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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
New Insights in Heart Rate Variability Through Non-Linear Methods for Conditioning Assessment in Horses. Chronic exercise induces significant adaptations across multiple physiological systems due to increased metabolic demand. Heart rate variability (HRV) has emerged as a prominent, non-invasive method for monitoring fitness, enabling inference of sympathovagal balance from time-series variations in electrocardiograms. Notably, nonlinear analyses have a strong capacity to detect and estimate complex mechanisms underlying cardiovascular modulation. In this context, HRV was evaluated in the time and frequency domains, as well as through nonlinear methods, in 12 young purebred Arabian horses undergo...
The effect of romifidine on endoscopic grading of laryngeal function in horses. To our knowledge, the effect of sedation with romifidine on the grading of laryngeal function in horses has not been studied. Our objective was to examine the effects of romifidine on the grading of laryngeal function and the cross-sectional area of the rima glottis (CSARG). Methods: Ten horses underwent three endoscopic examinations of the larynx: once while unsedated (group R1), once after being sedated with romifidine (0.04 mg/kg intravenously; group R2) and once again, while still sedated, after receiving a repeat dose of romifidine (0.08 mg/kg intravenously, total dose; group R3). The r...
Evaluation of Circadian Variations of Central Corneal Thickness and Its Correlation With Intraocular Pressures in Healthy Horses. Circadian variations in central corneal thickness (CCT) and their correlation with intraocular pressure (IOP) have not been reported in horses. This information may be clinically relevant when interpreting IOP readings. Methods: Twenty-four eyes of 6 healthy adult gelded males and 6 healthy adult intact mares were evaluated. Rebound tonometry (TonoVet, Jorgensen Laboratories) followed by ultrasonic pachymetry (iPac Pachymeter, Reichert technologies) was performed in both eyes every 3 h over 24 h during the natural 14-h daylight summer photoperiod. Results: Central corneal thickness varied ...
Mitochondrial dysfunction in equine ageing: Current evidence and clinical implications for geroscience. Ageing is a complex biological process affecting a growing geriatric human and equine population worldwide. Mitochondrial dysfunction is considered one of the hallmarks of ageing, representing a multifaceted process. This review synthesises current findings on mitochondrial dysfunction in aged equines, drawing parallels with human medicine and identifying current knowledge gaps. Integrating findings from human and equine research may bridge existing challenges and offer new opportunities, including the development of novel translational models for ageing research. Furthermore, it highlights th...
Heart rate variability in horses with naturally occurring gastric ulcers: Response to omeprazole and sucralfate treatment. Equine gastric ulcer syndrome (EGUS) is the most common disease affecting the equine stomach. Heart rate variability (HRV) describes and quantifies the variability between consecutive heartbeats due to the neurohormonal regulation of the heart. It has been considered a non-invasive method to detect autonomic tone changes that can be influenced by pain and disease. Unassigned: This study aimed to assess the HRV indices in horses affected by EGUS submitted or not to treatment. Unassigned: A cohort of 45 mares underwent baseline gastroscopy (T0); 24/45 mares diagnosed with Equine Squamous Gastric...
A scoping review of neuroendocrinological biomarkers with potential for use in equine behavioral medicine practice. BACKGROUND: Equine emotion and welfare are of increasing concern to the general public, equestrians and researchers. There is growing demand for more objective indicators of specific emotional states, as well as the well-being of horses in a variety of contexts. Such markers may also assist in both the diagnosis and selection of biological therapies within equine behavioral medicine. RESULTS: This scoping review summarizes and appraises the published findings relating to relevant biological measurements from the last two decades. Particular attention is given to methodological, subject-related...
ATAC-seq and RNA-seq reveal key genes and pathways regulating lactation in the mammary gland of Yili horses. BACKGROUND: Mammary gland development and lactation are dynamic biological processes governed by coordinated changes in chromatin accessibility and gene expression. RESULTS: We performed paired ATAC-seq and RNA-seq profiling to characterize stage-associated chromatin accessibility and transcriptional programs in the Yili horse mammary gland. Using a conservative overlap-based integration, we prioritized candidate genes showing concordant changes across both layers as hypothesis-generating signals for future functional studies. We sequenced mammary gland tissues from early lactation (S1) and pe...
