Showing papers in "Equine Veterinary Journal in 1983"

Kinematics of the equine thoracolumbar spine

Abstract: At least three types of movement take place in the joint complexes of the equine thoracolumbar spine: dorsoventral flexion and extension, axial rotation and lateral bending. Using the standard right-handed Cartesian coordinate system, these movements may be defined as rotation about the x, y and z axes respectively. Except in cases of intervertebral fusion, all three types of movement occur in each joint complex of the equine back. The greatest amount of dorsoventral movement takes place at the lumbosacral and the first thoracic intervertebral joints. The greatest amount of axial rotation and lateral bending was measured in the mid-thoracolumbar spine at the level of the 11th or 12th thoracic intervertebral joints. The caudal thoracic and the lumbar spine is the least mobile region of the equine back. In the mid-thoracic spine, lateral bending was always accompanied by a "coupled" axial rotation. The presence of the rib cage stabilised the cranial thoracic vertebrae against axial rotation.

Prognosis in equine colic: A study of individual variables used in case assessment

Abstract: The individual merit of the use of 43 variables to assess the prognosis of equine colic cases was examined. The following variables revealed highly significant (P less than 0.001) differences between cases which survived and those which died: blood pressure; heart rate; oral mucosal capillary refill time; degree of mental depression; venous haemoglobin concentration, haematocrit, erythrocyte count, urea concentration and lactate concentration; peritoneal fluid lactate concentration; and haematocrit/plasma protein and serum protein concentration ratios. Thus, in general, variables which assessed cardiovascular function were good prognostic guides.

Prognosis in equine colic: A comparative study of variables used to assess individual cases

Abstract: ummary The present retrospective study compared objectively the prognostic value of many variables routinely used in the assessment of equine colic cases. The best prognostic variables were those which assessed the integrity of cardiovascular function. Ranked in order of decreasing merit the following variables were able to discriminate between horses which lived and those which died: systolic pressure, blood lactate concentration, oral mucous membrane capillary refill time, diastolic pressure, arterial pulse amplitude, degree of mental depression, blood urea concentration, haematocrit, heart rate, haematocrit/plasma protein ratio, oral mucous membrane colour, jugular filling rate, frequency of gut sounds, differential blood leucocyte count, blood glucose concentration and respiratory rate. Assessment of systolic pressure alone appropriately classified the outcome (survival or death) of 86 per cent (64 out of 73) cases examined. Combined assessment of systolic pressure, blood lactate concentration, blood urea concentration and haematocrit permitted accurate classification of 93 per cent (68 of 73) of the cases examined. Outcome classification formulae for these four variables, alone and in all combinations, are presented. Resume Dans cette etude, on compare objectivement la valeur pronostique de nombreuses variables retenues dans l'approche clinique des coliques chez le cheval. Les variables de meilleure valeur pronostique sont celles qui apprecient l'integrite du systeme cardiovasculaire. Classees par ordre decroissant de validite les variables suivantes ont pu permettre de distinguer les chevaux qui allaient survivre de ceux qui allaient mourir: la pression systolique, la lactacidemie, le temps de repletion capillaire de la muqueuse buccale, la pression diastolique, l'amplitude du pouls arteriel, le degre de depression cerebrale, le taux, d'uremie, l'hematocrite, le rythme cardiaque, le rapport hematocrite/proteines du plasma, la coloration de la muqueuse buccale, le taux de repletion jugulaire, la frequence des borborygmes des intestinaux, la formule leucocytaire, la glycemie et le rythme respiratoire. L'appreciation de la pression systolique permit a elle seule de distinguer le devenir -mort our survie- de 86 pour cent des cas etudies de coliques (64 sur 73). La combinaison de l'appreciation de la pression systolique, de la lactacidemie, de l'uremie et de l'hematocrite a favorise la classification pronostique de 93 pour cent des cas etudies (68 sur 73). On indique des formules pronostiques fondees sur ces quatre variables seules ou associees. Zusammenfassung Diese retrospektive Studie zieht einen objektiven Vergleich des prognostischen Werts vieler Variablen, die fur die Beurteilung von Kolikfallen haufig herangezogen werden. Die nutzlichsten dieser Variablen sind diejenigen, die die kardiovaskulare Integritat des Patienten zu beurteilen erlauben. Die folgenden Variablen waren imstande zwischen uberlebenden und eingegangenen Pferden zu unterscheiden (Reihenfolge nach abnehmender Zuverlassigkeit): Systolischer Druck, Blut-Lactat-Konzentration, Kapillarfullungszeit an der Maulschleimhaut, diastolischer Druck, arterielle Pulsamplitude, Grad der Apathie, Blut-Harnstoff-Spiegel, Haematokrit, Herzfrequenz, Haematokrit/Plasmaprotein-Verhaltnis, Farbe der Maulschleimhaut, Fullungszeit der Jugularis, Haufigkeit von Darmgerauschen, Differentialblutbild, Blutzucker-Konzentration und Atemfrequenz. Die Messung des systolischen Drucks allein klassierte das Ergebnis (Ueberleben oder Tod) in 86% (64 von 73) der untersuchten Falle. Die kombinierte Berucksichtigung des systolischen Drucks, der Blut-Laktat-Konzentration, des Blutharnstoffspiegels und des Haematokrits erlaubte die Klassierung von 93% der Falle. Klassierungsformeln fur diese vier Variablen werden, allein und in allen Kombinationen, angegeben.

Haematological response to racing and training exercise in Thoroughbred horses, with particular reference to the leucocyte response.

