bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of equine lymphocyte β‐adrenoceptors under the influence of clenbuterol and dexamethasone
Authors: ABRAHAM G. , BRODDE O. ‐E. , UNGEMACH F. R.
Published: April 2007

In 12 healthy horses, the effects of the β2‐agonist clenbuterol and the glucocorticoid dexamethasone on the lymphocyte β2‐adrenoceptor density and affinity (determined by (‐)‐[125I]‐iodocyanopindolol binding) as well as its responsiveness (assessed by lymphocyte cyclic AMP [cAMP] responses to 10 μmol/l (‐)‐isoprenaline) were studied. Clenbuterol treatment, 2 × 0.8 μg/kg/day i.v. for 12 days, decreased significantly ICYP binding sites by ˜30–40%; concomitantly, lymphocyte cAMP response to (‐)‐isoprenaline was reduced. After withdrawal of clenbuterol, β2‐adrenoceptor density and responsiveness gradually increased, reaching predrug levels after 4 days. The effects of dexamethasone on clenbuterol‐induced desensitisation were further investigated. Administration of dexamethasone (1 × 0.1 mg/kg/day, i.v. for 5 days) immediately after clenbuterol withdrawal accelerated β2‐adrenoceptor recovery: only 24 h after administration dexamethasone restored the number of binding sites and cAMP response to (‐)‐isoprenaline to levels statistically indistinguishable from values before clenbuterol treatment. Three days after dexamethasone administration, lymphocyte β2‐adrenoceptors were further increased about 2‐fold the pretreatment values, and this increase declined gradually after dexamethasone withdrawal, reaching baseline values after 4 days. Furthermore, in groups exposed simultaneously to both drugs, dexamethasone completely prevented clenbuterol‐induced decrease in lymphocyte β2‐adrenergic receptor density and responsiveness. No significant change was observed in the dissociation constant for ICYPin any of the situations.

We conclude that dexamethasone (glucocorticoids) can reverse and prevent Clenbuterol‐induced desensitisation (down‐regulation) of the lymphocyte β2‐adrenoceptors and therefore, a combined therapy with clenbuterol and dexamethasone may be potentially beneficial in horses suffering from chronic obstructive pulmonary disease (COPD).
Pharmacokinetics of imidocarb dipropionate in horses after intramuscular administration
Authors: BELLOLI C. , CRESCENZO G. , LAI O. , CAROFIGLIO V. , MARANG O. , ORMAS P.
Published: April 2007

The objective of this study was to determine the pharmacokinetic behaviourof imidocarb in horses following a single i.m. injection at the dose commonly administered to treat Babesia caballi infections or to prevent babesiosis. Eight horses were injected i.m. with a single dose of 2.4 mg imidocarb dipropionate/kg bwt and blood, faecal, urine and milk samples were collected.

For imidocarb determination, a high‐performance liquid chromatographic method (HPLC) was used afterweak cation‐exchange solid phase, or liquid‐liquid, extraction procedures. Twelve hours after treatment, no detectable plasma concentrations were recorded in any of the treated animals. The distribution and elimination patterns of the drug suggested that it is quickly sequestrated in some storage tissues and remains in the body for a long time. Its prolonged presence in the body may confer a reservoir effect to imidocarb in some tissues, therefore making it undetectable in the plasma of animals but sufficient to produce its described therapeutic and prophylactic activities.
Longitudinal development of kinematics in Shetland ponies and the influence of feeding and training regimes
Authors: BACK W. , SCHAMHARDT H. C. , BARNEVELD A. , WEEREN P. R. van
Published: April 2007

Nowadays, ponies are used more and more for competitive equine sports, driving and racing. The locomotorperformance of ponies, however, has been evaluated in only a few kinematic and kinetic studies. To compare the longitudinal development of locomotor characteristics in the pony to the same process in the horse, the kinematics of 23 Shetland ponies were recorded at the trot on a treadmill (3 m/s) at ages 4 and 30 months using a modified CODA‐3 apparatus. Furthermore, the influence of specific feeding and training regimes on this development was evaluated. It appeared that stride and stance duration increased with age, but the swing duration and pro/retraction range were similar at foal and mature age. Fore‐ and hindlimb maximal joint flexion at swing was larger in the mature ponies compared to foals. The elbow and shoulder joint were kept in a more extended position and the stifle joint more flexed, while scapula and pelvis were kept in a more vertical position. These effects are similar to those found in horses. The majority of both temporal and angular kinematic variables correlated significantly between foals and mature ponies.