Post exercise hydration responses to an electrolyte, glycerol, and creatine supplement in horses: a preliminary study. Electrolyte supplementation is utilized to support hydration in horses. However, limited data are available on formulations that include osmotically active compounds such as glycerol and creatine. These additional ingredients may enhance fluid retention, yet their physiologic effects in equine athletes have not been evaluated. This preliminary study assessed hematologic responses, body mass recovery, and voluntary water intake following moderate exercise with and without supplementation using a commercially available hydration supplement containing electrolytes, creatine, and glycerol. Six hea...
Social enrichment mitigates facial expressions and physiological indicators of short-term stress in horses. This study aimed to evaluate the ability of social noncontact environmental enrichment to facilitate social buffering and to characterize the emotional experience of horses subjected to restraint in stock by assessing physiological parameters and facial expressions. Pantaneiro horses (n = 11) were evaluated in a crossover design with two treatments: social noncontact enrichment during stock restraint and social isolation during stock restraint. Physiological parameters (heart rate, heart rate variability, respiratory rate, ocular temperature by infrared thermography, and auricular temperat...
Milk productivity of mares. To determine the milk productivity of Kazakh horses of the Adai region in variants of selection and technological indicators of milk for the production of cumus in the conditions of the Mangyshlak peninsula of the Republic of Kazakhstan. The object of the study was the Kazakh horse of the Adai intra-breed type at "Taushyk" LLP (Tupkaragan District, Mangystau Region). Mares with a more pronounced milk production were selected and analyzed . they have investigated the quality of milk for further processing. A characteristic feature of the dynamics of milk sugar content during lactation has been ...
Relationship between the estrus duration in cyclic mares and the endometrial gene expression on day 7 post-ovulation. This study investigated the effect of estrus duration on endometrial gene expression in cyclic mares on Day 7 post-ovulation, focusing on transcripts relevant to early pregnancy: uterocalin (P19), insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2), progesterone receptor (PGR), and estrogen receptor alpha (ESR1). Twelve mares were classified according to the estrus duration in long estrus (LE, ≥ 3 days of endometrial edema; n = 7) or short estrus (SE, 0.1). ESR1 expression was undetectable in all samples. These findings suggest that prolonged estrus enhances P19 e...
Microbiome analysis reveals the positive effects of exercise on the gut microbiota in horse. Gut microbiota is vital to host health, involving many aspects including immunity, metabolism and digestion. Exercise is recognized as a significant factor influencing the gut microbiota. However, the effects of exercise on the gut microbiota in horses remain unclear. Here, this study aims to investigate the effects of exercise on the gut bacterial and fungal communities in the horses using 16S rDNA and ITS genes amplicon sequencing. Results indicated that exercise significantly increased the ACE, Chao1 and Shannon indices of the gut bacterial community, accompanied by significant alterations ...
Physiological and nutritional adaptation of broodmares during the transition from late pregnancy to early lactation: Digestibility changes and the role of uNDF as an internal marker. Nutritional management of broodmares during late pregnancy and early lactation is essential for maternal health and foal well-being. This study evaluated a targeted dietary adaptation during the transition from late gestation to early lactation, monitored nutrient digestibility, and applied undigested neutral detergent fiber (uNDF) as an intrinsic digestibility marker. A prospective nutritional study was conducted on 11 clinically healthy Trotter broodmares (3 primiparous, 8 multiparous) monitored under standardized conditions. Mares received a forage-based diet with controlled starch intake a...
Atropine induces narrowing of the superior and inferior iridocorneal angle and ciliary cleft in normal horse eyes. To investigate the effects of atropine on the iridocorneal angle (ICA) and ciliary cleft (CC) of normal equine eyes using ultrasound biomicroscopy (UBM). Unassigned: 12 normal adult horses underwent measurement of intraocular pressure (IOP), vertical and horizontal pupil diameter, and UBM of the superior, temporal, inferior, and nasal ICA/CC in both eyes. Measurements were repeated 2 hours following ophthalmic atropine 1% solution application. Measurements of the ICA and CC, including pectinate ligament distance (PLD), CC length (CCL), height of opening distance (HOD), CC area (CCA), and pecti...
