Effect of left-sided valvular regurgitation on mortality and causes of death among a population of middle-aged and older horses.

The effect of left-sided valvular regurgitation (LSVR) on the mortality of middle-aged and older horses was investigated in a prospective cohort study involving 19 yards and 1153 horses. The horses were examined to determine whether they had a cardiac murmur and its type, and their age, sex, breed type and occupation were recorded. They were followed up at intervals of two years by postal questionnaire, and after four years information on 773 horses was available. There was no significant difference in the mortality of the horses with and without LSVR, but small horses had a significantly higher risk of having LSVR than small ponies (odds ratio [OR] 2.33), and older horses were slightly more likely to have LSVR than young horses (OR 1.07). Twenty-nine per cent of the deaths reported by the owners were due to orthopaedic problems, 23.3 per cent to gastrointestinal problems, and only 7.9 per cent to cardiovascular problems. Orthopaedic problems were the main cause of death in the horses, and gastrointestinal problems were the main cause of death in the ponies.

Novel oblique radiographic projection of the temporomandibular articulation of horses.

A novel radiographic projection is described for assessing part of the temporomandibular articulation of horses. It minimises the superimposition of osseous structures of the cranium that limit the usefulness of conventional projections and permits improved imaging in cases of suspected disease.

Platelets in equine recurrent airway obstruction.

Platelets contribute to the pathogenesis of human allergic airway disease. The aim of this study was to compare platelet activating factor (PAF)-induced platelet aggregation and thromboxane (Tx) production, plasma Tx and 5-hydroxytryptamine (5-HT) in ponies with recurrent airway obstruction (RAO), an hypersensitivity to inhaled antigens, and normal ponies, before and after antigen exposure. Plasma 5-HT was significantly higher in ponies with RAO but was not further increased by antigen challenge. There was no difference between PAF-induced platelet aggregation or Tx production, or in plasma Tx before or after challenge. These data suggest there may be a difference between platelet 5-HT uptake in RAO and normal ponies but do not provide evidence of platelet activation following antigen exposure.

Incisional complications following exploratory celiotomy: does an abdominal bandage reduce the risk?

REASONS FOR PERFORMING STUDY: Post operative complications following exploratory laparotomy can be potentially life-threatening, increase post operative morbidity and result in an increase in the length of hospitalisation of the affected individual. No study has evaluated the efficacy of specific strategies to reduce the incidence of post operative incisional complications. HYPOTHESIS: The use of an abdominal bandage following colic surgery through a celiotomy incision would significantly reduce the prevalence of post operative incisional complications. METHODS: A controlled, randomised clinical trial to test the hypothesis was devised. Horses eligible for inclusion in the study were assigned randomly either to the study or control group following recovery from general anaesthesia. Any post operative incisional complications occurring during hospitalisation were recorded. Long-term follow-up was obtained via telephone questionnaires. Absolute risk reduction (ARR) and number needed to treat (NNT) were calculated. Multivariable analyses were conducted for all outcomes of interest. RESULTS: There was an ARR of the likelihood of developing a post operative incisional complication of 45% when using compared to not using an abdominal bandage in the post operative period. Therefore, it would be necessary to treat 2.2 horses with an abdominal bandage in order to prevent one horse developing any post operative incisional complications. CONCLUSIONS: Although incisional complications continue to be a problem following an exploratory celiotomy for colic, the proportion of horses affected was significantly reduced by use of a bandage. POTENTIAL RELEVANCE: Using an abdominal bandage following an exploratory laparotomy may help reduce the prevalence of post operative incisional complications, and prevent the development of potentially life-threatening complications.

Ultrasonographic assessment of the atlanto-occipital space in healthy Thoroughbred foals and Thoroughbred foals with neonatal maladjustment syndrome.