Abstract: ummary The haematological response to racing and to fast and slow training exercise was investigated in studies involving two populations of horses which differed widely in geographical location, climatic factors and management (Newmarket and Hong Kong) The well documented elevations in erythrocyte parameters were demonstrated and changing responses in leucocyte parameters, resulting in variations in the neutrophil to lymphocyte (N/L) ratio were described It was shown that the immediate response to the anticipation or stress of exercise was a decrease in N/L ratio in association with an increase in lymphocyte numbers The magnitude of the lymphocyte increases was similar in the two populations of horses producing a reversal of the N/L ratio (lymphocytes predominating) in the British but not the Hong Kong horses, owing to the higher resting ratio of the latter population At 3 and 4 h after exercise, an increase in N/L ratio occurred in association with an increase in neutrophils and decrease in lymphocytes All parameters had returned to resting level by 6 h following exercise Those and the many other factors associated with alterations in equine N/L ratios are discussed in terms of the need for care when interpreting the results of haematological examinations Resume On a etudie le response hematologique a la course, a l'entrainement rapide ou lent sur des populations equines differentes par leur situation geographique, par le climat et par leur environnement hygienique (Newmarket et Hong Kong) L'elevation des parametres erythrocytaires — bien connue — fut constatee;on observa des responses variables pour les parametres leucocytaires, variations dans le rapport des neutrophiles aux lymphocytes On remarqua que la reponse immediate a l'anticipation ou au stress de l'exercice etait une diminution du rapport neutrophiles/leucocytes (N/L), provoque par une elevation des lymphocytes L'importance de l'elevation des lymphocytes etait de meme ampleur dans les deux populations equines, produisant une inversion du rapport N/L (dominante de lymphocytes) chez les chevaux anglais, mais non chez les chevaux de Hong Kong, caracterises par un rapport plus eleve en repos Trois et quatre heures apres l'exercice, une elevation du rapport N/L se produisait en association avec une elevation des neutrophiles et une reduction du nombre des lymphocytes Tous les parametres retrouvaient leur valeur de repos 6 heures apres l'exercice Ces faits et d'autres facteurs associes a l'alteration du rapport N/L chez le cheval sont discutes On souligne la prudence qu'il convient d'avoir dans l'examen critique des hemogrammes Zusammenfassung Die haematologische Reaktion auf Rennen, auf schnelle und langsame Trainingsarbeit wurde in zwei Pferdepopulationen untersucht, die unter sehr verschiedenen geographischen, klimatischen und pflegerischen Bedingungen gehalten werden (Newmarket und Hong Kong) Die gut bekannten Anstiege der Erythrocytenparameter konnten festgestellt werden und Veranderungen in der Leukocytenzusammensetzung werden beschrieben, — resultierend in Variationen im Verhaltnis von Neutrophilen zu Lymphocyten Es wurde gezeigt, dass die unmittelbare Antwort auf die Erwartung der Arbeit oder die Anstrengung selbst in einer Abnahme des Ne: Lyverhaltnisses besteht, hervorgerufen durch eine Zunahme der Lymphocytenzahl Das Ausmass dieser Zunahme in den beiden Populationen fiel ahnlich aus, produzierte aber eine Umkehr des Ne: Ly-Verhaltnisses (hohere Lymphocytenzahl) nur bei den englischen Pferden, weil diejenigen in Hong Kong in Ruhe einen hoheren Quotienten aufwiesen Drei und 4 Stunden nach Anstrengung nahmen die Neutrophilen zu, die Lymphocyten ab und das Verhaltnis verschob sich entsprechend Alle Werte fielen 6 Stunden nach Austragung auf die Ruhegrossen zuruck Diese und viele andere Faktoren, die mit dem Verhaltnis Ne: Ly verknupft sind, werden diskutiert, und es wird betont, dass man bei der Interpretation haematologischer Untersuchungsergebnisse vorsichtig sein muss

Clinical aspects of lymphosarcoma in the horse: a clinical report of 16 cases.

Abstract: Summary This paper describes the clinical and laboratory findings in 16 horses suffering from lymphosarcoma and the autopsy results in 13 of these cases which were examined at the Large Animal Medicine Clinic, State University of Utrecht, from 1969 to 1981. The cases were classified into four groups, designated multicentric, alimentary, thymic and cutaneous forms, according to the situation of the tumours. Resume Cet article decrit les observations cliniques et de laboratoire faites sur 16 chevaux atteints d'un lymphosarcome; et rapporte les resultats d'autopsies faites sur 13 de ces animaux. Tous furent examines a la Clinique Medicale pour Grands Animaux de l'Universite d'Utrecht entre 1969 et 1981. Ces cas furent classes en quatre groupes, designant des formes multicentrique, alimentaire, thymique ou cutanee, suivant la localisation de la tumeur. Zusammenfassung Dieser Artikel beschreibt die klinischen Befunde und die Laborergebnisse, die bei 16 Pferden mit Lymphosarkom erhoben werden konnten, dazu die Ergebnisse der Sektionen von 13 dieser Tiere, die an der medizinischen Grosstierklinik der Universitat Utrecht von 1969 bis 1981 erhoben werden konnten. Die Falle wurden in vier Gruppen eingeteilt, namlich: multizentrische Formen, Tumoren des Verdauungsapparats, der Thymus und der Haut, je nach der Localisation der Geschwulste.

Treadmill for equine locomotion analysis

Abstract: A treadmill for equine locomotion analysis is described and its potential considered for locomotive research and clinical investigation. The treadmill comprised an endless belt driven by a hydraulic motor at various speeds up to 14 m/sec and the direction of belt movement was reversible. The carrying side of the belt ran over a steel-concrete table which acted as a flat support. The belt itself consisted of a steel base on to which was glued a rubber belt and the surface was covered with a layer of coir matting which permitted some forward sliding of the landing hooves simulating the conditions on an ordinary track. The treadway could be inclined up to 10 degree in the longitudinal and 7.5 degrees in the transverse direction. To minimise the risk of injuries a special emergency stop system was installed. Horses adapted well to exercising on the treadmill, even without any previous experience. A good correlation was found between the gait repetitiveness on the racetrack and that displayed on the treadmill. One horse recorded both on the racetrack and on the treadmill showed significantly shorter strides on the treadmill but this did not invalidate the treadmill as a useful research tool in the study of equine locomotion.

Current concepts of infectious polyarthritis in foals

Abstract: Summary Because the majority of foals afflicted with “joint ill” also have infectious (poly)osteomyelitis, previous definitions no longer suffice. In this article the different syndromes are described and classified and the pathogenesis, prognosis and treatment of the disease complex are discussed. Resume Puisque la majorite des foals souffrant “d'arthrite” ont aussi des (poly) osteomyelites, les definitions jusqu'a a present retenues ne conviennent plus. Dans cet article, les differents syndromes sont decrits, classes, et la pathogenese, le pronostic et le traitement du complexe morbide sont discutes. Zusammenfassung Weil die Mehrheit aller Fohlen mit “joint ill” (annahernd gleich “Fohlenlahme”) auch an infektioser (Poly)Osteomyelitis leidet, lassen sich die fruheren Definitionen nicht langer verwenden. In diesem Artikel werden die verschiedenen Syndrome beschrieben und klassiert. Die Pathogenese, die Prognose und die Behandlung des Krankheitskomplexes werden diskutiert.

Leptospiral infection in horses in Northern Ireland: serological and microbiological findings.