Ponies that were restricted in their feeding, resulting in a low body condition score, demonstrated a flatter gait than ponies fed ad lib (4 cm more height, 60 kg more weight), which trotted at the same velocity with significantly more joint flexion. Extra sprint training on top of free paddock exercise did not significantly influence the longitudinal development of kinematics.

From these data, it can be concluded that the longitudinal development of locomotor characteristics in ponies is similar to that in horses. Fatter animals show a more animated gait, while extra sprint training added to free paddock exercise has no detectable effect on the development of kinematics. Aside from training or feeding regimes, in the Shetland pony breed, it appears possible to recognise ‘good movers’ at a young age.
Distribution and numbers of mucous glands in the horse trachea
Authors: WIDDICOMBE J. H. , PECSON I. S.
Published: April 2007

Horses commonly suffer from respiratory diseases associated with excess secretions in the airway lumen, some of which are presumably derived from airway mucous glands. However, these structures have been little investigated in the horse. Accordingly, we describe here the number, distribution and size of equine tracheal mucous glands, and compare the data with similar information for other mammalian species. Two types of gland acini were present. In the thick connective tissue, up to 400 μm beneath the epithelium, gland acini were grouped in thin sheets that, in cross‐section, averaged 20 μm thick and were up to 4.0 mm in length. However, it is probable that most sheets had maximal diameters much less than 4.0 mm. Between 400 to 900 μm below the epithelium, the connective tissue was much more diffuse, and glands were larger and more globular. Gland volume in the ventral portion was ˜1.7 μl/cm2 of mucosal surface, and ˜1.1 μl/cm2 in the dorsal portion. Glands were somewhat more abundant between, rather than over, the cartilaginous rings, but the difference between the 2 locations was not marked. Mucous gland openings were small (20 μm diameter) and very unevenly distributed, generally occurring about 100 μm apart in longitudinal rows of about 5. Average frequency of openings in the ventral portions of 3 tracheas was ˜1.0/mm2 of mucosal surface. The volume of individual glands was therefore ˜17 nl. Although the frequency of gland openings in the horse trachea is similar to that for the tracheas of other large mammalian species, horse tracheal gland volume was only about 15% that of the other species. Therefore, the excess ‘mucous’ secretions seen in equine recurrent airway obstruction and other respiratory diseases are unlikely to be caused by comparatively high levels of airway mucous gland secretion. Instead, they may be caused mainly by hyperplasia of the mucus‐producing cells of the surface epithelium or by vascular transudation.
Pharmacokinetics of gentamicin C1, C1aand C2in horses after single intravenous dose
Authors: STEINMAN A. , ISOHERRANEN N. , ASHOACH O. , SOBACK S.
Published: April 2007

Gentamicin pharmacokinetics has not been studied in horses. Pharmacokinetics of gentamicin C1, C1aand C2components following i.v. administration of total gentamicin at 6.6 mg/kg bwt to 6 healthy mature horses was determined. Significant differences in clearance, half‐life (t1/2), and mean residence time (MRT) between the gentamicin C1aand the 2 other components were found. The total body clearance (CL) of gentamicin C1awas 1.62 ± 0.50 ml/min × kg and similar to the glomerular filtration rate (GFR) reported for horses. The CL of gentamicin C1and C2were 1.03 ± 0.08 ml/min × kg and 1.10 ± 0.15 ml/niin × kg, respectively, and significantly slower than that of gentamicin C1a. The values of apparent volume of distribution at steady state were 0.22 ± 0.05, 0.26 ± 0.12 and 0.23 ± 0.05 l/kg for gentamicin C1, C1aand C2, respectively. The MRT values were mean ± s.d. 3.6 ± 0.5, 2.7 ± 0.3 and 3.5 ± 0.4 h and thet1/2values were 3.1 (2.5–4.0), 2.4 (2.0–3.2) and 3.3 (2.4–4.3) h (harmonic mean and range) forgentamicin C1, C1aand C2, respectively. The MRT andt1/2values for gentamicin C1awere significantly shorter than those of gentamicin C1and C2. It was concluded that the difference in pharmacokinetics between the gentamicin components has potential pharmacological and toxicological implications.
Serum level of cartilage oligomeric matrix protein (COMP) in equine osteoarthritis
Authors: MISUMI K. , VILIM V. , HATAZOE T. , MURATA T. , FUJIKI M. , OKA T. , SAKAMOTO H. , CARTERS S. D.
Published: April 2007

