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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.
Evaluation of the role of superoxide anions in endotoxin-induced impairment of beta-adrenoceptor-mediated vasodilation in equine digital veins. To investigate the role of superoxide anions in the lipopolysaccharide (LPS)-induced impairment of beta-adrenoceptor-mediated equine digital vein (EDV) vasodilation. Methods: EDVs isolated from forelimbs of 24 healthy adult horses. Methods: Endothelium-intact or endothelium-denuded EDV rings were incubated with or without LPS (10 microg/mL) of Escherichia coli (O55:B5) for 4 hours. Cumulative concentration-relaxation curves resulting from administration of isoprenaline, a nonselective beta-adrenoceptor agonist, or from administration of SR 58611A, a selective beta(3)-adrenoceptor agonist, were...
Associations of horse age, joint type, and osteochondral injury with serum and synovial fluid concentrations of type II collagen biomarkers in Thoroughbreds. To determine the effects of horse age, osteochondral injury, and joint type on a synthesis biomarker and 3 degradative biomarkers of type II collagen in Thoroughbreds. Methods: Healthy rested adult (3- to 12-year-old) Thoroughbreds (n = 19), yearling (1- to 2-year-old) Thoroughbreds (40), and Thoroughbred racehorses (2 to 7 years old) undergoing arthroscopic surgery for removal of osteochondral fragments that resulted from training or racing (41). Methods: Samples of blood and metacarpophalangeal, metatarsophalangeal, or carpal joint synovial fluid (SF) were collected from all horses. Commerci...
Comparison of macrostructural and microstructural bone features in Thoroughbred racehorses with and without midbody fracture of the proximal sesamoid bone. To compare macrostructural and microstructural features of proximal sesamoid bones (PSBs) from horses with and without PSB midbody fracture to gain insight into the pathogenesis of PSB fracture. Methods: PSBs from 16 Thoroughbred racehorses (8 with and 8 without a PSB midbody fracture). Methods: Parasagittal sections of fractured and contralateral intact PSBs from horses with a PSB fracture and an intact PSB from age- and sex-matched control horses without a PSB fracture were evaluated for visual, radiographic, microradiographic, histologic, and his-tomorphometric differences in bone porosity,...
Serum thyroid hormone, insulin, glucose, triglycerides and protein concentrations in normal horses: association with topical dexamethasone usage. The aim of this study was to determine if topical application of dexamethasone affected the serum concentrations of thyroid hormones (triiodothyronine T(3) and thyroxine T(4)), glucose, triglycerides, total protein and insulin in normal horses. Ten horses were treated twice daily for 10 days with 50 g dexamethasone using an ointment formulation. Thyroid hormones and insulin were assayed using standard radioimmunoassay methods, while glucose, triglycerides and total protein were determined using a standard enzymatic method and the Biuret reaction, respectively. An increase in serum glucose and ...
Electrophoretically mediated microanalysis for the evaluation of interspecies variation in cholinesterase metabolism. This study describes an electrophoretically mediated microanalysis method, suitable for the preclinical evaluation of the hydrolysis of ester drugs by the serum of different animals and for further characterization of human-animal correlation. Dog, cat, cow, horse, sheep, rat and human serum were diluted (25%) in the appropriate buffer and replaced the enzyme solution usually used in electrophoretically mediated microanalysis methods for the study of enzyme kinetics. They were then compared in terms of the ability to hydrolyze acetylthiocholine and butyrylthiocholine (0.25 mM) by in-capillary ...
Comparative studies on bull and stallion seminal DNase activity and interaction with semen extender and spermatozoa. We performed a series of comparative studies of bull and stallion seminal plasma (SP) and its role on sperm-neutrophil binding as well as the interaction between semen extender and seminal DNase. Because of contrasting roles of SP on sperm-neutrophil binding between horses and cattle, it was suspected there were some species-specific differences on sperm interaction with SP proteins due to the variations in the natural location of semen deposition (uterus compared to vagina). Bull frozen-thawed sperm removed from egg yolk extender showed similar results to fresh sperm, but this also caused ext...
