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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.
Tissue-cage model for the collection of inflammatory exudate in ponies. In a series of experiments to examine equine inflammatory exudates for the presence of metabolites of arachidonic acid, including prostaglandin E2 (PGE2), a model for the induction and collection of exudates in ponies has been developed. Multiperforated polypropylene practice golf balls implanted subcutaneously in the mid-neck region were well tolerated and proved to be the most successful model. One such cage was implanted in the neck of each of seven ponies. Inflammatory exudates were induced by injecting 3.0 or 0.5 ml carrageenin into the cages and aspirates collected between three and 48 h...
Inbreeding and reproductive performance in standardbred horses. The relationship between inbreeding and both conception and foaling rates in Standardbred horses (trotters and pacers) was examined for 1194 breeding years. There was a statistically significant (P less than 0.05) trend for conception and foaling rates to decrease with increased inbreeding; however, this relationship accounted for less than 2 percent of the variation. Additionally, the relationship between reproductive performance and inbreeding was not consistent between trotters and pacers. For trotters (F = 0.103) there was a trend for an increase in conception and foaling rates with increa...
Functional and ultrastructural evaluation of neutrophils from foals and lactating and nonlactating mares. Neutrophils from 4 pony foals, 3 lactating pony mares, and 3 nonlactating mares were evaluated ultrastructurally and by in vitro function tests. Neutrophils from foals had significantly (P = 0.05) less random migration than neutrophils from mares; values in tests for iodination and Staphylococcus aureus ingestion were also lower with foal neutrophils. Neutrophils from lactating mares had lower responses to iodination, antibody-dependent cell-mediated cytotoxicity, and random migration tests than did neutrophils from nonlactating mares. Ultrastructurally, granule concentration did not differ si...
Studies on the pathogenesis of equine tendonitis following collagenase injury. The histological and morphological characteristics of the scar tissue formed during healing after traumatic equine tendon injury have been compared with those of scar tissue produced in response to an enzyme-induced pony tendon injury. Several techniques are currently in use in the treatment of equine tendon sprain and this work formed part of a study of their respective efficacy. It was concluded that the enzyme-induced lesion is resolved by a reparative process very similar in its prognosis and extent to that following a naturally occurring tendon sprain. It may therefore justifiably be used...
Cauda equina neuritis: a chronic idiopathic polyneuritis in two horses. Two cases of cauda equina neuritis are compared and contrasted. Neurological deficits of the tail and perineum were noted and functional deficits were seen in gait, urination, defecation and cranial nerve function. Lesions consisted of nonsuppurative inflammation of the nerve trunks and proliferation of the perineurium of the cauda equina. Cranial nerve involvement in one case supported a diagnosis of polyneuritis equi rather than cauda equina neuritis. The possible etiologies and pathogenesis of this disease are discussed.
Fibre types, enzyme activities and substrate utilisation in skeletal muscles of horses competing in endurance rides. Venous blood samples and middle gluteal muscle biopsies were obtained from 21 horses taking part in 100 km or 50 km endurance rides. Group A consisted of seven horses competing over 100 km (four horses completed the ride). Group B consisted of the six horses that were among the 10 best over 50 km while the other eight horses of Group C completed 50 km at a slower speed. Blood lactate, glycerol and creatine kinase increased in all groups while aspartate aminotransferase levels were higher only in Group A. No changes was found in blood glucose in Groups B and C while horses in Group A had lower ...
Arterial oxygen and carbon dioxide tensions in conscious laterally recumbent ponies. Six adult ponies were trained calmly to assume and maintain left lateral recumbency without the use of sedative or immobilising agents. During a 30 min recumbent period, pHa, arterial oxygen and carbon dioxide tensions (PaO2 and PaCO2) and heart and respiratory rates were monitored at regular intervals to evaluate ventilatory response. Overall, there were no statistically significant differences found between mean control and recumbent or final standing values. When lightweight ponies were compared to heavyweight ponies, only mean PaO2 at 10 mins recumbency was different. This information supp...
Relationship between paired plasma and serum viscosity and plasma proteins in the horse. The relationship between paired plasma and serum viscosity measurements and plasma proteins, including fibrinogen, were compared in 106 horses with both normal and abnormal serum protein levels. There is a highly significant positive correlation between serum viscosity and total serum proteins and total globulin levels. The difference between plasma and serum viscosity correlated well with clottable fibrinogen concentration. Albumin levels showed a negative correlation with plasma and serum viscosity, globulins and fibrinogen. Simultaneous estimation of serum and plasma viscosity improves the ...
