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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.
The genes of all seven CYP3A isoenzymes identified in the equine genome are expressed in the airways of horses. In the present study, we examined the gene expression of cytochrome P450 3A (CYP3A) isoenzymes in the tracheal and bronchial mucosa and in the lung of equines using TaqMan probes. The results show that all seven CYP3A isoforms identified in the equine genome, that is, CYP3A89, CYP3A93, CYP3A94, CYP3A95, CYP3A96, CYP3A97 and CYP3A129, are expressed in the airways of the investigated horses. Though in previous studies, CYP3A129 was found to be absent in equine intestinal mucosa and liver, this CYP3A isoform is expressed in the airways of horses. The gene expression of the CYP3A isoenzymes varied...
Effect of feeding glucose, fructose, and inulin on blood glucose and insulin concentrations in normal ponies and those predisposed to laminitis. Identification of ponies (Equus caballus) at increased risk of pasture-associated laminitis would aid in the prevention of the disease. Insulin resistance has been associated with laminitis and could be used to identify susceptible individuals. Insulin resistance may be diagnosed by feeding supplementary water-soluble carbohydrate (WSC) and measuring blood glucose and insulin concentrations. The aim of this study was to assess the glycemic and insulinemic responses of 7 normal (NP) and 5 previously laminitic (PLP), mixed breed, native UK ponies fed glucose, fructose, and inulin [1 g/(kg·d) fo...
Tendon regeneration in human and equine athletes: Ubi Sumus-Quo Vadimus (where are we and where are we going to)? Tendon injuries are one of the most common orthopaedic problems in both human and equine athletes. When a damaged tendon heals naturally, it loses a substantial part of the original strength and elasticity. Therefore, tendons recover structurally (reparation) but not functionally (regeneration) after conservative medical or surgical treatment. Since the structure and matrix composition of human and equine tendons share many similarities, the nature of tendon injuries are also strongly comparable in both species. Therefore, the evaluation of regenerative therapies in horses may have application...
Non-genomic action of beclomethasone dipropionate on bronchoconstriction caused by leukotriene C4 in precision cut lung slices in the horse. Glucocorticoids have been proven to be effective in the therapy of recurrent airway obstruction (RAO) in horses via systemic as well as local (inhalative) administration. Elective analysis of the effects of this drug on bronchoconstriction in viable lung tissue offers an insight into the mechanism of action of the inflammatory cascade occurring during RAO which is still unclear. The mechanism of action of steroids in treatment of RAO is thought to be induced through classical genomic pathways. We aimed at electively studying the effects of the glucocorticoid beclomethasone dipropionate on equi...
Biosynthesis of oestrogen by the early equine embryo proper. The embryo proper in early equine pregnancy has recently been shown to have a remarkable capacity for metabolism of oestrogens. High concentrations of oestrogens in yolk-sac fluid could provide substrate for local metabolism in tissues of the embryo proper and this activity could have significance for early development. Due to the high level of oestrogen metabolism in the embryo proper we examined the possibility that it could also biosynthesise oestrogens. Conceptuses were collected in the fourth week of pregnancy (n=23) and the embryo was separated from extraembryonic tissues for incubation ...
Follicular fluid leptin concentrations and expression of leptin and leptin receptor in the equine ovary and in vitro-matured oocyte with reference to pubertal development and breeds. There is no published information about follicular-fluid leptin concentrations or the presence of leptin and leptin receptor in the equine ovary or oocyte. Three groups of mares - adult draft mares, draft fillies and adult Standardbred mares - were included in the study. Leptin and leptin receptor were detected in all immature oocytes by immunofluorescence with higher intensity in oocytes from draft mares compared with draft fillies and Standardbred mares. After in vitro maturation a higher proportion of oocytes reached metaphase II in draft mares than in draft fillies and Standardbred mares, ...
Morphology of twin and triplet equine conceptuses during weeks 3 and 4 of pregnancy. Twin ovulations are common in horses, but twin pregnancies are rarely carried to term. Theories of how one or both twins is/are naturally eliminated in early pregnancy, termed 'embryo reduction', have been based on ultrasonographic, not morphological, studies. Here we describe conceptuses recovered transcervically between Days 15 and 28 from 31 twin and two triplet pregnancies. Signs of contact between conceptuses were deduced from those seen in one pair that remained attached by their capsules on Day 18. Signs were found on capsules in two of 10 pairs before or during fixation (immobilisation...
