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.
SAXENA BB, McSHAN WH, MEYER RK.Fresh horse-pituitary glands were extracted with 40% ethanol and the gonadotropins were recovered by increasing the alcohol concentration to 85% followed by drying with acetone. This preparation was further extracted with water at pH 5, and the extract was adjusted to pH 7 and lyophilized. The follicle-stimulating hormone in the pH-5-souluble fraction was purified by zone electrophoresis and resolved into six components by starch-gel electrophoresis. One of these components contained follicle-stimulating hormone which was recovered in the elution cell and the contaminating starch was separated...
Science (New York, N.Y.)September 21, 1962
Volume 137, Issue 3534 979-980 doi: 10.1126/science.137.3534.979
STEINBERG S, BOTELHO S.Congenital myotonia, similar to that which has been reported in humans and in goats, is here reported for the first time in another species. Evidence is given to show (i) that the myotonic phenomenon is present despite complete block of neuromuscular transmission; (ii) prior to injection of curare, synchronous activity of muscle fibers may result not only from ephaptic stimulation of neighboring fibers but also from reflex firing; and (iii) water deprivation does not relieve the myotonia.
Specht TE, Miller GJ, Colahan PT.The breaking strength (stress at failure) of equine third metacarpal bones, with and without clustered drill holes, was determined in vitro. Paired ossa metacarpalia II-IV of 39 horses (n = 39) between 2 and 7 years old were tested in palmarodorsal 3-point bending. Four treatments were compared. Clustered 2.7- or 3.5-mm drill holes, in a 4- or 7-hole pattern, were made in the dorsal cortex of the distal diaphysis of the left third metacarpal bone. Undrilled right third metacarpi were used as controls. Bones with clustered drill holes failed by an oblique fracture through 1 or more drill holes,...
Rich T, Henderson LB, Becker DL, Cornell H, Patterson-Kane JC.Superficial digital flexor tendon (SDFT) injuries of horses usually follow cumulative matrix microdamage; it is not known why the reparative abilities of tendon fibroblasts are overwhelmed or subverted. Relevant in vitro studies of this process require fibroblasts not already responding to stresses caused by the cell culture protocols. We investigated indicators of replicative damage in SDFT fibroblast monolayers, effects of this on their reparative ability, and measures that can be taken to reduce it. Results: We found significant evidence of replicative stress, initially observing consistent...
Briant C, Ottogalli M, Guillaume D.With the objective of controlling the day of ovulation, 40 mares were assigned to a control or three treated groups: A3d, A4d, and A5d. The treated groups received antarelix (Teverelix 0.01 mg/kg, i.v., twice a day) for 3, 4, or 5 days from the day the dominant follicle (F1) reached 28 mm (=D0), and one injection of hCG (1600 IU, i.v.) on D1, D2, or D3, respectively. Control mares received one injection of hCG when F1 reached 35 mm. Plasma LH, FSH, progesterone, and total estrogens were assayed. In the A3d, A4d, and A5d groups, 9 (90%), 6 (60%), and 5 (50%) out of 10 mares, respectively, ovula...
Dietz HH.Diagnostic tests in horses showing signs of gastrointestinal diseases are reviewed. The use of rectal exploration is emphasized, and paracentesis as a diagnostic aid is mentioned. Special attention is given to the absorption tests as they are easy to conduct and give a relative measure of the absorptive capability of the intestinal epithelium. Glucose, D(+)-xylose and carbohydrate digestion-absorption tests are compared, and the D(+)-xylose absorption test is preferred because of the univocal curve of absorption (see Figure 1 and 2). The absorption curve in a horse suffering from alimentary ly...
Kurosawa M, Nagata S, Takeda F, Mima K, Hiraga A, Kai M, Taya K.Our aim was to investigate plasma catecholamine responses to so-called 'doping' drugs and exercise in Thoroughbreds. Plasma adrenaline (Ad) and noradrenaline (NA) were determined after the administration of caffeine and promazine hydrochloride (PRZ) using a high performance liquid chromatographic method. Caffeine or PRZ was administered i.m. to Thoroughbreds and its effects on plasma catecholamines at rest and during exercise were compared with the saline control. The treadmill exercise was performed 1 h after administration. A dose of 5.0 mg/kg bwt caffeine was found to significantly increase...
