Caudal cervical vertebral morphological variation is not associated with clinical signs in Warmblood horses.

BACKGROUND: Variation in equine caudal cervical spine morphology at C6 and C7 has high prevalence in Warmblood horses and is suspected to be associated with pain in a large mixed-breed group of horses. At present no data exist on the relationship between radiographic phenotype and clinical presentation in Warmblood horses in a case-control study. OBJECTIVES: To establish the frequency of radiographically visible morphologic variation in a large group of Warmblood horses with clinical signs and compare this with a group without clinical signs. We hypothesised that occurrence of morphologic variation in the case group would not differ from the control group, indicating there is no association between clinical signs and morphologic variation. STUDY DESIGN: Retrospective case-control. METHODS: Radiographic presence or absence of morphologic variation of cervical vertebrae C6 and C7 was recorded in case (n = 245) and control horses (n = 132). Case and control groups were compared by univariable Pearson's Chi-square and multivariable logistic regression for measurement variables age, sex, breed, degenerative joint disease and morphologic variation at C6 and C7. Odds ratio and confidence intervals were obtained. A P≤0.05 was considered statistically significant. RESULTS: Morphologic variation at C6 and C7 (n = 108/377 = 28.6%; Cases 58/245 = 23.7%; Control 50/132 = 38%) was less frequent in horses with clinical signs in univariable testing (OR 0.48, 95% CI 0.3-0.8, P = 0.001). Age, sex, breed and degenerative joint disease were not retained in the final multivariable logistic regression step whereas morphologic variation remained significantly less present in horses with clinical signs. MAIN LIMITATIONS: Possible demographic differences between equine clinics. CONCLUSIONS: Morphologic variation in the caudal cervical spine was detected more frequently in horses without clinical signs. Therefore, radiographic presence of such variation does not necessarily implicate the presence of clinical signs.

Phosphorus content of muscle tissue and muscle function in dairy cows fed a phosphorus-deficient diet during the transition period.

Phosphorus (P) deficiency and hypophosphatemia are believed to be associated with muscle function disturbances in dairy cows, particularly around parturition. The objective of this study was to determine the effect of dietary P deprivation during late gestation and early lactation on muscle P homeostasis and muscle function in periparturient dairy cows. Thirty-six multiparous dairy cows in late gestation were randomly assigned either to undergo dietary P depletion or to be offered a diet with adequate P content from 4 wk before to 4 wk after parturition. Phosphorus-deficient rations for dry and lactating cows contained 0.15 and 0.20% P on a dry matter basis, respectively. Blood and muscle tissue for biopsy were obtained and electromyographic examinations were conducted on biceps femoris and intercostal muscles in regular intervals throughout the study. Muscle tissue was analyzed for the total P, adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, creatine phosphate, and tissue water content. Dietary P deprivation resulted in a pronounced and sustained decline of the plasma phosphate concentration, reaching a nadir at calving with mean values below 1.5 mg/dL and remaining below 2.0 mg/dL during the first 4 wk of lactation. Hypophosphatemia was not associated with signs of clinically apparent muscle weakness or disturbed muscle function and was not associated with a decline in the content of any of the studied P-containing compounds in muscle tissue. Accordingly, no association between plasma phosphate concentration and muscle tissue P content was found. Electromyographic examination identified subclinical effects on motor unit action potentials that are indicative of disturbed neuromuscular functionality. Increasing occurrence of pathologic spontaneous activity possibly resulting from membrane instability of nerve or muscle cells and suggestive of myopathy was also recorded as P deprivation progressed. These effects were predominantly observed in intercostal and to a lesser degree biceps femoris muscles. Electromyographic parameters affected by P deprivation were found to be associated primarily with the plasma phosphate and to a lesser extent with the amounts of energy storing P-containing compounds contained in muscle tissue. These results indicate that prolonged and pronounced dietary P deprivation in transition dairy cows leads to marked sustained hypophosphatemia without altering the muscle tissue P homeostasis or causing clinically apparent muscle function disturbances.

The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses.