Biomarkers of in vivo fertility in sperm and seminal plasma of fertile stallions. The global proteome of sperm and seminal plasma of fertile stallions was investigated to determine whether associations with relative in vivo fertility exist. Seven stallions at stud in a commercial breeding station were collected throughout the breeding season and bred to a total of 164 mares to determine conception rates. On three occasions during the breeding season, raw semen was obtained from a regular collection for proteomic analysis using two-dimensional electrophoresis and also assessed for routine semen quality end points. First cycle conception rate was negatively related to ejacula...
Delta opioid receptor on equine sperm cells: subcellular localization and involvement in sperm motility analyzed by computer assisted sperm analyzer (CASA). Opioid receptors and endogenous opioid peptides act not only in the control of nociceptive pathways, indeed several reports demonstrate the effects of opiates on sperm cell motility and morphology suggesting the importance of these receptors in the modulation of reproduction in mammals. In this study we investigated the expression of delta opioid receptors on equine spermatozoa by western blot/indirect immunofluorescence and its relationship with sperm cell physiology. Methods: We analyzed viability, motility, capacitation, acrosome reaction and mitochondrial activity in the presence of naltri...
Identification and characterization of β-adrenergic receptors in isolated primary equine tracheal epithelial cells. Responses and functions of airway epithelial cells are stimulated by β₂-agonists via the β₂-adrenergic receptors (β₂-ARs)-G(s)-protein-cAMP-system, thus, affecting airway inflammation such as in asthma and equine recurrent airway obstruction (RAO). Though horses can be used as large animal model for human asthma, evaluation of the expression and functions of the β-AR system in primary equine airway epithelial cells has not been yet carried out. Thus, for the first time, we determined the β-AR density and subtype distribution by [¹²⁵I]-iodocyanopindolol (ICYP) binding, examined ...
Changes in cortisol release and heart rate and heart rate variability during the initial training of 3-year-old sport horses. Based on cortisol release, a variety of situations to which domestic horses are exposed have been classified as stressors but studies on the stress during equestrian training are limited. In the present study, Warmblood stallions (n=9) and mares (n=7) were followed through a 9 respective 12-week initial training program in order to determine potentially stressful training steps. Salivary cortisol concentrations, beat-to-beat (RR) interval and heart rate variability (HRV) were determined. The HRV variables standard deviation of the RR interval (SDRR), RMSSD (root mean square of successive RR di...
Characterization of the equine skeletal muscle transcriptome identifies novel functional responses to exercise training. Digital gene expression profiling was used to characterize the assembly of genes expressed in equine skeletal muscle and to identify the subset of genes that were differentially expressed following a ten-month period of exercise training. The study cohort comprised seven Thoroughbred racehorses from a single training yard. Skeletal muscle biopsies were collected at rest from the gluteus medius at two time points: T(1) - untrained, (9 +/- 0.5 months old) and T(2) - trained (20 +/- 0.7 months old). Results: The most abundant mRNA transcripts in the muscle transcriptome were those involved in mus...
Plasma leptin level in hyperlipidemic mares and their newborn foals. The aim of this study was to evaluate the relationship between plasma leptin and lipid levels in breeding mares and their newborn foals. The study was conducted on 17 Polish cold-blood mares and their newborn foals. The mares were divided into two groups, according to the course of delivery. These groups were seven mares which had a normal delivery and 10 mares which had required veterinary intervention during their delivery. Blood samples were taken from the jugular vein of both the mares and their foals. The blood samples were taken within 30 min after delivery, as well as on four successive...
Differences in seasonal changes of fecal androgen levels between stabled and free-ranging Polish Konik stallions. Blood and feces samples were collected from Polish Konik stallions kept under conventional stable conditions and in the forest reserve during a 1-year study period. Levels of testosterone (T) and androstenedione (A(4)) were measured using radioimmunoassay. Positive correlation between fecal and plasma concentrations of androgens was observed. Fecal T concentrations increased in April and May reaching peak value mid-April in the stallions from the reserve group and 2 weeks later in the stallions from the stable group. Comparatively, concentrations of T were higher in the stable group. Levels of...
Patient variation in veterinary medicine: part I. Influence of altered physiological states. In veterinary medicine, the characterization of a drug's pharmacokinetic (PK) properties is generally based upon data that are derived from studies that employ small groups of young healthy animals, often of a single breed. These are also the data from which population predictions are often generated to forecast drug exposure characteristics in the target population under clinical conditions of use. In veterinary medicine, it is rare to find information on the covariates that can influence drug exposure characteristics. Therefore, it is important to recognize some of the factors that can alter...
