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.
Rigoglio NN, Smith OE, Matias GSS, Miglino MA, Smith LC.Because of the growing importance of horses in leisure and several sports, somatic cell nuclear transfer (SCNT) is being used more frequently for cloning animals for performance and reproductive purposes. However, because of the need to perforate the zona pellucida during microsurgical reconstruction of the oocyte, it is possible that SCNT-derived embryos undergo premature hatching, resulting in embryo bisection and twinning. Therefore, because equine twin pregnancies often lead to abnormal embryo development and pregnancy failure, we performed a detailed comparative assessment of equine twin ...
Cunningham FM, Andrews M, Landoni MF, Lees P.Calcium ionophore A23187 induced time and concentration dependent production of immunoreactive leukotriene (LT) B4 by equine heparinized whole blood in vitro. Time dependent production of immunoreactive LTB4 by equine neutrophils and immunoreactive LTC4 by equine eosinophils in vitro was also demonstrated. The 5-lipoxygenase activating protein (FLAP) inhibitors, BAY X 1005 and BAY Y 1015, produced concentration dependent inhibition of ionophore-induced LTB4 synthesis by equine whole blood (mean +/- SEM IC50s n = 5; 6.14 +/- 0.28 microM vs. 12.30 +/- 0.75 microM for BAY Y 1015 and BAY X 1005, r...
Braun J, Muto Y, Sato K, Schallenberger E.Semen from three stallions was collected weekly for six months (December through May) to determine semen parameters and hormones (testosterone and estradiol-17 beta) in seminal plasma. Once a month three ejaculates were collected at intervals of one hour and examined accordingly. Testosterone and estradiol-17 beta were also determined in peripheral blood plasma (V. jugularis) collected twice a week. Semen parameters (volume, gel-free volume and sperm concentration) were clearly influenced by season. The testosterone concentration in peripheral blood plasma was lowest during December whereas in...
Morlock M, Nassutt R, Bonin V.INTRODUCTION:: Cohesive bandages are applied to the legs of racehorses and horses with limb injuries for protection (prevention of abrasion) and support (reduction of movement at the fetlock joint). The support capacity of all commercially available bandages has been questioned. Consequently, the protection aspect of bandaging and the negative side effects, which can be caused by bandaging (eg pressure induced ischemia with subsequent necrosis), were emphasized. High pressures underneath bandages were shown to cause reduced blood flow. Pressures underneath certain types of bandages were shown ...
Kearns CF, Lenhart JA, McKeever KH.Erythropoietin (EPO) is the primary hormone of erythropoiesis. Administration of recombinant human erythropoietin (rhuEPO) to improve racing performance in the horse represents a new form of blood doping, which has been associated with increased mortality. While immunoassay kits have become plentiful, very few commercial hormone assays are made specifically for equine research. There is a strong degree of sequence homology reported for EPO among species, which has allowed antibodies designed for human EPO research to be used to determine EPO concentration in other species. The objective of the...
Reitnour CM, Salsbury RL.Protein digestion, nitrogen retention, plasma protein, plasma urea, and plasma-free amino acids were determined for ponies fed 3 different protein supplements. Substitution of casein, corn gluten meal, or corn gluten meal plus lysine for a portion of the cornstarch in a low-protein basal ration increased apparent digestion of protein. Substitution with either casein or corn gluten meal plus lysine produced a significant increase (P less than 0.05) in nitrogen retention, whereas the corn gluten meal substitution did not. Nitrogen retention, expressed as percentage of nitrogen absorbed, was incr...
Söylemez Z, Ozer I.The inhibition of horse plasma cholinesterase by propranolol showed characteristics which depended upon the identity of the substrate used. With butyrylthiocholine as substrate, the inhibition showed a first-order dependence on inhibitor concentration, and was characterized by a Ki of 8 microM (pH 7.4, 20 degrees C). With p-nitrophenylbutyrate as substrate, a biphasic v-1 versus [I] relationship was obtained. The biphasic curve could be resolved into two components, with apparent Ki's of 9 microM and 1.3 mM. Use of butyrylthiocholine as alternative substrate resulted in partial inhibition of p...
