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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.
Seasonal fluctuations in body weight during growth of Thoroughbred racehorses during their athletic career. Domesticated horses adapt to environmental conditions through seasonal fluctuations in their metabolic rate. The seasonal change of metabolic rates of domesticated horses in pastures is documented. However, there are few investigations on seasonal body weight change of domesticated horses housed in stables, which are provided constant energy intake throughout the year. Both seasonal changes and gain in body weight of racehorses during their athletic career is known to a lesser extent because their body weight are not measured in most countries. Here, we used a seasonal-trend decomposition meth...
The relationship between intestinal and oral mucosa microcirculation in anaesthetized horses. To compare alteration in intestinal blood flow in anaesthetized horses with changes in oral mucosa blood flow. Methods: Prospective, randomized clinical study. Methods: Eight warmblood horses. Methods: After induction with guaifenesin and ketamine, anaesthesia was maintained with isoflurane at 1.5 vol% in oxygen. The tissue blood flow was measured using laser Doppler flowmetry at the jejunum, colon, rectal mucosa, oesophageal mucosa and the oral mucosa. After three baseline measurements, blood flow was first increased by dobutamine infusion and thereafter decreased by increasing isoflurane con...
18 F-sodium fluoride positron emission tomography of the equine distal limb: Exploratory study in three horses. Positron emission tomography (PET) is a cross-sectional, functional imaging modality that has recently become available to the horse. The use of 18 F-sodium fluoride (18 F-NaF), a PET bone tracer, has not previously been reported in this species. Objective: To assess the feasibility of 18 F-NaF PET in the equine distal limb and explore possible applications in the horse in comparison with other imaging modalities. Methods: Exploratory descriptive study involving three research horses. Methods: Horses were placed under general anaesthesia prior to intravenous (i.v.) administration of 1.5 MBq/kg...
Inflammation and fertility in the mare. A transient uterine inflammation post-breeding is a normal physiological reaction in the mare, and it is believed that the inflammatory response is necessary to eliminate bacteria and excess spermatozoa introduced into the uterine lumen. A tight balance between multiple pro- and anti-inflammatory factors is required for resolving the breeding-induced inflammation within 24-36 hr in the reproductively healthy mare, whereas a subpopulation of mares is susceptible to development of a persistent infection that can interfere with fertility. The aetiology of persistent endometritis can be either ba...
Redox cycling induces spermptosis and necrosis in stallion spermatozoa while the hydroxyl radical (OH•) only induces spermptosis. Oxidative stress is a major factor explaining sperm dysfunction of spermatozoa surviving freezing and thawing and is also considered a major inducer of a special form of apoptosis, visible after thawing, in cryopreserved spermatozoa. To obtain further insights into the link between oxidative stress and the induction of apoptotic changes, stallion spermatozoa were induced to oxidative stress through redox cycling after exposure to 2-methyl-1,4-naphthoquinone (menadione), or hydroxyl radical formation after FeSO exposure. Either exposure induced significant increases (p < 0.05) in two marke...
Uneven distribution of enamel, dentine and cementum in cheek teeth of domestic horses (Equus caballus): A micro computed tomography study. Hypsodont equine cheek teeth possess large dental crowns, resting partly in the bony alveolus. Over a horse's life cheek teeth erupt continuously to compensate for occlusal wear of 3-4 mm per year. Parts of the crown initially resting in the bony alveolus become progressively exposed at the occlusal surface with time. Hitherto, it is unclear whether the typical structure of the equine occlusal surface, composed of a complex arrangement of enamel, dentin and cementum, remains constant or undergoes structural changes with age. Therefore, we tested the hypothesis that the occlusal surface composi...
Evaluation of an intravaginal triptorelin acetate gel for inducing ovulation in mares. The objective of these studies was to investigate the efficacy of an intravaginal triptorelin acetate (TA) gel as an ovulation-inducing agent in mares. In Exp. 1, 24 mares were blocked using a combination of parity and age and randomly assigned to 1 of 3 treatment groups: 5 mL TA gel (TA5), 10 mL TA gel (TA10), or 5 mL vehicle gel only (CON). Following the appearance of a follicle ≥ 25 mm, a blood sample was obtained for measurement of LH from each mare every 24 h until treatment administration. When a follicle ≥ 35 mm was observed, treatments were administered intravaginally. Following tr...