Abstract: ummary Thirteen strains of pathogenic leptospires were isolated from 12 of 91 horses; seven strains belonged to the Australis serogroup (serotype bratislava) with three, two and one strains belonging to the Icterohaemorrhagiae, Hebdomadis (serotype hardjo) and Autumnalis serogroups respectively. Using leptospires isolated from horses and others representing the known parasitic Leptospira serogroups, a sample of 650 mares' sera was tested for agglutinating antibodies. Antibodies were found in 89.1 per cent of sera. The predominant reaction was to serotype bratislava, strain S/1334/79, isolated in this study, antibodies to which were detected in 81.8 per cent of sera. It is suggested that serotype bratislava may be adapted to, and maintained by, the horse population in Northern Ireland. Resume On a isole 13 souches de leptospiroses pathogenes sur 12 individus d'une population de 91 chevaux; sept souches appartenaient au serogroupe Australis (serotype bratislava); trois souches appartenaient au serogroupe Icterohaemorrhagiae, deux au serogroupe Hebdomadis (serotype hardjo) et un au serogroupe Autumnalis. En utilisant des leptospires isoles sur des chevaux et d'autres representant les serogroupes connus de leptospires parasites, on a teste 650 juments et recherche des anticorps agglutinants. Des anticorps furent trouves dans 89.1 pour cent des serums. La reaction dominante fut celle avec le serotype bratislava souche s/1334/79 isolee au cours de cette etude (81.8 pour cent des juments). On avance l'idee que le serotype bratislava peut s'etre adaptea la population equine d'Irlande du Nord et peut s'y maintenir. Zusammenfassung Dreizehn pathogene Leptospirenstamme wurden aus zwolf von 91 untersuchten Pferden isoliert. Sieben Stamme gehorten zur Australis-Serogruppe (Serotyp Bratislava) — drei, zwei und ein Stamm zu Icterohaemorrhagiae, Hebdomadis (Serotyp Hardjo), beziehungsweise Autumnalis. Die Pferdeisolate und andere Reprasentanten der pathogenen Leptospiren-Serogruppen wurden zur Untersuchung von 650 Stutenseren verwendet. Agglutinierende Antikorper konnten in 89.1 prozent der Seren festgestellt werden. Die haufigste Reaktion erfolgt gegen den Serotyp Bratislava S/1334/79, isoliert im Laufe dieser Arbeit) mit 81.8 prozent positiver Seren. Es wird vermutet, dass der Serotyp Bratislava sich in Nord-Irland ans Pferd adaptiert hat und dass er uber das Pferd erhalten bleibt.

Training and growth induced changes in the middle gluteal muscle of young Standardbred trotters.

Abstract: The middle gluteal muscle of five, two-year-old untrained trotters was investigated by repeated needle biopsy sampling over a training period of six months. A second group of five, three-year-old untrained horses was included to examine the effect of growth. After the training period increases were found in the relative distribution of slow twitch (ST) fibres from 18 per cent to 25 per cent and fast twitch (FTa) fibres from 36 per cent to 45 per cent, and a decrease in FTb fibres from 46 per cent to 30 per cent. A proportionally equal reduction (approximately 18 per cent) in the cross sectional area of all fibre types was observed after the first two months of training succeeded by an increase to approximately pretraining levels at the end of the period. The number of capillaries per fibre was enhanced from 1.7 to 2.4. Proliferation of capillaries occurred around fibres of all types. The metabolic adaptations showed increases in the activities of 3-hydroxy-acyl-CoA dehydrogenase (HAD) (50 per cent) and citrate synthase (31 per cent). Growth had no effect on the relative fibre type distribution nor the capillary per fibre ratio, but as the mean fibre area increased 36 per cent (primarily because of increases in FT fibres) the number of capillaries/mm2 was lower in the older untrained horses (350 capillaries/mm2) compared with the younger untrained ones (460 capillaries/mm2). Increase with growth was found in the activity of phosphorylase and HAD and a decrease was seen in the activity of hexokinase. It is concluded that the training programme exclusively induced alterations which improved the aerobic capacity of the muscle.

Review of 30 cases of peritonitis in the horse

Abstract: Thirty cases of peritonitis, in which the diagnosis was based on a peritoneal fluid white blood cell count in excess of 10 x 10(9)/litre, are described Colic, ileus, pyrexia, weight loss and diarrhoea were common presenting signs Treatments included intravenous fluids, anti-inflammatory analgesics, broad spectrum antibiotics and anthelmintics Duration of treatment was determined by the clinical condition of the horse and sequential analyses of the peritoneal fluid and the haemogram In the majority of cases the primary cause of peritonitis was not accurately determined, but 21 horses (70 per cent) recovered All the horses with diarrhoea were killed after marked deterioration in their clinical condition despite intensive treatment No individual laboratory parameter was of value in determining prognosis, although of the eight (27 per cent) horses from which bacteria were identified in the initial peritoneal fluid by Gram stain, four (50 per cent) were subsequently killed

A review of research on equine locomotion and biomechanics

Abstract: A review of the literature about equine locomotion and biomechanics is presented to summarise available knowledge and provide perspective to current and proposed research programmes. It is evident that much past research has failed to provide sufficient information on basic principles of these two disciplines and that information is now required before progress can be made on more applied research topics. However, useful contributions have been made in gait typology, analysis of racetrack surface and design and limb kinetics, kinematics and coordination.

Sweet itch: responses of clinically normal and affected horses to intradermal challenge with extracts of biting insects.