Ultrasonography of the atlanto-occipital (AO) space may be useful as a non-invasive diagnostic tool in neonatal foals. The aims of the study were establish a range of values for ultrasonographic measurements of the AO space in healthy Thoroughbred foals and to compare these variables in healthy foals with foals diagnosed with neonatal maladjustment syndrome (NMS). Ultrasonography of the AO space was performed on 38 healthy Thoroughbred foals and 28 Thoroughbred foals with NMS≤4days of age. Transverse image spinal cord height (P=0.001), width (P<0.001) and spinal cord cross sectional area (P<0.001), and longitudinal image dorsoventral diameter of the ventral spinal artery, were significantly smaller in foals with NMS than in healthy foals. Ratios of spinal canal to cord width and cross sectional area were significantly smaller in healthy foals than in foals with NMS (P<0.001). Spinal canal variables were not significantly different between groups. Several ultrasonographic measurements of the AO space were significantly different between healthy foals and foals with NMS. Further investigation is warranted to investigate the clinical application of this technique.

The effect of mare obesity and endocrine function on foal birthweight in Thoroughbreds.

BACKGROUND: Birthweight of Thoroughbred foals has increased in recent years. It is unknown whether this is associated with increased broodmare obesity or endocrine dysfunction. OBJECTIVES: To determine insulin, leptin and triglyceride concentrations in Thoroughbred mares throughout gestation and investigate their association with obesity and foal birthweight. STUDY DESIGN: Cohort study. METHODS: A total of 66 mares were included from 40 days post-breeding. Body condition score (BCS), weight and blood samples were obtained every 60 days throughout gestation. Serum/plasma insulin, leptin and triglyceride concentrations and foal birthweight were recorded. Associations between hormone/triglyceride concentration with BCS, stage of gestation and birthweight were analysed using a linear mixed effects model. RESULTS: Serum insulin concentrations were greater at 1-60 days (4.31 µiu/mL) compared with 241-300 days (3.13 µiu/mL) and 61-120 days (5.33 µiu/mL) compared with 181-240, 241-300 and 301-360 days (3.78, 3.13, 3.37 µiu/mL) gestation (P<0.05). There was no significant hyperinsulinaemia and no association of insulin concentration with BCS. Leptin concentration was greater at 181-240 days (2.28 µg/L, P<0.0001) compared with all other time points and correlated with BCS (P<0.0003). Triglyceride concentration was greater at 241-300 days (0.245 mmol, P<0.02) compared with earlier time points, but was not associated with BCS. Foal birthweight was weakly positively correlated with BCS (r = 0.13, P<0.001) and inversely correlated with leptin concentrations at 61-120 and 241-300 days gestation (r = -0.64, P<0.05). MAIN LIMITATIONS: Reduction in sample size over the study and tight clustering of BCS. CONCLUSIONS: Mare BCS correlated with foal birthweight; obese mares had heavier foals. Significant hyperinsulinaemia was not identified in this population. Increased leptin concentration in early and late gestation was associated with decreased foal birthweight. Further work is required to establish whether leptin concentration in late gestation could predict foal birthweight.

What is the likelihood that a horse treated for septic digital tenosynovitis will return to its previous level of athletic function?

REASONS FOR PERFORMING STUDY: Septic digital tenosynovitis is a serious problem in the horse, with a poor prognosis being reported for recovery. HYPOTHESIS: The occurrence of septic digital tenosynovitis would significantly reduce the likelihood of a horse returning to its previous level of athletic function. METHODS: Medical records of 90 horses treated for septic digital tenosynovitis were reviewed. Data retrieved included age, sex, location of inciting cause of sepsis, time from onset of clinical signs to presentation for treatment, and whether the horse survived to be discharged. Long-term outcome was determined through telephone questionnaires. Univariate analyses of categorical variables were conducted for each outcome. RESULTS: Overall, 87.8% of horses (79/90) survived to be discharged from the hospital. Only one factor examined was shown to have a significant effect on outcome. A delay of 1-7 days between onset of clinical signs and presentation for treatment reduced significantly the likelihood of the horse surviving to be discharged from the hospital. Of the horses discharged from the hospital, long-term follow-up was available for 72 horses, with 54.2% (39/72) returning to their previous level of athletic function. CONCLUSIONS: Only approximately 50% of horses treated for septic digital tenosynovitis returned to their previous level of athletic function following resolution of synovial sepsis. POTENTIAL RELEVANCE: Accurate figures allowing a realistic assessment of the athletic future of a horse following treatment for septic digital tenosynovitis are of value to both the owner and treating veterinarian.

Demonstration of regional differences in equine ventricular myocardial velocity in normal 2-year-old Thoroughbreds with Doppler tissue imaging.