Age-related differences in prostaglandin E2 synthesis by equine cartilage explants and synoviocytes. Time- and concentration-related actions of lipopolysaccharide (LPS) on the synthesis of prostaglandin E(2) (PGE(2)) were investigated in cartilage explants and synoviocytes harvested from 3 age groups of horses, all with clinically normal joint function: group A 20 years. Cartilage explants from group A horses were least and those from group C were most sensitive to LPS. Significant increases in PGE(2) concentration (P <or= 0.01) were obtained in group C horses in response to LPS concentrations of 1.0 microg/mL (and higher) after exposure for 24, 36 and 48 h, whereas explants from group A h...
Gender differences in exercise–induced intravascular haemolysis during race training in thoroughbred horses. Exercise-induced intravascular haemolysis and "sport anemia" are widely reported in human sports medicine. It has been recognized also in horses, however, the clinical importance and the onset of this condition seem different than in human. In this study we investigated the episodes of intravascular haemolysis, indicated by the increase in plasma haemoglobin and the decrease in serum haptoglobin levels, after routine training sessions in race horses. Heart rate and changes in haematological parameters confirmed, that the exertion was relatively high. Intravascular haemolysis did not appear in ...
Quantitative analysis of stress echocardiograms in healthy horses with 2-dimensional (2D) echocardiography, anatomical M-mode, tissue Doppler imaging, and 2D speckle tracking. Stress echocardiography is used to diagnose myocardial dysfunction in horses, but current methods are not well standardized. The influence of heart rate (HR) on measurements is largely unknown. Objective: To investigate the use of 2-dimensional echocardiography (2DE), anatomical M-mode (AMM), tissue Doppler imaging (TDI), and 2D speckle tracking (2DST) at rest and after exercise for quantification of regional and global left-ventricular (LV) function. Methods: Five athletic Warmblood horses; 11.6+/-3.6 years; 529+/-48 kg. Methods: Prospective study. Three separate echocardiographic examination...
Localization of insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) in equine testes. The insulin-like growth factor-I (IGF-I) is a key regulator of reproductive functions. IGF-I actions are primarily mediated by IGF-IR. The main objective of this research was to evaluate the presence of IGF-I and IGF-I Receptor (IGF-IR) in stallion testicular tissue. The hypotheses of this study were (i) IGF-I and IGF-IR are present in stallion testicular cells including Leydig, Sertoli, and developing germ cells, and (ii) the immunolabelling of IGF-I and IGF-IR varies with age. Testicular tissues from groups of 4 stallions in different developmental ages were used. Rabbit anti-human polyclona...
Single layer centrifugation of stallion spermatozoa through Androcoll™-E does not adversely affect their capacitation-like status, as measured by CTC staining. This study was designed to evaluate the effect of single layer centrifugation (SLC) and subsequent cold storage on stallion sperm capacitation-like status and acrosome reaction. Three stallions were included in the study, with three ejaculates per stallion. The samples were examined 4, 24 and 72 h after collection, extension and SLC, with storage at 6°C. Sperm capacitation-like status was investigated using the fluorescent dye chlortetracycline (CTC). There was no difference in capacitation-like status between colloid-selected and non-selected spermatozoa. Sperm motility decreased significant...
Protein composition of seminal plasma in fractionated stallion ejaculates. Seminal plasma (SP) contains several types of compounds derived from the epididymides and accessory glands. The aim of this study was to examine the protein composition of different ejaculate fractions. Trial I: fractionated ejaculates were collected from two normal and two subfertile stallions. Samples containing pre-sperm fluid and the first sperm-rich jets (HIGH-1), the main sperm-rich portion (HIGH-2), the jets with low sperm concentrations (LOW), and a combined whole-ejaculate (WE) sample was centrifuged, and the SP was filtered and frozen. A part of each SP sample was stored (5°C, 24 h)...
The use of adrenocorticotrophic hormone as a potential biomarker of pituitary pars intermedia dysfunction in horses. Elevated concentrations of plasma adrenocorticotrophic hormone (ACTH) in horses with pituitary disturbances are often associated with dysfunction of the pituitary's pars intermedia. The majority of such animals exhibit an increased susceptibility to laminitis, particularly during the autumn. The 24h plasma ACTH profiles of horses with pituitary pars intermedia dysfunction (PPID), and those of matched controls, were determined in March, June, September and December. Differences in ACTH concentrations between the groups were significant (P<0.0001), regardless of photoperiod, and persisted thr...