BACKGROUND: In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking. OBJECTIVES: The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA). ANIMALS AND METHODS: The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 ± 217 kg (mean ± SD) and aged 10 ± 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 ± 178 kg, aged 13 ± 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means. RESULTS: The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29-2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82-1.45). CONCLUSION AND CLINICAL RELEVANCE: In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids.

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.

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.

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

REASONS FOR PERFORMING STUDY: In cases of laminitis, an increased muscle force or contracture of the deep digital flexor muscle (DDFM) is suggested, but evidence-based research is lacking. OBJECTIVES: To test if the DDFM of laminitic equines shows an increased muscle force detectable by needle-EMG including Interference Pattern Analysis (IPA). STUDY DESIGN: Cross-sectional study. METHODS: Three groups consisted of Group 0 (control): 6 Royal Dutch Sport horses, 3 Shetland ponies and one Welsh pony (healthy, sound adults, mean ± s.d. weight 411 ± 217 kg). Group 1: 3 Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, 2 Welsh ponies, one miniature Appaloosa and 6 Shetland ponies (adults, mean ± s.d. weight 310 ± 172 kg) suffering from acute or chronic laminitis. EMG measurements including firing frequency (F) and IPA parameters Turns/Second (T), Amplitude/Turn (M) and Ratio M/T (R) were performed. ANOVA was used to analyse data. P values of P<0.05 were considered significant. RESULTS: Mean ± s.d. F of Group 0 and Group 1 was 53 ± 11 and 72 ± 21 Hz, mean ± s.d. T was 112 ± 57 and 106 ± 42, mean ± s.d. M was 284 ± 51 and 254 ± 38 µV and mean ± s.d. R was 0.39 ± 0.17 and 0.42 ± 0.16%, respectively. The firing frequency of Group 1 was significantly higher compared to Group 0 (P = 0.02), whereas other differences were not significant. CONCLUSIONS: In human medicine, an increased firing frequency is a characteristic of increased muscle force [1,2]. Thus, the increased firing frequency of the DDFM in case of laminitis suggests an elevated muscle force. As all parameters show a high variance, a repeated study including a larger test group is advised. Ethical animal research: Data collection from controls was approved by the Animal Welfare Committee of Utrecht University, approval number 2008.III.07.061 and 2013.III.01.012. Clinical cases were privately owned and written owner consent was obtained. SOURCE OF FUNDING: None. Competing interests: None declared.

The effect of transient, moderate dietary phosphorus deprivation on phosphorus metabolism, muscle content of different phosphorus-containing compounds, and muscle function in dairy cows.

Hypophosphatemia is a common finding in periparturient and anorectic cattle. Although the clinical relevance of hypophosphatemia in cattle is uncertain, it has been empirically associated with persistent recumbency, specifically in periparturient dairy cows. The objective of the present study was to determine if transient dietary phosphorus (P) deprivation over a course of 5 wk, by feeding an approximately 40% P-deficient ration to lactating dairy cows, would result in altered muscle function or muscle P metabolism severe enough to present a risk for animal health and well-being. In addition, we wanted to determine the association between the plasma phosphate concentration ([Pi]) and muscle tissue P content to assess to what extent intracellular P deprivation of muscle cells could be extrapolated from subnormal plasma [Pi]. Ten healthy multiparous, mid-lactating dairy cows received a ration with a P content of 0.18% over a period of 5 wk. Following the P-deprivation phase, the same ration supplemented with P to obtain a dietary P content of 0.43% was fed for 2 wk. Blood and urine samples were collected regularly and muscle biopsies were obtained repeatedly to determine the P content in muscle tissue. Function of skeletal and heart muscles was evaluated by electrocardiography and electromyography conducted repeatedly throughout the study. Feeding the P-deficient ration resulted in the rapid development of marked hypophosphatemia. The lowest plasma [Pi] were measured after 9 d of P depletion and were, on average, 60% below predepletion values. Plasma [Pi] increased thereafter, despite ongoing dietary P depletion. None of the animals developed clinical signs commonly associated with hypophosphatemia or any other health issues. Urine analysis revealed increasing renal calcium, pyridinoline, and hydroxypyridinoline excretion with ongoing P deprivation. Biochemical muscle tissue analysis showed that dietary P depletion and hypophosphatemia were not associated with a decline in muscle tissue P content. Electromyographic examination revealed increased occurrence of pathological spontaneous activity in striated muscles after 2 wk of dietary P depletion in several cows, which could be suggestive of neuromuscular membrane instability. No effect on heart muscle activity was identified electrocardiographically. These results suggest that counter-regulatory mechanisms were sufficient to maintain normal muscle tissue P content during transient and moderate P deprivation. Muscle function was not grossly affected, although the increased occurrence of pathological spontaneous activity suggests that subclinical neuropathy or myopathy, or both, may have occurred with ongoing P deprivation. The results presented here indicate that plasma [Pi] is unsuitable for assessing muscle tissue P content in cattle.

