Detection of equine herpesvirus-1 (EHV-1) in urine samples during outbreaks of equine herpesvirus myeloencephalopathy.

BACKGROUND: Real-time PCR is the diagnostic technique of choice for the diagnosis and control of equine herpesvirus-1 (EHV-1) in an outbreak setting. The presence of EHV-1 in nasal swabs (NS), whole blood, brain and spinal cord samples has been extensively described; however, there are no reports on the excretion of EHV-1 in urine, its DNA detection patterns, and the role of urine in viral spread during an outbreak. OBJECTIVES: To determine the presence of EHV-1 DNA in urine during natural infection and to compare the DNA detection patterns of EHV-1 in urine, buffy coat (BC) and NS. STUDY DESIGN: Descriptive study of natural infection. METHODS: Urine and whole blood/NS samples were collected at different time points during the hospitalisation of 21 horses involved in two EHV-1 myeloencephalopathy outbreaks in 2021 and 2023 in Spain. Quantitative real-time PCR was performed to compare the viral DNA load between BC-urine samples in 2021 and NS-urine samples in 2023. Sex, age, breed, presence of neurological signs, EHV-1 vaccination status and treatment data were recorded for all horses. RESULTS: A total of 18 hospitalised horses during the 2021 and 2023 outbreaks were positive for EHV-1, and viral DNA was detected in urine samples from a total of 11 horses in both outbreaks. Compared with BC samples, DNA presence was detected in urine samples for longer duration and with slightly higher concentration; however, compared with NS, detection of EHV-1 in urine was similar in duration with lower DNA concentrations. MAIN LIMITATIONS: Limited sample size, different sampling times and protocols (BC vs. NS) in two natural infection outbreak settings. CONCLUSIONS: EHV-1 was detected in the urine from naturally infected horses. Urine should be considered as complimentary to blood and NS in diagnosis of EHV-1 infection.

HISTORIAL: PCR en tiempo real es la técnica diagnostica de preferencia para el diagnóstico y control del herpes virus equino­1 (EHV­1) en una situación de brote. La presencia de EHV­1 en torulas nasales (TN), muestras de sangre entera, cerebro, y medula espinal ha sido descrita en forma extensa; sin embargo, no hay informes de excreción de EHV­1 en orina, la detección del patrón de ADN, y el rol de la orina en la propagación vírica durante un brote. OBJETIVOS: Determinar la presencia de ADN de EHV­1 en muestras de orina durante un brote infeccioso natural y comparar los patrones de detección de ADN de EHV­1 en orina, capa leucocitaria (CL) y TN. DISEÑO DEL ESTUDIO: Estudio prospectivo en una infección natural en caballos hospitalizados. MÉTODOS: Muestras de orina y sangre entera/TN fueron recolectadas a distintos tiempos durante la hospitalización de veintiún caballos involucrados en dos brotes de mielo encefalopatía por EHV­1 en 2021 y 2023 en España. PCR a tiempo real cuantitativo fue llevado a cabo para comparar la carga de ADN viral entre muestras de CL­orina en 2021 y muestras TN­orina en 2023. Sexo, edad, raza, presencia de síntomas neurológicos, estatus de vacunación y datos de tratamiento fueron anotados para todos los caballos. RESULTADOS: Un total de diez y ocho caballos hospitalizados durante los brotes de 2021 y 2023 resultaron positivos a EHV­1, y ADN viral fue detectado en muestras de orina en un total de 11 caballos de ambos brotes. En comparación a muestras de CL, la presencia de AND fue detectado por mas largo tiempo y con una concentración ligeramente mas alta; sin embargo, en comparación a TN, la detección de EHV­1 en orina fue similar en tiempo pero demostró menor concentración de ADN. LIMITACIONES PRINCIPALES: Tamaño de muestra limitado, tiempos de muestreo diferentes, y de protocolos (CL vs. TN) en dos situaciones de brotes naturales. CONCLUSIONES: Se detecto EHV­1 en orina de caballos infectados naturalmente. La recolección, no invasive, de orina debería considerarse como un complemento a las muestras de sangre y TN en el control de caballos infectados en situaciones de brote.

Acid base imbalances in ill neonatal foals and their association with survival.

