 90°. Cow Pain Scale Cattle Ears kept straight backwards or very low (“lamb’s ears”). Gleerup et al. (Bos taurus) (146) Donkey Donkeys Both ears might be back down, one ear forward, and one to the side. One ear to the side and one to the back, Orth et al. (125) Grimace Scale (Equus asinus) or one forward and one down. Feline Grimace Cats Ears flattened and rotated outwards. Evangelista et al. Scale (Felis catus) (116) Ferret Grimace Ferrets Ears are pulled back against the body, forming a pointed shape. They may fold over. Reijgwart et al. Scale (Mustela putorius (222) furo) Goat Grimace Goats Ears pinned backwards. Weeder et al. (124) Scale (Capra hircus) Horse Grimace Horses The ears are held stiffly and turned backwards. Thus, the space between the ears may appear wider relative

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) Scale (Capra hircus) Horse Grimace Horses The ears are held stiffly and turned backwards. Thus, the space between the ears may appear wider relative to Dalla Costa et al. Scale (Equus caballus) the baseline. (9) Lamb Grimace Sheep Tense ears pointing backwards or downwards, the inner part of the ear is not visible. Ears appear narrower Guesgen et al. Scale (Ovis aries) and dorsally flattened. (123) Mouse Grimace Mice Ears rotate outwards and/or backwards, away from the face, forming a pointed shape. The space between the Langford et al. Scale (Mus musculus) ears increases. (223) Piglet Grimace Pigs Ears drawn back from forward (baseline) position. Viscardi et al. Scale (Sus scrofa (135) domesticus) Rabbit Grimace Rabbits Ears become more tightly folded/curled in shape. They rotate from facing towards the source of sound to Keating et al. (134) Scale (Oryctolagus facing towards the hindquarters. Ears may be held closer to the back or sides of the body cuniculus) Rat Grimace Rats Ears curl inwards and are angled forward to form a pointed shape and the space between the ears increases. Sotocinal et al. Scale (Rattus (118) norvegicus) Sheep Grimace Sheep Flattened and hanging ears. Häger et al. (136) Scale (Ovis aries) Sow Grimace Pigs Ears facing backwards. Navarro et al. Scale (Sus scrofa (120) domesticus) the changes in the ear position of a feline patient with idiopathic connections of these structures with the motor cortex cause the motor cystitis (151). or reflex responses to noxious stimuli (20, 155). The tension of the tail and hiding it between the hindlimbs is due to the contraction of the coccygeus, sacrocaudalis ventralis, dorsalis, and caudae muscles, 3.2 Tail position and movement which stabilize the spine. As a compensatory response to exceeding the

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audalis ventralis, dorsalis, and caudae muscles, 3.2 Tail position and movement which stabilize the spine. As a compensatory response to exceeding the nociceptive threshold, the animal modifies the posture of the Tail position and movement have also been considered indicators spine, including the tail, to achieve postural balance and provide of pain in animals (152). They have been particularly studied during greater support and protection (115). routine procedures in farm animals such as surgical castration or tail Changes in tail position have been reported in several species docking (84, 153). During these events, animals in pain maintain their (Figure 7) (48, 154, 156, 157). For example, in cats, Pereira et al. (158) tail stiff, hide it, or swing it abruptly (153). mention that tail flicking (along with other behaviors and body Changes in tail position or movement respond to adjacent postures) indicates pain. For example, in domestic dogs with diseases nociceptors that send information through the pudendal and perineal that generate chronic pain (such as osteoarthritis, cruciate ligament nerves (154). These nerves reach the dorsal root ganglia of the spinal rupture, patellar luxation, pancreatitis, and neuropathic pain) 20% of cord and deploy a neuronal and molecular communication circuit at the owners observed changes in tail posture, keeping it hidden the brain level. Within the brain, the reception and refinement of this between the pelvic limbs or directed downwards with tension (48). In information translates into an immediate pain response, coordinated addition, these changes were accompanied by behaviors associated by the amygdala, hypothalamus, and periaqueductal gray matter. The with pain, such as directed aggression and vocalizations (48). Frontiers in

