Low dose of dichloroacetate infusion reduces blood lactate after submaximal exercise in horses

The acute administration of an indirect activator of the enzyme pyruvate dehydroge-nase (PDH) in human athletes causes a reduction in blood lactate level during and after exercise. A single IV dose (2.5m.kg-1) of dichloroacetate (DCA) was administered before a submaximal incremental exercise test (IET) with five velocity steps, from 5.0 m.s-1 for 1 min to 6.0, 6.5, 7.0 and 7.5m.s-1 every 30s in four untrained mares. The blood collections were done in the period after exercise, at times 1, 3, 5, 10, 15 and 20 min. Blood lactate and glucose (mM) were determined electro-enzymatically utilizing a YSI 2300 automated analyzer. There was a 15.3% decrease in mean total blood lactate determined from the values obtained at all assessment times in both trials after the exercise. There was a decrease in blood lactate 1, 3, 5, 10, 15 and 20 min after exercise for the mares that received prior DCA treatment, with respective mean values of 6.31±0.90 vs 5.81±0.50, 6.45±1.19 vs 5.58±1.06, 6.07±1.56 vs 5.26±1.12, 4.88±1.61 vs 3.95±1.00, 3.66±1.41 vs 2.86±0.75 and 2.75±0.51 vs 2.04±0.30. There was no difference in glucose concentrations. By means of linear regression analysis, V140, V160, V180 and V200 were determined (velocity at which the rate heart is 140, 160, 180, and 200 beats/minute, respectively). The velocities related to heart rate did not differ, indicating that there was no ergogenic effect, but prior administration of a relatively low dose of DCA in mares reduced lactatemia after an IET.

Jugular thrombophlebitis in horses: A review of fibrinolysis, thrombus formation, and clinical management

Thrombophlebitis of the jugular vein is commonly observed in horses, particularly during intensive care, and leads to local and systemic inflammatory responses as well as head and neck circulatory impairment. Thrombolytic therapy is widely used in human practice with the aim of thrombus dissolution and recanalization of the injured vessels. There are similarities between human and horse coagulation and fibrinolytic processes. This review examines the fibrinolytic system, thrombus formation, and the clinical management of jugular thrombophlebitis, including thrombolytic therapy. There is evidence that early regional thrombolytic therapy for jugular thrombophlebitis in horses may be effective to achieve sustained recanalization.

Effects of Jugular Vein Occlusion on Cardiovascular Parameters in Horses During Exercise on a Treadmill

The purpose of the present investigation was to examine the effects of unilateral and bilateral jugular vein occlusion by temporary surgical ligature on the heart rate and arterial and venous blood pressure in sedentary horses during progressive treadmill exercise. Six horses performed three exercise tests (ET). ET1, considered the control, was performed in horses without jugular occlusions. ET2 and ET3 were performed with unilateral and bilateral occlusion by temporary surgical ligature of the jugular veins, respectively. Heart rate, arterial pressure, and pressure of the occluded jugular vein were evaluated. Clinically, the horses presented apathy, head edema, congested mucous membranes, increased capillary refill time, and dysphagia. These signs were observed with the unilateral jugular vein occlusion and became more evident with the bilateral occlusion. Comparing ETs, no differences were observed in heart rate. However, jugular occlusions promoted a decrease in the mean arterial pressure and a severe increase in jugular pressure. Head edema caused by the jugular vein occlusion in the horses could interfere with the autonomic cardiovascular regulation of arterial blood pressure during exercise, likely leading to an impairment of tissue perfusion. Jugular occlusion, even unilateral, also causes severe head venous congestion, leading to venous hypertension that was aggravated by exercise, which could risk development of cerebral edema and neurological damage. The present results obtained from sedentary horses are preliminary data that lead us to suggest that sport horses presenting jugular occlusive thrombophlebitis, even unilateral, may be prevented from performing athletic activities. © 2013 Elsevier Inc. All rights reserved.

Intravenous Tramadol Injection has no Antinociceptive Effect in Horses Undergoing Electrical and Thermal Stimuli

Tramadol combines an μ opiate and nonopiate analgesic mechanism and might be a useful opioid in horses. This study evaluated the effect of IV tramadol on spontaneous locomotor activity (SLA), head height, and hoof withdrawal reflex (HWR) after thermal or electrical nociceptive stimuli in horses. Doses of 2 and 3 mg/kg tramadol did not affect HWR after electrical and thermal nociception, respectively. Head height and SLA were not modified by 2, 3, or 5 mg/kg tramadol. All horses treated with 5 mg/kg tramadol developed trembling in pectoral triceps, and gluteal muscles and adopted a base-wide stance. In conclusion, 2 and 3 mg/kg tramadol IV neither induced sedation nor prolonged HWR after thermal or electrical stimuli in conscious horses. The dose of 5 mg/kg tramadol IV produced excitement, and it is apparently unsuitable for clinical use. © 2013 Elsevier Inc. All rights reserved.