REASONS FOR PERFORMING STUDY: Acid-base imbalances observed in human paediatric patients are associated with outcome. Likewise, neonatal foals may have different acid-base imbalances associated with diagnosis or prognosis. OBJECTIVES: To determine acid-base imbalances by the quantitative method in ill neonatal foals and assess their association with diagnosis and prognosis. STUDY DESIGN: Observational prospective clinical study. METHODS: This study included 65 ill neonatal foals (32 septic, 33 nonseptic) admitted to an equine referral hospital from 2005 to 2011with acid-base parameters determined on admission and a control group of 33 healthy neonatal foals. Blood pH, pCO2 , sodium, potassium, chloride, L-lactate, albumin and phosphate concentrations were determined. Bicarbonate, globulin, measured strong ion difference (SIDm ), nonvolatile weak buffer concentrations (Atot ), base excess and its components were calculated. Analysis of covariance (ANCOVA) and multiple linear regression statistical analyses were performed. Results are summarised as mean ± s.d. for normally distributed variables and median [25-75th percentiles] for non-normally distributed ones. RESULTS: A total of 63% of ill foals had respiratory alkalosis and 58.5% had SIDm acidosis. The combination of both alterations was detected in 21 of 65 ill foals and abnormal pH was found in 24 of 65. Compared with healthy foals, ill foals had significantly lower SIDm (nonseptic 31.6 ± 6.3 [P<0.01] and septic 32.0 ± 6.4 [P<0.01] vs. control 40.3 ± 3.1 mmol/l), potassium (nonseptic 3.5 [3.3-3.8; P<0.01] and septic 3.6 [3.2-4.3; P = 0.01] vs. control 4.2 [3.8-4.5] mEq/l) and higher L-lactate (nonseptic 5.1 ± 4.2 [P = 0.01] and septic 5.0 ± 3.7 [P = 0.03] vs. control 2.5 ± 1.3 mmol/l). Significantly higher L-lactate and venous pCO2 were found in nonsurviving (6.4 ± 3.5 mmol/l [P = 0.04] and 51 ± 13 mmHg [P<0.01]) compared with surviving foals. CONCLUSIONS: The most common acid-base imbalances observed in ill foals were respiratory alkalosis, SIDm acidosis or mixed respiratory alkalosis with strong ion acidosis. Increased venous pCO2 and blood L-lactate concentration were associated with poor outcome.

Association Between Necropsy Evidence of Disseminated Intravascular Coagulation and Hemostatic Variables Before Death in Horses With Colic.

BACKGROUND: Disseminated intravascular coagulation (DIC) is frequent in horses with severe gastrointestinal disorders. Postmortem studies have found fibrin microthrombi in tissues of these horses, but studies relating these histopathological findings with antemortem hemostatic data are lacking. HYPOTHESIS: Antemortem classification of coagulopathy is related to the presence and severity of fibrin deposits observed postmortem in horses with severe gastrointestinal disorders. ANIMALS: Antemortem hemostatic profile data and postmortem tissue samples (kidney, lung, liver) from 48 horses with colic. METHODS: Tissue samples were stained with phosphotungstic acid hematoxylin and immunohistochemical methods for histological examination. A fibrin score (grades 0-4) was assigned for each technique, tissue and horse, as well as the presence or absence of DIC at postmortem examination. D-dimer concentration, prothrombin time (PT), activated partial thromboplastin time (aPTT), and antithrombin (AT) activity, as well as the clinicopathological evidence of coagulopathy, were determined from plasma samples collected 0-24 hours before death or euthanasia. Histologic and clinicopathologic data from the same horses were compared retrospectively. RESULTS: No association was found between antemortem classification of coagulopathy and postmortem diagnosis of DIC based on tissue fibrin deposition. None of the hemostatic parameters was significantly different between horses with or without postmortem diagnosis of DIC. There was no association between horses with fibrin in tissues or different cut-offs for D-dimer concentration and postmortem evidence of DIC. CONCLUSIONS AND CLINICAL IMPORTANCE: Abnormalities of the routine clotting profile, including D-dimer concentration, were not useful in predicting histologic evidence of DIC at necropsy in horses with severe gastrointestinal disorders.

Quantitative motor unit action potential analysis of supraspinatus, infraspinatus, deltoideus and biceps femoris muscles in adult Royal Dutch sport horses.