Abstract: Summary In a study of the skin reactivity of horses with lesions of sweet itch, six clinically normal horses and seven affected horses were challenged intradermally with extracts of Culicoides, Stomoxys, Tabanidae and Culex species. All the affected horses and three of the normal horses responded strongly to the culicoides extract. The skin reactions in the affected horses reached their maxima within 4 h in the majority of animals. Skin reactivity to culicoides was transferred to normal horses with serum from affected animals confirming that the reaction was an immediate hypersensitivity reaction. Three of the seven affected animals gave both immediate and delayed reactions when challenged with the culicoides extract. When the dermal reactions of 12 clinically normal and 10 affected horses were compared at 20 mins and 1 h after challenge, the reactions produced by the culicoides extract were significantly (P<0.025) greater in the affected than in the normal horses. Individual horses gave strong reactions to extracts of Stomoxys, Culex and Tabanidae species, but no consistent response was evident among the affected animals. Serum from horses with sweet itch sensitised the skin of normal horses to challenge with extracts of the biting flies and the transferred antibodies remained bound to the skin of the recipient horse for 72 h or longer. Although some variation among the affected horses occurred in passive transfer experiments, the response to Culicoides species extracts was consistently greater than for the other insect extracts tested. Resume Pour etudier la reactivite cutanee des chevaux atteint de dermite estivale recidivante, six chevaux normaux et sept malades furent intradermo inocules avec des extraits de Culicoides, de Stomoxys, de Tabanides et de Culex. Tous les chevaux malades et trois des chevaux normaux reagirent fortement a l'extrait de culicoides. Les reactions cutanees maximales furent atteints en moins de 4 heures chez la plupart des chevaux malades. La sensibilite cutanee aux culicoides fut conferee aux chevaux sains par l'administration de serum de chevaux malades. Cela confirmait l'existence d'une reaction immediate d'hypersensibilite. Trois des sept chevaux malades presenterent deux reactions aux extraits de culicoides, l'une immediate et l'autre differee. Lorsqu'on compara les reactions dermiques de 12 chevaux normaux et de 10 chevaux malades, 20 minutes, puis 1 heure apres l'injection declenchante, on observa que les reactions produites par l'extrait de culocoides etaient plus importantes de maniere significative (P<0.025) chez les chevaux malades. Certains chevaux eurent des reactions individuelles marquees aux extraits de Stomoxys, Culex et Tabanides, sans qu'aucune reaction ne puisse etre consideree comme interpretable. Le serum preleve sur des chevaux atteints de dermite estivale sensibilise — rait la peau des chevaux normaux a l'injection d'extraits de mouches piqueuses; les anticorps ainsi transferes restaient presents dans la peau des receveurs 72 heures et plus. A quelques variations pres constatees durant ces experiences d'immunosite passive conferee, on constatait une reponse immunitaire plus forte avec les extraits de Culicoides qu'avec les extraits provenant des autres especes utilisees. Zusammenfassung Anlasslich einer Untersuchung der Hautempfindlichkeit von Pferden mit Sommerekzemlasionen (“Sweet Itch”) wurden sechs klinisch gesunde und sieben erkrankte Pferde provoziert mit Extrakten von Culicoides, Stomoxys, Tabaniden und Culex sp. Alle kranken und drei normale Pferde reagierten stark auf Culicoidesextrakt. Die Hautreaktionen der erkrankten Tiere erreichten ihr Maximum innert vier Stunden bei der Mehrheit der Pferde. Die Hautreaktivitat gegen Culicoides konnte mit Serum kranker Pferde auf normale ubertragen werden, ein Beweis, dass es sich um eine Sofortreaktion handelt. Drei der sieben erkrankten Pferde wiesen sowohl Sofortreaktionen wie auch verzogerte Reaktionen gegen Culicoidesextrakt auf. Die Hautreaktionen von 12 klinisch gesunden und 10 erkrankten Pferde wurden 20 Minuten und 1 Stunde nach der Exposition verglichen; die Reaktionen gegen Culicoidesextrakt erwiesen sich bei affizierten Tieren als signifikant starker (p<0.025) als bei normalen Pferden. Einzeltiere reagierten heftig gegen Stomoxys-, Culex- und Tabanidenextrakte, aber es liess sich keine konsistente Antwort herauslesen. Serum von Pferden mit Sommerekzem vermochte die Haut normaler Pferde gegen Extrakte von Stechfliegen zu sensibilisieren und die ubertragenen Antikorper blieben wahrend 72 Stunden oder langer in der Haut nachweisbar. Obgleich eine gewisse Variation unter den erkrankten Pferden in diesen passiven Uebertragungsversuchen festzustellen war, ubertraf die Reaktion gegen Culicoidesextrakt immer diejenige gegen andere Insektenextrakte.

Guidelines for the future of equine locomotion research.

Abstract: Summary This paper describes the major areas that require investigation in equine locomotion and outlines a plan for such research in both the Thoroughbred and Standardbred. Fifteen topics for future investigation have been selected and given an order of priority. These topics deal with characteristics of normal locomotion, factors which influence locomotion, the epidemiology and economics of lameness and the clinical identification of lameness. Resume Cet article etudie les domaines principaux de la locomotion equine ou une recherche est necessaire. Un plan d'investigation est esquisse tant pour le pur sang que pour le trotteur. Quinze sujets propres a une recherche future sont selectionnes et hierarchises par priorite. Ces topiques concernent la locomotion normale; les facteurs qui influencent la locomotion, l'epidemiologie, les consequences economiques des boiteries, enfin l'identification clinique des boiteries. Zusammenfassung Dieser Artikel beschreibt Gebiete, die eine weitere Erforschung der Fortbewegung des Pferdes bonotigen. Es wird ein Plan fur derartige Forschungsarbeiten bei Vollblutern und amerikanischen Trabern vorgelegt. 15 Themen fur eine zukunftige Bearbeitung wurden ausgewahlt und in eine Prioritatsreinhenfolge eingestuft. Diese Themen umfassen Charakteristika der normalen Fortbewegung, Faktoren, die die Bewegungsablaufe beeinflussen, die Epidemiologie und wirtschaftliche Probleme von Lahmheiten und die klinische Erhebung von Lahmheit.

Chronic obstructive pulmonary disease in the horse 1: Nature of the disease

Abstract: The aetiology, pathophysiological changes, pathology and clinical signs of the disease as presently understood are discussed. The condition appears to be a hypersensitivity of the respiratory system in some horses to poor quality hay and straw. Micropolyspora faeni is the chief agent identified in the northern part of the United Kingdom. In other locations, the chief agent is probably different. The principal changes are spasm of the airways and bronchiolitis of the small airways. Onset may be acute or insidious. The chief clinical signs are well known but the disease process is reversible if the source of the antigen is removed. In early cases, determination of increased maximum intrathoracic pressure changes and co-existent subnormal arterial oxygen pressure are the best objective confirmation of diagnosis. The same measurements may be made on asymptomatic horses if they have been challenged 4 to 5 h earlier by inhalation of the appropriate antigen, or even exposed to poor quality hay or straw. Other methods available to the clinician are discussed.

An energetic basis of equine performance.