Leucocyte counts in the healthy English Thoroughbred in training. Total and differential leucocyte counts have been determined by electronic counting techniques in 474, two-to-four-year-old healthy Thoroughbreds in training. The ranges of values observed (particular those for neutrophils and lymphocytes) were narrower than previously described. Absolute and percentage lymphocyte values were significantly decreased with advancing age causing a relative increase in percentage neutrophils. The fall in absolute lymphocyte numbers was the main cause for a significant decrease in total leucocytes with age. Frequency plots for each variable showed that, with the ex...
Antagonism of xylazine and ketamine anesthesia by 4-aminopyridine and yohimbine in geldings. Thirty-six fasted, mixed horse breed geldings (6 groups of 6 animals each) were anesthetized with xylazine and ketamine, and when maximally sedated, were given 1 of the following antagonists: saline solution, 4-aminopyridine (4-AP), small-dose yohimbine, large-dose yohimbine, 4-AP plus low-dose yohimbine, or 4-AP plus high-dose yohimbine. Measured data included mean standing time (MST), heart rate, respiratory rate, rectal temperature, and mean total recovery time ( MTRT ). Emergence phenomena were also observed and recorded as smooth, fairly smooth, fairly rough, or rough. Groups given 4-AP a...
Clinical biochemical and hematologic values of the American Miniature Horse: reference values. Sixteen clinical biochemical determinations and 13 hematologic measurements were performed on 49 healthy American Miniature Horses of mixed age and both sexes. Serum triiodothyronine and thyroxine values were also determined. Serum biochemical test results from American Miniature Horses compared favorably with values for full-sized horses, whereas differences in hematologic test results were noticed between American Miniature Horses and full-sized horses.
Blood metabolite profiles of broodmares and foals. Serum amino acid profiles and other serum characteristics of broodmares and their foals wee studied. Compared with mares, foals had significantly higher concentrations of serum leucine, threonine, aspartic acid, asparagine, glutamic acid, glutamine, proline and tyrosine, glucose, cholesterol, creatinine and phosphorus. Foals had significantly less serum histidine, glycine, cystine, taurine, protein and urea nitrogen. Lysine and/or methionine supplementation of pregnant and lactating broodmare diets were conducted. Changes in serum amino acid profiles caused by dietary amino acid supplemented w...
Bone strain in the equine tibia: an in vivo strain gauge analysis. Rosette strain gauges were bonded to the cranial, caudal, and medial surfaces of the tibia in the middiaphyseal region of 6 adult ponies. While the ponies were walking, the cranial side was mainly subjected to tension, and the caudal side, to compression. The compression strain on the caudal side was 1.5 times greater than the tension strain on the cranial side. None of these principal strains was aligned along the long axis of the bone; both deviated laterally from the long axis. On the medial surface, the principal strain deviated caudally about 40 degrees from the long axis. From analysis o...
Cellular constituents of clinically normal foal bronchoalveolar lavage fluid during postnatal maturation. Bronchoalveolar lavage was performed 5 times, sequentially, on 3 healthy foals when each was between 2 and 63 days of age. Total and differential counts were performed on recovered cells. The lungs of foals less than 19 days of age contained few alveolar macrophages recoverable by bronchoalveolar lavage. This number increased sharply during the first 2 to 3 weeks of life, but remained relatively constant subsequently. Approximately 86% of the alveolar cells in the lungs of foals up to 3 weeks of age were alveolar macrophages. During the first 2 months of life, this number decreased to approxim...
The acute inflammatory process, arachidonic acid metabolism and the mode of action of anti-inflammatory drugs. Arachidonic acid is a polyunsaturated fatty acid covalently bound in esterified form in the cell membranes of most body cells. Following irritation or injury, arachidonic acid is released and oxygenated by enzyme systems leading to the formation of an important group of inflammatory mediators, the eicosanoids. It is now recognised that eicosanoid release is fundamental to the inflammatory process. For example, the prostaglandins and other prostanoids, products of the cyclooxygenase enzyme pathway, have potent inflammatory properties and prostaglandin E2 is readily detectable in equine acute in...
Seasonal enzyme activity changes in two aminotransferases AspAT and AlAT, acid and alkaline phosphatases and aldolase in the serum of Thoroughbred horses during a racing season. Twenty Thoroughbred 3 year old horses (10 stallions and 10 mares), trained and raced at the Warsaw Race-Course were studied from March through November. Blood was taken approximately every 8 weeks to determine the activities of aspartate and alanine transaminases, acid and alkaline phosphatases and aldolase. It was observed that the activities of aspartate aminotransferase and alkaline phosphatase reached their maxima in July and alanine transaminase in May. The activities of acid phosphatase and aldolase showed their minima in July. Comparing these data with the literature it was noted that t...
