Veterinary medicine for horses encompasses the study and application of medical practices to diagnose, treat, and prevent diseases in equine species. This field involves a comprehensive understanding of equine anatomy, physiology, pathology, and pharmacology. Veterinary practitioners employ a range of diagnostic tools and therapeutic interventions to address health issues in horses, including lameness, gastrointestinal disorders, respiratory conditions, and infectious diseases. Preventative care, such as vaccination and deworming programs, is also a significant aspect of equine veterinary medicine. This page gathers peer-reviewed research studies and scholarly articles that explore various aspects of veterinary medicine as it pertains to horses, including advancements in diagnostic techniques, treatment protocols, and preventive health strategies.
Illera JC, Illera M, Hamlin RL.Electrocardiograms were obtained from 100 male crossbred horses. In addition to standard limb leads, leads were taken from 12 points on the thorax. The QRS complexes were categorized into 1 of 8 forms on the basis of configuration and amplitudes of component deflections. Relative uniformity of QRS was determined for each lead, using the percentage of horses that possess a particular configuration. All unipolar thoracic leads, except those coplanar with the frontal plane, and lead aVR had great uniformity, with greater than 80% of the horses with a QRS of similar contour.
Roger T, Ruckebusch Y.The motor responses of the caecum and colon to stimulation of alpha 2-adrenoceptors by xylazine and detomidine at the recommended dose levels of 0.6 and 0.1 mg/kg were investigated in three ponies. The motor changes of the left ventral colon induced by continuous intra-arterial infusion of a prostaglandin (PGF2 alpha) were used to assess the relative inhibitory effects of xylazine and detomidine in a colic model. The administration of alpha 2-agonists inhibited the spiking activity on the whole of the large intestine for 20-30 min (xylazine) or 2-3 h (detomidine). However, the detomidine-induc...
Spensley MS, Carlson GP, Harrold D.During the growth interval encompassing age 2 days through 24 weeks, plasma, RBC, total blood, and extracellular fluid (ECF) volumes were determined in 7 healthy, resting foals. Evans blue dye and sodium thiocyanate were used to estimate plasma and ECF volumes, respectively. Absolute plasma volume remained stable from 2 days through 2 weeks of age, then increased progressively through 24 weeks of age. After decreasing between 2 days and 2 weeks of age, absolute RBC and total blood volumes progressively increased. Absolute ECF volume increased progressively from 2 days of age through 24 weeks o...
Tyler RD, Cowell RL, Clinkenbeard KD, MacAllister CG.Normal reference ranges and pertinent background information on equine hematology are presented and briefly discussed. Diagnostic interpretation of hematologic data is discussed and three diagnostic algorithms and two diagnostic tables are provided to facilitate the use of the presented information for diagnosis. Two cases are presented and the information presented in the article is used to interpret the case data.
de Waal DT, Potgieter FT.Rhipicephalus evertsi evertsi larvae were fed on the ears of rabbits. Seven days after larval infestation, unfed, newly moulted nymphae were manually removed to infest a splenectomized donkey showing a patent Babesia caballi infection. Engorged nymphae were collected from the donkey and the ensuing adult ticks were placed on a susceptible horse. The horse contracted a B. caballi infection showing a prepatent period of 19 days after tick infestation. A very low parasitaemia, (highest score 2), which was patent for only 10 days, was recorded. The lowest packed cell volume recorded was 16%.
Craig AM, Blythe LL, Appell LH, Slizeski ML.Dimethyl sulfoxide (DMSO) had been postulated to be a 'masking agent' when used concurrently with therapeutic or prohibited drugs in racing animals. Eight drugs (flunixin, furosemide, caffeine, apomorphine, phenylbutazone, lidocaine, cocaine, and acepromazine maleate) were administered to six horses singly and with concurrent intravenous DMSO. Urine samples were analyzed for the presence of the drugs and/or their metabolites by thin layer chromatography. Direct comparison of thin layer chromatograms of extracts of positive urine samples with and without DMSO verified that DMSO did not interfer...