Effects of polymyxin-B on TNF-α production in equine whole blood stimulated with three different bacterial toxins. Polymyxin-B is used to treat equine systemic inflammation. Bacterial toxins other than lipopolysaccharide (LPS) contribute to systemic inflammation but the effects of polymyxin-B on these are poorly defined. Whole blood aliquots from six healthy horses diluted 1:1 with RPMI were incubated for 21 hr with 1 μg/ml of LPS, lipoteichoic acid (LTA) or peptidoglycan (PGN) in the presence of increasing concentrations of polymyxin-B (10-3000 μg/ml). A murine L929 fibroblast bioassay was used to measure TNF-α activity. Polymyxin-B significantly inhibited the effects of all three bacterial toxins. ...
Stallion Sperm Cryopreservation Using Various Permeating Agents: Interplay Between Concentration and Cooling Rate. In this study, modeling and experimental approaches were used to investigate the interplay between cooling rate and protectant concentration for cryopreservation of stallion sperm. Glycerol (GLY), ethylene glycol (EG), dimethylformamide (DMF), propylene glycol (PG), and dimethyl sulfoxide (DMSO) were tested as cryoprotective agents (CPAs), using concentrations up to 1500 mM and cooling rates ranging from 5°C to 55°C min. Modeling of the extent of sperm dehydration during freezing was done using previously determined values of the sperm membrane permeability to water to predict optimal cool...
Stallion sperm selection prior to freezing using a modified colloid swim-up procedure without centrifugation. The aims of this study were to: 1) develop a new method for stallion sperm selection using a modified swim-up procedure through a colloid and 2) evaluate its impact in good quality ejaculates from bad freezers in comparison to methods involving centrifugation such as single layer centrifugation and sperm washing. Ejaculates were processed before freezing using three different procedures: sperm washing (SW), colloid single layer centrifugation (SLC) and a modified colloid swim-up (SU). After semen processing, sperm recovery rates were measured and sperm were frozen. Post-thaw sperm motility (as...
Relationship Between β-cell Response and Insulin Sensitivity in Horses based on the Oral Sugar Test and the Euglycemic Hyperinsulinemic Clamp. A hyperbolic relationship between β-cell response and insulin sensitivity (IS) has been described in several species including rodents, dogs, and humans. This relationship has not been elucidated in the horse. Objective: To determine whether the hyperbolic relationship between β-cell response and IS exists in horses by using indices of β-cell response from the oral sugar test (OST) and IS measurements from the euglycemic hyperinsulinemic clamp (EHC). A second aim was to compare how well IS estimates from the OST and EHC correlate. Methods: Forty-nine horses with different degrees of insulin...
Characterization of Circulating Low-Density Neutrophils Intrinsic Properties in Healthy and Asthmatic Horses. Low-density neutrophils (LDNs) are a subset of neutrophils first described in the bloodstream upon pathological conditions, and recently, in the blood of healthy humans. LDNs may have an enhanced pro-inflammatory (low-density granulocytes, LDGs) or an immunosuppressive (Granulocytic myeloid-derived suppressor cells, G-MDSCs) profile. Whether these characteristics are specific to LDNs or related to disease states is unknown. Thus, we sought to investigate the properties of LDNs in both health and disease states, and to compare them to those of autologous normal-density neutrophils (NDNs). We st...
Equine skeletal muscle adaptations to exercise and training: evidence of differential regulation of autophagosomal and mitochondrial components. A single bout of exercise induces changes in gene expression in skeletal muscle. Regular exercise results in an adaptive response involving changes in muscle architecture and biochemistry, and is an effective way to manage and prevent common human diseases such as obesity, cardiovascular disorders and type II diabetes. However, the biomolecular mechanisms underlying such responses still need to be fully elucidated. Here we performed a transcriptome-wide analysis of skeletal muscle tissue in a large cohort of untrained Thoroughbred horses (n = 51) before and after a bout of high-intensity exe...