Abstract: Summary Although different physiological and behavioural attributes are needed for various types of equine competition, successful racing depends primarily on the animal's metabolic ability to convert chemical energy to mechanical energy — the function of muscle. Components of these energetic processes include the rate, efficiency and interaction of aerobic and anaerobic metabolism in muscle and the supply and utilisation of fuel. In anaerobic work like racing, fatigue processes may be largely regarded as a function of an intramuscular fuel (phosphogen) depletion, despite the fact that substrates are supplied via the circulation. Physical work capacity in the horse depends then mainly on the rate of aerobic metabolism and the capacity of the anaerobic processes to supply energy for continued muscle contraction. Underlying these processes are physiological limitations of the cardiovascular system and the ultrastructure and biochemistry of muscle. A model is proposed whereby prediction of equine performance is based entirely on parameters of energy metabolism. Resume Des aptitudes physiologiques et des qualites de comportement sont necessaires pour satisfaire aux exigences variees de la competition equine. Nonobstant ceci le succes en course depend d'abord de l'aptitude metabolique de l'animal a convertir l'energie chimique en energie mecanique: c'est le role des muscles. Les facteurs de ces phenomenes energetiques sont en particular la rapidite l'efficacite et les interactions des metabolismes aerobies et anaerobies dans le muscle; aussi l'alimentation et l'aptitude a utiliser les sources d'energie. Dans une activite anaerobic telle que la cour se, les phenomenes de fatigue peuvent etre consideres comme dependant largement d'un appauvrissement des sources musculaires d'energie (phosphogene); ceci en depit des apports energetiques du systeme circulatoire. L'aptitude du cheval au travail physique depend donc beaucoup de la rapidite du metabolisme aerobic et de la capacite des phenomenes anaerobics a fournir l'energie pour la contraction musculaire. Mais le muscle — dans sa structure profonde et dans sa biochimieet le systeme cardiovasculaire comportent des limites physiologiques. On propose un modele pour lequel la prevision des performances est fondee sur des parametres du metabolisme energetique. Zusammenfassung Obgleich verschiedene physiologische und verhaltensbestimmende Attribute fur die verschiedenen Zweige des Pferdesports notwendig sind, kann man festhalten, dass Erfolge im Rennsport vor allem abhangen von der Fahigkeit des Tieres, chemische Energie in mechanische zu verwandeln: die Funktion der Muskulatur. Diese energetischen Vorgange setzen sich zusammen aus der Geschwindigkeit, der Effizienz und der Interaktion aerober und anaerober Stoffwechselprozesse im Muskel und der Versorgung und Verbrennung von Brennstoff. Wahrend einer anaeroben Arbeit (Rennen) konnen Ermudungserscheinungen vor allem als Funktion einer intramuskularen Brennstoffunterversorgung (Phosphogen) angesehen werden, trotz des Umstandes, dass Substrate uber die Zirkulation zur Verfugung gestellt werden. Die physikalische Arbeitskapazitat des Pferdes hangt vornehmlich ab von der Umsatzgeschwindigkeit des aeroben Metabolismus und von der Kapazitat der anaeroben Prozesse, Energie fur die kontinuierliche Muskelkontraktion zur Verfugung zu stellen. Physiologisch begrenzt werden diese Vorgange durch das cardiovaskulare System, die Ultrastrukturen und die Biochemie des Muskels. Es wird ein Modell vorgestellt, das eine Leistungsvoraussage allein auf der Grundlage von Parametern des Energiestoffwechsels erlauben soll.

Leptospiral infection in aborted equine foetuses

Abstract: During an investigation of equine abortion, leptospiral infection was demonstrated in nine out of 22 foetuses examined by immunofluorescence and culture. Strains belonging to four serogroups (Australis, Pomona, Hebdomadis and Icterohaemorrhagiae) were isolated. The age of leptospira infected foetuses ranged from six months to term.

Aspects of the pathology of stifle bone cysts in the horse

Abstract: The gross and histological appearance of subchondral bone cysts in six Thoroughbred or partbred horses is described. The lesions were all situated in the centre of the medial femoral condyle and were not associated with any other damage to the articular surface of the femorotibial or femoropatellar joints. In three cases the cysts were unilateral but had an early non-cystic lesion present in the opposite stifle. All the cysts had a narrow channel at their distal extremity which communicated with the femorotibial joint. The more recently developed ones were fluid filled and contained fibrous strands, while those in the older horses contained dense fibrotic detritus. No signs of significant ossification of the cysts were detected. The likely pathogenesis of these lesions is discussed in the light of the pathological findings.

Treatment of equine cutaneous neoplasia by radiotherapy using iridium 192 linear sources.

Abstract: The treatment of equine cutaneous tumours by conventional or cryosurgical techniques can be limited where the position of the tumour makes radical excision or freezing impractical or dangerous. Radiotherapy provides an effective and practical alternative. The use of iridium pins with guide needles allows accurate positioning of sources and uniform radiation fields to be achieved. The subsequent removal of the pins reduces the period of incapacity and reduces the radiation risk when compared to permanently implanted sources. Twenty-seven tumours on 26 horses were treated by this method with a 100 per cent success rate after a single irradiation. The technique of implantation is described and the criteria used to select cases and to assess the efficacy of this treatment are discussed.