REASONS FOR PERFORMING STUDY: Doppler tissue imaging (DTI) is a novel noninvasive method by which myocardial velocity can be assessed directly and it allows regional, rather than global, cardiac function to be evaluated. HYPOTHESIS: That regional differences in myocardial velocities exist within the equine ventricle. OBJECTIVES: To develop a repeatable examination technique for DTI in horses, describe DTI findings in various regions of the normal equine ventricle, compare colour (CDTI) and spectral (SDTI) techniques of DTI, and document regional differences in myocardial velocity. METHODS: Five regions of the ventricles (right ventricular wall, interventricular septum and left, right and caudal regions of the left ventricle) were evaluated using SDTI and CDTI in 20 clinically normal Thoroughbreds age 2 years. Individual repeatability of the method was determined by examination of one 6-year-old Thoroughbred on 6 occasions. RESULTS: Three major movements were observed in the ventricular walls in systole, early diastole and late diastole. The interventricular septum had a complex pattern of movement. The left region of the left ventricle and interventricular septum had the most rapid movement. The individual repeatability of CDTI was poor, while in systole and early diastole, but not late diastole, SDTI produced repeatable estimates of maximal myocardial velocity. The different velocity estimates obtained with SDTI and CDTI are not interchangeable. Regional differences in the peak mean and maximal myocardial velocities were found in systole and early diastole (P<0.05), but were not identified in late diastole. CONCLUSIONS: The SDTI modality appears to produce the most repeatable data. There are regional differences in myocardial velocity within the equine ventricles for systole and early diastole. POTENTIAL RELEVANCE: DTI shows potential as a tool for studying regional myocardial movement both in clinical cases suspected of having myocardial dysfunction and in a research setting. In particular, SDTI offers potential as a direct and noninvasive means to study early diastolic function of the equine ventricles.

Factors associated with the wastage and achievements in competition of event horses registered in the United Kingdom.

The aims of this study were to estimate the wastage of horses registered for eventing in Britain, to investigate the reasons for this wastage and to evaluate factors affecting the horses' achievement of grade I status (at least 61 points) while registered. An analysis of the database of the British Eventing register found that 33.7 per cent of horses registered for the first time in 1999 were not re-registered for eventing in subsequent years. By using multivariable logistic regression analysis, it was shown that horses that were kept at an event yard were more likely to be re-registered than those kept on other premises (odds ratio [or] 2.0, 95 per cent confidence interval [ci] 1.2 to 3.2), and those that took part in showjumping while registered were also more likely to be re-registered (or 1.5, 95 per cent ci 1.1 to 2.2). Horses that took part in unaffiliated eventing while registered were less likely to be re-registered the following year (or 0.7, 95 per cent ci 0.5 to 0.9), as were those that were not insured (or 0.7, 95 per cent ci 0.5 to 1.0) and those from outside the British Isles (or 0.6, 95 per cent ci 0.3 to 1.0). Veterinary problems were the most commonly cited explanation (35.1 per cent) why horses that remained in their original ownership were not re-registered with British Eventing the following year. Horses from Australia were more likely to achieve grade I status than horses from the British Isles (or 9.7, 95 per cent ci 7.1 to 13.2), as were horses from New Zealand (or 6.4, 95 per cent ci 5.0 to 8.2), the usa (or 5.2, 95 per cent ci 3.8 to 7.2) and France (or 2.8, 95 per cent ci 2.1 to 3.7), but horses from the Netherlands (or 0.5, 95 per cent ci 0.3 to 0.9) and Belgium (or 0.3, 95 per cent ci 0.1 to 0.9) were less likely to achieve grade I status. Mares were less likely to achieve grade I status than geldings (or 0.4, 95 per cent ci 0.4 to 0.5).