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ociated by the amygdala, hypothalamus, and periaqueductal gray matter. The with pain, such as directed aggression and vocalizations (48). Frontiers in Veterinary Science 08 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 5 Description of the ear changes in some domestic mammals when perceiving pain. Frontiers in Veterinary Science 09 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 6 Ear changes in domestic animals during the perception of acute pain. (A) A prostrated male Quarter Horse with equine colic due to acute and severe abdominal pain. Facial changes, such as ear flattening, can be observed. (B) Feline with idiopathic cystitis. Note the changes in ear position, such as flattening, outward rotation, and being slightly pulled apart. Photos taken by the authors. FIGURE 7 Tail posture as a pain sign. (A) In cats, a tail kept or tucked between the hindlimbs, close to the body, is a sign of pain. (B) Dogs experiencing pain might exhibit a tucked tail, similar to what is observed in cows (C). In the case of dogs, a tucked tail might also indicate fear. Thus, posture changes need to be interpreted together with other ethological evaluations. Similarly, the position and laterality of tail movement change In cattle, vigorous tail swinging vertically or horizontally is depending on the context and can be associated with emotional states suggested as a key indicator for pain recognition; however, a static (159) such as fear, pain (160), or pleasurable situations (161, 162). In position or complete immobility of the tail is also associated with pain. pigs, as reviewed by Camerlink and Ursinus (163), victims of tail In this regard, Tom et al. (165) assessed pain indicators in adult cows biting suffering from pain and (chronic) fear of

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rsinus (163), victims of tail In this regard, Tom et al. (165) assessed pain indicators in adult cows biting suffering from pain and (chronic) fear of being targeted keep undergoing caudectomy with a rubber ring. Cows subjected to this their tail low and often tucked between their legs. procedure, regardless of analgesic treatment, reduced the frequency Miller et al. (164) evaluated tail position in piglets after surgical of tail shaking up to 6 days after tail-docking (0.8 ± 0.2), in addition castration with or without administration of local analgesics. It was to maintaining a straight, ventral position, which results in pressure found that piglets castrated without local analgesics had a higher against the hindquarters (between the anus and vulva) (24 animals). frequency of changes in tail position, tail wagging, and maintained a The authors suggested that pressing the tail towards the hindquarters straight (i.e., not curled) tail; in contrast, the non-castrated piglets kept counteracts the painful stimulation caused by the rubber ring and their tail curled and hanging. Similarly, after cautery iron tail docking, might reduce pain and inflammation (154, 156). Therefore, piglets maintained an immobile tail in a horizontal position for longer maintaining the tail static reduces the perception of pain in (up to 20 s) than sham-docked piglets (approximately 16 s) (145). sensitized tissue. Frontiers in Veterinary Science 10 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 The importance of tail movements is the reason why production the musculoskeletal system is carried out by sensory nerves located units have focused on the tail to develop sophisticated technologies within the periosteum, spinal cord, and cortical bone (173, 174). such as birth sensors

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have focused on the tail to develop sophisticated technologies within the periosteum, spinal cord, and cortical bone (173, 174). such as birth sensors (166). These sensors collect the number of times The expression of pain through changes in the position of the trunk the tail is raised before calving, as this change in body posture is or back could be explained by the fact that nerve impulses are projected considered an imminent sign of the onset of calving due to the pain from peripheral endings processing pain, to the dorsal horn of the spinal promoted by uterine contractions (167). The same posture has been cord to the higher structures of the Central Nervous System, specifically observed in species such as the pig (168) and mice (169). However, tail the somatosensory cortex (20, 175). Activation of the somatosensory movements in the peripartum might not always be entirely due cortex excites relevant regions such as the primary motor cortex, which is to pain. involved in the formation of motor actions, such as the withdrawal reflex Therefore, tail position is a key indicator to recognize acute pain, or postural changes in response to tissue injury (40, 176, 177). providing valuable information during clinical assessment. However, An example of change in posture is during parturition, as observed variability in position and activity is wide across species and animal by Ison et al. (178) periparturient sows show a distinctive posture of back conditions or affective states. Like ear position, it should be considered arching, accompanied by hindlimbs pointing forward due to uterine an event that manifests together with multiple pain-related signs. contractions and the expulsion of the piglets. Furthermore, the complete Thus, an integrated, multimodal assessment