Carnevale EM, Squires EL, McKinnon AO.Forty equine embryos collected 7 d post-ovulation were stored at 5 C for 24 h in one of two culture media (n = 20/group): 1) Ham's F10 + 10% heat-treated fetal calf serum (FCS) buffered by gassing with 5% CO2, 5% O2 and 90% N2 and 2) Ham's F10 + 10% FCS with Hepes buffer (25 mM). Embryos cultured in Ham's F10 + CO2 maintained a better quality score and had a larger average increase in diameter (+34.8 micron) than embryos stored in Hepes buffered Ham's F10 (-10.2 micron). Embryos were transferred surgically into recipient mares that ovulated -3 to +1 d in relation to the donor mare. Twenty embr...
Perryman LE, Bue CM, Magnuson NS, Mottironi VD, Ochs HS, Wyatt CR.Thirty-eight foals with combined immunodeficiency (CID) received transplanted fetal liver cells, fetal liver and thymus cells, histocompatible bone marrow cells, or equine lymphocyte antigen (ELA) haploidentical bone marrow cells in an attempt to reconstitute their deficient immune systems. Engraftment was infrequent, partial, and unpredictable when fetal cells were employed. Three of five CID foals receiving ELA haploidentical bone marrow cells demonstrated partial reconstitution, but engraftment was only temporary. Administration of histocompatible bone marrow cells resulted in rapid, full a...
MacDonald MH, Richardson DW, Morse CC.A 23-year-old Thoroughbred stallion was admitted to the hospital for treatment of acute esophageal obstruction. Clinical examination and contrast radiography confirmed the presence of an esophageal obstruction. The horse was euthanatized, and examination revealed a bolus of feed material occluding the esophageal lumen 6 cm caudal to the thoracic inlet, with underlying necrosis of the esophageal mucosa. A large pulsion diverticulum was identified in the caudocervical portion of the esophagus. Apparently, the phytobezoar was formed within the esophageal diverticulum and subsequently became dislo...
Roger T, Ruckebusch Y.The contractile activity of the equine large intestine exhibited a biphasic response to feeding: enhancement of migrating complexes passing along the colon and an increase of 50% in cyclic variations in smooth muscle at intervals of 20 min on the left ventral colon for a period of 5 to 7 h postfeeding. The cholinergic agonist, bethanechol (50 micrograms/kg subcutaneously), induced both the migrating complexes and the cyclic variations at intervals of 10-15 min. In contrast, the intra-arterial infusion of PGF2 alpha (3 micrograms/kg/min) increased the contractile activity during infusion, but w...
Morris CF, Robertson JL, Mann PC, Clark S, Divers TJ.A syndrome characterized clinically by oliguria, progressive severe azotemia, and edema of the abdomen and groin was seen in 2 horses. Treatment with fluids, diuretics, and corticosteroids administered intravenously was ineffective, and the horses were euthanatized. Microscopically, there was severe necrotizing angiopathy with profuse fibrin deposition in renal glomeruli and sinusoids of peripheral lymph nodes. The signs observed in the horses resembled hemolytic-uremic syndrome in human beings.
Sweeney RW.Malassimilation should be suspected in horses with weight loss in spite of a good appetite. Malassimilation is usually confirmed with oral glucose or D-xylose absorption tests, whereas the oral lactose tolerance test can be used to evaluate lactase deficiency in foals. Once malassimilation is confirmed, other diagnostic tests such as abdominocentesis, rectal mucosal biopsy, or exploratory laparotomy with intestinal biopsies may determine the etiology of malassimilation.
Sirois J, Betteridge KJ, Brault A.Embryo transfer was used in an equestrian teaching center in order to produce as many foals as possible from their preferred mares during a single breeding season. Embryo collection by uterine lavage was attempted in five donor mares on 25 occasions 6.5 days after ovulation. Sixteen of the collection attempts (64%) yielded a total of 17 blastocysts. Of these 17 embryos, 13 were immediately transferred transcervically into recipient mares that had ovulated within two days of the time of ovulation in the donors, three were frozen for later transfer, and one was lost. Eight of the freshly transfe...