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

REASONS FOR PERFORMING STUDY: The birthweight of Thoroughbred foals has increased in recent years. It is unknown whether this is associated with increased broodmare obesity or endocrine dysfunction. OBJECTIVES: To determine insulin, leptin and triglyceride concentrations in obese and non-obese Thoroughbred mares throughout gestation and to investigate their association with foal birthweight. STUDY DESIGN: Prospective, cohort study. METHODS: Fifty-seven pregnant Thoroughbred mares were included in the study. From 40 days post-breeding, body condition score (BCS), weight and venous blood samples were obtained every 60 days throughout gestation. Feed was withheld for 6 h before blood sampling. Serum/plasma insulin, leptin and triglyceride concentrations were measured using validated/standard methods. Foal birthweight was recorded. Association of hormone or triglyceride concentration with time, BCS and birthweight were analysed using a linear mixed effects model. A Pearson correlation co-efficient was calculated between hormone or triglyceride concentration, BCS and birthweight. RESULTS: Serum insulin concentrations were significantly greater (P<0.05) at 0-59 days compared with 240-299 days and at 60-119 days compared with 180-359 days gestation. 55% of mares had BCS ≥ 7. There was 1.5% incidence of fasting hyperinsulinaemia throughout gestation and no association of fasting insulin concentration with BCS. Leptin concentration was significantly (P<0.0001) greater at 180-239 days compared with all other time points and was significantly (r = 0.29, P<0.0003) correlated with BCS. Triglyceride concentration was significantly (P<0.02) greater at 240-299 days compared with earlier time points but was not associated with BCS. Foal birthweight was significantly positively correlated with BCS (r = 0.13, P<0.001) and inversely correlated with leptin concentration at 60-119 days and 240-299 days gestation (r = -0.64, P<0.05). CONCLUSIONS: Mare BCS correlated with foal birthweight such that obese mares had heavier foals. Significant fasting hyperinsulinaemia was not identified in this population. Increased leptin concentration in early and late gestation was associated with decreased foal birthweight and may be useful to predict foal birthweight. Ethical animal research: Informed client consent was obtained for all animals used in the study. SOURCE OF FUNDING: Private donor. Competing interests: None declared.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

REASONS FOR PERFORMING STUDY: Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. OBJECTIVES: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. STUDY DESIGN: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. METHODS: Forty-nine horses treated with quinidine were identified (29 Warmbloods, 20 Thorougbreds, 1 Anglo-Arabian). Details of signalment, history, duration physical examination and echocardiography including left atrial size and presence of mitral regurgitation were retrieved. Clinical details including mean weight, age and left atrial size were compared between clinics using independent samples t test. Association between variables and cardioconversion were evaluated in a backwards logistic regression using Akaike's information criterium (AIC) and odds ratios were calculated. Factors were sex, clinic, breed, mitral regurgitation, duration and poor performance. Covariates were age, weight and the size of the left atrium. Significance was set at 0.05. RESULTS: Fifty-one horses (mean age 8.8 s.d. 4.5 years) were treated with quinidine sulfate, 18 also received digoxin. Eighty per cent converted to sinus rhythm. In 8 horses the known duration was less than 3 months. The only factor associated with successful treatment was the use of digoxin in combination with quinidine sulfate (odds ratio 12.4; 95% CI 2.61 and 91.85 according to AIC analysis). CONCLUSIONS: In this retrospective case series, there is much potential for bias in the data; however, the use of digoxin in addition to quinidine was associated with improved conversion rates regardless of breed even though AF duration was unknown in most horses. Ethical animal research: Research ethics committee oversight not currently required by this conference: retrospective study of clinical records. Explicit owner informed consent for inclusion of animals in this study was not stated. SOURCE OF FUNDING: None. Competing interests: None declared.

A comparison of large-scale Sf9 insect cell growth and protein production: stirred vessel vs. airlift.

A simple and relatively inexpensive stirred-vessel system for the large-scale growth of insect cells (Sf9) is described. Sf9 cell growth in a stirred-vessel fermentor and an airlift fermentor were compared on the basis of maximum cell density and average population doubling time. Also, both fermentor systems were compared with respect to the large-scale production of a recombinant human protein (protein kinase C-eta). No significant differences in Sf9 cell growth or protein expression levels were apparent between the two fermentor systems. However, large differences in cost and scale-up of each system are discussed with respect to the large-scale production of recombinant proteins.

Identification and quantification of amines in the equine caecum.