Endocrinopathic laminitis. In laminitis occurring in the field, as opposed to laminitis occurring during hospitalization or severe illness, endocrinopathic laminitis is the predominant form of laminitis. Prevalent causes of endocrinopathic laminitis are ECS and EMS. Exclusion of inflammatory or weight bearing causes of laminitis and focussing on the identification and treatment of underlying endocrine conditions will improve laminitis management strategies.
A study of the correlation between objective and subjective indices of recovery quality after inhalation anaesthesia in equids. To examine the association between objective and subjective descriptors used for assessing recovery quality in horses after anaesthesia. Methods: Prospective clinical study. Methods: Two hundred and seventy-six equids (110 mares, 85 entire males and 81 geldings), ASA 1-5, weighing 50-850 kg and aged 1 month - 25 years. Methods: Recoveries after general anaesthesia were assisted with head and tail ropes by two anaesthetists. One scored dichotomous objective descriptors (DOD) of recovery. Two dichotomous objective scales (DOS) were then generated from those descriptors. The same individual also ...
Endocrinopathic laminitis: reducing the risk through diet and exercise. Certain individual animals appear predisposed to recurrent pasture-associated laminitis, but the exact mechanisms underlying their predisposition remain a fundamental question in laminitis research. The risk of endocrinopathic laminitis can be reduced if steps are taken to improve insulin sensitivity and reduce inflammation using strategies based on exercise and diet. Exercise has been shown to reduce insulin resistance and suppress inflammation, and dietary manipulation can significantly affect insulin sensitivity.
Toxic effects induced by mycotoxin fumonisin B1 on equine spermatozoa: assessment of viability, sperm chromatin structure stability, ROS production and motility. Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium species that exerts its toxic effect through interference with the sphingolipid pathway by inhibiting ceramide synthase. A FB1-dependent sperm toxicity was reported in boars. No information on FB1-related reproductive toxicity in stallions, the most sensitive animal species, has been reported. The aim of the present study was to assess the in vitro toxicity of FB1 on fresh and frozen-thawed equine spermatozoa by analyzing sperm viability, chromatin stability (SCSA) and reactive oxygen species (ROS) production by flow cytometry and sperm mo...
A morphological and quantitative immunohistochemical study of the interstitial cells of Cajal in the normal equine intestinal tracts. The interstitial cells of Cajal (ICC) play a key role in the control of intestinal motility and have been implicated in several human gastrointestinal dysmotility syndromes, in equine grass sickness and in other intestinal disorders where a significant reduction in ICC density was observed. Objective: To investigate the density of ICC in clinically normal horses, ICC c-Kit expression was evaluated by image analysis in order to obtain numerical data. Methods: Intestinal samples from the jejunum to small colon from 5 clinically normal horses were studied. Immunohistochemical labelling of ICC was...
An investigation of the relationship between race performance and superficial digital flexor tendonitis in the Thoroughbred racehorse. There is limited information regarding the number of races and the period for evaluation of outcome which is critical for assessment of SDF tendonitis treatments. Objective: To evaluate the re-injury rate and racing performance of Thoroughbred racehorses that sustain SDF tendonitis in relation to matched controls in terms of number of races post treatment and maximum racing performance ratings before and after injury. Methods: Clinical records and racing histories of 401 racehorses with a first occurrence of SDF tendonitis diagnosed by ultrasonography. Controls were of the same age, sex and we...
Effects of semen storage and separation techniques on sperm DNA fragmentation. To determine the effect of semen storage and separation techniques on sperm DNA fragmentation. Methods: Controlled clinical study. Methods: An assisted reproductive technology laboratory. Methods: Thirty normoozospermic semen samples obtained from patients undergoing infertility evaluation. Methods: One aliquot from each sample was immediately prepared (control) for the sperm chromatin dispersion assay (SCD). Aliquots used to assess storage techniques were treated in the following ways: snap frozen by liquid nitrogen immersion, slow frozen with Tris-yolk buffer and glycerol, kept on ice for 24...