Moran CT, James ER.Eyes from 292 old (15-20 years) horses originating in the eastern, southeastern and midwestern United States were examined for the presence of Onchocerca cervicalis microfilariae (mf) and concurrently for anterior and posterior segment ocular pathological changes. One-hundred-fifty-three animals (52.4%) were positive for dermal mf (range 0.03-5,364/mg). Of these, 60 animals had anterior segment changes. An additional 58 animals with pathological changes had no dermal mf. Mf were recovered from the ocular tissues of 18% of animals (range 0.07-29/mg). All animals with ocular mf were positive for...
Seide RK, Jacobs RM, Dobblestein TN, Kehoe JM.A novel myeloma paraprotein has been isolated from a horse with a lymphoid tumor. The protein was a euglobulin and consequently was readily isolated from serum in pure form and high yield by simple dilution in distilled water. The purified intact protein had a molecular weight of 150,000 and was composed of heavy and light chains, both of which had blocked amino-termini and were thus not susceptible to amino-terminal sequence analysis. The amino acid compositions of these respective chains corresponded to those of comparable chains from immunoglobulins of other species. Peptide maps of parapro...
Lavoie JP, Morris DD, Zinkl JG, Lloyd K, Divers TJ.Pancytopenia was evaluated in a mature Quarter Horse gelding. A diagnosis of bone marrow aplasia was made on the basis of bone marrow hypocellularity. History of drugs administered included penicillin, oxytetracycline, trimethoprim-sulfadiazine, phenylbutazone, dipyrone, flunixin meglumine, and isoxsuprine. Clinical remission was observed after treatment with glucocorticoids, androgens, and broad-spectrum antimicrobials.
Romagnoli SE, Momont HW, Hilbert BJ, Metz A.Two yearling, paternal half-sibling Appaloosa fillies were ovariohysterectomized for treatment of multiple uterocervical leiomyomas. The tumors recurred in both fillies, originating from cervical tissue that could not be removed at surgery. Previously reported cases of uterine leiomyoma in the mare have been of solitary tumors in older mares that were treated successfully by surgical removal.
Bertone JJ, Paull KS, Wingfield WE, Boon JA.M-mode echocardiographic structures, and cardiac function indices, PCV, and total plasma protein values were determined for 34 endurance equine athletes before (base line) and after (after race) a 161-km endurance competition and were compared. The PCV (base-line mean, 37%; after-race mean, 46%) and total plasma protein value (base-line mean, 6.9 g/dl; after-race mean, 7.5 g/dl) increased. Compared with base-line echocardiography, after-race echocardiography indicated an increase in heart rate, as determined from the simultaneous ECG recorded on the echocardiograph (base-line mean, 41 beats/mi...
Kohn CW, Chew DJ.Laboratory evaluation of renal function in horses has advanced dramatically in the last 10 years largely as a result of the interest generated by the creative approach to diagnostic indices taken by Brobst, Traver, Coffman, and others. Some methods of assessing renal function discussed here are clearly outside the scope of a practice environment but are available in referral hospitals for use in difficult or unusual cases. Other methods described, such as calculation of fractional excretions and urine to serum creatinine ratios, are accessible and readily interpreted by the veterinary practiti...
Bayly WM.It is the purpose of this article to review much of the information that is available regarding the adjunctive use of clinicopathologic data in evaluations of performance horses by veterinarians. Wherever possible, distinctions are made between findings that pertain to racehorses and those that apply most specifically to horses involved in "submaximal" events like combined training and endurance races. It is hoped that the material presented will clarify some of the problems associated with the interpretation of this data, and possibly stimulate the dissemination of additional information that...