This study was designed to assay and compare cartilage oligomeric matrix protein (COMP) in horse sera, in samples from normal and joint diseased horses, and to investigate the relationships between COMP in sera and synovial Quids (SF) with keratan sulphate (KS) data. Sera from 38 horses free of any joint pathology (controls) and from horses with aseptic joint disease (AJD horses, n = 40) were assayed for COMP and KS concentrations. Of the 78 horses in the study, 53 were also assayed for COMP and KS concentrations in SF. COMP and KS were measured by inhibition ELISA, using monoclonal antibodies 12C4 and 5D4, respectively. The COMP concentration in sera from AJD horses (mean ± s.d. 10.7 ± 7.4 μg/ml) was significantly (P<0.02) lowerthan in control sera (14.8 ± 7.8 μg/ml). The joint disease sera also had significantly lower (P<0.01) KS levels (180.5 ± 61.8 ng/ml) than controls (237.1 ± 116.1 ng/ml). A significant correlation (r= 0.52, n = 53, P<0.001) was seen between serum and SFin COMPlevels; no such relationship was seen in KS levels. It is possible that serum COMPconcentration could be a more specific marker of equine joint disease than any other described to date.
Effect of chronic airway inflammation and exercise on pulmonary and systemic antioxidant status of healthy and heaves‐affected horses
Authors: KIRSCHVINK N. , SMITH N. , FIÉVEZ L. , BOUGNET V. , ART T. , DEGAND G. , MARLIN D. , ROBERTS C. , GÉNICOT B. , LINDSEY P. , LEKEUX P.
Published: April 2007

In heaves‐affected horses the relation between oxidant status, airway inflammation (AI) and pulmonary function (PF) is unknown. The oxidant status of blood and pulmonary epithelial lining fluid (PELF) of healthy (H, n = 6) and heaves‐affected horses in clinical remission (REM, n = 6) and in crisis (CR, n = 7) was assessed at rest, during and afterstandardised exercise test by measurement of reduced and oxidised glutathione, glutathione redox ratio [GRR%]; uric acid and 8‐epi‐PGF2α. Oxidant status was related to PF parameters (mechanics of breathing and arterial blood gas tension) and AI parameters (bronchoalveolar lavage [BAL] neutrophil% and AI score). Haemolysate glutathione was significantly different between groups and was correlated with PF and AI parameters; GRR in PELF was increased during CR and was correlated with PF and AI parameters. Exercise induced an increase of plasma uric acid that was significantly higherboth in REM and CR. PELF 8‐epi‐PGF2αwas significantly increased in CR and correlated with PF and AI parameters. These results suggest that oxidative stress occurring in heaves is correlated with PF and AI and may be locally assessed by PELFglutathione status, uric acid and 8‐epi‐PGF2α. Systemic repercussions are reflected by assay of GSH in resting horses and by uric acid in exercising horses.
A description of the motion of the navicular bone during in vitro vertical loading of the equine forelimb
Authors: van DIXHOORN I. D. E. , MEERSHOEK L. S. , HUISKES R. , SCHAMHARDT H. C.
Published: April 2007

Motion of the navicular bone might play a role in the development of navicular disease in horses but is difficult to asses. In the present study, 3‐dimensional motion of this bone was determined using roentgen stereophotogrammetric analysis. Tantalum pellets were inserted, in vitro, in the bones of 6 forelimbs of mature Shetland ponies and kinematics were measured during vertical loading up to 2 kN. The motions of the navicular bone and coffin joint were limited to flexion/extension, there were no substantial out‐of‐plane motions. There was only little flexion between the navicular bone and the coffin bone, which was correlated (r = 0.66) with coffin joint flexion. There was substantial flexion between the navicular bone and the short pastern, which was highly correlated with coffin joint flexion (r = 0.97). We conclude that the navicular bone, generally, follows the coffin bone during coffin joint flexion, although there are small but consistent motions between the navicular bone and the coffin bone. These motions might play a role in the development of navicular disease in horses.
High intensity exercise conditioning increases accumulated oxygen deficit of horses
Authors: HINCHCLIFF K. W. , LAUDERDALE M. A. , DUTSON J. , GEOR R. J. , LACOMBE V. A. , TAYLOR L. E.
Published: April 2007