Comparative analysis of serotonin in equine plasma with liquid chromatography–tandem mass spectrometry and enzyme-linked immunosorbent assay. Serotonin is regularly measured in equine platelet-poor plasma in research settings. However, reported reference values vary between studies, partially because plasma serotonin concentrations are very low and a reliable and affordable detection method is lacking. A simple, rapid, and sensitive method for serotonin determination in equine platelet-poor plasma using liquid chromatography--tandem mass spectrometry (LC-MS/MS) was developed and validated. Results of a commercially available enzyme-linked immunosorbent assay (ELISA) were compared to the LC-MS/MS results, in order to validate a test ...
Finite element analysis of stress in the equine proximal phalanx. To improve understanding of the internal structure of the proximal phalanx (P1), response of the bone to load and possible relation to the pathogenesis of fractures in P1. Objective: To model the P1 and replicate the loads experienced by the bone in stance, walk, trot and gallop using finite element analysis. Methods: The geometry of the P1 was captured using micro-computed tomography (μCT) and was reconstructed in 3 dimensions. Values for material properties and forces experienced at stance, walk, trot and gallop were taken from the literature and were applied to the reconstructed model. Usi...
Assessing fitness in endurance horses. A field test and a standardized treadmill test were used to assess fitness in endurance horses. These tests discriminated horses of different race levels: horses participating in races of 120 km and more showed higher values of VLA4 (velocity at which blood lactate reached 4 mmol/L) and V200 (velocity at which heart rates reached 200 beats per min) than horses of lower race levels. Un test sur le terrain et un test sur tapis roulant ont été utilisés pour évaluer la condition physique des chevaux d’endurance. Ces tests ont séparé les chevaux de différents niveaux de course : les cheva...
The effect of palatal dysfunction on measures of ventilation and gas exchange in Thoroughbred racehorses during high intensity exercise. The effect of palatal instability (PI) on measures of ventilation and gas exchange is not well understood. Objective: To assess to what degree different severities of naturally occurring palatal dysfunction affect ventilation and gas exchange during strenuous exercise. Methods: A retrospective study was performed using data collected from 40 Thoroughbred racehorses diagnosed with naturally occurring dynamic palatal dysfunction during high speed treadmill exercise. Upper airway videoendoscopic recordings were made concurrently with measurements of ventilation and gas exchange. Three categories ...
A preliminary study into the correlation of stiffness of the laminar junction of the equine hoof with the length density of its secondary lamellae. The relationship between mechanical behaviour and microscopic structure of the laminar junction of equine hooves under testing conditions requires elucidation. Objective: To determine mechanical parameters and 2D length density of profiles of secondary lamellae of the laminar junction in the dermal region and to assess possible correlations. Methods: Specimens (25 samples in total) of the laminar junction were taken from front, quarter and heel parts from 3 equine hooves and exposed to a uniaxial tensile test until rupture to obtain Young's moduli of elasticity, ultimate stress and strain. Nei...
Short-term incubation of equine laminar veins with cortisol and insulin alters contractility in vitro: possible implications for the pathogenesis of equine laminitis. This study investigated the effects of cortisol and insulin, hormones that affect both glycaemic status and vascular function, on the in vitro contractility of isolated healthy equine small laminar veins. Small veins (150-500 μm) draining the digital laminae from healthy horses or ponies were investigated by wire myography. Concentration response curves were constructed for noradrenaline (NA), phenylephrine (PE), endothelin-1 (ET-1) and 5-hydroxytryptamine (5-HT) in the presence of either cortisol (10(-6 ) m) or insulin (1000 μIU/mL). Cortisol significantly increased the maximum contractilit...
Ovine amniotic epithelial cells: in vitro characterization and transplantation into equine superficial digital flexor tendon spontaneous defects. In vitro expanded and frosted ovine amniotic epithelial cells (oAECs) were evaluated for their phenotype, stemness and attitude to differentiate into tenocytes. Fifteen horses with acute tendon lesions were treated with one intralesional injection of oAECs. Tendon recovery under controlled training was monitored. In vitro expanded oAECs showed a constant proliferative ability, a conserved phenotype and stable expression profile of stemness markers. Differentiation into tenocytes was also regularly documented. US controls showed the infilling of the defect and early good alignment of the fibers...
Mechanisms of oxidative injury in equine disease. Oxygen is essential to aerobic life, but it is also associated with the production of highly reactive compounds that can pose danger to physiologic systems when the oxygen concentration is excessive. Reactive oxygen species (ROS) are required for normal physiologic processes, but when produced in excess, they can overwhelm endogenous antioxidants, resulting in significant cellular damage and, eventually, cell death. Ischemic events can initiate numerous pathophysiologic mechanisms leading to increased production of ROS, loss of cellular energy production, and lipid peroxidation. Although reper...
