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.
Simić V, Ilić A.The caecum in man as a part of the large colon (intestinum crassum) differs morphologically and topographically from the caecum of domestic mammals. The caecum in domestic mammals differs not only from the human caecum but also comparatively morphologically and topographically among the domestic mammals. The appendix vermiformis does not exist in domestic mammals, which represents the main difference between the human caecum and that of domestic mammals. There are certainly some differences in the physiological function of the caecum in man and the caecum in domestic mammals, which are carnivo...
Pavelka M, Ronge HR, Stockinger G.Tracheal epithelia of ten different mammals were investigated with the light and the electron microscope. Characteristic differences were found concerning the thickness of the epithelia, the length of the cilia, the density of the cells in the epithelia, the numerical distribution of the different cells and their ultrastructure. Special attention was paid to the morphology of the kinetosomes. Brush cells and chromaffin cells, which are sparsely distributed in the different tracheal epithelia, were discussed.
Rejnö S.Synovial fluid samples from 51 light horses were examined with respect to their rhéologie properties. The analyses were made with a Rotovisco RV3 rotational viscosimeter. Samples from carpal, stifle and hock joints and from healthy joints, joints with synovitis and joints with infectious arthritis were studied. The analyses showed that synovial fluids from both healthy and diseased joints have complex rhéologie properties. In most samples the viscosity varied with the shear rates, the main exceptions being synovial fluids from joints with infectious arthritis. Flow curves (flow behaviour), r...
Stewart M.The structure of vertebrate skeletal muscle is reviewed. The mechanism of muscular contraction and its control is then discussed from the point of view of molecular structure. Contraction takes place by a sliding filament mechanism produced by cross-bridges which form between thick and thin filaments. Control is exercised by tropomyosin and troponin. When the calcium concentration is low, these proteins interfere with the formation of cross-bridges and prevent contraction, but when the calcium concentration is increased, they no longer interfere and contraction proceeds.
Holmes JR.The paper describes the spatial vector changes during ventricular depolarisation in 190 horses using a semi-orthogonal ECG lead system. The replacement of planar vector loops by a plot of 3 parameters to depict the changing spatial vector, with a time base on the X axis, is described and illustrated. Some horses with diastolic murmurs and some with a history of respiratory problems formed 2 distinct groups. As a result of these findings a possible relationship between the vector changes and the anatomical siting of the ventricles is suggested and discussed. Attention is drawn to certain measur...
Velle W.This presentation is limited to the three groups of steroid sex hormones which alone or in combination have been shown to be anabolic when used in farm animals. It seems essential for realistic evaluation of public health aspects of use of these hormones that the discussions include naturally occurring levels of the hormones. The following topics will be dealt with for each group of hormones: 1. Types and sources; 2. Production rates; 3. Plasma levels; 4. Tissue concentrations; 5. Metabolism and excretion. Gestagens. Progesterone and 20-dihydroprogesterones are mainly produced in ovaries and p...
Kooistra LH, Ginther OJ.At day 24 of gestation, pregnant mares were allotted to 1 of 5 treatment groups (3 to 5 mares/group): group A--nontreated controls; group B--intraembryonic injection of 4 mg of colchicine on day 24; group C--removal of embryo on day 24; group D--subcutaneous injection of 1.25 mg of prostaglandin F2alpha (PGF2alpha) on day 32; and group E--removal of embryo on day 24 and subcutaneous injection of PGF2alpha on day 32. In all mares treated with colchicine (group B), the fetal bulge was absent within 2 days. The interval from injection of colchicine to onset of estrus was very short (mean, 4 days)...
Anwer MS, Chapman TE, Gronwall R.Variables of glucose metabolism determined by the use of [U-14C]glucose were compared in fed and fasted ponies. Relative recycling of glucose carbon with respect to tritium in fed animals was negligible for 6-T and 3-T and 16% for 2-T studies; in fasted animals relative recycling was 12 and 14% for 6-T and 3-T studies, respectively. Minimal mass of total-body glucose decreased significantly in the fasted ponies. Based on relative recycling of carbon to tritium, a negligible fraction of plasma glucose was produced via the Cori cycle or from glycerol in fed ponies; recycled tricarbon units contr...