REASONS FOR PERFORMING STUDY: Reference values for quantitative electromyography (QEMG) in shoulder and hindlimb muscles of horses are limited. OBJECTIVES: To determine normative data on QEMG analysis of supraspinatus (SS), infraspinatus (IS), deltoideus (DT) and biceps femoris (BF) muscles. STUDY DESIGN: Experimental observational study and retrospective case series. METHODS: Seven adult healthy Royal Dutch sport horses underwent quantitative motor unit action potential analysis of each muscle using commercial electromyography equipment. Measurements were made according to published methods. One-way ANOVA was used to compare quantitative motor unit action potential variables between muscles, with post hoc testing according to Bonferroni, with significance set at P<0.05. The QEMG and clinical information from horses with lower motor neuron disorders (n = 7) or myopathy (n = 4) were summarised retrospectively. RESULTS: The 95% confidence intervals of duration, amplitude, phases, turns, area and size index of quantitative motor unit action potential were 8.7-10.4 ms, 651-867 µV, 3.2-3.7, 3.7-4.7, 1054-1457 µV·ms and 1.1-1.5 for SS, 9.6-11.0 ms, 779-1082 µV, 3.3-3.7, 3.8-4.7, 1349-2204 µV·ms and 1.4-1.9 for IS, 6.0-9.1 ms, 370-691 µV, 2.9-3.7, 2.8-4.5, 380-1374 µV·ms and 0.3-1.3 for DT and 5.7-7.8 ms, 265-385 µV, 2.7-3.2, 2.6-3.1, 296-484 µV·ms and 0.2-0.5 for BF, respectively. Mean duration, amplitude, number of phases and turns, area and size index were significantly (P<0.01) higher in SS and IS than in DT and BF muscles. In addition, 4 of 7 normal horses had >15% polyphasic motor unit action potentials in SS and IS muscles. CONCLUSIONS: Differences between muscles should be taken into account when performing QEMG in order to be able to distinguish normal horses from horses with suspected neurogenic or myogenic disorders. These normal data provide the basis for objective QEMG assessment of shoulder and hindlimb muscles. Quantitative electromyography appears to be helpful in diagnosing neuropathies and discriminating these from myopathies.

Plasma Procalcitonin Concentration in Healthy Horses and Horses Affected by Systemic Inflammatory Response Syndrome.

BACKGROUND: The diseases most frequent associated with SIRS in adult horses are those involving the gastrointestinal tract. An early diagnosis should be the goal in the management of horses with SIRS. OBJECTIVE: The objective of this study was to evaluate the plasma procalcitonin (PCT) concentration in healthy and SIRS horses to assess differences between the two groups. ANIMALS: Seventy-eight horses (30 healthy and 48 SIRS). METHODS: Prospective in vivo multicentric study. Horses were classified as SIRS if at least 2 of the following criteria were met: abnormal leukocyte count or distribution, hyperthermia or hypothermia, tachycardia, tachypnea. Healthy horses showed no clinical or laboratory signs of SIRS. Plasma PCT concentrations were measured with a commercial ELISA assay for equine species. Results were expressed as mean±standard deviation. T-test for unpaired data was performed between healthy and SIRS group. SIRS group was divided in 4 subgroups and t-test was performed between healthy versus each subgroup. RESULTS: PCT concentrations in healthy and SIRS horses were 18.28 ± 20.32 and 197.0 ± 117.0 pg/mL, respectively. T-test showed statistical differences between healthy versus SIRS group and between healthy versus all subgroups. CONCLUSIONS AND CLINICAL IMPORTANCE: Results showed an increase in PCT concentration in SIRS horses as previously reported in humans and dogs. PCT could be used as a single assay in equine practice for detection of SIRS.

Metabolic and endocrine profiles in sick neonatal foals are related to survival.