Hayami A, Darwish WS, Ikenaka Y, Nakayama SM, Ishizuka M.There is little information about drug metabolism and pharmacokinetics in horses. Therefore, it is necessary to characterize the profiles of drug metabolites for the safe use of drugs. In this study, we focused on cytochrome P450 enzymes (CYPs), which represent an important enzyme group to determine pharmacological effects of drugs. We chose diazepam as the drug of choice for this study. The aim of this study was to elucidate the metabolic pathway of diazepam in horses in comparison with rats, and to clarify CYP subfamilies responsible for diazepam metabolism in horses. Our results showed tema...
Tsolov V, Tsolov A, Tsankov R.A comparative analysis is made of the correlation between the life of erythrocytes in various species of animals and some parameters of the gallbladder and its secretion. Due attention is paid to the presence of the bladder, its size, and the concentration and intensity of secretion as well as to the effect of the various bile components on the surface tension of water, the water solution of salts, and the erythrocyte membrane. It is believed that both the composition of bile and the structure of erythrocyte membrane are homeostatically determined. It has been found that the mechanism of aging...
Kingston JK, McCutcheon LJ, Geor RJ.To quantify total fluid loss in sweat of Thoroughbreds during >3 hours of low-intensity exercise in controlled conditions and to calculate and compare estimated ion losses in sweat, according to 3 methods. Methods: 6 exercise-trained Thoroughbreds. Methods: Fluid and ion losses in sweat were measured in 6 horses exercising at 40% of the speed that elicited maximum oxygen consumption for 45 km. Horses were given a 15-minute rest period at the end of three 15-km exercise phases. Horses completed 2 exercise trials. Ion losses in sweat were calculated, using measurements of local sweating rate and...
Selwet M.The research concerned the determination of the frequency of occurrence of selected virulence genes (cadF, flaA, iam) and genes responsible for the formation of the CDT cytotoxin (cdtA, cdtB, cdtC) in Campylobacter spp. The research object consisted of 100 faecal samples collected from stallions showing no symptoms of campylobacteriosis. The presence of bacteria of the genus Campylobacter spp. Was found in 25 individuals (25%). The molecular biology techniques used in the research allowed us to distinguish the following species from the positive samples: C. jejuni (68%); C. coli (28%) and C. l...
Böing L, Heun F, Gasse H.The extremely complex surface architecture of the equine brain does not allow a uniform transfer of anatomical data from other mammalian species, e.g., dog or cat. Rather, a special approach is required to elucidate the equine-specific patterns of cerebral vascular ramifications. Therefore, a novel cartographic system was applied. Prior attention was paid to the A. cerebri media (MCA) and to the A. corporis callosi (CA), as they spread over the widest part of the neopallium's Facies convexa (i.e. the lateral and dorsal surface), thus being of particular interest in terms of surgical treatment ...
Ferrante PL, Freeman DE, Ramberg CF, Kronfeld DS.Multicompartmental analysis was applied to study the kinetics of D-xylose distribution after IV administration to healthy mares deprived of food for 12 and 96 hours. Urinary excretion of D-xylose was measured over a 15-hour period after administration. The plasma D-xylose concentrations in this study were in the range found after oral tolerance testing. The disposition of D-xylose was described by a two-compartment model with linear kinetic characteristics. Total volume of distribution decreased significantly (P < 0.025) from 0.270 L/kg of body weight after the 12-hour period of food depriv...
Ludewig T.The purpose of the study was to give a histological picture of the different skin regions of the mammary gland in mares. Special emphasis on the dark coating in the sulcus intermammarius was given. As a result, the dark pigmented udder skin can be subdivided into the skin of the Corpus mammae, the sulcus intermammarius and the teat skin. In the sulcus intermammarius the whole epidermis was considerably thicker than usual, especially the stratum corneum (up to 70 layers of cornified layers) and the stratum spinosum. In general, the squamous keratinocytes were unusually large. The histological p...
Duckworth DH, Madison JB, Calderwood-Mays M, Souba WW.Glutamine has been shown to be an important metabolic substrate of enterocytes in many animals, including cats, dogs, hamsters, human beings, monkeys, rabbits, rats, and sheep. To determine whether glutamine is important in the metabolism of cells of the equine gastrointestinal tract, we examined transintestinal differences in glutamine concentrations in the arterial and venous circulation, and measured activity of the major glutamine catabolizing enzyme, glutaminase. Arteriovenous differences provide an index of the amount of a given substrate removed by the tissue across which the measuremen...