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with multiple pain-related signs. contractions and the expulsion of the piglets. Furthermore, the complete Thus, an integrated, multimodal assessment incorporating multiple lateral tilt of the torso (animal lying down) was observed for 90% of the behavioral and physiological indicators is recommended to increase time between the onset of uterine contractions and 6 h after the expulsion diagnostic sensitivity and efficacy. of the first piglet. The authors state that these behavioral adjustments are indicators of pain and not simply assistive postures in the expulsion of the fetus through the birth canal. This was also observed in periparturient rats 4 Assessment of pain through postural by Catheline et al. (169), where the administration of oxytocin, which is a changes potent intensifier of uterine contractions, increased torso stretching accompanied by abdominal tension (<6 times/min) during parturition. One of the most significant changes in animals experiencing pain The visceral pain experienced during natural parturition is promoted by is postural alterations to minimize pain perception (30, 170). Back several mechanical factors such as uterine contractions, distension, arching, lateral or ventral tilt of the torso, and contraction of the elongation, and tearing of tissue, and pressure applied to adjacent abdominal muscles can indicate the presence of pain (Figure 8). anatomical structures (pelvis and perineum) (179, 180). Postural changes are triggered by modifications in the length of The adoption of these postures has been observed in other disorders muscles, soft tissues, and the musculoskeletal system, influencing where visceral pain is intense. For example, in horses with colic syndrome, spinal alignment to reduce energy expenditure and change body abdominal

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ng where visceral pain is intense. For example, in horses with colic syndrome, spinal alignment to reduce energy expenditure and change body abdominal pain comes mainly from visceral smooth muscles, which, weight distribution to facilitate balance (171, 172). Interception within when undergoing sudden changes such as stretching, tearing, perforation, FIGURE 8 Some examples of body postures associated with pain in domestic animals. Frontiers in Veterinary Science 11 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 or strangulation, exceed their nociceptive threshold (181). Fereig (182) an arched back posture in response to a decrease in ambient temperature, associated excessive abdominal stretching with cranial and caudal a back posture that has also been correlated with other behavioral extension of the fore and hindlimbs, respectively, to relieve mesenteric indicators of pain, such as facial expressions (143). Following abdominal pressure caused by the accumulation of gas and fluid in the gastrointestinal surgical procedures such as OVH in companion animals, marked tract. Laleye et al. (183) mention that early detection of abdominal pain abdominal contraction is observed, along with exacerbated kyphosis in foals is based primarily on the identification of postural changes or (187), consistent with observations in surgically castrated piglets (164). behavioral modifications, among which abnormal body posture of In particular, the kyphosis manifested during pain in cats caused by complete lateral tilt and abdominal contraction were frequently reported musculoskeletal diseases progressively decreases after the administration by owners (47%) and veterinarians (78%). Figure 9 shows an example of of analgesic treatment, which suggests that the presentation of

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e administration by owners (47%) and veterinarians (78%). Figure 9 shows an example of of analgesic treatment, which suggests that the presentation of antalgic postural changes in donkeys suffering from laminitis. postures is associated with the intensity of pain (65). This can also be observed in domestic dogs with the so-called antalgic Similarly, abnormal postures occur following routine handling “prayer posture,” where animals stretch cranially the forelimbs and procedures in farm animals. Castration in piglets causes back arching maintain a convex curvature of the back. By extending the thoracic and abdominal tension (164). In small ruminants, Zebaria et al. (188) region, this posture releases the abdominal pressure by the declination of reported an increase in abnormal standing (standing unsteadily with the organs toward the cranial region. This posture is frequently observed tail wagging, 6.83%) in kid goats undergoing ear tagging. This is when the origin of the pain is visceral and is used as an indicator of similar to what Fonseca et al. (98) reported in goats subjected to postsurgical pain (155). Other postures related to pain in dogs are rigid, orchiectomy, where the occurrence of an unstable posture increased hunched or tense, or guarding the affected area (45). Figure 10 shows after the surgery (33.5%). In dairy cows with hoof trauma, Flower and frequently observed pain-related postures in companion animals due to Weary (189) reported marked dorsal arching in animals with plantar visceral pain, kidney disease, and spinal and thoracic injury (25, 155, hemorrhages and ulcers. These changes were also accompanied by 184–186). sudden head movements, decreased mobility, and reduced balance in Pain-related postures are not exclusively manifested during