Sweeney CR, Whitlock RH, Meirs DA, Whitehead SC, Barningham SO.Complications associated with Streptococcus equi infection developed in 15 (20.3%) of 74 horses on one farm included death, guttural pouch empyema, purpura hemorrhagica, upper respiratory tract obstruction, pneumonia, pleuropneumonia, agalactia, mesenteric lymph node abscessation, and periorbital abscessation. Death was attributed to pneumonia in 3 horses and to upper respiratory tract obstruction in 2 horses. One horse was euthanatized because of severe purpura hemorrhagica.
López ML, de Souza W, Bustos-Obregón E.The structure, relative density, and distribution of anionic sites on the surface of epididymal and ejaculated spermatozoa were studied using polycationic ferritin (CF), colloidal iron hydroxide (CIH), various enzymatic treatments, methylation, and de-acetylation. Macro-molecules containing sugar residues, probably sialic acid, are part of the sperm membrane and show a characteristic distribution and density that is dependent of the sperm region and of its origin. Unlike the spermatozoa of other eutheria examined, the exposure of the stallion spermatozoa to neuraminidase treatment did not prod...
Meyers KM, Menard M, Wardrop KJ.This is a review of equine hemostasis and is divided into three sections. The initial portion describes the normal hemostatic system and includes platelet function, coagulation, fibrinolysis and control processes. The second phase is devoted to laboratory tests of hemostasis, and the last section provides information on specific alterations.
Dyer KR, Duncan ID.The intraneural course of nerve fibres in the equine recurrent laryngeal nerve was investigated by partially ligating the nerve at a proximal site, and 3-8 weeks later, tracing the course and spatial relationships of intact and degenerating fibres along the distal stump. This nerve was chosen because of its great length, the fact that it is a nonbranching motor nerve and because of debate about the course of abductor and adductor nerve fibres in the recurrent laryngeal nerve. Six ponies were used and in each the recurrent nerve was partially ligatured about 20 cm from the larynx, using a fine ...
Ravis WR, Duran SH, Pedersoli WM, Schumacher J.The pharmacokinetics of phenobarbital were determined in six mature horses after a single oral dose. Horses were administered a 5.5 mg/kg of body weight oral dose of phenobarbital tablets. Based on the combined evaluation of i.v. and oral results, phenobarbital displayed two-compartment pharmacokinetics in the horse with a terminal half-life of 19.0 +/- 4.4 (mean +/- SD) h. This half-life is considerably shorter than those reported for dogs and humans. The steady-state volume of distribution (Vdss/F) and the total body clearance (Clt/F) of phenobarbital were 0.753 +/- 0.115 l/kg and 27.9 +/- 9...
Wiśniewski E, Kuźma K.The normal level of plasma lysozyme of 9 Tarpane-like horses was 0.922pg/ml. This was
calculated from determinations performed 5 times in a period of 14 months. Observations on the
normal plasma level of lysozyme in the horse revealed marked variations in individual animals, as well
as in the whole group and in the mean values calculated for individual horses. The model for the
subsequent studies was an experimental fever evoked by the administration of E. colz LPS in a dose of
0.1 pg/kg body weight. Blood samples from the jugular vein were taken just before LPS injection, and
then for 8...
Winston S, Fiscus S, Hesterberg L, Matsushita T, Mildbrand M, Porter J, Teramoto Y.The development of three separate rapid ELISAs for detecting antibodies in host serum to three different viruses is described. These include: 1. A direct antigen assay using enzyme labelled anti-canine Ig for detecting antibodies to canine parvovirus, 2. A competitive ELISA using a feline infectious peritonitis virus-specific monoclonal antibody labelled with enzyme, and 3. A competitive ELISA using an equine infectious anemia virus-specific monoclonal antibody and enzyme labelled antigen, p. 26. The utility and benefits of each of the three approaches is emphasized.