Nutrition and performance of racing Thoroughbreds

Abstract: Summary Performance records for all the races (563) run by all of the three- and four-year-old Thoroughbreds (171) which were stabled by seven trainers at the same racetrack were obtained for the entire autumn 1979 season. Data on distance of race, time to finish (secs), place of finish and relative place of finish (“performance index”) were fitted to a nested model. Weighted average estimates of the variance of time to finish among horses was 2.31 secs2 and of time to finish among races by individual horses was 2.06 secs2. These data suggest that the variability of an individual's speed from race to race was similar to the variability in average speed from horse to horse. Weighted average estimated variances of the place of finish among horses and among races, and of the “performance index” among horses and among races were 2.63, 5.19, 0.03 and 0.06 respectively. Regression analysis indicated that less than 25 per cent of the variation in relative place of finish (and therefore success) was directly attributable to differences in speed. Feeding regimes were also recorded. All trainers fed oats and concentrate mixtures, some added small quantities of additional energy or protein supplements and all fed timothy or timothy-clover hays. Total daily feed intake ranged from 13.3 to 18.6 kg as fed (2.7 to 3.7 per cent of body weight). Grains provided 34 to 52 per cent of the total ration, 43 to 59 per cent of the digestible energy (DE) intake and 39 to 64 per cent of the crude protein (CP) intake. DE intake averaged 163.2 MJ per 500 kg body weight. This may or may not exceed the National Research Council's recommendations, depending on definitions of energy expenditure. CP intake averaged 1,686 g, 270 per cent of NRC recommendations. DE and CP intakes were positively correlated with time to finish. Depending on the race distances, average times to finish increased by 1 to 3 secs for every 1000 g of CP ingested in excess of NRC recommendations. It may be advisable to decrease the protein concentration of the high energy rations fed to racing Thoroughbreds. Resume On a etudie les 563 performances en course de 171 chevaux, des Pur Sang de 3 et 4 ans stationnes chez sept entraineurs sur le meme champ de course durant la saison 1979. Des donnees parmi lesquelles la distance courue, le temps a l'arrivee exprime en secondes, la place a l'arrivee et la place corrigee a l'arrivee (indice de performance) ont ete comparees a une reference etalon. La variance entre les temps des chevaux a l'arrivee etait de 2.31 secondes2. La variance entre les temps a l'arrivee d'une course a l'autre pour chaque cheval etait de 2.06 secondes2. Les indications montrent que les variations dans la vitesse d'un individu d'une course a l'autre sont semblables aux variations de la vitesse moyenne d'une cheval a l'autre. Les variances moyennes pour les places a l'arrivee d'un cheval ' l'autre et d'une course a l'autre par chaque cheval, l'indice de performance entre les chevaux et d'une course a l'autre furent respectivement de 2.63, 5.19, 0.03 et 0.06. La regression lineaire indiquait que les differences relatives des places a l'arrivee dependaient de la vitesse pour moins de 25 pour cent. Les regimes alimentaires ont eteetudies. Tous les entraineurs utilisaient l'avoine et des melanges concentres et pour certains un supplement energetique ou protidique; tous distribuaient un foin de fleole ou d'un melange fleole — trefle. En poids la quantite d'aliment absorbee variait de 13.3 kg a 18.6 kg (2.7 a 3.7 pour cent du poids de l'animal). Les cereales representaient 34 a 52 pour cent du poids total de la ration; 43 a 59 pour cent de l'energie digestible absorbee, 39 a 64 pour cent des proteines brutes absorbees. L'energie digestible etait de 163.2 MJ pour 500 kilos vifs. Cette valeur depasse plus ou moins les recommandations du NRC selon la definition qu'on retient pour les depenses energetiques. La quantite ingeree de proteines brutes, en moyenne 1.686 g, representait 270 pour cent du taux recommande par le NRC. On trouva une relation entre le temps a l'arrivee et les quantites d'energie digestible et de proteines brutes ingerees. Bien que variani avec la distance parcourue, on trouva que le temps a l'arrivee augmentait de 1 a 3 secondes pour chaque 1000 g de proteines absorbees en exces des recommendations du NRC. Il semble donc judicieux de diminuer la concentration proteinique des rations tres energetiques distribuees aux Pur Sang. Zusammenfassung Die Leistungsausweise fur alle Rennen (563), die von allen 3- und 4-jahrigen Vollblutern (171) bestritten worden waren, konnten fur die vollstandige Herbstsaison 1979 ausgwertet werden. Die Pferde wurden von sieben Trainern im selben Trainingszentrum betreut. Die Daten uber die Renndistanzen, die im Finish gemessenen Zeiten, Placierung und relativer Platz im Finish (“Leistungsindex”) wurden einem mathematischen Modell angepasst. Der gewichtete mittlere Schatzwert der Varianz der “Finishzeiten” zwischen den Pferden betrugen 2.31 sec2 und zwischen den Rennen fur die individuellen Pferde 2.06 sec2. Dieses Resultat lasst annehmen, dass die Variabilitat der individuellen Geschwindigkeit von Rennen zu Rennen ahnlich ist wie die Variabilitat der durchschnittlichen Geschwindigkeit von Pferd zu Pferd. Die gleichen Varianzberechnungen fur die Placierung zwischen den Rennen und fur den “Leistungsindex” zwischen Pferden und zwischen Rennen ergaben 2.63, 5.19, 0.03 und 0.06. Die Regressionsanalyse zeigt an, dass weniger als 25 Prozent der Variation fur den relativen Platz im Finish — und deshalb fur den Erfolg — direkt einem Unterschied in der Geschwindigkeit zuzuschreiben warn. Die Futterungsgewohnheiten wurden ebenfalls untersucht. Alle Trainer futtern Hafer und Konzentratmischungen, einige fugen noch kleine Mengen von Energie- oder Proteinsupplementen zu und alle futtern Timothee- oder Thimothee-Klee-Heu. Der tagliche Gesamt-Futterverzehr schwankt von 13.3 bis zu 18.6 kg Futter, d.h. von 2.7 bis 3.7 Prozent der Gesamtration, 43 bis 59 Prozent der verdaulichen Energie (DE) und 39 bis 64 Prozent des Roheiweisses (CP). Die Aufnahme von DE betrug durchschnittlich 163.2 MJ pro 500 kg Korpergewicht, ein Wert, der die NRC-Empfehlungen je nach der Definition der Energieausgabe ubersteigt oder auch night. Der CP-Verzehr betrug im Durchschnitt 1′686 g oder 270 Prozent der NRC-Empfehlungen. DE- und CP-Verbrauch waren positiv korreliert mit der “Finish-Zeit”. In Abhangigkeit von der Renndistanz nahm die “Finishzeit” um 1 bis 3 sec zu pro je 1′000 g Roheiweiss, die uber die NRC-Empfehlungen hinaus verfuttert wurden. Es mag ratsam sein, die Eiweisskonzentration der hohen Energierationen, die dem Vollblutpferd im Training gefuttert werden, zu reduzieren.

Outbreak of ragwort (Senecio jacobea) poisoning in horses

Abstract: Five out of 20 horses (25 per cent) on one farm died from an acute hepatic encephalopathy typical of ragwort toxicosis. Circumstantial evidence implicated pasture rather than hay as the principal source of the toxic alkaloids. Plasma levels of gamma glutamyl transferase (GGT) were determined on three occasions in all surviving ragwort-exposed horses. Elevated GGT levels were a useful early indicator of hepatic damage although not all horses with this biochemical sign developed clinical disease.

Behaviour of Thoroughbred foals during nursing

Abstract: Thoroughbred foals were found to nurse in bouts of nursing activity delimited by intervals of non-nursing activity lasting 27 secs or longer. Nursing activity included nosing, sucking and interval behaviour. During the first week after birth, foals nursed, on average, seven times an hour with a mean bout duration of 147 secs but were not successful at sucking during all nursing bouts. Time spent nursing decreased as the foals grew older until before weaning, at 24 weeks of age, the foals were nursing once an hour with a mean bout duration of 74 secs. The dams hindered their foals' nursing activity in several ways during Weeks 2 and 3 post partum and it was suggested that at this time nursing was painful for the dams.

Biochemical and haematological effects of phenylbutazone in horses.