Determination of equine deep digital flexor muscle volume based on distances between anatomical landmarks.

In equine medicine the use of Botox® is experimental. Dosages are determined from human treatment-protocols and limited numbers of equine studies. Determination of target-muscle volume can be helpful to extrapolate human dosages. The aim of the study was to calculate a formula enabling the estimation of the deep digital flexor muscle (DDFM) volume based on distances between anatomical landmarks. Nineteen cadaveric limbs were collected and distance A (top of olecranon to Os carpi accessorium) and B (circumference of limb) were measured. Converting mathematical formulas, C was calculated: π × (((0.5B)/π)(2)) × A. DDFM volume was determined by water displacement. Linear Regression Analysis was used to analyse data. The line best fitting the observed points was: Ln(volume[ml]) = -1.89 + 0.98 × Ln(value C[cm(3)]). Correlation was highest when natural logarithm was applied to both variables and was 0.97. The calculated formula enables estimating DDFM volume of a living horse. This estimated volume can be useful to apply human Botox® treatment-protocols.

The equine cervical spine: comparing MRI and contrast-enhanced CT images with anatomic slices in the sagittal, dorsal, and transverse plane.

BACKGROUND: The impact of cervical pathology on performance is of great importance to the horse industry. Accurate diagnosis of cervical disease with imaging modalities, including computed tomography (CT) and magnetic resonance imaging (MRI), requires thorough appreciation of normal cervical anatomy. OBJECTIVES: (1) To describe in detail the anatomy of the equine cervical spine by comparing anatomical sections with corresponding MR and contrast-enhanced CT images in the sagittal, dorsal, and transverse plane. (2) To discuss the ability of MR and contrast-enhanced CT imaging to visualize anatomical structures in the cervical spine. ANIMALS AND METHODS: Three cervical spines of young adults (3-8 years), collected immediately after humane euthanasia, were used. The spine was stabilized on a frame in a natural flexed position with an angle of 20°. MR and contrast-enhanced CT imaging was performed within six hours after euthanasia. Anatomical sections of 1 cm were made in the sagittal, dorsal, and transverse plane and compared with corresponding CT and MR images. The intervertebral disk thickness, facet joint angle, sagittal dural space diameter and ventromedial facet joint projection were quantified. RESULTS: The anatomic location of clinically important structures including the facet joints, spinal cord, cervical nerve roots and intervertebral disks were reliably identified in the anatomical sections and their corresponding MR images. Contrast-enhanced CT images depicted all osseous borders, whereas MR images were superior for soft tissue structures. CONCLUSION AND CLINICAL IMPORTANCE: This study enhances our understanding of normal cervical spine anatomy and the diagnostic usefulness of cervical MRI and contrast-enhanced CT in the horse.

Effect of different head and neck positions on behaviour, heart rate variability and cortisol levels in lunged Royal Dutch Sport horses.

