Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
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.
Topographic distribution of pulmonary ventilation and perfusion in the horse. The regional distribution of ventilation to perfusion ratios (VA/Q) in the lungs of 8 healthy standing Thoroughbred geldings (4.4 +/- 1.5 years, 465.7 +/- 46.6 kg) was studied, using steady-state inhalation and IV infusion of the radioactive gas krypton-81m. The VA/Q was uniformly distributed within a vertical lung strip centered over the 9th rib on the right side. Ventilation per unit of alveolar volume (V/VA) assessed from the clearance of inhaled radioactive gas in 5 horses increased from 0.49 +/- 0.13 (arbitrary units) in nondependent lung zones to 1.45 +/- 0.16 in dependent lung zones. Se...
Quantitative analysis of long-bone growth in the horse. Long-bone growth at the distal ends of the radial bones, the distal ends of the 3rd metacarpal bones, the distal ends of the 3rd metatarsal bones, and the proximal ends of the proximal phalangeal bones (of thoracic and pelvic limbs) was quantitatively analyzed in 9 Thoroughbred-Quarter Horse foals from birth to 2 years of age. Metal growth markers were surgically implanted in the bones of the animals at 2 to 4 days of age. Radiographs of the bones were made on the day of surgical manipulation, the next day, and then once a week for 8 months, and once a month thereafter for an additional 18 mon...
Lymphocyte alloantigens of the horse. II. Antibodies to ELA antigens produced during equine pregnancy. Evidence is presented for a reproducible maternal immune response to histocompatibility antigens during equine pregnancy. Mares were stimulated as a result of pregnancy to produce cytotoxic antibodies to paternal lymphocyte alloantigens. The majority of these antibodies were directed against antigens of the equine lymphocyte antigen (ELA) system, which is the major histocompatibility complex (MHC) of the horse. In 16 experimental pregnancies produced using 12 mares and 4 stallions which had been typed for ELA antigens, there was correlation between ELA incompatibility between sire and dam and ...
Studies related to the metabolism of anabolic steroids in the horse: the phase I and phase II biotransformation of 19-nortestosterone in the equine castrate. The metabolism of 19-nor[4-14C]testosterone has been studied in the equine castrate. Following XAD-2 extraction of aliquots of the 0-24 h urine samples, the glucuronic acid and sulphate conjugates were separated by Sephadex LH-20 column chromatography. After hydrolysis of the conjugates, the neutral phase I metabolites of 19-nortestosterone were extracted, purified and identified by g.l.c.-mass spectrometry. In phase I metabolism stereospecificity was observed in the reduction of the A-ring with the formation of the 5 alpha, 3 beta-isomers of estranediol. Epimerization at C-17 and hydroxylatio...
Nonrandom ventricular rhythm in horses with atrial fibrillation and its significance for patients. RR interval sequences during spontaneous atrial fibrillation in eight horses were analyzed as in previous studies in patients and dogs using histograms and serial auto-correlograms. In patients and dogs with spontaneous atrial fibrillation, ventricular rhythms were always random. In the horses, the histograms were skewed with median RR intervals of approximately 1,000 ms. A striking finding in these animals was the presence of long RR intervals up to 5,000 ms in duration. The shortest RR intervals lasted 400 to 600 ms. In contrast to findings in dogs and patients, the serial autocorrelograms s...
The distribution and origin of a novel brain peptide, neuropeptide Y, in the spinal cord of several mammals. The distribution of neuropeptide Y [NPY]-immunoreactive material was examined in the spinal cord and dorsal root ganglia of rat, guinea-pig, cat, marmoset, and horse. Considerable concentrations of NPY and similar distribution patterns of immunoreactive nerve fibres were found in the spinal cord of all species investigated. The dorsal root ganglia of the cat and the horse contained numerous immunoreactive nerve fibres, but in these species, as in the other three studied [rat, guinea-pig, marmoset], no positively stained cell bodies were found. Neuropeptide Y-immunoreactive nerves were observed...