Stewart JH, Rose RJ, Barko AM.The effect of oxygen administration on blood gas values was examined in six newborn foals from birth to seven days old. Three variables were studied: the effect of increasing age on the ability to elevate arterial oxygen tension (Pao2), the effect of duration of oxygen delivery on Pao2 and the effect of method of administration. The results demonstrated a significant effect of age on the ability to increase Pao2 values, with the highest Pao2 values being found at seven days old. The duration of oxygen administration caused little change in Pao2 values; peak values were reached after 2 mins of ...
Magee C, Bruemmer JE, Nett TM, Squires EL, Clay CM.Kisspeptides (KiSS) are a recently discovered family of neuropeptides with a central role in regulating the onset of reproductive function in all animals studied to date. We have established biological and physiological evidence for KiSS signaling in the mare. The objective of the current study was to evaluate the physiological and behavioral responses of mares repeatedly given the equine-specific kisspeptpin decapeptide (eKp-10, YRWNSFGLRY-NH(2)) in an effort to shorten the interovulatory period. Administration of eKp-10 (0.5 mg iv every 4 h) to mares beginning on Day 16 postovulation (Group ...
Pérez-Marín CC, Requena FD, Arando A, Requena L, Requena F, Agüera EI.The aim of this study was to determine the effects of various abiotic factors, such as light, physical stress (pipetting) and thermal shock, on the quality of fresh and cooled equine sperm. In experiment I, four sperm aliquots were subjected to different light exposures: (i) protected control samples (CTRL), (ii) exposed to UV light at 10 cm (UV10), (iii) exposed to UV light at 20 cm (UV20) and (iv) exposed to laboratory lighting (LAB). In experiment II, four semen aliquots were subjected to repeated pipetting for 0, 10, 20 and 30 times (CTRL, P10, P20 and P30, respectively). In experiment I...
Kaminski M.The detection of the recessive null allele of horse serum esterase (Es) is possible in heterozygotes Es+/EsO which by starch gel electrophoresis appear like homozygotes Es+/Es+. Two methods are proposed, the titration of enzymatic activity of esterase and the immunochemical titration of esterase as antigen. These methods can be applied to solve the cases of suspect parentage or in population studies.
McCann ME, Watson TD, Boudinot FD, Moore JN.We evaluated the pharmacokinetics of IV administered sodium heparin and the pharmacodynamic effect of heparin on lipoprotein lipase (LPL) activity. Horses were allotted to 3 groups. Plasma samples were obtained from each horse before and at various times for 6 hours after heparin administration for determination of heparin concentration, LPL activity, and activated partial thromboplastin time (APTT). The disposition of heparin was dose dependent. The area under the plasma heparin concentration vs time curve (AUC) increased more than proportionally with dose, indicating that heparin elimination...
Alef M, Oechtering G.The continuous fiberoptical measurement of the mixed venous partial oxygen saturation is described. It is an enrichment of the diagnostical possibilities in veterinary medicine. In the horse it is of great interest, because disturbances of the pulmonary gas exchange and the myocardial function are common in the anaesthetised horse, and reliable methods of assessing the cardiac output are rare. Using this monitoring technique in nearly 100 equine high risk patients facilitated insight into the complex changes of the pulmonary, cardiac and circulatory function in the anaesthetised horse. The reg...
Kennedy SR, Thompson DL, Pruett HE, Burns PJ, Deghenghi R.A series of experiments was performed to determine the factor(s) responsible for an apparent inhibition of GH secretion in mares administered the GH secretagogue EP51389 in combination with GnRH, thyrotropin-releasing hormone (TRH), and sulpiride. Experiment 1 tested the repeatability of the original observation: 10 mares received EP51389 at 10 microg/kg BW; five received TRH (10 microg/kg BW), GnRH (1 microg/kg BW), and sulpiride (100 microg/kg BW) immediately before EP51389, and five received saline. The mixture of TRH, GnRH, and sulpiride reduced (P = 0.0034) the GH response to EP51389, con...
Cornelissen BP.Sesamoiditis is characterized clinically by repeated lameness and radiologically by changes in the proximal sesamoid bones. This thesis, which was defended in June 1997, investigated two characteristics of sesamoiditis, namely the arterial blood supply and the innervation of the proximal sesamoid bones, in order to gain more insight into the etiopathogenesis of sesamoiditis. Experiments with patient material showed that the proximal sesamoid bones have an enormous arterial reserve, due in part to the formation of an arterial shift. Moreover, the sesamoid bones have their own sensory innervatio...
Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM.To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. Methods: Sixty eyes of 30 healthy adult horses aged 8-24 years. Methods: Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pres...