Different head-and-neck positions (HNPs) are discussed in relation to potential welfare issues. To evaluate the effect on welfare, seven Royal Dutch Sport horses were studied in five predetermined HNPs: (1) unrestrained (HNP1); (2) neck raised, bridge of nose around the vertical (HNP2); (3) neck lowered and considerably flexed, bridge of nose pointing towards the chest (HNP4); (4) neck raised and extended, bridge of nose in front of the vertical (HNP5), and (5) neck lowered and flexed, bridge of nose pointing towards the carpus (HNP7). A standardised exercise test (SET) of 34 min consisted of trot, canter and walk. Behaviour was recorded with a pre-defined ethogram and R-R intervals measured using telemetry. Cortisol concentrations were taken at the start, 5 and 30 min after the SET. Behaviour around the SET was scored separately. Conflict behaviours increased significantly during HNP2 when compared with HNP1, HNP4 and HNP7 during the SET, and there was significant negative anticipation before HNP2 and HNP7. The heart rate variability (HRV) frequency domain for HNP2 showed a significantly increased low frequency peak (LFpeak) compared with other HNPs, and there was a decrease in very low frequency (VLF%) compared with HNP1. HNP4 showed a significant increase in LF% and decrease in VLF% compared with HNP1. Saliva cortisol concentrations were significantly increased in HNP2 at 5 and 30 min after exercise. Increased conflict behaviour was mostly observed in HNP2, but there was a raised HRV suggesting a sympathetic shift in HNP2 and HNP4, and increased cortisol concentrations during HNP2 indicated a stress response.

Pressure plate analysis of toe-heel and medio-lateral hoof balance at the walk and trot in sound sport horses.

Empirically, equine distal limb lameness is often linked to hoof imbalance. To objectively quantify dynamic toe-heel and medio-lateral hoof balance of the vertical ground reaction force in sound sport horses, seven Royal Dutch Sport Horses were led at the walk and trot over a dynamically calibrated pressure plate. Forelimb hoof prints were divided into a toe and heel region and a medial and lateral zone. Toe-heel and medio-lateral hoof balance of the vertical ground reaction force were calculated throughout the stance. Toe-heel balance was highly symmetrical between contralateral limbs at both gaits. At the walk, medio-lateral balance of both forelimbs presented higher loading in the lateral part of the hoof throughout the stance. However, at the trot, left medio-lateral balance presented higher loading of the medial part of the hoof at impact, whereas the right limb showed higher loading of the lateral part of the hoof in all horses, and both limbs presented increased lateral loading at the end of the stance. This study provides objective data for toe-heel and medio-lateral hoof balance in sound sport horses.

The applicability of ambulatory electroencephalography (AEEG) in healthy horses and horses with abnormal behaviour or clinical signs of epilepsy.

BACKGROUND: Short-duration electroencephalography (EEG) recordings in horses are helpful in diagnosing intracranial disorders. Potentially, long-duration ambulatory EEG (AEEG) recordings in horses will enhance the chance of detecting abnormal brain activity independent of the presence of an insult. OBJECTIVE: The objective of this study was to test if AEEG recordings in unsedated horses can be acquired and benefit diagnosing abnormal brain activity. ANIMALS AND METHODS: Recordings were taken from 8 adult control horses and 10 patients suspected of intracranial abnormalities. Self-adhesive electrodes and the 'Porti-5' recording system were used. Filter settings were 0.5 Hz high pass and 35 Hz low pass. The records were analysed offline at a 50-200 µV/division and 10 seconds/division scale. Abnormal activity was defined as a spike or sharp wave, a period of generalised slow wave rhythmical activity or a generalised fast rhythmical discharge. The recording time ranged from 5 to 49 hours. RESULTS: In the control group, one horse showed pathological activity. In the patient group, six out of nine horses showed abnormal activity during the recordings. Magnetic resonance imaging confirmed the presence of an intracranial mass in one patient. Long-term recordings of high quality can be obtained in unsedated horses by allowing daily activity using AEEG, resulting in a reasonable chance of recording (inter)ictal abnormal brain activity indicating epileptic or seizure-like activity in the absence of clinical signs or seizures. CONCLUSIONS: It is concluded that abnormal behaviour can be expressed intermittently, and with the availability of AEEG a useful tool is added to the diagnostic scenario for horses.