High intensity exercise is associated with production of energy by both aerobic and anaerobic metabolism. Conditioning by repeated exercise increases the maximal rate of aerobic metabolism, aerobic capacity, of horses, but whether the maximal amount of energy provided by anaerobic metabolism, anaerobic capacity, can be increased by conditioning of horses is unknown. We, therefore, examined the effects of 10 weeks of regular (4–5 days/week) high intensity (92 ± 3 %V̇O2max) exercise on accumulated oxygen deficit of 8 Standardbred horses that had been confined to box stalls for 12 weeks. Exercise conditioning resulted in increases of 17% in V̇O2max(P<0.001), 11% in the speed at which V̇O2maxwas achieved (P = 0.019) and 9% in the speed at 115% of V̇O2max(P = 0.003). During a high speed exercise test at 115%V̇O2max, sprint duration was 25% longer (P = 0.047), oxygen demand was 36% greater (P<0.001), oxygen consumption was 38% greater (P<0.001) and accumulated oxygen deficit was 27% higher (P = 0.040) than values before conditioning. VLa4was 33% higher (P<0.05) after conditioning. There was no effect of conditioning on blood lactate concentration at the speed producing V̇O2maxor at the end of the high speed exercise test. The rate of increase in muscle lactate concentration was greater (P = 0.006) in horses before conditioning. Muscle glycogen concentrations before exercise were 17% higher (P<0.05) after conditioning. Exercise resulted in nearly identical (P = 0.938) reductions in muscle glycogen concentrations before and after conditioning. There was no detectable effect of conditioning on muscle buffering capacity. These results are consistent with a conditioning‐induced increase in both aerobic and anaerobic capacity of horses demonstrating that anaerobic capacity of horses can be increased by an appropriate conditioning programme that includes regular, high intensity exercise. Furthermore, increases in anaerobic capacity are not reflected in blood lactate concentrations measured during intense, exhaustive exercise or during recovery from such exercise.
Clinical and endoscopic evidence of progression in 152 cases of equine recurrent laryngeal neuropathy (RLN)
Authors: DIXON P. M. , McGORUM B. C. , RAILTON D. I. , HAWE C. , TREMAINE W. H. , PICKLES K. , McCANN J.
Published: April 2007

Examination of the long‐term histories and clinical findings was performed in 351 horses suffering from recurrent laryngeal neuropathy (RLN) to examine for possible evidence of progression of this disorder. Fifty‐two out of 351 cases (15%) had evidence of progression of the degree of laryngeal dysfunction over a median period of 12 months (range 1.5–48 months) with the onset of progression occurring at median age 7 years. In 30 cases, there was both endoscopic (median deterioration of 3 endoscopic grades; range 1–5 grades) and clinical evidence, with 29 (97%) of these horses concurrently developing sudden‐onset, abnormal exercise‐related respiratory ‘noises» and 13 (43%) concurrently reporting reduced exercise performance. In the remaining 22 horses there was solely clinical evidence of RLN progression, including the sudden onset of abnormal exercise‐related respiratory sounds in 16 (73%) and the worsening of such sounds in 6 (23%), associated with reduced exercise performance in 13 (59%) of these 22 cases. Endoscopically, 13 (59%) of the latter 22 cases had marked (total or almost total) RLN that did not appear compatible with their previous exercise‐performance histories. This evidence of progression of RLN may be of particular significance in disputes concerning horses that are apparently normal at pre‐purchase examination but are later shown to have RLN and also in the surgical treatment of less severe cases of RLN.
Ultrasonographic investigation of the atlanto‐occipital articulation in the horse
Authors: GOLLOB E. , EDINGER H. , STANEK C. , WURNIG C.
Published: April 2007

The purpose of this study was to evaluate ultrasonographic imaging as a means of easy and noninvasive diagnosis of articular and periarticular structures of the atlanto‐occipital articulation in the horse; and to find a safe approach to the atlanto‐occipital joint. Ultrasonographic investigations were performed on 6 healthy horses and 16 specimens from horses humanely destroyed age 2–17 years (mean 9.56 years). Preliminary examinations included anatomical studies and preparation of cross‐sections. On 4 horse specimens, puncture of the atlanto‐occipital joint under ultrasonographic guidance was performed and a new lateral approach undertaken. For ultrasonographic investigations, the neck was divided into 4 zones according to anatomical and clinical modalities: 1) insertion of the funiculus nuchae; 2) tuberculum dorsale of the atlas; 3) atlanto‐occipital joint and 4) region above the foramen alare. Each zone was examined in transverse and longitudinal planes proceeding from cranial to caudal. Ultrasonography was found to be useful for soft tissue imaging of this region and was performed down to the atlanto‐occipital joint of which the joint surfaces, joint capsule and collateral ligament could be delineated in both planes. We conclude that ultrasonography of the neck is a useful technique, representing an easy to use and safe method. However, further studies are indicated which should be performed on live subjects.
Urea as a measure of dilution of equine synovial fluid
Authors: GOUGH M. R. , MUNROE G. A. , MAYHEW I. G.
Published: April 2007