Antczak DF.A new polymorphic locus of the horse which has several unusual properties is described. The suggested name for the locus is ELY-2. The gene product of one allele at this locus, designated ELY-2.1, has been identified with antisera raised as a result of pregnancy. Antibody to ELY-2.1 was first detected on day 55 after conception in the serum of a mare in first pregnancy. This early onset of antibody is similar to that seen for antibody to ELA antigens, and suggests that the source of the antigenic stimulus may be the tissue of the equine endometrial cups. The antisera identifying ELY-2.1 are cy...
Melrose PA, Knigge KM.The present study describes and compares the topography of alpha-melanocyte-stimulating hormone (alpha-MSH)-immunoreactive neurons in the forebrain of rats and horses. Two groups of immunoreactive cells were present in both species. These groups were distinguished by their cross-immunoreactivity and topography. The topography of cell bodies with cross-immunoreactivity for peptides derived from pro-opiomelanocortin (POMC) including adrenocorticotropin, 16K, alpha-MSH and beta-endorphin was similar in both species. However, the topography of perikarya which stained only for alpha-MSH, and not fo...
Woods GL, Ginther OJ.The ability of a pituitary extract to induce ovulation and the effect of multiple ovulations on pregnancy rate and incidence of multiple fetuses were studied in seasonally anovulatory mares. The extract induced ovulation in 95% of mares having a greater than or equal to 25 mm follicle at the onset of treatment and in 64% the ovulations were multiple. The extract was less effective when the largest initial follicle was less than 25 mm. Approximately 50% of the treated mares that ovulated did not become pregnant or enter prolonged dioestrus before returning to an anovulatory condition. In treate...
Hinrichs K, Rand WM, Palmer E.Follicular fluid from small- to medium-sized follicles has been shown to have an inhibiting effect on luteinization of granulosa cells in vitro. This study was conducted to investigate the effect of in vivo removal of follicular fluid on luteinization, peripheral gonadotropin concentrations, and ovulation of secondary follicles in the mare. Follicular fluid was aspirated from the preovulatory follicles of mares when the diameter of the follicle was 30-34 mm (Group A), 35-39 mm (Group B), or 40-44 mm (Group C). Mares in Group D served as controls and the preovulatory follicle was not aspirated....
Manohar M, Goetz TE, Holste LC, Nganwa D.Diaphragmatic O2 and lactate extraction were studied in 10 healthy ponies at rest and during treadmill exercise. The phrenic vein was aseptically catheterized via a lateral thoracotomy 8-35 days before the study. Arterial and phrenic venous blood samples were obtained simultaneously at rest and at 30-s intervals during 4 min of exertion. Three levels of exertion were studied (moderate, 10 mi/h; heavy, 15 mi/h; maximal, 20 mi/h), and a rest period of at least 90 min was allowed between them. Each pony was studied twice at least 2-3 days apart. At rest the diaphragmatic venous PO2, O2 saturation...
Geiser DR, Andrews FM, Rohrbach BW, White SL, Maykuth PL, Green EM, Provenza MK.Blood ionized calcium (Ca2+) and pH; plasma lactate concentrations; and total protein, total calcium (CaT), albumin, and phosphorus concentrations in serum were determined in 40 healthy horses before (T1), at the finish line (T2), and 10 minutes after the finish (T3) of the cross-country phase of a 3-day-event competition. Mean (+/- SEM) Ca2+ concentrations decreased from 6.22 +/- 0.04 mg/dl at T1 to 5.04 +/- 0.07 mg/dl at T2 (P < or = 0.05). This decrease was accompanied by a nonsignificant increase in CaT between T1 and T2. The mean (+/- SEM) percent ionization of calcium decreased significa...
Ahmed JS, Schmid G, Hörchner F.Pony peripheral blood lymphocytes (PBL) were stimulated with a soluble fraction of Trypanosoma (T.) evansi (SF). As determined by 3H-thymidine incorporation, the cells underwent a proliferative response and were able to: a) produce a factor having the biological activities of interleukin 2 (IL-2) since their supernatants could support the in vitro growth of pony PBL stimulated with concanavalin A (Con A-blasts); b) undergo a further proliferative response when incubated in short term cultures with SF, human recombinant IL-2 (hrIL-2), or both c) bind specifically radiolabelled hrIL-2 (125I-hrIL...
