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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.
Laminar regulation of STAT1 and STAT3 in black walnut extract and carbohydrate overload induced models of laminitis. STAT1 and STAT3 are important signaling molecules in disorders of systemic inflammation and are likely to be involved in laminitis, as laminar and systemic inflammation have been well documented in experimental models of laminitis. Objective: The STAT1 and STAT3 activation (via phosphorylation of tyrosine and serine moieties) is occurring in the laminar tissue during the developmental and onset of lameness time points in both the black walnut extract (BWE) and carbohydrate overload (CHO) models of laminitis. Methods: Archived laminar tissue from horses. Methods: Experimental studies of induced...
Equine cloning: in vitro and in vivo development of aggregated embryos. The production of cloned equine embryos remains highly inefficient. Embryo aggregation has not yet been tested in the equine, and it might represent an interesting strategy to improve embryo development. This study evaluated the effect of cloned embryo aggregation on in vitro and in vivo equine embryo development. Zona-free reconstructed embryos were individually cultured in microwells (nonaggregated group) or as 2- or 3-embryo aggregates (aggregated groups). For in vitro development, they were cultured until blastocyst stage and then either fixed for Oct-4 immunocytochemical staining or maint...
Plasma clearance and half-life of prostaglandin F2alpha: a comparison between mares and heifers. Horses are about five times more sensitive to the luteolytic effect of prostaglandin F2alpha (PGF) than cattle, as indicated by a recommended clinical dose of 5 mg in horses and 25 mg in cattle. Novel evaluations of the PGF plasma disappearance curves were made in mares and in heifers, and the two species were compared. Mares and heifers (n = 5) of similar body weight were injected (Min 0) intravenously with PGF (5 mg per animal). Blood was sampled every 10 sec until Min 3, every 30 sec until Min 5, every 10 min until Min 60, and every 30 min until Min 240. The mean PGF concentration was great...
Farriery for the hoof with a sheared heel. Sheared heels develop as an adaptation-distortion of the hoof capsule as a result of an abnormal strike and loading pattern of the foot, which is generally a consequence of limb conformation. The growth rate around the circumference of the hoof should be approximately uniform, but regional disturbances in growth rate can occur to either increase or decrease growth. The primary conformational trait that is observed in horses that develop sheared heels is a rotational deformity of the distal limb and a narrow chest. Farriery is directed toward improving the hoof capsule distortion and decreasing...
Temperature regulation in horses during exercise and recovery in a cool environment. Clipping the winter coat in horses is done to improve heat dissipation during exercise and make grooming easier. It is often combined with blanketing to keep the horse warm. The aims of the present study were to investigate how clipping and the use of blankets affect thermoregulation during exercise and recovery in horses. Methods: One Gotland pony, one New Forest pony, and one warm-blooded horse exercised one after the other on a 6450 m long track. The horses walked, trotted and cantered according to a predetermined scheme, which took about 50 minutes including three stops. The scheme was rep...
Macrophage migration inhibitory factor is expressed by equine conceptuses and endometrium. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine expressed by a wide range of tissues, which has been implicated to be involved in reproduction. Relative abundance of MIF mRNA in conceptus and endometrial tissue was assessed using real-time RT-PCR. Western blot analysis and immunohistochemistry were used to detect MIF protein expression. MIF transcript abundance was lowest in conceptuses obtained 16 days after ovulation, while the remaining stages of conceptus development that were analysed showed relatively constant expression levels. Migration inhibitory factor expressi...
Forces and pressures on the horse’s back during bareback riding. The objectives of this study were to measure forces and pressure profiles when riding with a conventional saddle compared to bareback riding. An electronic pressure mat was used to compare contact area, mean total force and pressure variables for one rider riding seven horses at sitting trot with a conventional saddle or bareback. The use of a saddle was associated with a larger contact area and higher mean total force compared with the bareback condition. Mass normalized mean total force for bareback riding was lower than expected based on the rider's body mass, suggesting that shear forces e...
Measurement of tidal volume using respiratory ultrasonic plethysmography in anaesthetized, mechanically ventilated horses. To compare tidal volume estimations obtained from Respiratory Ultrasonic Plethysmography (RUP) with simultaneous spirometric measurements in anaesthetized, mechanically ventilated horses. Methods: Prospective randomized experimental study. Methods: Five experimental horses. Methods: Five horses were anaesthetized twice (1 week apart) in random order in lateral and in dorsal recumbency. Nine ventilation modes (treatments) were scheduled in random order (each lasting 4 minutes) applying combinations of different tidal volumes (8, 10, 12 mL kg(-1)) and positive end-expiratory pressures (PEEP) (0,...