Mutations in DMRT3 affect locomotion in horses and spinal circuit function in mice. Locomotion in mammals relies on a central pattern-generating circuitry of spinal interneurons established during development that coordinates limb movement. These networks produce left-right alternation of limbs as well as coordinated activation of flexor and extensor muscles. Here we show that a premature stop codon in the DMRT3 gene has a major effect on the pattern of locomotion in horses. The mutation is permissive for the ability to perform alternate gaits and has a favourable effect on harness racing performance. Examination of wild-type and Dmrt3-null mice demonstrates that Dmrt3 is exp...
Effects of the addition of endotoxin during perfusion of isolated forelimbs of equine cadavers. To examine the effect of endotoxins on metabolism and histopathologic changes of isolated perfused equine forelimbs. Methods: Forelimbs (comprising the metacarpus and digit) were collected from cadavers of 12 healthy adult horses after slaughter at an abattoir (14 limbs; 1 forelimb of 10 horses and both forelimbs of 2 horses). Methods: Forelimbs were perfused for 10 hours with autologous blood, with and without the addition of endotoxin (80 ng of lipopolysaccharide [LPS]/L). Two limbs of the endotoxin exposure group and 2 nonperfused limbs were loaded to failure of the suspensory apparatus of ...
Effects of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in Standardbreds. To determine the influence of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in horses and identify potential markers indicative of early overtraining. Methods: 12 Standardbred geldings. Methods: Horses underwent 4 phases of treadmill-based training. In phase 1, horses were habituated to the treadmill. In phase 2, endurance training was alternated with high-intensity exercise training. In phase 3, horses were divided into control and intensified training groups. In the intensified training group, training intensity, duration, ...
Evaluation of a diode laser for use in induction of tendinopathy in the superficial digital flexor tendon of horses. To evaluate use of a diode laser to induce tendinopathy in the superficial digital flexor tendon (SDFT) of horses. Methods: 4 equine cadavers and 5 adult horses. Methods: Cadaveric SDFT samples were exposed to a diode laser at various energy settings to determine an appropriate energy for use in in vivo experiments; lesion size was assessed histologically. In vivo experiments involved laser energy induction of lesions in the SDFT (2 preliminary horses [0, 25, 75, and 87.5 J] and 3 study horses [0 and 125 J]) and assessment of lesions. Study duration was 21 days, and lesions were assessed clini...
Evidence that in vitro susceptibility of CD3+ T lymphocytes to equine arteritis virus infection reflects genetic predisposition of naturally infected stallions to become carriers of the virus. We investigated the correlation between in vitro susceptibility of CD3(+) T lymphocytes to equine arteritis virus (EAV) infection and establishment of persistent infection among 14 stallions following natural infections. The data showed that carrier stallions with a CD3(+) T lymphocyte susceptibility phenotype to in vitro EAV infection may be at higher risk of becoming carriers than those that lack this phenotype (P = 0.0002).
Effects of continuous or intermittent lipopolysaccharide administration for 48 hours on the systemic inflammatory response in horses. To determine whether the method of lipopolysaccharide (LPS) administration (intermittent vs continuous) affects the magnitude and duration of the systemic inflammatory response in horses and whether prolonged (48 hours) endotoxemia induces laminitis. Methods: 12 healthy adult horses (10 mares and 2 geldings). Methods: Horses were randomly assigned to receive LPS (total dose, 80 μg; n = 4) or saline (0.9% NaCl) solution (80 mL/h; 4) via constant rate infusion or 8 bolus IV injections of LPS (10 μg, q 6 h;4) during a 48-hour period. Physical examinations were performed every 4 hours, inflammat...
Serum zinc levels and their relationship with diseases in racehorses. Zinc is one of the essential microelements involved in the regulation of enzyme activity, as well as metabolism of nucleic acid and proteins. There have been few reports on equine serum zinc concentrations during the training period, and little is known about the relationship between zinc levels and diseases in horses. In this study, we measured serum zinc levels in healthy Thoroughbred racehorses, as well as in other horses, under general disease or training conditions. The reference value for serum zinc levels in Thoroughbred horses was 41-79 μg/dl. There were no differences in serum zinc l...