Triglyceride concentrations in neonatal foals: Serial measurement and effects of age and illness. Few studies have evaluated the effects of age and illness on serum triglyceride concentrations in neonatal foals. The objectives of this study were to evaluate triglyceride concentrations in neonatal foals and their dams through serial measurement immediately postpartum and at 1-2 days and 10-12 days of age, as well as to measure them in sick foals. Serially measured serum triglycerides in seven healthy foals varied with age. Median (range) triglyceride concentrations were 28mg/dL (12-50mg/dL), 89mg/dL (51-264mg/dL), and 60mg/dL (28-135mg/dL) immediately postpartum, at 1-2 days of age, and 10-...
From Peptide Masses to Pregnancy Maintenance: A Comprehensive Proteomic Analysis of The Early Equine Embryo Secretome, Blastocoel Fluid, and Capsule. Early pregnancy in the mare is a poorly understood, high risk period during which the embryo communicates its presence to the maternal endometrium. Remarkably, the maternal recognition of pregnancy signal is unknown in the horse. This study aimed to profile the proteins secreted by equine blastocysts into their immediate environment, along with proteins contained in the blastocoel and within the acellular embryo capsule. Embryos were recovered on day 8 after ovulation and cultured for 48 hours. Secretomes of day 9 and day 10 embryos were analyzed by LC-MS/MS and supported by analysis of blast...
Right ventricular function during pharmacological and exercise stress testing in horses. The disproportionate rise of pulmonary artery pressure compared to systemic blood pressure during exercise can lead to detrimental right ventricular remodelling in endurance athletes. Horses may act as an extreme model of these athletic cardiovascular adaptations, as they show a three fold increase in pulmonary pressures during exercise. Right ventricular function was examined in ten healthy horses using post-exercise and pharmacological stress echocardiography in a randomised cross-over design. Exercise testing was performed on a treadmill while pharmacological testing was performed using an ...
Age associated changes in peripheral airway smooth muscle mass of healthy horses. Peripheral airway smooth muscle (ASM) mass is increased in severe equine asthma, but no information is available on age related changes in ASM. In this study, peripheral ASM dimensions were determined in healthy horses of different ages. The thickness of the peripheral ASM layer was constant in horses of different ages, but ASM occupied a greater proportion of the inner wall area in young horses compared to older horses. This finding suggests that equine airways experience a decrease in the relative abundance of ASM with age.
Hyaluronan supplementation as a mechanical regulator of cartilage tissue development under joint-kinematic-mimicking loading. Articular cartilage plays an essential role in joint lubrication and impact absorption. Through this, the mechanical signals are coupled to the tissue's physiological response. Healthy synovial fluid has been shown to reduce and homogenize the shear stress acting on the cartilage surfaces due to its unique shear-thinning viscosity. As cartilage tissues are sensitive to mechanical changes in articulation, it was hypothesized that replacing the traditional culture medium with a healthy non-Newtonian lubricant could enhance tissue development in a cartilage engineering model, where joint-kinemati...
Spectroscopic Study of the Interaction between Horse Heart Myoglobin and Zirconium(IV)-Substituted Polyoxometalates as Artificial Proteases. A recent study [Angew. Chem. Int. Ed. 2015, 54, 7391-7394] has shown that horse heart myoglobin (HHM) is selectively hydrolyzed by a range of zirconium(IV)-substituted polyoxometalates (POMs) under mild conditions. In this study, the molecular interactions between the Zr-POM catalysts and HHM are investigated by using a range of complementary techniques, including circular dichroism (CD), UV/Vis spectroscopy, tryptophan fluorescence spectroscopy, and H and P NMR spectroscopy. A tryptophan fluorescence quenching study reveals that, among all examined Zr-POMs, the most reactive POM, 2:2 Zr -...
Spatially offset Raman spectroscopy for photon migration studies in bones with different mineralization levels. The ability of Spatially Offset Raman Spectroscopy (SORS) to obtain chemically specific information from below the sample surface makes it a promising technique for non-invasive in vivo diagnosis of bone conditions by sampling bone through the skin. The depth below a surface interrogated by SORS depends on the system's optical properties and is difficult to estimate for complex bone material. This paper uses 830 nm laser excitation to investigate the influence of bone mineralization on photon migration properties in deer antler cortex, equine metacarpal cortex and whale tympanic bulla. Thin sl...