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accompanied by 184–186). sudden head movements, decreased mobility, and reduced balance in Pain-related postures are not exclusively manifested during visceral a static state. In another study by Stojkov et al. (190) in cows, dorsal pain. For example, mouse models suffering from sickle cell disease adopt arching was associated with pain caused by inflammation of the FIGURE 9 Postural alterations linked to nociception in the metacarpal and metatarsal regions, with clinical signs of laminitis in donkeys. (A) The animal displays a posterior shift of body weight, with the forelimbs slightly extended cranially and overextension of the right metacarpal and left metatarsal regions. This abnormal posture results from excessive hoof wall overgrowth. Such a stance is typical of animals experiencing hoof or joint pain, as they attempt to unload the affected areas. A tense facial expression indicative of discomfort is also evident. (B) Marked overgrowth of the hoof wall is observed in the right pelvic limb, with clear deformation of the hoof’s natural conformation. This alteration predisposes the animal to chronic pain due to abnormal pressure distribution, joint inflammation, and increased tendinous load. Lack of routine trimming compromises equine biomechanics, significantly altering weight distribution (C) The donkey adopts a non-weight-bearing stance, with overextension of the left thoracic limb and complete withdrawal of the right pelvic limb. This postural pattern is consistent with chronic pain, likely associated with laminitis or long-standing podal discomfort. Photos taken by the authors. Frontiers in Veterinary Science 12 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 10 Pain-related postural changes in companion animals. (A) Prayer posture in a

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12 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 FIGURE 10 Pain-related postural changes in companion animals. (A) Prayer posture in a 2-year-old mixed-breed dog, showing extended pelvic limbs and a lowered head, allowing the pelvis to be raised towards the back. This relieves abdominal pressure when perceiving severe visceral pain. (B) Severe acute abdominal pain in a cat. A 6-year-old male cat with severe acute abdominal pain due to chronic kidney disease. The patient maintains a posture with the pelvic and thoracic limbs flexed towards the belly and a lowered head. (C) A male cat with the Schiff-Sherrington posture, characterized by extended thoracic limbs and an arched spine (kyphosis), and associated with a spinal injury. (D) A 4-year-old dog with a thoracic injury. The dog has an extended neck, with elbows abducted laterally and flexed pelvic limbs. This posture is known as orthopneic stance and occurs in cases of thoracic pain. It is important not to confuse the prayer posture position with the play bow. Play bows occur when a dog is inviting play, whereas the prayer posture is typically associated with discomfort or pain. The dog’s head is usually down when it performs the prayer posture and it is usually up during a play bow. A dog in a playful state is active and energetic, whereas a dog in pain tends to show reduced activity. Photos taken by the authors. uterine wall (metritis), while Rialland et al. (191) associated back arching with gastric problems such as traumatic reticulopericarditis. Figure 11 shows the pain-related postural changes observed in cattle and other species due to mastitis and fractures (192, 193). Back arching is often accompanied by other body adjustments in the pelvic and thoracic limbs, tail position, neck tension, and

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d fractures (192, 193). Back arching is often accompanied by other body adjustments in the pelvic and thoracic limbs, tail position, neck tension, and head position (30). For example, after surgical castration of bulls, Esteves- Trindade et al. (194) found that the main changes associated with pain were extension of the head and neck, position of the head below the animal’s shoulders, and extended limbs. Recognizing these changes is important for veterinarians and also owners, as reported by Demirtas et al. (48), who evaluated the ability of dog owners to recognize postural changes. These authors observed that, limited joint movement of the caudal vertebrae, arching of the back, and reduced overall activity was present were the most frequently recognized postural changes. Similarly, Laleye et al. (183) evaluated early recognition of colic pain through 66 clinical histories of 40 horses (over 5 years old) and 26 foals (under 4 weeks old). The results indicated that more than 50% of physicians and caregivers use postural modifications as an early sign for colic pain recognition. 5 The importance of animals’ FIGURE 11 Postural changes in cattle and other species. (A) Postural changes in nonverbal language as a clinical a cow with clinical mastitis. A Holstein dairy cow maintains a low indicator of pain for veterinarians and head posture with abducted or clubbed pelvic limbs. This posture animal scientists helps to reduce contact of the limbs with the udder and diminishes local pain. (B) Posture of a rabbit with a fracture in the pelvic limb. A prostration posture and laterally lying on the affected limb apply Pain recognition and assessment are essential to promote pressure to the limb to reduce the pain. Photos taken by the authors. animals’ health and welfare (8,