BACKGROUND: Sick neonatal foals suffer from a variety of endocrine and metabolic derangements that may be related to outcome. There are several hepatic and lipid metabolism blood markers that have never been assessed in neonatal foals. OBJECTIVES: Assess panel of endocrine and metabolic variables in group of sick and healthy neonatal foals in order to describe their relationship with diagnosis and survival. ANIMALS: All neonatal foals referred to Unitat Equina-Fundació Hospital Clínic Veterinari during 3 consecutive foaling seasons and a group of healthy foals. METHODS: Observational prospective study. Blood samples were obtained on admission and, when possible, after 24-48 h of hospitalization and immediately before discharge or death. Measured variables were triglycerides, nonsterified fatty acids, glucose, creatinine, urea, γ-glutamyltransferase, glutamate dehydrogenase (GLDH), insulin, cortisol, bile acids, and adrenocorticotropic hormone (ACTH). ACTH/cortisol and glucose/insulin ratios were calculated. RESULTS: Urea, creatinine, and cortisol had median concentrations in septic and nonseptic foals 2- to 8-fold higher than in the control group (P < .001). Median ACTH concentration in the septic group was approximately 4 times higher than in nonseptic and control foals (P < .001). ACTH/cortisol ratio was significantly lower in sick foals compared to control foals (P < .001). A score was designed including creatinine, GLDH, and cortisol. When ≥ 2 of these variables were altered (P < .001), the foal had 32 times more risk of dying (OR, 31.7; 95% CI, 7.7-130.3). CONCLUSIONS AND CLINICAL IMPORTANCE: Plasma creatinine, GLDH, and cortisol should be determined in sick newborn foals on admission because of their association with survival.

Energy expenditure of critically ill neonatal foals.

REASONS FOR PERFORMING STUDY: Nutritional support in critically ill neonatal foals is of great importance given their high metabolic rate and minimal stores of energy and protein. Nutrient requirements of healthy growing foals have been estimated based on daily milk intake; however, little is known about the resting energy expenditure (REE) of sick foals. OBJECTIVES: To determine REE in critically ill neonatal foals (sepsis and/or hypoxic-ischaemic encephalopathy [HIE] and compare this with REE in control foals. METHODS: Critically ill newborn foals admitted to the Fundació Hospital Clinic Veterinari, Universitat Autònoma de Barcelona, Spain from March 2009 to February 2011 were included in this study. Healthy neonatal foals and foals with nonsystemic conditions were used as controls. Oxygen consumption and CO2 production were measured with a respiratory monitor connected to a tight fitting facemask and REE (kcal/kg bwt/day) was calculated with the abbreviated Weir formula. Measurements were performed within 24 h of admission and repeatedly during hospitalisation. RESULTS: Twenty-seven foals were included (16 critically ill foals and 11 controls) and a total of 47 measurements were performed. In the critically ill, REE was reduced (mean +/- s.e. 49.5 +/- 2.1 kcal/kg bwt/day) on admission relative to the controls. In surviving foals (n = 5), REE before hospital discharge was not different (68.4 +/- 7.0 kcal/kg bwt/day) from control foals (64.8 +/- 2.7 kcal/kg bwt/day). CONCLUSIONS: REE was lower in critically ill foals upon admission (40-50 kcal/kg bwt/day) and normalised before hospital discharge (60-80 kcal/kg bwt/day). POTENTIAL RELEVANCE: Critically ill neonatal foals tolerating enteral feeding would receive approximately their REE when given 10% of their bodyweight in mare's milk daily. For sick neonates unable to tolerate enteral nutrition, provision of 50 kcal/kg bwt/day would be a reasonable goal for parenteral nutrition.

Clinical findings in 10 foals with bacterial meningoencephalitis.

REASONS FOR PERFORMING THE STUDY: Bacterial meningoencephalitis is a severe complication in septic foals and there is scarce and often unclear information in the equine literature. OBJECTIVES: To report the most frequent clinical signs, clinicopathological findings, causative agents, treatments given and outcome of a group of foals with confirmed bacterial meningoencephalitis. METHODS: Foals aged < 6 months of age admitted to the Universitat Autonoma de Barcelona (2004-2009) with confirmed bacterial meningoencephalitis were retrospectively included in the study Diagnosis of bacterial meningoencephalitis was made by cerebrospinal fluid (CSF) culture, CSF analysis consistent with bacterial infection, observation of bacteria in CSF cytology or postmortem confirmation. RESULTS: Nine neonates and one 5-month-old foal were included. The most frequently observed clinical signs were alterations in mental status (10/10), recumbency (8/10), weakness (8/10), abnormal pupillary light reflexes (6/10), decreased suckling-reflex (6/9), seizures and/or nystagmus (4/10). Common clinicopathological alterations included hyperfibrinogenaemia (8/9), hyperlactataemia (7/7), and neutropenia (5/10) or neutrophilia (5/10). Most neonates (8/9) developed bacterial meningoencephalitis despite having a sepsis score near the cut-off value (median = 12). On CSF analysis, pleocytosis (9/9), increased total protein concentration (5/6) and intracellular bacteria (6/9) were detected. The most frequently isolated bacterium was Escherichia coil. Once bacterial meningoencephalitis was diagnosed, antimicrobial therapy was switched to third and fourth generation cephalosporins. CONCLUSIONS: The diagnosis of bacterial meningoencephalitis is established based on CSF analysis and culture. Clinical recognition of bacterial meningoencephalitis is difficult and can be easily overlooked. Moreover, severe sepsis is not necessary to develop bacterial meningoencephalitis. POTENTIAL RELEVANCE: CSF analysis should be considered more often in sick newborn foals with signs indicative of central nervous system (CNS) involvement. Cerebrospinal fluid (CSF) cytology and culture would help to confirm or rule out unnoticed bacterial meningoencephalitis, and to choose appropriate antimicrobial therapy