Zobel G, Kolb FE.Acid phosphatase of erythrocytes of several species was investigated, with three isozymes having been recorded from swine (three types), three (two types) from horse, four (one type) from dog, two (two types) from cat, two (three types) from duck, and two (one type) from fowl. The Michaelis constant of the enzyme varied between 3.5 and 5 X 10(-4) M for the species involved. The species, however, differed slightly for the optimum pH of the enzyme. The average enzymatic activities were (5.68 +/- 0.42 for dog, 4.46 +/- 1.0 for horse, 3.8 +/- 0.24 for swine, 3.72 for cat, 2.5 +/- 0.62 for duck, an...
Bodurov N, Filipov Zh.Comparative clinical and experimental investigations were carried out on 18 clinically normal horses. It was found that the single transfusion of in vitro UV-treated autogenous blood, following a previously described method, was tolerated well by horses and did not lead to any deviations from the normal indices. Under the effect of the treated blood there was an increase in the hemoglobin content, rise in the erythrocyte and leukocyte count with slightly expressed hyperleukocytosis and weak neutrophilia (simple regeneration of the blood). The sedimentation of erythrocytes also showed higher ra...
Francfort P, Schatzmann HJ.It is shown that the concentration of ouabain necessary for 50 per cent inhibition of the Na+K activated membrane ATPase of red cells is similar in man and horse. This is taken to indicate that the two species have similar sensitivity towards cardiac glycosides in general. In five adult healthy horses plasma digoxin concentration was measured with a radioimmunoassay technique after a single intravenous injection of 1 mg/100 kg body weight digoxin. The half time of elimination was 23 h and the apparent volume of distribution 7.3 litres/kg. An approximate estimate of plasma protein binding of di...
Targowski SP.All chronically diarrheal horses given (orally) 2 series of treatments with normal horse serum recovered in 2 to 4 weeks. However, mild diarrhea sometimes persisted several months in the group of horses with severe diarrhea. Weight gains were approximately 35% in horses with severe diarrhea and approximately 10% in horses with mild diarrhea. Serum specimens from 12 diarrheal and 20 normal horses were examined for immunoglobulins by single radial immunodiffusion technique. Concentration of immunoglobulin A in serum of diarrheal horses was approximately 50% lower than that in serum of normal hor...
O'Neill HJ, Gershbein LL.The lipids of human and equine smegma pools were saponified and the total fatty acids submitted to temperature programmed gas chromatography (GC) analysis. In contrast to the human products, the horse smegma fatty acids contained very low odd saturated as well as olefinic branched chain acid contents. The cyclopropane fatty acid, 9,10-methyleneoctadecanoic acid, occurred in smegma sampled from men over 35 years of age but could not be detected in the pool from persons of 17-20 years of age nor in any of the equine mixtures. The alcoholic fraction from horse smegma contained about 85% sterol, t...
Cappugi G, Chellini PC, Nassi P, Ramponi G.A ninhydrin-negative peptide fraction obtained from tryptic digest of carboxymethyl acylphosphatase was isolated by chromatography on a column of PA 28 Beckman resin and analysed for the amino acid composition. Degradation with carboxypeptidase B and A indicated that the sequence of this peptide was: X-Thr-Ala-Arg. The amino-terminal residue was identified as N-acetylserine by high voltage electrophoresis. It is therefore suggested that the sequence of the NH2-terminal portion of CM-acylphosphatase is N-acetyl-Ser-Thr-Ala-Arg. Digestion with carboxypeptidase A and B indicated also that the COO...
Heinze W, Ptak W.The metacrylate and latex corrosion techniques were used to establish that the vascular system of testes is based on one coherent principle in common domestic mammals. The cone-shaped Plexus pampiniformis consists of numerous venous rami, between 0.25 mm and 1.0 mm in thickness and forming a dense vascular network, which practically encase the spiral-shaped A. spermatica interna (cooling coil principle). The testicular veins and arteries in the Tunica albuginea constitute a somewhat voluminous layer of vessels for dissipation of heat, with rami branching off radially into the testicular parenc...
Robie SM, Janson CH, Smith SC, O'Connor JT.Concentrations of serum phospholipids, triglycerides, total cholesterol, nonesterified fatty acids, and glucose were determined for 9 months (September, 1972, to May, 1973) in 19 fasting horses and ponies (8 Morgan horses, 7 Thoroughbred horses, and 4 Shetland Ponies). Morgan horses had higher concentrations of total lipid than did Thoroughbreds, although the relative proportions of each type of lipid were similar in the 2 breeds. Shetland Ponies had higher nonesterified fatty acid and lower glucose concentrations than did either breed of horse. In both breeds of horses, concentrations of seru...