This paper tests the hypothesis that serum and synovial urea concentrations are similar and that urea concentration can be used as an accurate marker for synovial fluid dilution in normal equine joints. Serum and synovial fluid urea concentrations were compared in 42 horses and were equivalent for individual horses (P<0.0001). Mean ± s.e. serum concentration was 6.1 ± 0.552 mmol/l and synovial concentration 6.0 ± 0.459 mmol/l. The normal range for synovial urea concentration was determined as 2.5–7.7 mmol/l. The synovial urea concentration from different synovial structures in individual horses were compared and were equivalent (P = 0.002). Known dilutions of synovial fluid with saline were made. The actual and expected synovial urea concentrations were compared and were equivalent (P<0.001). An accurate method of calculating synovial fluid dilution has been determined.
Antigen challenge increases adherence of circulating neutrophils in horses with chronic obstructive pulmonary disease
Authors: MARR K. A. , LEES P. , CUNNINGHAM F. M.
Published: April 2007

Activation of circulating neutrophils has been observed following challenge of horses with chronic obstructive pulmonary disease (COPD) and may facilitate the accumulation of these cells in the airways. In this study, no significant difference was observed between adherence to protein coated plastic of blood neutrophils from asymptomatic COPD‐susceptible and normal horses stimulated by the mediators PAF, human recombinant (hr)IL‐8 and hrC5a. Twenty‐four hours after the start of a 7 h antigen challenge, adherence of unstimulated neutrophils from COPD‐susceptible horses increased from 2.5 (0.5–4.1)% and 3.4 (0.6–6.6)% to 19.6 (16.9–20.3)% and 21.8 (10.6–23.1)% adherence for cells in medium containing 0.1% or 0.2% BSA, respectively; (median [range]; n = 4). Adherence of cells from normal horses remained unchanged. Addition of an anti‐CD18 monoclonal antibody, H20A, inhibited the increase in adherence at 24 h by 96 (45–100)%, n = 3. The percentage of neutrophils in bronchoalveolar lavage fluid at 24 h increased from 1 (0–2) to 80 (65–94), (median (range), n = 4). These results suggest that antigen challenge results in exposure of circulating equine neutrophils to one or more factors that prime, or activate, these cells, which may enhance their recruitment to the lungs. Inhibition of circulating neutrophil activation may therefore represent a therapeutic target.
Normal ultrasonographic anatomy and injury of the patellar ligaments in the horse
Authors: DYSON S. J.
Published: April 2007

The purposes of this study were to investigate the ultrasonographic appearance of the patellar ligaments in clinically normal horses and to describe the clincical features, diagnosis and outcome of patellar ligament injury. The medial, middle and lateral patellar ligaments of 5 Thoroughbred and 5 Warmblood horses, free from lameness and in full work, were examined ultrasonographically. The ligaments were all of uniform echogenicity and each ligament was fairly consistent in its shape. The size of the ligaments of the Warmblood horses tended to be bigger than the lighter bodyweight Thoroughbred horses. The bone surfaces were smooth at the ligament insertions on the patella and tibia. Nine horses, including 7 showjumpers, were identified with a unilateral hindlimb lameness associated with ultrasonographic evidence of damage to one or more patellar ligaments. Four horses had primary desmitis of the middle patellar ligament, one of which had concurrent intermittent upward fixation of the patella and a second had abnormal movement of the patella. Two additional horses had desmitis of the middle patellar ligament associated with previous medial patellar desmotomy. Two horses had desmitis of both the middle and lateral patellar ligaments, and one horse had desmitis of the lateral patellar ligament alone. None of the 9 horses were able to return consistently to their former level of competition. Careful clinical evaluation and ultrasonographic examination of the patellar ligaments should be considered in horses with hindlimb lameness of otherwise undetermined cause.
Immunological and haematinic consequences of feeding a standardised Echinacea (Echinacea angustifolia) extract to healthy horses
Authors: O'NEILL W. , McKEE S. , CLARKE A. F.
Published: April 2007