Feed restriction enhances the depressive effects of erythromycin on equine hindgut microbial metabolism in vitro. Equine typholocolitis is a sporadic diarrheal disease causing high mortality rates. One of the risk factors responsible for this is the oral application of the macrolide antibiotic erythromycin. The aim of the present in vitro study was to investigate whether erythromycin in combination with feed restriction provokes changes in microbial hindgut metabolism and could therefore be involved in the pathogenesis of equine typhlocolitis. As application of erythromycin and feed restriction are risk factors for equine typhlocolitis, both factors were chosen to investigate their individual and combined...
A comparative review of vitamin E and associated equine disorders. Vitamin E is a primary chain-breaking antioxidant that prevents cyclic propagation of lipid peroxidation. Across species, vitamin E is essential for normal neuromuscular function by acting as a potent antioxidant, as well as by modulating the expression of certain genes, inhibiting platelet aggregation and stabilizing plasma membranes. This review focuses on vitamin E structure, absorption, metabolism, current equine dietary recommendations, the interplay between antioxidants and exercise, a discussion of the necessity of vitamin E supplementation in the horse above the Nutritional Research Co...
Lithium dilution, pulse power analysis, and continuous thermodilution cardiac output measurements compared with bolus thermodilution in anaesthetized ponies. This study compares cardiac output (CO) measurements obtained by lithium dilution (LiDCO), pulse power analysis (PulseCO), and continuous thermodilution (CTD) with bolus thermodilution (BTD) in ponies. Methods: Eight isoflurane-anaesthetized Shetland ponies received xylazine, ketamine, and midazolam infusions (0.3, 1.2, and 0.018 mg kg(-1) h(-1), respectively). CO was measured with BTD, CTD, LiDCO, and PulseCO. Lithium was injected into the jugular vein and blood was sampled from the facial artery for lithium detection and this artery was also used for PulseCO. Measurements were obtained durin...
Distribution of insulin receptor and insulin-like growth factor-1 receptor in the digital laminae of mixed-breed ponies: an immunohistochemical study. Hyperinsulinaemia has been implicated in the pathogenesis of laminitis; however, laminar cell types responding to insulin remain poorly characterised. Objective: To identify laminar cell types expressing insulin receptor (IRc) and/or insulin-like growth factor-1 receptor (IGF-1R); and to evaluate the effect of dietary nonstructural carbohydrate (NSC) on their expression. Methods: Mixed-breed ponies (n = 22) received a conditioning hay chop diet (NSC ∼6%); following acclimation, ponies were stratified into lean (n = 11, body condition score [BCS]≤4) or obese (n = 11, BCS ≥7) groups and ea...
Feasibility of infrared spectroscopy with pattern recognition techniques to identify a subpopulation of mares at risk of producing foals diagnosed with failure of transfer of passive immunity. To assess the feasibility of a serum-based test using infrared spectroscopy to identify a subpopulation of mares at risk of producing foals susceptible to failure of passive transfer of immunity (FPT) because of mare-associated factors. Methods: Serum was collected from post-parturient mares (n = 126) and their foals at 24-72 h of age. A radial immunodiffusion IgG test was used to determine each foal's serum IgG concentration. Infrared absorbance spectra of dam sera were collected in the wave number range of 400-4000 cm(-1). Following data preprocessing, pattern recognition techniques were use...
Effect of hypoxia on equine mesenchymal stem cells derived from bone marrow and adipose tissue. Mesenchymal stem cells (MSCs) derived from bone marrow (BM-MSCs) and adipose tissue (AT-MSCs) are being applied to equine cell therapy. The physiological environment in which MSCs reside is hypoxic and does not resemble the oxygen level typically used in in vitro culture (20% O2). This work compares the growth kinetics, viability, cell cycle, phenotype and expression of pluripotency markers in both equine BM-MSCs and AT-MSCs at 5% and 20% O2. Results: At the conclusion of culture, fewer BM-MSCs were obtained in hypoxia than in normoxia as a result of significantly reduced cell division. Hypoxi...
Thyroid hormone concentrations differ between donkeys and horses. Reference intervals for thyroid hormones (TH) concentrations have not been previously established for donkeys, leading to potential misdiagnosis of thyroid disease. Objective: To determine the normal values of TH in healthy adult donkeys and compare them to TH values from healthy adult horses. Methods: Thirty-eight healthy Andalusian donkeys and 19 healthy Andalusian horses from 2 different farms were used. Donkeys were divided into 3 age groups: 11 years and into 2 gender groups. Serum concentrations of fT3, tT3, rT3, fT4 and tT4 were quantified by radioimmunoassay. All blood samples were col...