Acid-base imbalances during a 120 km endurance race compared by traditional and simplified strong ion difference methods.

REASONS FOR PERFORMING STUDY: Acid-base disturbances are traditionally assessed using the Henderson-Hasselbach equation. The simplified strong ion approach describes more accurately the complex acid-base and electrolyte abnormalities present in endurance horses. OBJECTIVE: To describe acid-base and electrolytes changes in fit horses competing in a FEI*** 120 km endurance race and to compare the traditional vs. strong ion approaches. METHODS: Thirty horses were initially enrolled in the study. Venous blood samples were obtained before the race (n = 25), at the second (n = 29; 65.4 km) and third vet-gates (n = 23, 97.4 km) and upon race completion (n = 17). Blood gas analysis was performed to determine pH, PCO(2), PO(2), Na(+), K(+) and iCa(++), and calculate HCO(3)(-), base excess and tCO(2). Packed cell volume and total protein, globulin, albumin, lactate, phosphate, glucose and creatinine concentrations, as well as muscle enzymes activities, were also determined. Calculated variables included strong ion difference (SIDm), strong ion gap (SIG) and nonvolatile buffer concentration (A(tot)). A longitudinal linear model using the general estimating equation methodology was used for statistical analysis. RESULTS: Mild but significant increases in PCO(2), SIDm, lactate, plasma protein, globulins and A(tot), as well as a decrease in potassium concentrations were observed from the second vet-gate to race finish when compared to prerace values (P < 0.05). Using the strong ion approach, 67% samples showed acid-base disturbances vs. 70% when using the traditional method, but their interpretations only matched in 24% of measurements. CONCLUSIONS: A complex acid-base imbalance characterised by a mild strong ion alkalosis (hypochloraemia attenuated by hyperlactataemia), nonvolatile buffer acidosis and compensatory mild respiratory acidosis were present in most horses, although pH did not significantly change during a 120 km endurance race. The strong ion approach to interpretation of acid-base balance should be favoured over the traditional approach in endurance horses, given the frequent and complex alterations in PCO(2), SIDm and A(tot) during a race.

Association of admission plasma D-dimer concentration with diagnosis and outcome in horses with colic.

BACKGROUND: Coagulopathies detected in horses with gastrointestinal problems seem to be associated with poor outcome. Plasma D-Dimer concentration is a sensitive test for assessing coagulopathies. HYPOTHESIS: Plasma D-Dimer concentration tested on admission is related to diagnosis and outcome in horses with colic. ANIMALS: Four hundred and ninety three horses referred for evaluation of abdominal pain. METHODS: Prospective observational clinical study. Horses were grouped according to diagnosis (medical and surgical intestinal obstructions, ischemic disorders with and without intestinal resection, enteritis, peritonitis), outcome (survivors, nonsurvivors), and number of coagulopathies (normal profile, 1 or 2 coagulopathies, subclinical disseminated intravascular coagulation [DIC]). Blood samples were collected on admission and plasma D-Dimer concentration, clotting times (PT and aPTT), and antithrombin activity were determined. Positive likelihood ratios (LR+) were calculated for evaluation of D-Dimer cut-off values, which were later tested in a logistic regression model. RESULTS: Horses with enteritis or peritonitis had significantly (P<.001) higher plasma D-Dimer concentrations and more severe coagulopathies on admission than horses with other diagnoses. Nonsurvivors also had significantly (P<.001) higher plasma D-Dimer concentrations at presentation than did survivors, and those horses with subclinical DIC on presentation had an odds ratio (OR) 8.6 (95% confidence interval [CI], 3.3-22.5, P<.001) for nonsurvival. Finally, D-Dimer concentrations>4,000 ng/mL had a LR+ of 5.9 and an OR 8.8 (95% CI, 4.5-17.1, P<.001) for nonsurvival. CONCLUSION AND CLINICAL IMPORTANCE: Plasma D-Dimer concentration measured on admission can be used to facilitate diagnosis and outcome prediction in horses with colic. A potential cut-off value for nonsurvival was found at approximately 4,000 ng/mL.