The analysis of densitometric and geometric parameters of bilateral proximal phalanges in horses with the use of peripheral quantitative computed tompgraphy. Proximal phalanges in horses are among bones that are most prone to injuries. So far, the detailed analysis of densitometric and geometric parameters of both front legs proximal phalanges in horses has not been investigated. The aim of this study was to compare the densitometric and geometric parameters between proximal phalanges in equine both front legs with the use of peripheral quantitative computed tomography (pQCT). Methods: The study material comprised isolated both front legs proximal phalanges derived from 22 horses. The structure analysis of the proximal phalanges was conducted with ...
A pilot study on the corneal curvatures and ocular dimensions of horses less than one year of age. Intraocular lenses (IOLs) have been implanted in adult equine eyes after cataract surgery. Foals and weanlings comprise a large proportion of those horses undergoing cataract surgery. Due to potential differences in the size and corneal curvature of the juvenile eye, it is not currently known whether implantation of adult IOLs is appropriate in foals and weanlings. The objective of the study was to measure the anterior chamber depth (ACD), central lens thickness (CLT), vitreous chamber depth (VCD), axial globe length (AGL) and corneal curvature of horses less than one year of age. The axial di...
Stallion spermatozoa selected by single layer centrifugation are capable of fertilization after storage for up to 96 h at 6°C prior to artificial insemination. One of the challenges faced by equine breeders is ensuring delivery of good quality semen doses for artificial insemination when the mare is due to ovulate. Single Layer Centrifugation (SLC) has been shown to select morphologically normal spermatozoa with intact chromatin and good progressive motility from the rest of the ejaculate, and to prolong the life of these selected spermatozoa in vitro. The objective of the present study was a proof of concept, to determine whether fertilizing ability was retained in SLC-selected spermatozoa during prolonged storage. Results: Sixteen mares were insemi...
The proximal aspect of the suspensory ligament in the horse: How precise are ultrasonographic measurements? To evaluate intra- and interobserver variability in ultrasonographic measurements of the proximal aspect of the suspensory ligament (PSL) in the horse. Objective: A minimum difference of ≥20% is required to differentiate reliably between physiological and pathological alterations related to dimensions. Methods: Two operators examined the PSL in all 4 limbs of 14 horses twice using different techniques and different probes with and without standoff pads. Measurements were taken from the longitudinal and transverse images. Inter- and intraoperator variability was evaluated using agreement indi...
Similar slow down in running speed progression in species under human pressure. Running speed in animals depends on both genetic and environmental conditions. Maximal speeds were here analysed in horses, dogs and humans using data sets on the 10 best performers covering more than a century of races. This includes a variety of distances in humans (200-1500 m). Speed has been progressing fast in the three species, and this has been followed by a plateau. Based on a Gompertz model, the current best performances reach 97.4% of maximal velocity in greyhounds to 100.3 in humans. Further analysis based on a subset of individuals and using an 'animal model' shows that running spe...
Autologous point-of-care cellular therapies variably induce equine mesenchymal stem cell migration, proliferation and cytokine expression. Autologous cellular therapy products including adipose-derived stromal vascular fraction (SVF), bone marrow mononuclear cells (BMMNs), cord blood mononuclear cells (CBMNs) and platelet rich plasma are options for treatment of acute orthopaedic lesions while mesenchymal stem cells (MSCs) are culture expanded. These products may contribute to healing by secreting matrix proteins or growth factors, but they may also act on endogenous MSCs to facilitate healing. Objective: To determine the effects of cell therapy products on MSCs function in vitro. The hypothesis was that cell therapy products pro...
Periodontal biomechanics: finite element simulations of closing stroke and power stroke in equine cheek teeth. In equine dentistry periodontal diseases, especially periapical inflammation, are frequently occurring problems. Anachoresis is believed to be the most common cause for the development of such disorders. Nevertheless, there is still no substantiated explanation why settlement of pathogen microorganisms occurs in equine periodontal tissues. It is expected that excessive strains and stresses occurring in the periodontal ligament (PDL) during the horse's chewing cycle might be a predisposing factor. In this study this assumption was examined by finite element (FE) analyses on virtual 3-D models o...