Ascorbate reduction of horse heart cytochrome c. A zero-energy reduction reaction. The ascorbate reduction of horse heart ferricytochrome c in 0.05 M phosphate + 0.25 M sodium sulfate, at pH 7.3, as a function of temperature, 12-36 degrees C, and at alkaline pH 8.4 using stopped flow technique has been examined. The data have been analyzed in terms of a two-step mechanism, binding followed by reduction (Myer, Y.P., Thallam, K.K., and Pande, A. (1980) J. Biol. Chem. 255, 9666-9673). At neutral pH and up to about 26 degrees C, the first order reduction constant is independent of temperature, i.e. with zero or near-zero activation energy. At higher temperatures, it becomes temp...
Studies on equine prematurity 4: Effect of salt and water loss on the renin-angiotensin-aldosterone system in the newborn foal. Plasma renin substrate concentration was measured in 18, four-day-old pony foals after the administration of the natriuretic agent frusemide. Thirteen foals had been delivered spontaneously; labour had been induced in the remaining five mares. Plasma aldosterone concentration was measured in 12 of the spontaneously delivered foals. Renin substrate concentration had risen sharply within 15 mins (P less than 0.005) and peaked at 1 h. The response was consistently greater in the induced foals. Serum sodium concentration fell rapidly in the induced foals (P less than 0.002 by 60 mins) but was bett...
Some aspects of equine placental exchange and foetal physiology. THERE is no shortage of anatomical information on the equine foetus and its placenta, from the early work of Ruini in the 16th century to the recent studies of Steven and colleagues (Steven 1982); by contrast, knowledge of the physiology of the foal in utero is sparse. In other domestic animals there have been considerable ads ances in foetal and neonatal physiology and endocrinology in recent years due mainly to the develop-ment of the chronically catheterised foetal preparation in which sequential observations can he made in the conscious animal (Silver 1981). Some information about the deve...
Respiratory studies in foals from birth to seven days old. Respiratory measurements and blood-gas and acid-base values are reported in nine term induced foals. Measurements were performed at 2, 15, 30 and 60 mins, 4, 12, 24 and 48 h, and four and seven days after birth. Minute respiratory volume was significantly lower at birth than values from 12 h old. Tidal volume peaked at 60 mins old, while respiration rate decreased significantly at 15 mins after birth. Oxygen consumption was high at birth and decreased to its lowest values at 24 and 48 h. The respiratory exchange ratio and ventilatory equivalent showed few significant changes to seven days, as ...
Developments in management of the newborn foal in respiratory distress 2: Treatment. New developments in therapy for foals in respiratory distress are discussed. Therapy is based on preservation of the foal's life by maintenance of a patent airway, resuscitation with fluids and warmth, provision of humidified oxygen to raise the fractional concentration of inspired oxygen sufficient to avoid hypoxia and provision of ventilatory support when hypercapnia becomes critical. Ventilatory support described includes assisted and controlled ventilation, positive end expiratory pressure, continuous positive airway pressure and intermittent mandatory ventilation. The aims of these techni...
Drug disposition in the neonatal animal, with particular reference to the foal. Differences between neonatal and adult animals in their response to drugs can usually be attributed to altered disposition (ie, distribution, metabolism and excretion) processes during the neonatal period. These alterations affect the plasma concentrations as well as the concentrations of drug attained at the receptor site. Some characteristics of the neonatal period include greater absorption from the gastrointestinal tract, lower extent of plasma protein binding, increased apparent volume of distribution of drugs that distribute in extracellular fluid or total body water, increased permeabil...