Low-molecular-weight heparin dosage in newborn foals.

BACKGROUND: Heparin is used in humans as prophylaxis of hypercoagulable states and disseminated intravascular coagulation (DIC). However, babies need a higher heparin dose than do adults. Septic neonate foals are at high risk of hypercoagulable state and DIC, and there is limited objective information about heparin dose for equine neonates. OBJECTIVE: To assess whether neonate foals require higher dosages of low-molecular-weight heparin (LMWH) than adults. ANIMALS: Eighteen healthy and 11 septic neonate foals. METHODS: Experimental and clinical studies. Firstly, healthy foals were randomly distributed in 2 groups, 1 receiving 50 IU/kg SC of dalteparin and the 2nd group receiving 100 IU/kg SC of dalteparin, once daily for 3 days. Blood samples were collected before and 3, 6, 27, and 51 hours after the 1st LMWH administration. Plasma antifactor-Xa activity was measured, together with hemostatic and hematologic parameters used to assess the risk of bleeding. Subsequently, septic foals were treated blindly either with placebo (saline) or 100 IU/kg of dalteparin for 3 days. Plasma antifactor-Xa activity and other hemostatic parameters were determined before and after treatment. RESULTS: Plasma antifactor-Xa activity in healthy foals was below prophylactic activity when using the adult dosage (50 IU/kg), whereas prophylactic activities were achieved when using the double dosage (100 IU/kg). No hemorrhagic events and erythrocyte-related complications were observed with either dosage. In the clinical study, only 4/6 septic foals had plasma antifactor-Xa activity adequate for prophylaxis. CONCLUSIONS AND CLINICAL IMPORTANCE: Equine neonates require higher dosages of LMWH compared with adults to reach prophylactic heparinemia.

Enteral fluid therapy in 108 horses with large colon impactions and dorsal displacements.

To assess the effect of enteral fluid therapy (EFT) in horses with colic, 78 adult horses with colon impactions and 30 with left dorsal colon displacements received an isotonic electrolyte solution via a nasogastric tube at a rate of 8 to 10 l every two hours until resolution of clinical signs. Clinical progression was monitored closely, and plasma biochemistry was evaluated before, during and after treatment. Volume of fluids, time to resolution, and outcome were also recorded. EFT was well tolerated by 102 of 108 horses and was an effective method to resolve 99 per cent of colon impactions and 83 per cent of displacements. For both groups, the mean (sd) time to resolution was 20.2 (5.2) hours and the volume of fluid administered was 118.6 (34.5) l. No relevant abnormalities were observed in most plasma biochemistry parameters during treatment, except for a mild haemodilution effect in 63 per cent of horses.

Effects of oral electrolyte supplementation on endurance horses competing in 80 km rides.