Abstract: Summary Five matched pairs of horses were used to investigate the effects of phenylbutazone on a range of physiological, biochemical and haematological variables. The drug was given by mouth daily for 15 consecutive days at the manufacturer's recommended dose rates to one group of horses (Group A); the second group (Group B) received equivalent doses of a placebo. For some of the measured parameters, significant changes were recorded in both groups, indicating background instability. Significant decreases in serum total protein, albumin, plasma pH, viscosity and magnesium, and an increase in albumin: globulin ratio occurred in Group A, but not in Group B. These changes were, therefore, attributed to phenylbutazone or its metabolites. Toxicologically, the change in pH is probably unimportant but the decrease in protein concentration may have resulted from a protein losing enteropathy and/or from decreased synthesis in the liver. In one animal which received phenylbutazone, clinical signs of toxicity (lethargy, inappetance, oedema) were observed and evidence of hepatotoxicity and haematological changes were also noted in this horse. It is concluded that recommended dose rates of phenylbutazone should never be exceeded and that the period for which the highest dose (4.4 mg/kg body weight twice daily for four days) is administered should be reduced. In clinical cases, where phenylbutazone toxicity is suspected, measurement of serum or plasma protein concentration might provide an indication of the need to reduce dose levels or stop therapy. Resume Cinq paires de chevaux comparables ont ete utilises pour rechercher les effets de la phenylbutazone sur un ensemble de variables physiologiques, biochimiques, hematologiques. Le medicament fut administrea un groupe de chevaux (Groupe A), par voie orale, chaque jour durant 15 jours consecutifs; on respectait les posologies recommandees par le fabricant. Un second groupe (Groupe B) recut dans les memes conditions un placebo. Pour quelques parametres, des changements significatif furent constates dans les deux groupes ce qui indique une instabilite des conditions fixes de l'experience. Au sein du Groupe A, une diminution significative se produisit pour les proteines totales, pour l'albumine, pour le pH plasmatique, pour la viscosite et pour le magnesium plasmatiques et une augmentation dans le rapport globuline albumines. Les modifications ne se produisirent point au sein du Groupe B. Les changements furent en consequence attribues a la phenylbutazone ou a ses metabolites. Sur le plan toxicologique, la variation du pH est probablement sans importance; l'abaissement de la concentration en proteines peut resulter d'une enteropathie spoliatrice ou (et) d'une synthese hepatique diminuee. Chez un animal recevant de la phenylbutazone, des signes cliniques de toxicite (lethargie, oedeme et inappetence) furent observes; des signes d'hepatotoxicite et des sanguines furent remarques chez ce cheval. On en conclue que les posologies recommandees pour la phenylbutazone ne devraient jamais etre depassees: la periode pendant laquelle la dose maximum est administree (4.4 mg/kg de poids vif deux fois par jour durant 4 jours) devrait etre reduite. Dans les cas ou l'on suspecte une action toxique de la phenylbutazone, la mesure des taux plasmatique ou serique des proteines peut donner une indication sur la necessite de reduire les doses, voire d'interrompre le traitement. Zusammenfassung Funf passende Pferdepaare wurden benutzt, um die Wirkungen von Phenylbutazon auf eine Reihe physiologischer, biochemischer und haematologischer Variablen zu untersuchen. Das Medikament wurde oral taglich wahrend 15 aufeinanderfolgenden Tagen in der handelsublichen Dosis der Gruppe A verabreicht; die Gruppe B erhielt aequivalente Dosen eines Placebos. Fur einige Parameter wurden in beiden Gruppen signifikante Veranderungen registriert, die auf eine naturliche Instabilitat (background instability) hindeuten. Signifikante Abnahmen von Gesamtprotein, Albumin, Plasma-pH, Viskositat und Magnesium und eine Zunahme des Albumin: Globulin Verhaltnisses traten nur in Gruppe A auf. Diese Veranderungen wurden deshalb dem Phenylbutazon oder seinen Metaboliten zugeschrieben. Toxikologisch ist wohl die pH-Aenderung uninteressant, aber die Abnahme der Eiweiss-Konzentration konnte von einer eiweiss-verlierenden Enteropathie und/oder einer unterdruckten Synthese in der Leber herruhren. Bei einem Pferd wurden klinische Anzeichen von Toxizitat (Lethargie, Inappetenz, Oedeme) festgestellt, und Anhaltspunkte fur das Vorliegen einer Hepatopathie, sowie haematologische Veranderungen wurden ebenfalls beobachtet. Es wird gefolgert, dass die empfohlene Dosis von Phenylbutazon nie uberschritten werden darf, und dass die Anwendungsdauer fur die hochste Dosis (4.4 mg/kg Korpergewicht zweimal taglich fur vier Tage) herabgesetzt werden sollte. In klinischen Fallen und Verdacht auf Phenylbutazonvergiftung kann die Messung der Serum- oder Plasma-Eiweisskonzentration Hinweise darauf liefern, dass die Dosis zu reduzieren oder die Behandlung abzubrechen ist.

Serum concentrations of penicillin in the horse after administration of a variety of penicillin preparations

Abstract: Twelve geldings were used to evaluate serum levels of penicillin following the intravenous (iv) and intramuscular (im) injection of benzylpenicillin, im procaine penicillin and im fortified benzathine penicillin, at a variety of dose rates. Blood samples were collected up to 7 h after iv and im benzylpenicillin, up to benzathine penicillin. Results were analysed using an analysis of variance and regression analyses were used to calculate the time taken for the serum penicillin concentration to decline to 0.5 micrograms/ml. As a result of the experiments the following dosage regimes could be recommended for each drug. Benzylpenicillin should be administered im at a dose rate of 10,000 iu/kg at the commencement of treatment. Procaine penicillin should be injected at a dose rate of 15,000 iu/kg every 12 h or 30,000 iu/kg every 24 h. In serious infections 10,000 iu/kg of benzylpenicillin im should be used concomitantly to begin therapy. Fortified benzathine penicillin appears to have little value for antimicrobial therapy in the horse.

Methods for the treatment of twin pregnancy in the mare

Abstract: Within a group of 130 mares which, in the event, carried twin pregnancies, 29 (22.3 per cent) produced their twins following diagnosis of a single palpable follicle at service and a single pregnancy 42 days later. The whole group of 130 twin-pregnant mares gave birth to only 17 live foals (13 per cent). Breeding results for the following season were available for 102 of these mares, when 38 (37 per cent) produced live foals. Thus over the two seasons an average 23 per cent of this group produced live foals. In a second group, comprising 70 mares, twin pregnancy had been diagnosed in all of them by rectal palpation. Five methods of treatment were then applied to five subgroups of mares and 20 (28 per cent) of the 70 mares produced live foals that season. Breeding results for the following season were available for 53 of these mares; 33 (61 per cent) then produced live foals. Thus over the two seasons an average 46 per cent of the treated group produced live foals. The administration of a prostaglandin analogue at less than 35 days of gestation was outstandingly successful as a method of treatment.

Studies on isoxsuprine hydrochloride for the treatment of navicular disease

Abstract: A peripheral vasodilating agent, isoxsuprine hydrochloride, administered as an oral paste, was evaluated to determine its efficacy for the treatment of navicular disease. In a clinical trial, 13 horses with navicular disease were treated at a dose rate of 0.6 mg/kg body weight (bwt) twice daily for periods of six to 14 weeks. Twelve of the horses became completely sound while being treated, although two required a 50 per cent increase in dose. Nine of the horses have remained sound two to 10 months after ceasing therapy. In a controlled randomised double blind clinical trial, 16 horses with navicular disease were assigned to treatment with either a placebo paste or isoxsuprine paste for three weeks and then re-examined. All the horses treated with isoxsuprine showed improvement in gait, with seven of eight horses becoming sound, whereas only two horses treated with a placebo paste showed slight improvement. This difference in response was highly significant (P less than 0.001). To evaluate any physiological and biochemical effects of isoxsuprine, it was administered to five Standardbred geldings at dose rates of 0.6 mg/kg bwt and 1.2 mg/kg bwt. Complete blood counts, routine plasma biochemical parameters, cardinal signs and blood pressure measurements were performed up to 24 h after a single dose. No significant change in any of these parameters was found. To assess the peripheral vasodilatory action of isoxsuprine, infra-red thermography of the lower limb was performed before and up to 8 h after administration to horses. This revealed a significant increase in distal limb temperature which occurred from 90 to 480 mins after isoxsuprine administration. The maximum mean increase in distal limb temperature was 3.1 degrees C and this occurred 4 h after administration of the drug.