Riggs MW.Currently recognized equine immune deficiency disorders include failure of passive colostral immunoglobulin transfer, combined immunodeficiency, selective IgM deficiency, transient hypogammaglobulinemia, and agammaglobulinemia. Additional equine immune deficiency disorders probably exist. Immune deficiency should be suspected in any horse experiencing persistent or recurrent infections that are not responsive to conventional therapy.
Weber JM, Parkhouse WS, Dobson GP, Harman JC, Snow DH, Hochachka PW.Plasma lactate turnover rate of Thoroughbred racehorses was measured by bolus injection of [U-14C]lactate at rest and two levels of submaximal treadmill exercise (3-4 m/s trot, 6% incline, and 6.5 m/s horizontal canter). Our goals were 1) to determine the relative effects of changes in cardiac output and in plasma lactate concentration on turnover rate [using cardiac output data from Weber et al. (28)] and 2) to assess the importance of lactate as a metabolic fuel in a trained animal athlete. Lactate turnover rates were 9.3 mumol.min-1.kg-1 (rest), 75.9 mumol.min-1.kg-1 at the beginning of the...
Ramirez S, Seahorn TL, Williams J.This report describes a renal ultrasonographic abnormality (medullary rim sign), which was identified in 2 separate cases of spontaneously occurring disease associated with chronic and acute overdosage of phenylbutazone therapy. In horses, medullary rim sign has only been documented in neonatal foals experimentally administered large doses of phenylbutazone.
Boatwright RB, Williams DO, Rugh KS, Sarazan RD, Ross CR, Garner HE, Griggs DM.Coronary collateral growth was stimulated in chronically instrumented conscious ponies by a previously validated intermittent coronary occlusion method. Changes in regional myocardial function (sonomicrometry) and reactive hyperemia (Doppler method) were used to monitor collateral growth and to program measurements of regional myocardial blood flow (microsphere method). A serial analysis of the transmural and lateral distributions of collateral blood flow was performed at the native and three superimposed levels of collateral growth. Results in nine animals undergoing an average of 553 +/- 188...
Bohner J, Painer J, Bakker D, Haw AJ, Rauch H, Greunz EM, Egner B, Goeritz F.Etorphine is widely used in zoological medicine for the immobilization of large herbivores. All reported immobilization protocols for kulans use etorphine as the primary immobilizing agent. However, etorphine can trigger severe side effects and is highly toxic for humans, its availability is occasionally limited for use in wildlife medicine. Therefore, two different alpha-2 agonist-based protocols for the general anesthesia of kulans were investigated and compared with the standard etorphine immobilization. In total, 21 immobilizations were performed within the scope of routine husbandry manag...
Vernunft A, Löhrke B, Tuchscherer A, Weitzel JM, Viergutz T.Anti-Muellerian hormone (AMH) is synthesized only by granulosa cells in female mammals as an inhibiting factor for early follicular recruitment. Especially in preantral and small antral follicles, expression of AMH is very intensive. However, we hypothesize that AMH affects also the development of large follicles by an estrogenesis modification. This current investigation provides for the first time information about concentrations of AMH in equine follicular fluid and demonstrates their relationship to functional characteristics of follicle development. Therefore, fluids of follicles in diffe...
Hunyadi L, Papich MG, Pusterla N.The purpose of this study was to determine if a low dose of diclazuril (0.5mg/kg of 1.56% diclazuril pellets) given to six healthy adult horses every 3-4 days for a total of five administrations would achieve steady-state plasma concentrations known to be inhibitory to Sarcocystis neurona and Neospora caninum. Blood was collected via venipuncture immediately before (trough concentrations) and 10h after (peak concentrations) each diclazuril administration and analysed by high-pressure liquid chromatography. The mean population-derived peak concentration was 0.284μg/mL and the mean terminal hal...
Cox D.Many clinicians are experiencing consumer resistance to the prescription of equine HRT (that is hormone replacement therapy which has been manufactured from mare's urine). In this paper I consider the ethical implications of prescribing these preparations. I decide that patients should have a right to refuse such treatment but also ask whether a prescribing doctor should choose one preparation over another on moral grounds. I determine that there is prima facie evidence to suggest that mares may suffer and that prescription of equine HRT (instead of synthetic oestrogen-oestriol) would therefor...