Longitudinal assessment of hemostatic adaptations in pregnant mares: Evidence of a physiological hypercoagulable state. Pregnancy triggers intricate hemostatic adjustments that support placental maturation and prepare the maternal organism for delivery. We hypothesized that pregnant mares would progressively shift toward a procoagulant state throughout gestation, reflected in changes to coagulation and fibrinolytic markers. To test this hypothesis, 15 clinically healthy Spanish Purebred pregnant mares were monitored monthly from conception to term, alongside 15 non-pregnant controls of similar age and breed. A comprehensive hemostatic profile-including platelet (PLT) count, prothrombin time (PT), activated part...
Evaluation of Short-Term Stall Size Housing on the Behavior and Welfare of Domestic Horses (Equus caballus). Single-stall housing is a common system used for horses in various settings, including racing stables, riding schools, teaching and research facilities. Adequate stall space is necessary for horses to lie down and make postural adjustments, both of which are essential for equine rest and welfare. The Guide for the Care and Use of Laboratory Animals recommends a stall size of 144 ft2. However, not all stalls meet this size requirement, and there is limited literature supporting its use in terms of animal welfare. This study used a crossover design to compare behavioral and physiologic variables...
Anatomical description of the vertebrobasilar and carotid systems forming the cerebral arterial circle in the equine brain. The cerebral blood supply in horses is maintained by carotid and vertebrobasilar systems, which join the cerebral arterial circle to ensure continuous brain perfusion. This study aimed to comprehensively describe the origins, courses, and interconnections of the vertebrobasilar and carotid systems in the horse brain. Unassigned: Ten adult equine specimens were obtained from horses euthanized for non-neurological reasons. Following perfusion with 10% formaldehyde, colored latex was injected into the arterial system, and detailed dissections were performed to study major intracranial vessels. Un...
Comparative hematological and physiological responses to ground and pool training in Colombian Paso Horses. Exercise training causes physiological and hematological changes that are crucial for enhancing athletic performance in horses. While these responses have been extensively studied in various equine breeds, there is limited information regarding Colombian Paso Horses (CPH), especially concerning the comparative effects of different training methods. Ground-based training is frequently used to improve gait and speed, whereas aquatic exercise has become an alternative conditioning approach that lessens musculoskeletal stress. However, the physiological responses related to these training modaliti...
Effect of heat acclimation training frequency on the physiological adaptations of Thoroughbred horses. Heat acclimation enhances thermoregulation and cardiovascular function. While daily training protocols are typically recommended for humans, optimal training protocols for Thoroughbred horses remain unclear. Here, we compared the effects of two heat acclimation protocols, consecutive and intermittent, in Thoroughbred horses. In a randomized crossover study, eight trained Thoroughbred horses completed either a consecutive (CONS: 9 consecutive days) or an intermittent (INT: 3 days/week for 3 weeks) heat acclimation protocol, comprising 30 min of exercise in hot conditions (WBGT 30°C). Increment...
Decoding sebaceous gland functions and diseases: insights from domestic animals. Skin sebaceous glands (SGs) synthesize and secrete sebum, a mixture of lipids and cellular debris that defends the external body surface against physicochemical challenges. Recent data define the SG as a dynamic entity with potential functions beyond skin protection, including immunomodulatory actions and the regulation of energy metabolism. We postulate that the SG also has important, unrecognized roles in physiological and pathological processes in domestic animals. Conversely, data derived from domestic animals may have translational relevance for humans. This review article summarizes SG s...
Temporal variation in incretin and insulin secretion in ponies in association with dietary macronutrients. Equine insulin dysregulation (ID) is a common condition that predisposes to hyperinsulinaemia-associated laminitis. Improved pathophysiological understanding would enable better management of ID and reduce the risk of laminitis. The incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), augment the insulin response to dietary glucose and GLP-1 has been implicated in the pathophysiology of ID. However, their temporal variation in response to a low-energy diet has not been reported. This study determined the variation in GLP-1, GIP and insulin ...
QT interval and cardiac restitution dynamics in racehorses: Observations during maximal effort. Sudden cardiac death is a leading cause of athletic death in both humans and horses, making racehorses a potentially valuable model for investigating sudden cardiac death. Cardiac restitution ratio (QT/TQ interval) is used to assess arrhythmia risk in humans, but investigations in athletes are scarce. The objective was to characterize QT interval and cardiac restitution ratio in Thoroughbred racehorses during maximal effort. Automated restitution analysis was performed using 2709 pairs of cardiac cycles from 30 Thoroughbred horses during races. Cardiac cycles were obtained during: pre-race; ac...