Acute laminitis has been associated with the release of compounds, as yet unidentified, produced by hindgut fermentation which affect blood flow to the digit. The objectives of this study were to identify amine compounds in equine caecal and colonic contents, some of which are known to have vasoactive properties. In addition, the concentrations of amines in caecal contents of horses fed either grass or hay diets were compared. Fifteen amines were identified in equine hindgut contents in concentrations greater than 1 microM. The caecal concentrations of phenylethylamine, isoamylamine, cadaverine, diaminoheptane and spermidine were significantly higher in horses on spring/summer grass compared with those on winter grass or hay. These data show that many amines are present in the equine hindgut, some of which may have the potential to cause peripheral vasoconstriction if released into the circulation from the gastrointestinal tract.

Microwave thermography: a non-invasive technique for investigation of injury of the superficial digital flexor tendon in the horse.

Microwave thermographs were recorded from 77 normal horses. In 51% the lowest temperature was recorded in the mid-metacarpal region, and in 41% it was in the distal metacarpal region. The mean temperature of the normal limbs ranged from 25.04 to 37.4 degrees C. Maximum temperature differences between symmetrical points in both forelimbs ranged from 0 to 5.33 degrees C and differences in mean limb temperatures between both forelimbs ranged from 0 to 2.91 degrees C. In 48 horses with acute (less than 4 weeks' duration) injury of the superficial digital flexor tendon (SDFT) (36 unilateral, 12 bilateral) and 12 horses with acute injury of the soft tissues of the palmar metacarpal region other than the SDFT (all unilateral) 66% of forelimbs had acute SDFT injury, and 50% of those with other soft tissue injuries, had elevations of the temperature in the mid- or distal metacarpal region. Abnormal values for mean limb temperature, difference in mean limb temperature and maximum temperature difference between locations in opposite forelimbs were detected in 75% of the horses with SDFT injury and in only 16% of the horses with other soft tissue injury. The sensitivity of microwave thermography for the detection of SDFT injury was 81% and the specificity 74%. When 30 horses in National Hunt training were examined weekly for 5 weeks, 2 horses sustained SDFT injury during that period. The microwave thermographs recorded from these 2 horses, at 1 and 2 weeks before the onset of clinical signs, were abnormal. However, 16 horses which did not develop tendon injury also displayed thermographic abnormalities.

Density and binding characteristics of beta-adrenoceptors in the normal and failing equine myocardium.

Beta-adrenoceptors are important regulators of cardiac function and their characteristics are known to change in human and canine diseased myocardium. This study aimed to determine the density and subtypes of beta-adrenoceptors in the normal and failing equine ventricular myocardium. Membrane preparations of the left papillary muscles were incubated with increasing concentrations of the nonselective beta-adrenoceptor antagonist [3H]-CGP12177. Saturable and reversible binding of [3H]-CGP12177 to myocardial membranes was demonstrated with Kd values (+/- s.d.) of 0.49 +/- 0.40 and 0.43 +/- 0.22 nmol/l and Bmax values of 93.4 +/- 20.5 and 110.0 +/- 21.2 and fmol/mg protein for normal (n = 19) and heart failure (n = 10) tissues, respectively. Heart failure had no significant effect on the density of ventricular beta-adrenoceptors. The cardiac beta-adrenoceptors were further characterised by studying displacement of [3H]-CGP12177 (0.6 nmol/l) with the beta1-selective antagonists CGP20712A and the beta2-selective antagonist ICI118.551. In normal ventricular muscle, CGP20712A was 26 times more potent than ICI118.551 (Ki values 30.4 +/- 24.8 and 814.1 +/- 485.2 nmol/l, respectively). In heart failure cases, CGP 20712A curves were monophasic with a Ki value of 45.6 +/- 39.7 nmol/l. ICI 118.551 curves were biphasic in 5 horses where 11-31% of the cardiac beta-adrenoceptors had a high affinity for ICI 118.551. These data suggest that the normal equine ventricular myocardium possesses predominately beta1-adrenoceptors, with no evidence for co-existence of a significant population of beta2-adrenoceptors. The density of beta-adrenoceptors did not appear to change in heart failure, but the appearance of receptors with a high affinity for ICI118.551 may suggest that, in some cases, heart failure increases the expression of beta2-adrenoceptors in equine ventricular myocardium. This study provides an insight into the role of the adrenergic system in heart disease in the horse. Further studies in this area are warranted.

Repeatability of diagnostic ultrasonography in the assessment of the equine superficial digital flexor tendon.