Hepatoencephalopathy syndrome due to Cassia occidentalis (Leguminosae, Caesalpinioideae) seed ingestion in horses

Cassia occidentalis is a bush from the Leguminosae family, subfamily Caesalpinoideae, and is a toxic plant of veterinary interest due to the occasional contamination of animal rations. This report describes the clinical and histopathological findings of an outbreak of C.occidentalis poisoning in horses. Twenty mares were poisoned after consuming ground corn contaminated with 8% of C.occidentalis seeds. Of the 20 animals affected, 12 died: 8 mares were found dead, 2 died 6h after the onset of clinical signs compatible with hepatic encephalopathy and the 2 other animals were subjected to euthanasia 12h after the onset of the clinical signs. The remaining 8 mares presented with mild depression and decreased appetite, but improved with treatment and no clinical sequelae were observed. In 6 animals that underwent a necropsy, an enhanced hepatic lobular pattern was noted and within the large intestine, a large number of seeds were consistently observed. Hepatocellular pericentrolobular necrosis and cerebral oedema were the main histological findings. In one mare, there was mild multifocal semimembranosus rhabdomyocytic necrosis and haemorrhage. Seeds collected from intestinal contents and sifted from the culpable feedstuff were planted. Examination of the leaves, flowers, fruits and seeds of the resultant plants identified C.occidentalis. Horses poisoned by C.occidentalis seeds demonstrate clinical signs associated with hepatoencephalopathy and frequently die suddenly. Lesions primarily involve the liver and secondarily, the central nervous system. Cassia occidentalis poisoning should be considered a differential diagnosis in horses with hepatoencephalopathy and special caution should be taken with horse rations to avoid contamination with seeds of this toxic plant. © 2012 EVJ Ltd.

Morphological and Genomic Differences Between Cutting and Racing Lines of Quarter Horses

To investigate morphological and genomic differences between cutting and racing lines of Quarter Horses, 120 racing and 68 cutting animals of both sexes, registered at the Brazilian Association of Quarter Horse Breeders, were used. Blood samples were collected, and the following physical traits were measured: weight; height at withers; body length; length of the shank, pastern, rump, head, and neck; and chest, shank, and hoof circumference. For analysis of genomic differences, 54,602 single-nucleotide polymorphisms (SNPs) were genotyped using the Equine SNP50 BeadChip, and the quality of individual and SNP genotype data were evaluated. The fixation index, FST, was used to identify genome regions that were altered in the lines by selection. The results showed significant differences between the lines in all physical traits. Quality control led to the exclusion of four cutting animals with a call rate of <0.95. After filtering, 12,544, 13,815, and 13,370 SNPs were excluded for the whole population (n = 184), the 120 racing animals, and the 64 cutting animals, respectively. The number of informative polymorphisms detected in each line and in the whole population indicated that the Equine SNP50 BeadChip can be used in genetic studies of Quarter Horses. The fixation index, FST, identified 2,558 genome regions that may have been modified by divergent selection. © 2013 Elsevier Inc.

Intra-abdominal hypertension in horses

Intra-abdominal hypertension (IAH) may lead to a multiple organ dysfunction syndrome associated with significant dysfunction of the cardiovascular, respiratory, renal, gastrointestinal and central nervous systems of human patients. A recent prospective multicentre epidemiological investigation in man concluded that IAH was associated with an increased risk of mortality in critically ill patients. In this review, we present current information pertaining to the potential clinical importance of IAH in the context of equine clinical practice. In conclusion, consideration of intra-abdominal pressure should be a part of the clinical assessment of patient well-being in critically ill equine patients. © 2011 EVJ Ltd.

Behavioral and Antinociceptive Effects of Alfentanil, Butorphanol, and Flunixin in Horses

To determine the behavioral and antinociceptive effects of narcotic and non-narcotic analgesics administered by intravenous injection in horses, 10 thoroughbred mares weighing between 450 and 550 kg and ranging in age from 8 to 13 years old were analyzed. The effects of alfentanil, butorphanol, flunixin, and saline solution on the general activity of the horses were investigated by measuring spontaneous locomotor activity (SLA) and head height (HH) in two behavior stalls. The antinociceptive effects of alfentanil (0.02 mg kg-1), butorphanol (0.1 mg kg-1), flunixin meglumine (0.5 mg kg-1), and saline were determined by measuring skin twitch reflex latency (STRL) after thermal cutaneous nociceptive stimulation. A paired Student t-test was used to compare SLA and HH between the groups of horses receiving different doses of the same drug at various time points. The Tukey test was used to compare the antinociceptive effect of the treatments. Differences were considered significant when P value was <.05. Horses treated with opioid analgesics demonstrated excitation, as shown by a significant increase in SLA at all doses tested and by neighing and demonstrating attentive attitudes with movement of the ears, stereotypical walking, and ataxia in most of the animals. HH was elevated only in animals treated with alfentanil. Antinociception was observed at 5 and 30 minutes after administration of alfentanil and butorphanol, respectively. Increased SLA was observed at 30 and 90 minutes after administration of alfentanil and butorphanol, respectively. We observed no effect on antinociception in horses given flunixin. In conclusion, this study suggests that alfentanil has a faster onset and a shorter duration than butorphanol; however, both drugs are able to stimulate the central nervous system. © 2013 Elsevier Inc. All rights reserved.