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ognition and assessment are essential to promote pressure to the limb to reduce the pain. Photos taken by the authors. animals’ health and welfare (8, 195, 196). Failure to recognize pain Frontiers in Veterinary Science 13 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 in animals represents a welfare problem due to the physical and machine learning techniques can help to differentiate breeds and mental alterations, including activation of the sympathetic nervous cephalic types in addition to pain (212). Breed-specific morphology system, immunosuppression, metabolism, and healing processes, highly influences pain recognition in companion animals (213). as well as increased morbidity, disease progression, and prolonged This is particularly relevant for domestic dogs, as breed-specific recovery periods in surgical patients (2, 197). In human medicine, face anatomy makes it challenging to recognize pain through facial pain assessment is performed through verbal or written cues (214). However, Zhu et al. (215) have recently proposed the communication with the patient (198). In contrast, in veterinary application of machine learning to automatically identify pain medicine, pain is identified through nonverbal communication, in dogs. such as changes in physiological and endocrine parameters, body Similarly, the adoption of techniques known as “precision language, and behavior (56). livestock farming” or instruments that use artificial intelligence Pain assessment and management require the veterinarian’s techniques can help objectively and automatically recognize knowledge and objectivity. Therefore, physicians need to changes in ear or tail position in farm species. An example is incorporate behavioral and postural indicators associated with

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fore, physicians need to changes in ear or tail position in farm species. An example is incorporate behavioral and postural indicators associated with Feighelstein et al. (216), who used deep learning to detect pain pain into their daily practice (8, 30). The changes observed in from lateral images of horses undergoing routine castration. Using animals are an integrated response aimed at reducing the painful the Horse Grimace Scale (HGS) to embed the Facial Action Units stimulus (199). Moreover, owners need knowledge and awareness (previously described in Table 1), authors reported an accuracy of pain behaviors as they are key for the early recognition, between 73 and 79% to detect equine pain. This might improve assessment, and management of pain (48, 200–202). Therefore, animal management and welfare in routine procedures that are still veterinarians need to identify and familiarize themselves with considered “not as painful.” Similarly, Lencioni et al. (217) animal behaviors to detect and categorize pain, although factors developed a machine vision algorithm to detect acute pain in such as environment, species, age, body condition, and type of horses after surgical castration. Through facial expression, the disease must be considered (16, 203). Although behavioral scales authors found an overall accuracy of 75.8% when classifying pain exist to assess pain, surveys indicate that 73% of veterinarians into three categories (not present, moderately present, and consider these methods inadequate and have difficulty recognizing obviously present, according to the HGS), or 88.3% when behavioral changes (204, 205), which has a direct impact on representing absent/present pain. Recent studies have suggested patients’ quality of life and welfare (206). that the use of

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ch has a direct impact on representing absent/present pain. Recent studies have suggested patients’ quality of life and welfare (206). that the use of “regions of interest” instead of “facial landmarks” Although the study of these behavioral and body posture when using automatic detection of pain could increase the indicators has been explored in several domestic species, the feasibility of adopting artificial intelligence in animal pain anatomical differences must be considered to accurately evaluate detection (218). Moreover, although most of the research is focused pain. These changes should not be considered in isolation but as a on identifying facial changes associated with pain –in horses–, Kil part of a complementary evaluation considering physiological et al. reported a sensitivity of above 80% to detect behavioral parameters. Therefore, it would be appropriate to investigate changes in horses using machine learning (e.g., analysis of wither, whether including these changes in assessment scales improves the tail, and nose changes). sensitivity of these tools, as has been observed with facial In ruminants, Salzer et al. (219) developed an automatic expression (207). Similarly, standardizing changes in ear/tail warning system to identify mild pain (capsaicin application) in position and postures for each species and each pain-inducing cows. Through a machine-learning algorithm, the authors were event is necessary, which could help increase the specificity and able to identify that decreased rumination and restlessness are sensitivity and obtain an objective pain assessment. The present in animals experiencing pain with an accuracy of 82%. development of multidimensional scales that consider both Additionally, micro expressions have also been adapted