The pathogenesis of tendon microdamage in athletes: the horse as a natural model for basic cellular research. The equine superficial digital flexor tendon (SDFT) is a frequently injured structure that is functionally and clinically equivalent to the human Achilles tendon (AT). Both act as critical energy-storage systems during high-speed locomotion and can accumulate exercise- and age-related microdamage that predisposes to rupture during normal activity. Significant advances in understanding of the biology and pathology of exercise-induced tendon injury have occurred through comparative studies of equine digital tendons with varying functions and injury susceptibilities. Due to the limitations of in-...
Thermoregulation of the testicle in response to exercise and subsequent effects on semen characteristics of stallions. Stallions (n = 8) were implanted with a thermal sensory device in the muscle of the neck and the subcutaneous tissue of the scrotum and then assigned to either a nonexercise (Non-EX; n = 4) or exercise (EX; n = 4) group. A motorized equine exerciser was used to work EX stallions 30 min/d for 4 d/wk during a 12-wk period from July through October 2010. Temperatures (subcutaneous scrotal, intramuscular neck, and rectal) were recorded at 0, 22, and 30 min after the start of exercise, as well as 60 and 120 min post-exercise. Hourly ambient temperature and relative humidity data were also obtained....
Method for estimating maximum permissible load weight for Japanese native horses using accelerometer-based gait analysis. The aim of this study was to establish a method for estimating loading capacity for Japanese native horses by gait analysis using an accelerometer. Six mares of Japanese native horses were used. The acceleration of each horse was recorded during walking and trotting along a straight course at a sampling frequency of 200 Hz. Each horse performed 12 tests: one test with a loaded weight of 80 kg (First 80 kg) followed by 10 tests with random loaded weights between 85 kg and 130 kg and a final test with a loaded weight of 80 kg again. The time series of acceleration was subjected to fa...
Colloidal centrifugation of stallion semen results in a reduced rate of sperm DNA fragmentation. Stallion spermatozoa recovered and examined immediately after colloidal centrifugation resulted in a higher straight-line velocity (VSL) than sperm processed using direct conventional centrifugation (p = 0.000), but there was no differences in the progressive motility or sperm DNA fragmentation (SDF) as determined by the sperm chromatin dispersion assay. However, when centrifuged spermatozoa were incubated at 37 °C for 24 h to determine the rate of SDF (r-SDF), a lower r-SDF (p = 0.0011) was observed in those sperm recovered after colloidal separation (0.5 ± 0.1%/h) compared to direct (1.2 ...
Expansion under hypoxic conditions enhances the chondrogenic potential of equine bone marrow-derived mesenchymal stem cells. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are widely used in regenerative medicine in horses. Most of the molecular characterisations of BM-MSCs have been made at 20% O(2), a higher oxygen level than the one surrounding the cells inside the bone marrow. The present work compares the lifespan and the tri-lineage potential of equine BM-MSCs expanded in normoxia (20% O(2)) and hypoxia (5% O(2)). No significant differences were found in long-term cultures for osteogenesis and adipogenesis between normoxic and hypoxic expanded BM-MSCs. An up-regulation of the chondrogenesis-related genes...
Direct intra-abdominal pressures and abdominal perfusion pressures in unsedated normal horses. To determine whether direct intra-abdominal pressures (IAP) and calculated direct abdominal perfusion pressures (APP) are location dependent within the abdomen of standing horses. We hypothesize that IAP will be increased and calculated APP will be decreased at a ventral abdominal location (V) when compared to values obtained from the left (LFl) or right flank (RFl). Methods: Prospective experimental design. Methods: University-based equine research facility. Methods: Seven healthy adult horses, 4 geldings and 3 mares. Methods: Measurements of direct IAP obtained from the RFl, LFl, and V locat...
Immunohistochemical distribution of leptin receptor in the major salivary glands of horses. The presence of the leptin receptor (ObR) has already been highlighted in the human major salivary glands and it has been hypothesized that leptin may act by regulating the gland's growth. No data are reported on domestic animals so, considering the important role that these glands play, not only related to food ingestion and digestion, and the important functional role hypothesized to explain the presence of ObR in humans salivary glands, the aim of the present work was to investigate the presence and the distribution of the leptin receptor in horse parotid and mandibular glands, by immunohis...