A quantitative investigation of the variation that can occur during the course of ultrasonography of the equine superficial digital flexor tendons (SDFT) was undertaken. The aim of this investigation was to use an objective measure, namely the measurement of CSA, to quantify the variability occurring during the course of the ultrasonographic assessment of the equine SDFT. The effects of 3 variables on the CSA measurements were determined. 1) Image acquisition operator (IAc): two different operators undertaking the ultrasonographic examination; 2) image analysis operator (IAn): two different operators undertaking the calculation of CSA values from previously stored images; and 3) analytical equipment (used during CSA measurement) (IEq): the use of 2 different sets of equipment during calculation of CSA values. Tendon cross-sectional area (CSA) measurements were used as the comparative variable of 3 potential sources: interoperator, during image acquisition; interoperator, during CSA measurement; and intraoperator, when using different analytical equipment. Two operators obtained transverse ultrasonographic images from the forelimb SDFTs of 16 National Hunt (NH) Thoroughbred (TB) racehorses, each undertaking analysis of their own and the other operator's images. One operator undertook analysis of their images using 2 sets of equipment. There was no statistically significant difference in the results obtained when different operators undertook image acquisition (P>0.05). At all but the most distal level, there was no significant difference when different equipment was used during analysis (P>0.05). A significant difference (P<0.01) was reported when different operators undertook image analysis, one operator consistently returning larger measurements. Different operators undertaking different stages of an examination can result in significant variability. To reduce confounding during ultrasonographic investigations involving multiple persons, one operator should undertake image analysis, although different operators may undertake image acquisition.

What is the likelihood that Thoroughbred foals treated for septic arthritis will race?

REASONS FOR PERFORMING STUDY: Septic arthritis is a serious problem in the neonate, with a poor prognosis being reported for recovery. The impact of neonatal septic arthritis on the likelihood that Thoroughbred (TB) foals will start on a racecourse is not known. HYPOTHESIS: The development of septic arthritis in a TB foal significantly reduces the likelihood that it will race when compared to foals from the same dam. METHODS: Medical records of 69 foals treated for septic arthritis were reviewed. The dam's foaling records were reviewed and lifetime racing records were then retrieved for both the affected foals and at least one of their siblings (controls). Outcomes that were statistically evaluated included discharge from the hospital and whether the foal eventually raced. Univariate analyses of categorical variables were conducted for each outcome. The number of affected and unaffected foals that raced at least once were compared using regression analysis. Survival analysis was used to compare age at first race between the study and comparison groups. RESULTS: Foals with septic arthritis were less likely to start on a racecourse compared to controls (odds ratio [OR] 0.28; 95% confidence interval [CI] 0.12-0.62, P = 0.001), while those foals that were discharged from the hospital were also less likely to start on a racecourse compared to controls (OR 036; CI 0.15-0.83, P = 0.008). The presence of multisystem disease was associated with a decreased likelihood of surviving to be discharged (OR 0.13; 95% CI 0.02-0.90; P = 0.005), but did not affect the likelihood that they would start in at least one race if discharged successfully (OR 0.45; 95% CI 0.04-2.81; P = 0.34) compared to the other foals with septic arthritis. Log-rank comparison of survival curves confirmed that foals discharged following treatment for septic arthritis took significantly longer to start in their first race compared to the sibling population (mean age of study group 1757 days, CI 1604-1909; mean age of sibling group 1273 days, CI 1197-1349; P = 0.0006). CONCLUSIONS: The development of septic arthritis in a TB foal significantly reduces the likelihood that it will start on a racecourse when compared to controls. POTENTIAL RELEVANCE: Accurate figures allowing a realistic assessment of the athletic future of a foal following treatment for septic arthritis are of significance for both owner and treating veterinarian.

Equine hepatic disease: the effect of patient- and case-specific variables on risk and prognosis.