Hall MC, Fenelon AR, McDonald RD, Steel JD.Different techniques for monitoring cardiac responses to exercise in the horse have been described and evaluated. For experimental work of this type in a normal training and racing environment, the electrode system described when used with a portable magnetic tape recording system provided the best means of obtaining useful and reproducible data.
Robie SM, Smith SC, O'Connor JT.The serum of lipoproteins of 10 Morgan and 8 Thoroughbred horses were examined by 2 methods of polyacrylamide gel electrophoresis. A significant breed difference in the beta-lipoprotein to alpha-lipoprotein ratio was seen in gradient slab electrophoresis. A breed difference in the number of peaks, but no difference in beta-lipoprotein to alpha-lipoprotein ratio, was found in disc gel electrophoresis. These results have been correlated to indicate differences in charge of alpha-lipoprotein components and in size of beta-lipoprotein components between these 2 breeds of horses.
Robie SM, Janson CH, Smith SC, O'Connor JT.The serum lipoprotein fractions from 5 Morgan and 5 Thoroughbred horses were isolated by preparative ultracentrifugation, chemically analyzed for lipid composition, and studied by 2 methods of polyacrylamide gel electrophoresis to determine electrophoretic mobility. Breed differences were not seen in the relative percentages of the lipid classes found in the various fractions. Normally, horses, like most animals, carry the majority of their lipid in high-density lipoproteins. Electrophoretically, the only difference seen between breeds occurred on disc electrophoresis where the extra band, whi...
van der Mey GJ, Bos H.The study of the literature on a preliminary performance test for saddle horses (stallions) is concerned with European countries. Interest is found to be increasing in the various countries. Performance of the test in the Netherlands (since 1966) is described and the various criteria of evaluation are discussed in detail. The intensity of selection based on this test is referred to. In 1974, it was 78 per cent in the Netherlands. Part of studies on the relationship between some results of testing are reviewed. The traction test shows a very low coefficient of correlation with the other parts o...
Sharma OP.The concentrations of PGF-2alpha in the peripheral blood of five foaling mares were measured by radioimmunoassay. Low levels of PGF-2alpha were detected as early as 1 week before foaling in two of the mares. These levels increased steadily, reaching a peak (1-74 +/- 0-44 ng/ml) during fetal expulsion. A relatively high PGF-2alpha level was found in samples collected 60 min after foaling.
Douglas RH, Garcia MC, Ginther OJ.Luteolysis, determined by corpus luteum weight and progesterone concentration in jugular blood, occurred in uterine-intact and in hysterectomized mares after injection of prostaglandin F2alpha or of an antiserum against an equine pituitary fraction. Results indicated that luteolytic effects of exogenous prostaglandin F2alpha and inhibition of the endogenous luteotrophic activity of the hypophysis (pituitary gland) by antiserum did not involve the uterus.
Grosskopf JF, Smuts EG.Blood was collected from 28 zebra mare (Equus burchellia antiquorum) immediately after being shot in the Kruger National Park. The serum was separated within two hours after collection and then stored at -15 degrees C for later assay. Of these, thirteen selected samples were tested for gonadotrophic activity. The stage of pregnancy was determined from a foetal growth curve. Blood samples from pregnant horse mares were collected by venipuncture. Nine mares were sampled. Seven blood samples at different stages of pregnancy were collected from one mare, four from another and only one sample each ...
Shinjyo S, Abe H, Masuda M.The carbohydrate composition of horse spleen ferritin was studied. 1 mol of the apoferritin, the protein moiety of ferritin, contains 25 mol of hexose, 3 mol of hexosamine and 10 mol of fucose. Same carbohydrate composition was detected in the apoferritin from iron rich ferritins. These results indicate that horse spleen ferritin is composed of non-identical subunits as regards its carbohydrate composition.
Berger J, Valdez S, Puschner B, Leutenegger CM, Gardner IA, Madigan JE.Highly reactive horses may pose risks to humans involved in equestrian activities. Among the factors that may affect horses' reactivity to external stimuli are pesticides used for fly control in equine facilities. The organophosphorus (OP) insecticide tetrachlorvinphos (TCVP) is used as a feed-through larvicide to prevent completion of the fly larval life cycle in horse manure. TCVP exerts its effect by inhibiting the enzyme cholinesterase (ChE) leading to the accumulation of the neurotransmitter acetylcholine (AChE) in synapses of the central and peripheral nervous systems. The aim of the pre...