Contractile responses of isolated equine digital arteries under hypoxic or hyperoxic conditions in vitro: role of reactive oxygen species and Rho kinase. The underlying pathophysiological triggers for equine acute laminitis are unknown, although digital vasoconstriction, ischaemia, hypoxia and reperfusion injury may be involved. The contractile responses of isolated equine digital arteries (EDAs), harvested from the hindlimbs of normal horses postmortem at an abattoir, were studied acutely (up to 3 h) under hyperoxic (95% oxygen, 5% CO2 ) and hypoxic (95% nitrogen, 5% CO2 ) conditions in organ baths. Phenylephrine (PHE; 10(-6) m), 5-hydroxytryptamine (5-HT; 10(-7) m) and high potassium (K(+) ; 118 mm) caused contraction in EDAs which was signif...
Specialization of tendon mechanical properties results from interfascicular differences. Tendons transfer force from muscle to bone. Specific tendons, including the equine superficial digital flexor tendon (SDFT), also store and return energy. For efficient function, energy-storing tendons need to be more extensible than positional tendons such as the common digital extensor tendon (CDET), and when tested in vitro have a lower modulus and failure stress, but a higher failure strain. It is not known how differences in matrix organization contribute to distinct mechanical properties in functionally different tendons. We investigated the properties of whole tendons, tendon fascicles ...
Presumed case of “stiff-horse syndrome” caused by decreased gamma-aminobutyric acid (GABA) production in an American Paint mare. Glutamic acid decarboxylase (GAD) converts glutamic acid into the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Increased serum GAD (auto) antibody concentrations were found in a mare with increased postural musculature tone resulting in stiffness and recumbence. The mare was treated with dexamethasone which resulted in resolution of clinical signs and decreased GAD antibody concentrations. La glutamate décarboxylase (GAD) convertit l’acide glutamique en acide gamma-aminobutyrique (GABA), un inhibiteur des neurotransmetteurs. Des concentrations sériques accrues d’anticorps (a...
The effect of administering equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) post artificial insemination on fertility of lactating dairy cows. The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) and hCG post artificial insemination (AI) on fertility of lactating dairy cows. In Experiment 1, cows were either treated with eCG on Day 22 post AI (400 IU; n = 80) or left untreated (n = 84). On Day 29, pregnant cows were either treated with hCG (2500 IU; n = 32) or left untreated (n = 36). Pregnancy and progesterone were evaluated on Days 29 and 45. In Experiment 2, cows (n = 28) were either treated with eCG on Day 22 (n = 13) or left untreated (n = 15) and either treated with hCG on Day 29 (n = 14) or left untr...
Serum iron parameters and acute experimental EHV-1 infection in horses. Research in humans has demonstrated that high serum iron (sFe) concentration can predispose to infection, and many infections subsequently result in alterations of host sFe. A decrease in sFe concentration is an early and sensitive indicator of systemic inflammation caused by tissue necrosis, bacterial infections, or endotoxemia in horses. Serum iron parameters in acute equine herpesvirus type 1 (EHV-1) infection have not been evaluated previously. Objective: To document the sFe response to EHV-1 infection and to determine whether or not significant differences in sFe concentration exist betwe...
Effects of Platelet-Rich Plasma Composition on Anabolic and Catabolic Activities in Equine Cartilage and Meniscal Explants. To evaluate the effects of single- and double-spin preparations of platelet-rich plasma (PRP) on anabolic and catabolic activities of cartilage and meniscal explants in vitro. Methods: Single- and double-spin PRP was prepared using laboratory processing or commercial kits. The cellular contents were quantified, and each PRP was mixed in equal quantities with cell culture medium and added to cartilage or meniscus explant cultures, with or without interleukin 1 β (IL-1β). Extracellular matrix synthesis was quantified over 24 hours via (35)S-sulfate and (3)H-proline incorporation, while gene ex...
Effects of syringe type and storage conditions on results of equine blood gas and acid-base analysis. To determine effects of syringe type and storage conditions on blood gas and acid-base values for equine blood samples. Methods: Blood samples obtained from 8 healthy horses. Methods: Heparinized jugular venous blood was equilibrated via a tonometer at 37°C with 12% O(2) and 5% CO(2). Aliquots (3 mL) of tonometer-equilibrated blood were collected in random order by use of a glass syringe (GS), general-purpose polypropylene syringe (GPPS), or polypropylene syringe designed for blood gas analysis (PSBGA) and stored in ice water (0°C) or at room temperature (22°C) for 0, 5, 15, 30, 60, or 120 ...