Marjolin's ulcer in two horses with hereditary equine regional dermal asthenia

Two Quarter Horse mares with hereditary equine regional dermal asthenia (HERDA) were diagnosed with metastatic squamous cell carcinoma (SCC) associated with chronic nonhealing wounds. The lesions were similar to the development of SCC from chronic nonhealing ulcers, known as Marjolin's ulcers in humans. The horses showed recurrent skin wounds in the saddle and paralumbar regions and were confirmed by molecular techniques as having HERDA. Both horses were maintained as research animals for prolonged periods and received regular veterinary care and wound treatment. Both horses were ultimately euthanized because of their chronic progressive wounds, coupled with declining health. At necropsy, the nonhealing wounds were found to be complicated by infiltrative SCC; both horses had metastasis to lungs. Chronically inflamed, recurrent skin wounds that heal slowly and incompletely as a consequence of HERDA are proposed as a major pathogenetic factor in tumorigenesis. Consistent findings with respect to proliferation index (Ki-67) and mutations of p53 tumor suppressor gene were confirmed by immunohistochemistry in one horse. SCC consistent with Marjolin's ulcer has been previously suggested in association with chronic ulcers or burn scars in horses, but this is the first report of an association with chronic poor healing wounds in HERDA horses. © 2013 Elsevier Inc.

Attitude of Brazilian veterinarians in the recognition and treatment of pain in horses and cattle

Objective: The objective of this study was to assess the use of analgesics, describe the attitudes of Brazilian veterinarians towards pain relief in horses and cattle and evaluate the differences due to gender, year of graduation and type of practice. Study design: Prospective survey. Methods: Questionnaires were sent to 1000 large animal veterinarians by mail, internet and delivered in person during national meetings. The survey investigated the attitudes of Brazilian veterinarians to the recognition and treatment of pain in large animals and consisted of sections asking about demographic data, use of analgesic drugs, attitudes to pain relief and to the assessment of pain. Descriptive statistics were used to analyze frequencies. Simple post hoc comparisons were performed using the chi-square test. Results: Eight hundred questionnaires were collected, but 87 were discarded because they were incomplete or blank. The opioid of choice for use in large animals was butorphanol (43.4%) followed by tramadol (39%). Flunixin (83.2%) and ketoprofen (67.6%) were the most frequently used NSAIDs by Brazilian veterinarians. Respondents indicated that horses received preoperative analgesics for laparotomy more frequently (72.9%) than cattle (58.5%). The most frequently administered preoperative drugs for laparotomy in horses were flunixin (38.4%) and xylazine (23.6%), whereas the preoperative drugs for the same surgical procedure in cattle were xylazine (31.8%) and the local administration of lidocaine (48%). Fracture repair was considered the most painful surgical procedure for both species. Most veterinarians (84.1%) believed that their knowledge in this area was not adequate. Conclusions and clinical relevance: Although these Brazilian veterinarians thought that their knowledge on recognition and treatment of pain was not adequate, the use of analgesic in large animals was similar in Brazil to that reported in other countries. © 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

Comparison of the lactate minimum speed and the maximal lactate steady state to determine aerobic capacity in purebred Arabian horses

AIM: To compare five different protocols for estimating the lactate minimum speed (LMS) with that for estimating the maximal lactate steady state (MLSS) in Arabian horses, in order to obtain a more rapid method for monitoring aerobic capacity and prescribing training schedules. METHODS: Eight purebred Arabian horses were conditioned to exercise on a treadmill for 12 days then submitted to three to five exercise sessions to determine the MLSS. Blood samples were collected from a jugular catheter at specific intervals for measurement of lactate concentrations. The MLSS was the velocity maintained during the last 20 minutes of constant submaximal exercise, at which the concentration of lactate increased by no more than 1.0 mmol/L. The LMS test protocols (P1 - P5) included a warm-up period followed by a high-intensity gallop. The speed was then reduced to 4 m/s, and the incremental portion of the test was initiated. In P1, P2, and P3, the velocity increment was 0.5 m/s, and the duration of each incremental stage was three, five and seven minutes, respectively. In P4 and P5, the velocity increments were 1.0 and 1.5 m/s, respectively, and the duration of the stages was fixed at five minutes each. A second-degree polynomial function was fitted to the lactate-velocity curve, and the velocity corresponding to the lowest concentration of lactate was the LMS. RESULTS: Only the mean LMS determined by P1 and P2 did not differ from the velocity determined by the MLSS test (p > 0.1). There was a strong correlation (r >0.6) between P1 and the MLSS velocity. A limits of agreement plot revealed that the best agreement occurred between the MLSS test and P1 (mean bias = 0.14 m/s), followed by P2 (bias = -0.22 m/s). The lactate concentrations associated with the various LMS protocols did not differ. CONCLUSIONS: This study shows the variation between protocols of the LMS test for determining the onset of blood lactate accumulation but also reveals that, at least for Arabian horses, the P1 protocol of the LMS has good agreement with the MLSS. © 2013 Copyright New Zealand Veterinary Association.