REASONS FOR PERFORMING STUDY: Liver disease is fairly common in horses and, although previous literature suggests that fatality rates are high, impressions gained from current clinical practice suggest that this is no longer the case. OBJECTIVES: A case-control study was undertaken in 2 hospitals to investigate whether age, gender or breed type predisposed horses to developing hepatic disease, with the additional aim of determining whether these factors and disease category had any effect on outcome. METHODS: Eighty-eight cases were identified by review of computerised archives at 2 hospitals. Three cases admitted immediately before and after the cases were used as controls. Multivariant models were developed to explore the relationship between age, breed type and gender and the development of liver disease, and within the clinical cases, to identify whether any of these factors or specific forms of liver disease were associated with fatality rate. RESULTS: Ponies were more likely to develop hepatic disease than light riding horses, but neither age nor gender were significant risk factors. Overall, the fatality rate was fairly low; horses with unclassified hepatopathies had the lowest fatality rate and those with cholangiohepatitis, pyrrolizidine alkaloid toxicity and chronic active hepatitis had significantly higher fatality rates in comparison. However, age, breed type and gender had no detectable effect on outcome. CONCLUSIONS AND POTENTIAL RELEVANCE: Such data could be of particular value to equine practitioners, as the cases were drawn from both primary and referral practice, and were all seen within the last 5 years.

The effects of vasoactive amines found in the equine hindgut on digital blood flow in the normal horse.

REASONS FOR PERFORMING STUDY: Disturbances of digital blood flow are thought to be fundamental to the pathophysiology of acute laminitis. However, factors linking the initiating events in the equine hindgut with these disturbances in the foot remain to be determined. HYPOTHESIS: Amine compounds, formed by bacteria in the equine hindgut, have digital vasoconstrictor effects in vivo. METHODS: Tryptamine (1.6 microg/kg/min) and phenylethylamine (2.13 microg/kg/min) were infused i.v. into standing nonsedated horses. Digital blood flow was measured by Doppler ultrasound and foot surface temperature was monitored. Plasma 5-hydroxytryptamine (5-HT) concentrations were measured by HPLC. RESULTS: Tryptamine and phenylethylamine infusions had no effect on systemic arterial blood pressure or heart rate, but caused significant decreases in digital arterial blood flow (mean +/- s.e. 29.2 +/- 8.5 and 18.4 +/- 6.8%, respectively). Both amines also caused decreases in dorsal hoof wall temperature (0.6 +/- 0.1 and 0.5 +/- 0.1 degrees C for tryptamine and phenylethylamine, respectively) and concomitant increases in plasma 5-HT concentration. CONCLUSIONS: Tryptamine and phenylethylamine caused reduction of digital blood flow, effects which may have been mediated, in part, via displacement of 5-HT from platelets. POTENTIAL RELEVANCE: Amine compounds occurring in the equine hindgut, if released into the circulation following carbohydrate overload, could contribute to selective digital vasoconstriction. Further work in ponies and horses, with naturally occurring laminitis, is necessary to determine whether amines represent a therapeutic target in this disease.

Endotoxin-induced digital vasoconstriction in horses: associated changes in plasma concentrations of vasoconstrictor mediators.

REASONS FOR PERFORMING STUDY: Lipopolysaccharide (LPS) infusion reduces digital perfusion, but the mediators responsible remain undetermined. OBJECTIVES: To identify vasoconstrictor mediators released following LPS infusion and relate their appearance in plasma to digital blood flow alterations. METHODS: Blood flow in the lateral digital vessels of 6 Thoroughbred horses, following a 30 min infusion of LPS (E. coli 055:B5; 30 ng/kg), was measured using Doppler ultrasonography. Concomitant measurements of hoof wall and coronary band surface temperatures (HWST and CBST) were made. Serial blood samples were collected and plasma LPS, tumour necrosis factor alpha (TNFalpha), 5-HT, thromboxane B2 (TxB2) and endothelin measured. RESULTS: Plasma LPS concentrations reached a maximum of 13.2 pg/ml during the infusion, followed by an increase in plasma TNFalpha concentration. Digital arterial and venous blood flow decreased by 43 and 63%, respectively; HWST and CBST similarly decreased. Systemic blood pressure remained unaltered. Plasma concentrations of TxB2 and 5-HT increased, coinciding with the onset of digital hypoperfusion. Plasma endothelin concentrations remained unchanged. CONCLUSIONS: The temporal relationship between the onset of digital hypoperfusion and increases in plasma 5-HT and TxB2 concentrations is consistent with these platelet-derived mediators being associated with LPS-induced laminitis. POTENTIAL RELEVANCE: These experimental data support the use of anti-platelet therapy in the prevention of laminitis associated with endotoxaemic conditions.