Computer processing of transaortic valve blood pressures in the horse using the first derivative of the left ventricular pressure trace. A method is described of processing transaortic valve pressures in the horse using the first derivative of the left ventricular pressure to define the beginning and end of each systolic complex. To determine the beginning of each systole three definitions of left ventricular end diastolic pressure (LVEDP), based on a 100, 150 or 200 mmHg/sec rate of left ventricular diastolic pressure rise, were evaluated. These definitions were also evaluated for their ability to determine isovolumic contraction time (ICT) and pulse interval. The best of these, LVEDP 150, was defined as the last point in dias...
Serum levels of testosterone precursors, testosterone and estradiol in 10 animal species. Blood levels of testosterone precursors, i.e. pregnenolone, progesterone, 17 alpha-hydroxyprogesterone, androstendione, DHEA, and delta 5-androstendiol as well as testosterone and estradiol are measured in 10 animals each of 10 different species. The determination is done by radioimmunoassay with steroidspecific antibodies. Precursors of the delta 5-pathway (DHEA, androstendiol) are low in the red deer, dog, cat, rat and guinea pig. Precursors of the delta 4-pathway (progesterone, 17-hydroxprogesterone, androstendione) are lower in the bull, boar, ram, stallion and rabbit thus indicating a pre...
Natural protease inhibitors: qualitative and quantitative assay by fibrinogen-agarose electrophoresis. An electrophoretic procedure for the qualitative and quantitative assay of protein protease inhibitors is reported. This assay is particularly suited for investigations of crude biological materials when specific antisera are not available. The supporting medium consists of agarose into which denatured fibrinogen is incorporated as the substrate for proteases. The processing then is divided into two steps: (1) electrophoretic resolution of the inhibitor containing material and (2) detection of the inhibitor bands through their protease inhibiting activity. The inhibitor position is thus made v...
Isolation, partial identification and quantitative determination of four guaiphenesin glucuronides in plasma and urine of the horse by high-performance liquid chromatography. The isolation, partial identification and quantitative determination of four guaiphenesin glucuronides in plasma and urine of the horse is described. The identity of the glucuronides was checked by UV and fluorescence spectrophotometry, by NMR spectrometry and by mass spectrometry after permethylation. The applicability of the procedure to pharmacokinetic studies is demonstrated.
Continuous caudal epidural anesthesia in the horse. A technique for continuous caudal epidural anesthesia in the horse was developed in trials involving 8 healthy adult horses. The injection site was the first intercaudal (intercoccygeal) space. A Huber point directional needle (Tuohy or Hustead) with a stylet was preplaced into the epidural space, used as a guide for an epidural catheter, and then removed, leaving the catheter in situ in the epidural space. A 2% solution of lidocaine hydrochloride was used as the anesthetic agent at an initial dose of 8 ml for an adult animal (474 kg to 560 kg). Repeated 4-ml doses were administered immediatel...
Hemodynamics before and after conversion of atrial fibrillation to normal sinus rhythm in horses. Hemodynamic measurements were obtained from 17 horses with atrial fibrillation or flutter. Eight horses had atrial fibrillation of unknown duration. In 7 horses, atrial fibrillation developed during anesthesia. Atrial flutter developed during recovery from anesthesia in 2 horses. Hemodynamic measurements were considered normal in 7 of 8 conscious horses with atrial fibrillation. Cardiac output was decreased and pulmonary arterial blood pressure and right atrial pressure were increased in 1 conscious horse which had signs of congestive heart failure. Arterial blood pressure decreased in 5 of 7 ...
Production of cutaneous analgesia by electroacupuncture in horses: variations dependent on sex of subject and locus of stimulation. Cutaneous pain thresholds to pinprick, pinch, and heat stimuli were quantified during control and electroacupuncture trials in 23 horses. Pain thresholds for 8 areas of the body during control trials (no needles) were statistically compared with pain thresholds measured in the same areas of the same horse when given electroacupuncture treatment. Statistically significant increases of pain threshold were interpreted as induced analgesia and occurred mainly in 5 areas of the trunk, but not in the head or extremities. Analgesic efficacy varied between sexes and among 3 groups of points chosen fro...