Comparing the pharmacokinetics of a fourth generation cephalosporin in three different age groups of New Forest ponies.

REASONS FOR PERFORMING STUDY: To compare the pharmacokinetics of the fourth generation cephalosporin, cefquinome, in neonatal foals, 6-week-old foals and mature New Forest ponies in order to recommend appropriate dosage regimens for use of this drug. METHODS: Cefquinome was administered i.v. at 1 mg/kg bwt twice a day (q. 12 h), 1 mg/kg bwt 3 times a day (q. 8 h) or 4.5 mg/kg bwt q. 12 h to each age group (n = 6). Plasma cefquinome concentrations were analysed using high-performance liquid chromatography combined with electrospray tandem mass spectrometry. RESULTS: Both foal age groups had comparable pharmacokinetic data except for the volume of distribution at a steady-state (Vss), total body clearance (ClB) and mean residence time (MRT). Both ClB and MRT decreased as the age of the foals increased. Values of area under the curve increased, in a dose dependent manner, with significant increases for all age groups following administration of 4.5 mg/kg bwt q. 12 h. Total body clearance did not have comparable dose dependency. CONCLUSIONS: Cefquinome can be given at a dose of 1 mg/kg bwt q. 12 h for the treatment of infections caused by susceptible pathogens with MIC < 0.125 microg/ml. A higher dose of 4.5 mg/kg bwt q. 12 h is recommended for the treatment of bacterial pathogens with minimal inhibitory concentration (MIC) 0.125-0.5 microg/ml POTENTIAL RELEVANCE: Commonly used dosing regimens should be critically evaluated in neonatal foals due to the higher volume of distribution of less lipophilic drugs in this age group.

Quantitative motor unit action potential analysis in 2 paraspinal neck muscles in adult Royal Dutch Sport horses.

BACKGROUND: Reference values for quantitative electromyography (QEMG) in neck muscles of Royal Dutch Sport horses are lacking. OBJECTIVE: Determine normative data on quantitative motor unit action potential (QMUP) analysis of serratus ventralis cervicis (SV) and brachiocephalicus (BC) muscle. ANIMALS: Seven adult normal horses (mean age 9.5 standard deviation [SD] ± 2.3 years, mean height 1.64 SD ± 4.5 cm, and mean rectal temperature 37.6 SD ± 0.3°C). METHODS: An observational study on QMUP analysis in 6 segments of each muscle was performed with commercial electromyography equipment. Measurements were made according to formerly published methods. Natural logarithm transformed data were tested with ANOVA and posthoc testing according to Bonferroni. RESULTS: Mean duration, amplitude, phases, turns, area, and size index (SI) did not differ significantly among the 6 segments in each muscle. Mean amplitude, number of phases, and SI were significantly (P < .002) higher in SV than BC, 520 versus 448 µV, 3.0 versus 2.8 µV, and 0.48 versus 0.30 µV, respectively. In SV 95% confidence intervals (CI) for amplitude, duration, number of phases, turns, polyphasia area, and SI were 488-551 µV, 4.3-4.6 ms, 2.9-3.0, 2.4-2.6, 7-12%, 382-448, and 0.26-0.70, respectively; in BC this was 412-483 µV, 4.3-4.7 ms, 2.7-2.8, 2.4-2.6, 4-7%, 393-469, and 0.27-0.34, respectively. Maximal voluntary activity expressed by turns/second did not differ significantly between SV and BC with a 95% CI of 132-173 and 137-198, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: The establishment of normative data makes objective QEMG of paraspinal muscles in horses suspected of cervical neurogenic disorders possible. Differences between muscles should be taken into account.

Amino acid profile during exercise and training in Standardbreds.