Prolonged wireless measurement of intragastric pH in foals. The pathogenesis of gastric ulceration is not well understood in foals, and its relationship with gastric acidity requires further investigation. A wireless capsule, designed for intraesophageal pH monitoring in humans, was adapted to measure intragastric pH in adult horses. Objective: To (1) determine the feasibility of wireless intragastric pH measurement in foals; (2) determine capsule attachment duration; and (3) describe the intragastric pH profiles recorded. Methods: Eight healthy foals aged 24-98 days. Methods: Prospective interventional study. Capsules were attached to the glandular g...
The high fundamental frequency in horse whinnies is generated by an aerodynamic whistle. Understanding why the frequencies of some species' vocalizations are far above or below those predicted by body size is key for explaining the remarkable diversity of mammalian vocal behavior. Horses, among the largest terrestrial mammals, provide a clear example of such deviation: their whinnies contain a very high fundamental frequency (>1,000 Hz) in addition to a second, lower one (∼200 Hz). While the lower fundamental frequency of whinnies is readily attributed to vocal fold (laryngeal) vibrations, the biomechanical processes underlying the production of the higher one remain unknown....
Transthoracic impedance in adult Thoroughbred horses is similar to other species. To determine transthoracic impedance (TTI) in adult horses using an exponential biphasic defibrillator and investigate patient and technique factors influencing TTI. Unassigned: A randomized crossover design with 2 phases was used. Phase 1: TTI was measured in dorsal and lateral recumbency, with and without manual pressure on the electrodes in deceased horses immediately following euthanasia. Phase 2: TTI was measured in dorsal recumbency during inspiration and expiration using anesthetized live horses sourced from 2 terminal studies. Mixed-effects linear regression modeling was performed to a...
Facial hair whorl location, behavior, and ocular temperature as a physiological stress indicator in young Pura Raza Española dressage horses. Behavioral and emotional reactivity assessment in sport horses is essential for optimizing their management and sports performance, particularly in equestrian disciplines such as Dressage. This study investigates, in Pura Raza Española (PRE) horses, the association between facial hair whorl (FHW) patterns, behavioral traits, and physiological stress responses using ocular temperature (OT) assessed with infrared thermography as, an objective, non-invasive physiological stress indicator. Unassigned: A total of 98 male PRE horses, aged 4-6 years old and all gray coated, were evaluated during the...
Biomechanics of the Head and Neck. The horse's head and neck account for about 10% of body weight, and this, combined with the fact that they are cantilevered in front of the trunk, produces considerable leverage around the joints at the base of the neck. During locomotion, the neck is moved primarily by gravitational and inertial forces controlled by eccentric-concentric cycles of contraction in the topline muscles assisted by energy-saving, stretch-recoil cycles in the nuchal ligament. The functional part of the nuchal ligament is the caudal funicular region and the lamellae to the second cervical vertebra that acts as the po...
Effects of intravenous oxytocin on plasma serotonin and trainability in horses. Oxytocin (OXT) plays a crucial role in regulating the serotonin (5-HT) system and behavior. Although previous studies have reported significant relationships among OXT, 5-HT, and behavioral responses, the effects of OXT on 5-HT concentrations and behavioral traits in horses remain poorly understood. This study aimed to investigate the effects of intravenous OXT administration on plasma 5-HT concentrations and trainability in horses. A crossover design was employed using eight horses, each receiving either a 10-IU intravenous dose of OXT or normal saline. Blood samples were collected at baselin...
Commentary on MacKechnie-Guire et al. Measuring Noseband Tightness on the Lateral Aspect of the Horse’s Face. Animals 2015, 15, 537. The use of horses for sport is under scrutiny due to evidence that common practices such as tight nosebands may impair horse welfare. Restrictive nosebands prevent horses from performing normal comfort behaviour such as coughing and yawning. To address these concerns, the International Society for Equitation Science (ISES) developed a noseband tightness-checking device, the ISES "taper gauge," along with a validated method that assesses how far the device can be inserted beneath the noseband at the dorsal midline of the nasal planum. However, citing concerns about the reliability of dorsal mid...