Gentry PA, Feldman BF, O'Neill SL.The purpose of this study was to evaluate the effect of modifying commercial reagents for the laboratory evaluation of several haemostatic parameters in normal, non-pregnant mares. The routine coagulation screening assays, namely, the activated partial thromboplastin time (APTT) and the one-stage prothrombin time (PT), and the specific coagulation assays for the determination of the biological activity of Factors VII, VIII:C and IX, are discussed.
Montavon S.The aim of this review is to give the practitioner the ability to be familiar with the echographic exam of ovarian abnormalities. He should be able to recognize different stages of the development of these important structures and to estimate the effect that they can have on the normal cycle of the mare. Various specific criteria and details regarding the equine echography of ovarian abnormalities are reported and illustrated, using the last scientific data published on that particular topic.
MacDonald MH.Examination of the equine head should be a routine part of any complete physical examination. It can be performed rapidly and efficiently while providing important information about the health and function of several major body systems.
Doreau M, Martin-Rosset W, Barlet JP.In an experiment comparing pregnant then lactating mares with dry non-pregnant mares, the changes in plasma components were studied as indicators of the metabolic utilization of energy (glucose, non-esterified fatty acids, beta-hydroxybutyrate), nitrogen (urea, proteins) or minerals (calcium, phosphorus, magnesium). The mares were fed daily 2 kg concentrate and hay ad libitum. Beta-hydroxybutyrate, magnesium and to a lesser extent glucose were the only constituents whose levels were affected within the period starting one month before and ending one month after foaling. The increase in food in...
Seither RL, Brown OR, Babu BV.Rat, cow and foal lung extracts contained an inhibitor for the liver NAD biosynthetic-pathway enzyme, nicotinatemononucleotide pyrophosphorylase (carboxylating) [EC 2.4.2.19]. The inhibitor was not dialyzable, was labile at 100 degrees C, was retained by a 30,000 dalton pore size Amicon membrane and, when partially purified by precipitation at 40-100% ammonium sulfate, inhibited the enzyme stoichiometrically. Lung reportedly does not contain nicotinate-mononucleotide pyrophosphorylase or make NAD de novo. However, the inhibitor would mask detection of the enzyme in lung extracts. We detected a...
Fries RC, Clark-Price SC, Kadotani S, Stack JP, Schaeffer DJ, Lascola KM.To compare measurements of left ventricular volume and function derived from 2-D transthoracic echocardiography (2DE), transesophageal echocardiography (TEE), and the ultrasound velocity dilution cardiac output method (UDCO) with those derived from cardiac MRI (cMRI) in healthy neonatal foals. Methods: 6 healthy 1-week-old Standardbred foals. Methods: Foals were anesthetized and underwent 2DE, TEE, and cMRI; UDCO was performed simultaneously with 2DE. Images acquired by 2DE included the right parasternal 4-chamber (R4CH), left apical 4- and 2-chamber (biplane), and right parasternal short-axis...
van den Berg IS.An apparatus for collection of free-flow urine from female horses is described. This apparatus is a modification of a similar device described previously. It allows the collection of voided urine from adult female horses without confining them to metabolic stables or resorting to invasive procedures like bladder catheterisation. It is relatively easy to use after a short adaptation period.
Samuel CA, Allen WR, Steven DH.The various cell types in the adult anterior pituitary may be distinguished at the ultrastructural level of the sizes of the secretory granules within the cytoplasm. In the fetal adenohypophysis, with the exception of prolactin-producing cells, all types may be identified after Day 100 of gestation. Morphological evidence suggests that they are producing and secreting trophic hormones. The three constituent layers of the adrenal cortex are also discernible by Day 100 of pregnancy. The cells of the zona glomerulosa have large numbers of darkly stained inclusions within the cytoplasm. The zona f...
Engelking LR, Paradis MR.This article addresses clinical problems that present in equine liver disease. It also discusses the variety of laboratory tests available to the clinician that can differentiate the type and degree of liver dysfunction. This is followed by a more specific discussion regarding unique features of equine bilirubin and bile acid metabolism.
Dik KJ.The radiological interpretation of periosteal new bone formation in the horse induced by trauma is described and illustrated by some casereports. The better the margins of the new bone can be defined the lesser the activity. The greater the density of the new bone, the longer the duration of time since injury.