Correlation of dickkopf-1 concentrations in plasma and synovial fluid to the severity of radiographic signs of equine osteoarthritis. The purpose of this study was to determine whether there was a correlation between circulating and intra-synovial Dkk-1 and radiographic signs of equine osteoarthritis. Methods: Circulating and intra-synovial Dkk-1 levels were measured in clinical cases using a commercially available human Dkk-1 ELISA. Radiographs were performed of the joints from which fluid was collected and these were assessed and scored by a boarded radiologist for joint narrowing, subchondral bone sclerosis, subchondral bone lysis, and periarticular modelling. Comparisons were made between radiographic scores and the conc...
Influence of the Respiratory Cycle on Caudal Vena Cava Diameter Measured by Sonography in Healthy Foals: A Pilot Study. Intravascular volume assessment in foals is challenging. In humans, intravascular volume status is estimated by the caudal vena cava (CVC) collapsibility index (CVC-CI) defined as (CVC diameter at maximum expiration [CVC ] - CVC diameter at minimal inspiration [CVC ])/CVC × 100%. Objective: To determine whether the CVC could be sonographically measured in healthy foals, determine differences in CVC and CVC , and calculate inter- and intrarater variability between 2 examiners. We hypothesized that the CVC could be measured sonographically at the subxiphoid view and that there would be a differ...
The consistency and influence of environmental and animal factors on exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 in horses. This study was performed to determine the consistency of exhaled breath condensate (EBC) hydrogen peroxide (HO), pH and leukotriene B (LTB) measurements in asymptomatic horses and to define the influence of environmental and animal factors on these variables. Intra- and inter-day consistency for both HO and pH measurements were adequate, with intraclass correlation coefficients ≥0.8, whereas the consistency for LTB was poor. HO was influenced by ambient temperature (T), humidity, time of day and collection location (all P<0.01), while pH was influenced by respiratory rate during EBC colle...
Corrigendum to “Macroautophagy and Selective Mitophagy Ameliorate Chondrogenic Differentiation Potential in Adipose Stem Cells of Equine Metabolic Syndrome: New Findings in the Field of Progenitor Cells Differentiation”. [This corrects the article DOI: 10.1155/2016/3718468.].
The relationship between the welfare quality and stress index in working and breeding horses. The aim of this observational study was to investigate if a relationship exists between the calculated overall individual welfare score (as an indicator of the welfare quality) and the neutrophil:lymphocyte (N:L) ratio (as a stress indicator) in working (draught) and reproduction horses (breeding stallions and broodmares), in two different seasons. The welfare of the horses was assessed by a protocol which included health and behavioural parameters. An individual welfare score was computed, the total and differential WBC count was established and the N:L ratio was calculated for each of the 14...
Effect of exogenous progesterone administration on luteal sensitivity to PGF during the early development of the corpus luteum in mares and cows. The objective of this study was to determine the effect of exogenous progesterone administration at ovulation and during the early development of the CL, on its future sensitivity to a single administration of PGF2a in mares and cows. Horse Retrospective reproductive data from an equine clinic in the UK during three breeding seasons were used. Mares were divided into: control group, cycles with single ovulations; double ovulation group cycles with asynchronous double ovulations; and PRID group: cycles with single ovulations and treatment with intravaginal progesterone device (CIDR) immediately...
The Effects of Weaning Methods on Gut Microbiota Composition and Horse Physiology. Weaning has been described as one of the most stressful events in the life of horses. Given the importance of the interaction between the gut-brain axis and gut microbiota under stress, we evaluated (i) the effect of two different weaning methods on the composition of gut microbiota across time and (ii) how the shifts of gut microbiota composition after weaning affect the host. A total of 34 foals were randomly subjected to a progressive (P) or an abrupt (A) weaning method. In the P method, mares were separated from foals at progressively increasing intervals every day, starting from five min ...
Effect of kisspeptin-10, LH and hCG on serum testosterone concentrations in stallions, donkeys and mules. This study was conducted to determine the response of serum testosterone (T) in male equines (stallions, donkeys and mules) after administering intravenous doses of kisspeptin-10 (KP-10), human chorionic gonadotropin (hCG) and luteinizing hormone (LH) and saline as a control. The animals were divided into four groups of three each: Group I, 3 ml of 0.95% saline; Group II, 50 μg KP-10; Group III, 2500 IU hCG and group IV, 400 μg LH. The administration of KP-10 and hCG to stallions resulted in a significant increase in serum T concentration at 240 min; whereas it was significantly higher a...