Ake AS, Ayo JO.This study aimed to evaluate the effects of packing (load carrying) on the diurnal rhythms of respiratory and heart rates in donkeys during the hot-dry season. Twenty 2- to 3-years-old donkeys weighing 93 ± 2.7 kg were divided into two groups to serve as subjects: Group 1 was subjected to packing + trekking, while group 2 was subjected to trekking only. All donkeys trekked 20 km on each experimental day. The procedure was repeated three times at one-day intervals. Thermal environmental parameters were recorded. Respiratory rate (RR) and heart rate (HR) were measured before and immediately (15...
Martínez-Boví R, Cuervo-Arango J.The objectives were to determine: (i) whether intrafollicular administration of PGE2 and PGF2α to mares would hasten follicle collapse and (ii) the differences in reproductive hormone characteristics in mares with spontaneous and prostaglandin-induced follicle collapses. Six mares were followed for two oestrous cycles each: when the mares reached a follicle diameter of 30-35 mm and showed mild-to-moderate endometrial oedema, mares were administered a single 0.5 ml dose containing 500 μg PGE2 and 125 μg PGF2α (treatment cycle) or a placebo (0.5 ml of water for injection; control cycle) into...
Arns MJ, Webb GW, Kreider JL, Potter GD, Evans JW.Bovine serum albumin (BSA) diluents containing lactose, raffinose or sucrose were not different (P greater than 0.05) in their ability to maintain stallion sperm viability, as determined by percentage motile spermatozoa (PMS) and their rate of forward movement (RFM), when stored at 37 or 5 degrees C for 24 h. These diluents did promote a higher (P greater than 0.05) PMS and RFM, when compared with BSA diluents containing arabinose or galactose. The BSA-arabinose and BSA-galactose diluents did not differ (P less than 0.05) in their ability to support sperm viability and were detrimental to sper...
Wehrenberg WB, Fowler S, Kurhajec J, Hutz RJ.Forty-four female ranch mink, maintained out-of-doors under standard conditions, were exposed to natural photoperiod supplemented with a period of artificial light from approximately 2300 hr to 0300 hr from early January to mid February. Breeding was initiated on March 1. After repeated attempts to breed the animals, it was determined that the likelihood of their breeding was very low, presumably due to the artificial and asynchronous long-day photoperiod. In an attempt to induce breeding, the mink were randomly assigned to one of four treatment groups: saline, 25 International Units (IU) PMSG...
Miller PA, Lawrence LM.Six mature Quarter Horse mares were used in a crossover design to assess the effect of dietary protein level on metabolic response to exercise. After a 2-wk adaptation period to either a 12.9% (control) or an 18.5% CP (high-protein) diet, each mare performed a standard exercise test. The test consisted of a 15-min exercise period at 4.5 m/sec on a 9% grade motorized treadmill. Exercise resulted in an increase in heart rate (P less than .001), but there was no difference (P less than .05) between dietary treatments. In the jugular vein, lactate increased (P less than .01) from 6.3 to 52.0 mg/10...
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 ...
Brumbaugh GW, Davis LE, Thurmon JC, Savage DC.Opsonized Rhodococcus equi activated the respiratory burst of resident alveolar macrophages (AM) from adult horses in a logarithmic-linear, mass-related manner. The effect of R equi was not significantly different from that of equal masses of opsonized zymosan A. Therefore, R equi does not appear to attenuate the respiratory burst of equine AM. The stimulatory effect of R equi was not reflected by increased production of superoxide anion (O2-), but increased activity of the hexose monophosphate shunt was observed. These results suggest a similarity between the respiratory burst of AM from hors...
Sticht H, Willbold D, Rösch P.Two molecular dynamics (MD) simulations were performed in order to increase the understanding of the dependence of protein conformation on solvent environment. The protein used for these simulations is the transcriptional activator of the equine infectious anemia virus (EIAV-Tat). The structure of this protein has been determined by nuclear magnetic resonance (NMR) in aqueous solution (Willbold et al., Science 264, 1584 (1994)) and in 40% (v/v) trifluoroethanol (TFE) (Sticht et al., Eur. J. Biochem., submitted) showing considerable differences in the stability of the secondary structure elemen...