REASONS FOR PERFORMING STUDY: There is no evidence that use of oral electrolyte pastes enhances performance in competing endurance horses. OBJECTIVE: To ascertain whether oral administration of a high dose (HD) of sodium chloride (NaCl) and potassium chloride (KCl) to endurance horses would differentially increase water intake, attenuate bodyweight (bwt) loss and improve performance when compared to a low dose (LD). METHODS: A randomised, blinded, crossover study was conducted on 8 horses participating in two 80 km rides (same course, 28 days apart). Thirty minutes before and at 40 km of the first ride 4, horses received orally 02 g NaCl/kg bwt and 0.07 g KCl/kg bwt. The other 4 received 0.07 g NaCl/kg bwt and 0.02 g KCl/kg bwt. Horses received the alternate treatment in the second ride. Data were analysed with 2-way ANOVA for repeated measures (P<0.05). RESULTS: Estimated water intake was significantly greater with HD both at the 40 km mark and as total water intake; however, differences in bwt loss and speed between HD and LD were not found. Treatment significantly affected serum Na+, Cl-, HCO3, pH and water intake, but not serum K+ or bwt. Serum Na+ and Cl- were significantly higher at 80 km when horses received HD, but no differences were found in early recovery. Venous HCO3- and pH were significantly lower throughout the ride and in early recovery when horses received HD. CONCLUSIONS AND POTENTIAL RELEVANCE: Other than enhancing water intake, supplementing endurance horses with high doses of NaCI and KCl did not provide any detectable competitive advantage in 80 km rides. Further, the elevated serum electrolyte concentrations induced with HD might not be appropriate for endurance horses.

Changes in selected physiological and laboratory measurements in elite horses competing in a 160 km endurance ride.

REASON FOR PERFORMING STUDY: Limited information exists about the physiological changes and clinical problems that occur in elite horses competing in high-speed 160 km endurance races. OBJECTIVES: To provide initial data describing changes in physiological and laboratory measurements in horses competing in a high-speed, 160 km endurance race under temperate conditions and to compare data between horses that successfully completed the race and those that failed to finish. METHODS: Body mass (BM) was measured, blood samples were collected, and veterinary examinations performed on horses before, during, and at the finish of a CEI*** 160 km endurance race. RESULTS: Of 36 horses participating in the study, 22 (61%) completed the race. Twelve horses were eliminated for lameness and 2 for persistent heart rate elevation. Mean speed of finishers was 15.2 km/h. Mean +/- s.d. BM loss of finishers at the end of the race (5.7 +/- 2.6%) was not different (P = 0.58) from BM loss of nonfinishers at elimination (6.7 +/- 34%). Similarly, there were no significant differences in heart rate or veterinary assessment of hydration at the race end for finishers as compared to the elimination point for nonfinishers. PCV increased while sodium, chloride and potassium concentrations decreased with exercise but differences between finishers and nonfinishers were not detected. In contrast, both total and ionised calcium concentrations decreased in successful horses but remained unchanged in nonfinishers. CONCLUSIONS: Elite endurance horses are more likely to be eliminated from competition for lameness than metabolic problems; however, it remains unclear whether these conditions are entirely distinct. The magnitude of the decrease in sodium concentration in both finishers and nonfinishers was greater than in previous reports of 160 km rides. POTENTIAL RELEVANCE: These data should be of use for both organisers and participants in elite 160 km endurance races. The tendency toward hyponatraemia as well as the difference in calcium concentrations between finishers and nonfinishers warrant further study.

An echocardiographic and auscultation study of right heart responses to training in young national hunt thoroughbred horses.

REASONS FOR PERFORMING STUDY: There are few data available to determine the effect of training on cardiac valve function. OBJECTIVES: To investigate the effect of commercial race training on right ventricular (RV) and tricuspid valve function in an untrained group of National Hunt Thoroughbreds (TB). MATERIAL AND METHODS: Cardiac auscultation, guided M-mode echocardiography of the RV, and colour flow Doppler (CFD) tricuspid valve and right atrium were performed in 90 TB horses (age 2-7 years) 1998-2003. Forty horses were examined at least once and 48 horses were examined on at least 2 occasions. Examinations were then classified as: i) before commencement of race training, ii) after cantering exercise had been sustained for a period of 8-12 weeks and iii) at full race fitness. Tricuspid valve regurgitation (TR) murmurs were graded on a 1-6 scale and CFD echocardiography TR signals were graded on a 1-9 scale. Right ventricular internal diameter (RVID) in diastole and systole (RVIDd and RVIDs) was measured by guided M-mode. Associations between continuous RVID and TR measures and explanatory covariates of weight, age, heart rate, yard and stage of training were examined using general linear mixed models with horse-level random effects. RESULTS: On average, RVIDd and RVIDs increased by 0.08 and 0.1 cm, respectively, per year increase in age (P = 0.1 and 0.02) and by 0.3 and 0.4 cm, respectively between pretraining and race fitness (P = 0.07 and 0.005). Tricuspid regurgitation score by colour flow Doppler increased by 0.6/year with age (P<0.0001) and by 1.8 between pretraining and race fitness (P<0.0001). No significant associations were found between any outcomes and weight, heart rate and training yard. Due to the high level of colinearity between age and training, multivariable models including both terms were not interpretable. CONCLUSIONS AND CLINICAL RELEVANCE: Athletic training of horses exerts independent effects on both severity and prevalence of tricuspid valve incompetence. This effect should therefore be taken into account when examinations are performed. Dimensions of RV increase with age and training in TB horses in a manner that appears to be similar to that of the LV.