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iencing pain with an accuracy of 82%. development of multidimensional scales that consider both Additionally, micro expressions have also been adapted to physiological and behavioral/body posture/facial expression computer vision methods to detect painful conditions such as parameters could be the best option to comprehensively evaluate lameness, metritis, mastitis, and pre-calving pain with an average pain in domestic mammals. For example, the Colorado State precision of 83%. In other species, such as goats, Chiavaccini University Canine and Feline Pain Scale or the University of et al. (220) detected acute pain (due to conditions such as Melbourne Pain Scale consider physiological, behavioral, and castration, mastectomy, dental cleaning, among others) through postural responses to acute pain (45, 208, 209). the analysis of raw facial video footage with machine learning. Although behavioral, postural, and facial recognition of pain “Painful” and “non-painful” goats were differentiated with an can be performed manually by clinicians or stockpeople, automated accuracy of 60%. When automatically analyzing facial expressions techniques have been explored for multiple domestic species to of pain in sheep, studies have reported that artificial intelligence increase the accuracy of the evaluation and prevent subjectivity. outperforms human experts, which has significant applications For example, in companion animals, the Facial Action Coding in farms. System for cats (catFACS) was used as an anatomical basis for a Deep learning-based models and artificial intelligence are still machine learning model to recognize pain in cats undergoing under development for several species (224). However, these ovariohysterectomy (210). The accuracy of the technique was methods

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ain in cats undergoing under development for several species (224). However, these ovariohysterectomy (210). The accuracy of the technique was methods reduce human bias and the need to manually extract above 72%, indicating its usefulness for automating pain detection. information, which is time-consuming. Therefore, these methods Similar accuracy was reported by Martvel et al. (211), who used are current alternatives to improve pain assessment in domestic artificial intelligence to detect pain in cats by establishing 48 facial mammals for improving animal welfare, while preserving the landmarks in videos. The authors reported an accuracy of over 70% importance of training veterinarians and animal caregivers to in recognizing feline acute postsurgical pain. Furthermore, AI and correctly interpret animal behavior and body language. Frontiers in Veterinary Science 14 frontiersin.org Mota-Rojas et al. 10.3389/fvets.2025.1679966 6 Conclusion Funding Animal body language serves as a means of understanding the The author(s) declare that no financial support was received for emotional state of animals in response to positive and negative stimuli, the research and/or publication of this article. such as pain. In domestic animals, variations in behavioral responses such as vocalizations, grooming, scratching, avoidance, escape, tonic immobility, as well as aggression, among other behaviors, are associated with the perception of pain. Additionally, about farm Conflict of interest animals, changes in ear and tail position and in the overall posture have been reported to be indicative of pain in animals suffering from The authors declare that the research was conducted in the pain arising from, e.g., laminitis, visceral involvement, or routine absence of any commercial or

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thors declare that the research was conducted in the pain arising from, e.g., laminitis, visceral involvement, or routine absence of any commercial or financial relationships that could painful procedures. Understanding these signals as a nonverbal be construed as a potential conflict of interest. communication of pain allows the efficient identification of pain for The author(s) declared that they were an editorial board member timely intervention and optimized management. of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision. Author contributions Generative AI statement DM-R: Conceptualization, Project administration, Supervision, Validation, Visualization, Writing – original draft, Writing – review & The authors declare that no Gen AI was used in the creation of editing. AW: Writing – original draft, Writing – review & editing. LL: this manuscript. Writing – original draft, Writing – review & editing. CB-F: Writing – Any alternative text (alt text) provided alongside figures in this original draft, Writing – review & editing. AD-O: Conceptualization, article has been generated by Frontiers with the support of artificial Supervision, Writing – original draft, Writing – review & editing. intelligence and reasonable efforts have been made to ensure accuracy, AC-C: Writing – original draft, Writing – review & editing. VF: including review by the authors wherever possible. If you identify any Writing – original draft, Writing – review & editing. IH-A: Writing – issues, please contact us. original draft, Writing – review & editing. AB: Writing – original draft, Writing – review & editing. EN: Writing – original draft, Writing – review & editing. AO-H: Writing – original

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