The objective of this study is to assess the influence of acute exercise, training and intensified training on the plasma amino acid profile. In a 32-week longitudinal study using 10 Standardbred horses, training was divided into four phases, including a phase of intensified training for five horses. At the end of each phase, a standardized exercise test, SET, was performed. Plasma amino acid concentrations before and after each SET were measured. Training significantly reduced mean plasma aspartic acid concentration, whereas exercise significantly increased the plasma concentrations of alanine, taurine, methionine, leucine, tyrosine and phenylalanine and reduced the plasma concentrations of glycine, ornithine, glutamine, citrulline and serine. Normally and intensified trained horses differed not significantly. It is concluded that amino acids should not be regarded as limiting training performance in Standardbreds except for aspartic acid which is the most likely candidate for supplementation.

The incidence and severity of gastric ulceration does not increase in overtrained Standardbred horses.

REASONS FOR PERFORMING STUDY: Gastric ulceration can be caused by different pathophysiological mechanisms including dietary factors, psychological stress and exercise. Overtraining is a medical syndrome in performance horses associated with altered hormone levels, altered feed intake, altered behaviour and decreased performance. These components might lead to a higher incidence of gastric ulceration in overtrained horses. OBJECTIVES: To investigate whether the incidence of gastric ulceration is increased in overtrained compared to control horses. METHODS: A longitudinal training study with twelve 1.5 years old Standardbred horses was performed on a treadmill for a total of 32 weeks. Training was divided into 4 periods: (1) acclimatisation (2) training (3) intensified training, and (4) detraining. In period 3, the horses were randomly divided into 2 groups: control (C) and intensified trained group (IT). At the end of each period, gastroscopy was performed in conscious horses after withholding feed for 12 h and water for 6 h using a 3.5 m video gastroendoscope. Lesion scores were assigned to areas of the stomach and graded 1-4. Logistic regression was used for statistical calculations. RESULTS: Evaluation of the stomach revealed only minor changes (grades 1 or 2) on each occasion. There were no significant differences in gastric lesion scores between groups or periods. Most lesions (70%) were found around the minor curvature. After detraining no lesions (0%) were found in contrast to periods 1 (40%, P = 0.056), 2 (30%) and 3 (30%). CONCLUSIONS: Experimentally-induced overtraining does not increase the incidence of gastric ulceration in normally fed Standardbred horses and detraining appears to reduce gastric ulceration.

Effect of head and neck position on outcome of quantitative neuromuscular diagnostic techniques in Warmblood riding horses directly following moderate exercise.

REASONS FOR PERFORMING STUDY: There has been growing interest in training techniques with respect to the head and neck position (HNP) of the equine athlete. Little is known about the influence of HNP on neuromuscular transmission in neck muscles. OBJECTIVE: To test the hypothesis that different HNPs have effect on single fibre (SF), quantitative electromyographic (QEMG) examination and muscle enzyme activity directly after moderate exercise. METHODS: Seven Warmblood horses were studied using a standard exercise protocol in 5 HNPs: HNP1: unrestrained; HNP2: neck raised; bridge of nose around the vertical; HNP4: neck lowered and considerably flexed, bridge of nose pointing towards the chest; HNP5: neck raised and considerably extended; bridge of nose in front of the vertical; HNP7: neck lowered and flexed; bridge of nose pointing towards the carpus. Mean consecutive difference (MCD) of single muscle fibre potentials and motor unit action potential (MUP) variables (amplitude, duration, area, turns and phases) were recorded in each fixed position directly after exercise at rest using commercial EMG equipment. Muscle enzyme activity was measured before and 4, 6 and 24 h after exercise. RESULTS: Mean consecutive difference in all HNPs was higher than in HNP1 (22 µs, P < 0.001) of which HNP4 was highest with 39 µs compared to 30 µs in HNP2 (P = 0.04); MCD in HNP 5,7 was with 25 µs lower than in HNP 2 and 4 (P < 0.001). Odds ratio for MCD suggestive for conduction delay or block was 13.6 in HNP4 compared to HNP1 (P < 0.001). Motion unit action potential variables followed the same pattern as MCD. Lactate dehydrogenase (LDH) activity increased in HNP4 at 4 h (P = 0.014), 6 h (P = 0.017) and 24 h (P = 0.038) post exercise and in HNP5 and HNP7 at 4 h (P = 0.037; 0.029). CONCLUSIONS AND CLINICAL RELEVANCE: HNP4 in particular leads to a higher rise in LDH activity, MCD and MUP variables, indicating that HNPs have effect on variables characterising neuromuscular functionality.