Serial superficial digital flexor tendon biopsies for diagnosing and monitoring collagenase-induced tendonitis in horses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Use of PCR to estimate the prevalence of Equus caballus papillomavirus in aural plaques in horses

Aural plaques occur on the skin of the medial surface of the pinnae of horses. In this study the presence of Equus caballus papillomavirus (EcPV)-3 and -4 DNA was assessed in 45 such plaques using a 'touchdown' PCR. Papillomaviruses (PVs) were detected in 62.3% (28/45) of samples: EcPV-3 and -4 DNA in 8.89% (4/45) and 37.78% (17/45) of samples, respectively, with 15.56% (7/45) of samples exhibiting co-infection. Viral DNA was not detected in 37.78% (17/45) of samples, suggesting the possible existence of other equine PVs. Neither EcPV-3 nor -4 were detected in negative control skin. This study is the first to evaluate the prevalence of these two viruses in equine aural plaques. © 2013 Elsevier Ltd.

Serum activity of creatine kinase and aminotransferase aspartate enzymes of horses submitted to muscle biopsy and incremental jump test

The objective was to evaluate serum activity of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST), which are leakage enzymes responsive to muscle injury, of athletic horses that underwent muscle biopsy and incremental jump test (IJT) involving incremental jumps. The animals were grouped as follows: the first group, horses with history of superior performance (SP); the second, with a history of inferior performance (IP); and lastly, a control group (CG). All groups underwent biopsy of the gluteus medius muscle, while groups SP and IP were also submitted to the incremental jump test (IJT) 24 hours after biopsy. The IJT consisted of three stages with 40 jumps each, where jump height increased progressively, from 40 to 60 and last, 80cm. Blood samples were drawn before biopsy, and 6 and 24 hours after the exercise as well. The levels of CK serum activity increased 6 hours after exercise and decreased 24 hours later in all groups, including CG. AST activity did not increase after biopsy and exercise. There was no increase of both enzyme activities that could be attributed to the exercise, possibly due to exercise short duration and/or low intensity. We conclude that the muscle biopsy was able to show that there was enough stimulus to cause CK enzyme leakage into the plasma, and consequent detection of increased serum activity, while the incremental jump test did not.

Antinociceptive and Behavioral Effects of Methadone Alone or in Combination with Detomidine in Conscious Horses

The antinociceptive and behavioral effects of methadone (MET) alone or combined with detomidine (DET) were studied in horses. Intravenous treatments were randomly administered in a two-phase crossover study. In phase 1, six horses were treated with saline (control) or 0.2 or 0.5 mg/kg methadone (MET0.2; MET0.5, respectively). In phase 2, six horses were treated with 0.01 mg/kg DET alone or with DET combined with 0.2 mg/kg MET (DET/MET0.2). Thermal nociceptive threshold (TNT) and electrical nociceptive thresholds (ENT) were recorded by using a heat projection lamp and electrodes placed in the coronary band of the thoracic limbs, respectively. Spontaneous locomotor activity (SLA) was studied by movement sensors in the stall (phase 1). Chin-to-floor distance was assessed in phase 2. In phase 1, the TNT increased significantly for 30 minute after MET0.5 but not after saline or MET0.2. Hyperesthesia and ataxia were observed in 2 of 6 and 6 of 6 horses after MET0.2 and MET0.5, respectively. SLA increased significantly for 120 minutes after MET in a dose-dependent way, but not after placebo. In phase 2, DET and DET/MET0.2 significantly increased the TNT and ENT above baseline for 15 and 30 minutes, respectively; thresholds were significantly higher with DET/MET0.2 than with DET at the same times. Chin-to-floor distance decreased significantly from baseline for 30 minutes, and no excitatory behavior was observed in both treatments. Although the higher dose of MET induced short-acting antinociception, the associated adverse effects may contraindicate its clinical use. The lower dose of MET potentiated DET-induced antinociception without adverse effects, which might be useful under clinical circumstances. © 2013 Elsevier Inc. All rights reserved.