Use of an autogenous cancellous bone graft in the treatment of subchondral bone cysts in the medial femoral condyle of the horse.

Abstract: ummary The clinical features, diagnosis and radiological findings of eight cases of a subchondral bone cyst involving the medial condyle of the femur are described. Surgical treatment, which comprised performing an arthrotomy of the femorotibial joint, curetting and packing the cystic cavity with an autogenous cancellous bone graft, is described. Resume On decrit les carateres cliniques, le diagnostic et les observations radiographiques de huit cas de kystes sous chondraux du condyl medial (interne) du femur. Le traitement chirurgical est decrit: il implique une arthrotomie femoro tibiale, le curettage puis le remplissage de la cavite kystique avec un greffon osseux autogene. Zusammenfassung Die klinischen Erscheinungen, die Diagnose und die radiologischen Befunde von acht Fallen mit subchondralen Knochenzysten am medialen Condylus des Femurs werden beschrieben. Die chirurgische Behandlung bestand in einer Arthrotomie des Femoro-Tibialgelenks, Curettage und Auffullen dur Zystenhohle mit autogenem Spongiosamaterial.

Staphylococcus hyicus in skin lesions of horses

Abstract: Staphylococcus hyicus (subspecies hyicus) was isolated as the only pathogenic organism from two independent cases of dermatitis of the lower parts of the limbs (grease heel) in horses. The organism was recovered together with other pathogenic staphylococci from similar conditions in two other horses of different origins. These conditions were characterised by epidermolysis, alopecia and crust formation. They responded quickly to antibiotic treatment. The organism was also isolated from a long standing case of "summer eczema" which healed without antibiotic treatment, and from a horse with dermatophilosis (streptotrichosis, Dermatophilus congolensis infection). Experimentally, Staph hyicus caused epidermolysis, exudation and inflammation in the superficial layers of the skin.

Experimental studies of drug-induced impaction colic in the horse

Abstract: Summary Colic was induced in horses and ponies following topical or intravenous (iv) administration of amitraz, a formamidine acaricide. The condition was characterised by rapid cessation of intestinal sounds, stasis, extensive impaction and tympany throughout the large colon. Three animals that were necropsied had a faecalith obstructing the proximal small colon aboral to marked colonic impaction. A reproducible and reversible impaction colic syndrome could be induced by an iv injection of 1 mg amitraz/kg body weight in solvent. There were immediate central nervous system and intestinal signs. Large intestinal contents dried out rapidly, possibly indicating enhanced fluid absorption. The effects could be attributed to amitraz rather than to one of its known metabolites and was not shown by other formamidines. The action of amitraz in the horse is unclear. It could involve the mediation of neuromodulators (from the intrinsic enteric nervous system) which affect the coordination of myoelectrical activity from putative pacemaker regions in the large intestine and, possibly, fluid and ion transport. Naturally occurring impaction colic could have a similar pathogenesis. Drug-induced impaction colic might provide a unique model for studying the pathophysiology of impaired motor activity and ion transport in the equine large intestine. Resume On a provoque des coliques chez des chevaux et des poneys par administration locale ou intraveineuse d'amitraz, une formamidine ascaricide. La crise etait caracterisee par un arret rapide des bruits intestinaux, par une stase, par une surcharge importante et par un tympanisme du grand colon. Trois animaux autopsies avaient une obstruction du grele par fecolithe en amont de la surcharge colique. Un syndrome de coliques par surcharge reversible et reproductible put etre provoque par une injection iv d'amitraz de 1 mg/kg en solution. Les signes nerveux centraux et les signes intestinaux furent immediats. Le contenu du gros intestin se dessecha rapidement suggerant une absorption augmentee de fluide. Les effets purent etre attribues a l'amitraz plutot qu'a l'un de ses metabolites connus; ils ne furent point provoques par d'autres formamidines. L'action de l'amitraz sur le cheval n'est pas claire. Elle peut impliquer la mediation de neuro modulateurs (du systeme nerveux intrinseque de l'intestin). Cela affecterait la coordination de l'activiteemyoelectrique de pacemakers intestinaux et peut etre le transit des ions et des fluides. Les coliques par surcharge d'origine naturelle pourraient avoir une semblable pathogenie. Les coliques par surcharge provoquees par une induction medicamenteuse pourraient constituer un modele. Ce modele servirait a l'etude de la pathophysiologie des alterations motrices et des echanges d'ions dans le gros intestin du cheval. Zusammenfassung Die topische oder intravenose Anwendung von Amitraz, einem Formamidin Akarizid, rief bei Pferden und Ponys Kolik hervor. Die Erkrankung war gekennzeichnet durch die rasche Unterdruckung der Peristaltik gerausche, Stase, ausgedehnte Anschoppung und Tympanie im ganzen grossen Colon. Drei autoptisch untersuchte Pferde wiesen einen Darmstein auf, der das vordere kleine Colon aboral einer deutlichen Colonanschoppung verschloss. Die iv Injektion von 1 mg/kg Amitraz in Losung verursachte eine reproduzierbare und reversible Anschoppungskolik mit unmittelbar eintretenden zentralnervosen und intestinalen Symptomen. Der Inhalt des Dickdarms trocknete rasch ein, moglicherweise eine gesteigerte Flussigkeitsabsorption anzeigend. Diese Auswirkungen konnten dem Amitraz zugeschrieben werden und nicht einem der bekannten Metaboliten, und andere Formamidine rufen sie nicht hervor. Die Wirkungsweise von Amitraz beim Pferd ist unklar. Es konnte die Funktion von Neuromodulatoren im intrinsischen Nervensystem des Darms beeinflussen, die ihrerseits die Koordination der myoelektrischen Aktivitat in Schrittmacherregionen des Dickdarms kontrollieren, und moglicherweise auch den Flussigkeits- und Ionen transport. Die naturlicherweise auftretende Anschoppungskolik konnte eine ahnliche Pathogenese haben. Die medikamenten-induzierte Anschoppungskolik konnte ein einmaliges Modell zum Studium der Pathophysiologie einer gestorten motorischen Aktivitat und eines abnormen Ionentransports im Dickdarm des Pferdes abgeben.