The effect of ex vivo flexion and extension on intervertebral foramina dimensions in the equine cervical spine.

REASONS FOR PERFORMING STUDY: In dressage, the head and neck position has become an issue of concern as certain extreme positions may imply a welfare risk for the horse. In man, extension and flexion of the cervical spine cause a decrease and increase in intervertebral foramina dimensions, respectively. However, in horses, the influence of flexion and extension on foramina dimensions and its possible interference with peripheral nerve functioning remains unknown. OBJECTIVES: To determine the effect of ex vivo flexion and extension on intervertebral foramina dimensions in the equine cervical spine. METHODS: Computed tomography was performed on 6 cadaver cervical spines from adult Warmblood horses subjected to euthanasia for reasons unrelated to cervical spine abnormalities, in a neutral position, in 20 and 40° extension, and in 20 and 40° flexion. Multiplanar reconstructions were made to obtain transverse images perpendicular to the long axis of each pair of intervertebral foramina from C2-T1. Intervertebral foramina dimensions were measured in the 5 positions. RESULTS: Compared to the neutral position, 40° extension caused a decrease in foramina dimensions at segments C4-C5, C5-C6, C6-C7 (P < 0.001) and C7-T1 (P < 0.002); 20° extension caused a decrease in foramina dimensions at segments C5-C6 (P < 0.02), C6-C7 (P < 0.001) and C7-T1 (P < 0.01); 20° flexion caused an increase in foramen length at segment C6-C7 (P < 0.01). CONCLUSIONS: Ex vivo extension of the cervical spine causes a decrease in intervertebral foramina dimensions at segments C4-T1, similar to that found in man. POTENTIAL RELEVANCE: In vivo extension of the cervical spine could possibly interfere with peripheral nerve functioning at segments C4-T1. This effect may be even more profound in patients with a reduced intervertebral foramina space, for example in the presence of facet joint arthrosis.

A pilot study on objective quantification and anatomical modelling of in vivo head and neck positions commonly applied in training and competition of sport horses.

REASONS FOR PERFORMING STUDY: Head and neck positions (HNP) in sport horses are under debate in the equine community, as they could interfere with equine welfare. HNPs have not been quantified objectively and no information is available on their head and neck loading. OBJECTIVES: To quantify in vivo HNPs in sport horses and develop o a model to estimate loading on the cervical vertebrae in these positions. METHODS: Videos were taken of 7 Warmbloods at walk on a straight line in 5 positions, representing all HNPs during Warmblood training and competition. Markers were glued at 5 anatomical landmarks. Two-dimensional angles and distances were determined from video frames for the 5 HNPs and statistically compared (P < 0.05). A new simulation model was developed to estimate nuchal ligament cervical loading at these HNPs. RESULTS: The mean angles were significantly different between the 5 HNPs for the line between C1 and T6 with the horizontal and for the line connecting the facial crest (CF) and C1 with the vertical, while the vertical distance from CF to the lateral styloid process of the radius (PS) was significantly different between all 5 positions (P < 0.05). The estimated nuchal ligament loading appeared to be largest at the origin of C2 for all HNPs, except for the 'hyperextended' HNP5; the 'hyperflexed' HNP4 showed the largest loading values on the nuchal ligament origins at all locations. CONCLUSIONS: HNPs can be accurately quantified in the sagittal plane from angles and distances based on standard anatomical landmarks and home-video captured images. Nuchal ligament loading showed the largest estimated values at its origin on C2 in hyperflexion (HNP4). POTENTIAL RELEVANCE: Modelling opens further perspectives to eventually estimate loading for individual horses and thus ergonomically optimise their HNP, which may improve the welfare of the sport horse during training and competition.