Concentrations of 15-keto-13, 14-dihydro-prostaglandin F2 alpha in the mare during spontaneous and oxytocin induced foaling. Changes in plasma 15-keto-13, 14-dihydro-prostaglandin F2 alpha were monitored at frequent intervals before, during and after spontaneous deliveries (three mares) and foalings induced by oxytocin (eight mares). No evidence of increased concentrations of the prostaglandin metabolite was observed in the final 10 days of gestation. In spontaneously delivering mares, there was a marked increase from 3 ng/ml at -125 mins to 18 ng/ml at -65 mins to the highest observed value of 182 ng/ml at 20 mins pre-partum. Following delivery, concentrations declined rapidly to around 0.2 ng/ml. Further release o...
Concentration increase of unbound testosterone in plasma of the mare throughout pregnancy. Blood testosterone levels were measured by RIA and gas chromatography-mass spectrometry in the pregnant mare. They were found to increase from the very beginning of pregnancy, reaching peak values 10 times higher than the basal values at the seventh month and then to return to basal values by the week after parturition. Testosterone binding by plasma proteins was investigated in nonpregnant and pregnant mares throughout gestation. Equilibrium dialysis and gel equilibration methods did not reveal any blood specific testosterone-binding activity at any gestational stage. Hence, blood testosteron...
Echocardiography in foals from birth to three months old. Simultaneous echocardiograms, phonocardiograms and electrocardiograms were performed on 16 foals at the following times after birth: 15 mins, 60 mins, 2, 4, 12, 24, 48 h, four, seven, 14 days and four, eight and 12 weeks. Positive correlations were found between both age and body weight and the following measurements: left ventricular end-diastolic dimension, right ventricular end-diastolic dimension, left atrial dimension and aortic root dimension, posterior left ventricular wall thickness and interventricular septal thickness. Heart rate was negatively correlated with left ventricular electr...
Blood pressure, electrocardiogram and echocardiogram measurements in the growing pony foal. Twelve newborn pony foals underwent cardiovascular examinations (auscultation, arterial blood pressure measurements, electrocardiograms and M-mode echocardiograms) on their first day of life and then on Days 7, 14, 21, 30, 60 and 90. An age dependent, statistically significant, rapid increase of the arterial blood pressure in the first month was documented together with a slower decrease of the resting heart rate after two and three months of life. Innocent soft systolic murmurs were audible over the left heart base in a large number of the foals. The electrocardiograms showed age dependent in...
Pharmacokinetics of 4-aminopyridine in horses. The pharmacokinetics of 4-aminopyridine (4-AP), a drug capable of antagonizing nondepolarizing neuromuscular blocking drugs, as well as several classes of injectable sedative and anesthetic agents, were studied in 6 intact, awake horses. Plasma samples were assayed for 4-AP over a frequent sampling schedule for 8 hours after IV administration. The plasma 4-AP vs time data best fit a 2-compartment pharmacokinetic model. Distribution half-life was 7.4 minutes, elimination half-life was 259 minutes, volume of the central compartment was 0.89 L/kg, volume of distribution (area) was 1.98 L/kg, volu...
Haematology of foals up to one year old. Packed cell volume, haemoglobin concentration, erythrocyte counts, erythrocyte indices, serum iron, iron binding capacities, total and differential leucocyte counts, platelet counts, total plasma protein, fibrinogen, haptoglobin and icterus index values were determined at 14 different ages in eight Thoroughbred and 14 Quarterhorse foals during the first year of life. Absolute neutrophil numbers in blood decreased and lymphocyte numbers increased during the first months. Absolute eosinophil numbers tended to increase until three months old. Haemoglobin concentration and packed cell volume decre...
Studies on equine prematurity 1: Methodology. This paper describes the general management of mares and foals during the perinatal period and the methodology used in a collaborative research project on equine prematurity. Sixteen mares with dated pregnancies delivered 45 foals over three breeding seasons (1981 to 1983). In the majority, parturition was induced with oxytocin and/or fluprostenol; the remainder were allowed to foal spontaneously. Pre-colostral milk analysis provided a means of assessing the pre-foaling status of the mare. All were observed and monitored before, during and after parturition and the sampling protocol for both m...