Han Y, Tang C, Liao Q, Li Z, Deng L.Serum and plasma are commonly used in clinical practice considering the widely accepted fact that the "normal" protein expression pattern of a healthy animal changes under disease conditions. We herein used a label-free mass spectrometry-based quantitative proteomics approach to characterize the serum proteome of donkeys. A total of 277 unique proteins were identified from 2,388 unique peptides. Gene ontology analyses showed that the most frequent processes were related to metabolic activities and biological regulation, response to stimulus, and immune system processes. The main annotated area...
Bardell DA, Archer DC, Milner PI.Colic remains a life-threatening condition in the horse. Ischaemia and reperfusion following correction of small intestinal strangulation may produce oxidative stress. The ability to withstand oxidative stress depends on antioxidant levels and may be linked to horse survival. Objective: To measure peripheral antioxidant levels in horses undergoing exploratory laparotomy with small intestinal strangulation. Methods: Case-control study. Methods: Blood and plasma were collected from horses undergoing exploratory laparotomy for small intestinal strangulation and stored at -80°C. Controls involved...
Lowry TF, Forster HV, Forster MA, Murphy CL, Brice AG, Pan LG.The objective of the present study was to determine the effect of elevated inspired CO2 on respiratory dead space (VD) of 12 normal, 8 carotid body-denervated (CBD), 7 hilar nerve-denervated (HND), and 6 CBD+HND ponies. The Fowler technique was used to determine VD on a breath-by-breath basis while the ponies breathed room air and inspired CO2 at 3 and 6%. During room air breathing, tidal volume (VT) and VD were greater in HND ponies than in normal and CBD ponies (P less than 0.05), and VT was less and VD/VT was greater after CBD than before CBD. For all groups. VD, VT, and breathing frequency...
Lees MJ, Fretz PB, Bowen CV, Leach DH.Equine limb wounds often heal slowly by epithelialization, and large scars are a frequent end result. In some ways, they resemble the wound associated with human tibial injuries. The literature indicates that previous investigators have failed to transfer free skin flaps successfully in the horse. In this paper, we review our experimental work with the deep circumflex iliac flap in the horse. Dissections of 20 cadavers confirmed the anatomical consistency of the flap. Four flaps survived well when elevated as island flaps, but five orthotopic and nine heterotopic free flap transfers all failed...
Tinel JB, Veras MM, Waked D, Alonso MA, Fernandes CB.Mules are derived from crossing horse mares with a donkey, in which the interest is due to gentleness and ability to work and equestrian sports. As the placenta is responsible for fetal development and maturation, knowing its typical microstructure allows us to understand how fetomaternal interactions occur in this interspecific pregnancy. Thus, the study performed a comparative stereological evaluation of volumetric composition and fetomaternal contact surface in the uterine body (UB), gravid uterine horn (GUH), and nongravid uterine horn (NGUH) of Mangalarga Paulista mare's term allantochori...
Viu J, Armengou L, Ríos J, Muñoz A, Jose-Cunilleras E.To determine the strong ion difference (SIDa ) and total nonvolatile weak buffers (ATOT ) in healthy foals during the first year of life and to compare reference biochemistry laboratory with analyzers available during emergency hours. Methods: Prospective study performed over 2 years. Methods: University teaching hospital. Methods: Two hundred thirty-six healthy foals distributed in 6 groups: A (21 days-2 months), B (2-3 months), C (3-6 months), D (6-9 months), E (9-12 months), and 33 neonatal foals (< 21 days old). Methods: Blood samples were obtained to determine L-lactate, sodium, potass...
Rainger JE, Wardius S, Medina-Torres CE, Dempsey SM, Perkins N, van Eps AW.Regional hypothermia has shown promise as analgesic in horses when used to manage painful conditions of the distal limb such as laminitis. In this prospective study, the analgesic effects of regional hypothermia were assessed using mechanical nociceptive thresholds during distal limb cooling. The study population consisted of eight healthy adult Standardbred horses, selected from a teaching herd. A distal forelimb of each horse was cooled using water immersion at the following sequential target water temperatures: 34 °C, 20 °C, 10 °C, 5 °C, 1 °C, 5 °C, 10 °C, 20 °C. Limb surface temper...