Kalinskiĭ MI, Kamenetskaia OV, Skorik LG, Tishchenko GN.The paper deals with possibility to regulate in a proper direction the acid-base state in race horse blood administering carbostimulin at rest and under physical exercises. The preparation is shown to favour an increase in alkaline blood reserves in race hours at rest and to prevent acidotic changes caused by physical exercises. The results obtained show a promising use of carbostimulin for the directed correction of the acid-base state of blood in race horses aimed at increasing the efficiency of the training process.
Mählmann Ch, Steiger A.Persons involved in equine breeding, namely veterinarians, horse breeders and breeding association judges, often lack of an apropriate consciousness about the relevance of heritability or supposed heritability of common horses diseases, which might play a distinctive role in the aetiology of numerous of these diseases. Executing animal welfare rights in equine breeding, the major concern should focus on an objective evaluation of pain, suffering and damages caused by different hereditary diseases. The basis of assessment for hygienic breeding has to be defi ned according to the actual animal w...
Gronwall R, Engelking LR, Noonan N.Biliary excretion of bilirubin, including the conjugate composition, was studied during feeding and during a 2.5-day fast of three pony mares with chronic external biliary (T-tube) fistulas. Fasting bilirubin excretion (1.96 +/- 0.74 microgram/min/kg of body weight), after establishing a new steady state, was not different from excretion during feeding (1.99 +/- 0.45 microgram/min/kg). Hyperbilirubinemia of fasting resulted from a reduced removal of plasma bilirubin rather than from an increased input of bilirubin into the plasma. Relative plasma excretion of the individual conjugate fractions...
Adams GP, Bosu WT.This article reviews the reproductive events in the nonpregnant mare with emphasis on recent advances. The discussion is restricted to the salient features of puberty (prenatal and prepubertal events), seasonality (gonadotropins, photoperiod, and other modifying factors), and the estrous cycle (hormones, estrus, diestrus, and the control of cyclicity) in the nonpregnant mare.
Holbrook TC, Gilliam LL, Stein FP, Morgan SE, Avery AL, Confer AW, Panciera RJ.Caley Pea (Lathyrus hirsutus) is potentially toxic to horses, but large case series are not reported. Objective: To describe the clinical signs of horses intoxicated with Lathyrus hirsutus and speculate on the neuroanatomical lesion localization and pathogenesis based upon the observed clinical signs. Methods: Twenty-two of 25 horses ranging in age from 6 to 34 months were affected. Five affected horses were presented to the OSUCHVS for evaluation and treatment after having been attended at the ranch by a local veterinarian (ALA). An additional horse that had been euthanized was also presented...
Malekinejad H, Alizadeh-Tabrizi N, Ostadi A, Fink-Gremmels J.The pathogenesis of equine grass sickness (EGS) has not fully understood. A better understanding of the exact pathogenesis of diseases can help to make an accurate diagnosis. Previous studies reported some pathological damage of neuronal cells in EGS patients. In this study, primarily cytotoxicity of serum from three clinically EGS-diagnosed horses on PC12 Tet-off (PTO) cells was assessed. Subsequently, the apoptotic tests including cytochrome C release, caspase-3/7 activity measurement and DNA fragmentation assay were conducted to clarify the apoptotic effect of serum from EGS patients. Addit...
Butler CL, Houpt KA.The objectives of this study were to determine the prevalence of pawing behavior in a population of Standardbred racehorses and the relationship of pawing frequency to time of day. Standardbreds (n=41) were observed using instantaneous scan sampling twice daily, in the morning before training and in the afternoon after training. A majority of the horses, twenty-four (58.5%) of the 41 horses showed pawing behavior at least once (median=7, interquartile range=2-15). After training, there were a median of 4 (interquartile range 1-11) observations of pawing or 11.2% of total observations. In the m...