Chesworth M, Brandenberger O, Cheetham J, Windley Z, Schumacher J, Cochran K, Piercy RJ, Perkins JD. To investigate the effect of the transverse arytenoid ligament (TAL) on abduction of the arytenoid cartilage when performing laryngoplasty. Modified prosthetic laryngoplasty was performed on right and left sides of 13 cadaver larynges. Increasing force was sequentially applied to the left arytenoid cartilage at 3 N intervals from 0-24 N, when the force on the right arytenoid cartilage was either 0 or 24 N, before and after TAL transection. Digital photographs of the rostral aspect of the larynx were used to determine the left arytenoid abduction angles for these given force combinations and ...
Deaton CM, Marlin DJ, Smith NC, Roberts CA, Harris PA, Kelly FJ, Schroter RC.Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean...
Friesen KM, Johnson GD.Reproductive potential was assessed for stable fly cohorts fed cattle, chicken, or horse blood. Flies provided chicken blood oviposited 20% more eggs per day than did those fed cattle or horse blood. However, flies provided cattle or horse blood were fecund 50% longer. When both egg viability and number of eggs produced were considered, lifetime reproductive potential was almost twice as high for flies fed cattle or chicken blood than for flies fed horse blood. Maternal investment, which took egg production and volume into account, was higher in cohorts fed cattle blood (70 mm3) when compared ...
Ordakowski-Burk AL, Kronfeld DS, Williams CA, Gay LS, Sklan DJ.To identify changes in folate status of mares and foals during lactation and growth, respectively. Methods: 20 Thoroughbred mares and foals. Methods: Pregnant mares, and following foaling the same mares with their foals, were maintained on mixed grass-legume pasture and fed either a traditional dietary supplement rich in sugar and starch (SS) or a dietary supplement high in fat and fiber (FF). Blood samples were collected monthly from mares and foals up to 6 months after foaling. Total folate concentration in feed and forage was determined. Analyses of plasma folate, RBC folate, plasma homocys...
Floris B, Bini PP, Nuvole P, Di Meglio FG.The changes of some parameters in the blood serum of six Giara horses (3 males and 3 females) were checked weekly, in relation to the environmental temperature throughout a one winter and summer. T3, total lipids, triglycerides, urea nitrogen, creatinine, total protein, albumin, beta and gamma globulin showed significant difference between winter and summer and, with the exception of triglycerides, urea nitrogen and total protein were correlated to the environmental temperature. T4, glucose, uric acid and alpha globulin showed no difference between the two seasons and no correlation with the t...
Harvey JW, Kaneko JJ.Glutathione reductase (GR) was studied in erythrocytes of horses, cats, dogs, and man. Glutathione reductase activity was measured in hemolysates with and without preincubation of hemolysates with flavinadenine dinucleotide. The percentage saturation of GR apoenzyme with cofactor (flavin-adenine dinucleotide) was lower in cats and dogs than in horses or man. The greatest amount of inactive apoenzyme was in feline erythrocytes. Total GR activity listed in order by species is cat greater than man greater than dog greater than horse. Kinetic constants for oxidized glutathione and reduced nicotina...
Gastal MO, Gastal EL, Torres CA, Ginther OJ.The effects of oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol on uterine contractility and tone during anestrus and diestrus, and during mobility and postfixation of the embryonic vesicle were studied in 51 pony mares. Contractility was assessed by scoring real-time ultrasound images, and tone was assessed by transrectal digital compression. Scoring was done by an operator who had no knowledge of treatment assignments. In anovulatory mares primed with progesterone for 16 d, oxytocin did not significantly alter contractility but did stimulate an increase in tone, whereas clenbut...
Johnson ACB, Biddle AS.Thriftiness in horses has been associated with more efficient nutrient harvesting in digestion, absorption and/or utilization, but the relative contribution of the gut microbiome to host metabolic tendency is not well understood. Recognizing the unreliability of owner reported assignment of keeper status, this research describes a novel tool for calculating whether a horse is an easy (EK) or hard (HK) keeper and then characterizes microbiome differences in these groups. The Equine Keeper Status Scale (EKSS) was developed and validated based on data gathered from 240 horses. Estimates of dietar...
Carstanjen B.Effective, non-invasive bone assessment methods for screening, diagnosis and follow-up of the skeleton are more and more requested in veterinary medicine. In contrast to clinical parameters, invasive methods and imaging techniques, indices of bone turnover is a tool for bone metabolism evaluation of the whole skeleton. Biochemical bone markers therefore provide a more real-time assessment of the bone status with simple blood- or urine-analysis. This article surveys currently available biochemical marker of bone metabolism used in veterinary medicine. Additionally, information is provided about...