Cardiac arrhythmias during and after treadmill exercise in poorly performing thoroughbred racehorses.

REASONS FOR PERFORMING STUDY: The prevalence and severity of cardiac arrhythmias during exercise in athletic horses presented for poor performance is not well described. OBJECTIVES: To describe prevalence and severity of ventricular and supraventricular arrhythmias immediately before, during and immediately after standardised incremental treadmill exercise tests (IET) to fatigue in Thoroughbred horses during investigation of poor performance. METHODS: The electrocardiograms (ECG) of 88 Thoroughbred racehorses, judged to be free of significant heart disease or arrhythmia at rest, were used. A modified base-apex ECG was recorded throughout an IET to fatigue. Recordings were analysed independently by 2 observers. Twenty-eight horses were diagnosed with dorsal displacement of the soft palate, 25 had varying degrees of soft palate instability and aryepiglottic fold collapse, 8 had other respiratory problems and, in 27 cases, no definitive diagnosis was reached. RESULTS: Fifty-five horses had at least one ventricular (VPD) or supraventricular (SVPD) depolarisation, 23 had only VPDs, 17 had only SVPDs and 15 had both in at least one exercise period. Premature depolarisations were seen predominantly during the first min of recovery from IET. The range of premature beats after exercise was 1-30 VPDs, and 1-9 SVPDs. No significant associations were observed between age, sex, race type, diagnosis, peak heart rate or run time to fatigue during IET and occurrence of either > or =1 premature beat or of more severe arrhythmias (multiple singles [>5] or pairs or paroxysms of premature depolarisations during peak exercise or immediately after exercise). However, a larger sample size would be required to have greater confidence in these associations. CONCLUSIONS: Isolated VPDs and SVPDs are frequently detected in poor performing racehorses during IET but their clinical relevance remains to be determined. POTENTIAL RELEVANCE: The guidelines for interpretation and clinical relevance of premature depolarisations observed during and immediately after treadmill exercise tests in poor performing Thoroughbred racehorses deserves further evaluation.

Glycemic index of cracked corn, oat groats and rolled barley in horses.

Muscle glycogen synthesis depends on glucose availability. This study was undertaken to determine the glycemic and insulinemic response of horses to equal amounts of hydrolyzable carbohydrates (starch and sugar) in the form of one of three grain meals or intragastric administration of a glucose solution. In a randomized crossover design, seven horses were fed each of three grain meals (cracked corn, steamed oat groats, or rolled barley) or were infused intragastrically with glucose solution at 2 g of hydrolyzable carbohydrate (starch plus sugar) per kilogram of BW. The quantity of hydrolyzable carbohydrate ingested was not different among all treatments (P = 0.70). Plasma glucose concentration peaked in all four treatments by 1.5 to 2 h after feeding. Plasma glucose concentration remained higher than baseline in oat groats or barley-fed horses throughout 8 h, whereas plasma glucose returned to baseline by 5 to 6 h in corn-fed horses or after glucose administration. Meal consumption was slower in oat groats-fed horses than in corn-fed ones, which may confound the glycemic and insulinemic responses observed after grain feeding. Plasma glucose area under the curve (AUC) was 63% both in corn and oat groats and 57% in barley-fed horses compared with that of horses administered glucose (P = 0.13). Serum immunoreactive insulin concentration peaked between 2 and 3 h after feeding or glucose administration, and barley-fed horses had lower serum immunoreactive insulin concentration by 3 to 4 h than corn-fed horses or after glucose administration (P < 0.05). We conclude, in horses, ingestion of oat groats, corn, and barley result in similar plasma glucose AUC and, compared with the glycemic index of 100 as the glucose reference, corn, oat groats, and barley had a glycemic index of approximately 60.