This study was undertaken to compile new data on the efficacy of Echinacea in stimulating the immune system of the horse. Use of Echinacea is becoming widespread in horses, despite an absence of controlled laboratory research into its effectiveness or safety. This paper documents results of a double‐blind, placebo‐controlled, cross‐over trial investigating the effect of standardised Echinacea extract on 8 horses. Animals were supplemented with Echinacea or placebo for 42 days, and their response to supplements recorded. Treatment with Echinacea increased phagocytic ability of isolated neutrophils, boosted peripheral lymphocyte counts and appeared to stimulate neutrophil migration from peripheral circulation into the tissues. Echinacea supplement also increased the size and concentration of peripheral red blood cells, and the concentration of haemoglobin and packed cell volume. It was concluded that Echinacea effectively stimulates equine immunocompetence, and the plant extract behaves, in equine subjects, as a haematinic agent, i.e. one which improves the quality of blood by increasing haemoglobin levels and the numberof erythrocytes and which, by virtue of theireffects on oxygen transport cells, are considered to improve parameters of exercise physiology and performance.
Repeatability of back kinematics in horses during treadmill locomotion
Authors: FABER M. , JOHNSTON C. , VAN WEEREN P. R. , BARNEVELD A.
Published: April 2007

We tested the hypothesis that repeatability of a standardised protocol for quantifying back kinematics is sufficiently high not to prevent its use in the clinical evaluation of horses with back problems. We investigated the extent to which differences between laboratories may affect the results when a standardised protocol is used. As a clinical tool, movement analysis techniques are helpful for the objective and quantitative assessment of kinematics. Knowledge about the repeatability of the kinematic data is very important. The present study investigates the repeatability of back kinematics in 10 sound horses over5 successive days and in 2 laboratories (5 horses at each location). Measurements were performed on the treadmill during the walk and the trot. The between‐stride, between‐day and between‐horse repeatability were determined. A high degree of between‐stride and between‐day repeatability was observed in the spatiotemporal parameters and in the time‐angle diagrams of thoracic and lumbar vertebrae, the sacrum and the hindlimb during both the walk and trot. Much more variability was found between horses, with the highest degree of dissimilarity in the lateral bending rotation of the L1 vertebra. For range of motion values, the between‐day coefficient of variability was <14% and the between‐horse coefficient of variability was up to 4 times higher. Small differences were found in range of motion values between the 2 laboratories. It is concluded that an analysis of back kinematics in the horse can provide highly repeatable data, warranting clinical use.
Dietary soyabean oil depresses the apparent digestibility of fibre in trotters when substituted for an iso‐energetic amount of corn starch or glucose
Authors: JANSEN W. L. , GEELEN S. N. J. , KUILEN J. van der , BEYNEN A. C.
Published: April 2007

The aim of the present study was to establish whether the inhibitory effect of fat feeding on fibre digestion has been underestimated due to the substitution of fat for corn starch. A high fat intake has been shown to lower total intestinal tract apparent digestibility of crude fibre in horses but, since fat was substituted for nonstructural carbohydrates, including starch, the specific effect of fat could not be ascertained. The possibility could not be excluded that starch also inhibits fibre digestibility, so that the fat effect observed earlier would have been underestimated. In this study, the intakes of iso‐energetic amounts of soyabean oil, corn starch or glucose were compared as to fibre digestibility. Unlike starch, glucose is fully absorbed by the small intestine and, therefore, is not expected to influence fibre fermentation in the caecum and colon. Six trotters were fed rations high in soyabean oil (158 g/kg dry matter), corn starch (337 g/kg dry matter) or glucose (263 g/kg dry matter) according to a 3 × 3 Latin square design. Apparent crude fibre digestibility was similar for the rations with corn starch (mean ± s.d., 70.7 ± 3.06% of intake, n = 6) or glucose (71.0 ± 1.90%), but was significantly depressed by fat feeding (56.5 ± 7.65%). Similar observations were made for apparent digestibilities of neutral and acid detergent fibre and of cellulose. It was concluded that the addition of fat to the feed ration of horses has a specific inhibitory effect on fibre utilisation and, therefore, reduces the amount of energy provided by dietary fibre.
Chemoattractant properties of conditioned medium from equinecorpora luteacollected at various stages of the oestrous cycle
Authors: LAWLER D. F. , BRAZIL T. J. , DAGLEISH M. P. , WATSON E. D.
Published: April 2007

This study investigated the chemotactic activity of equine CL at different stages of the oestrous cycle. The purpose of this was to ascertain whether luteal tissue itself contributes to the massive influx of leucocytes around the time of natural and induced luteal regression.Corpora luteawere collected at different stages of dioestrus and after treatment with PGF2αCulture medium harvested afterincubation of luteal tissue for 20 h was chemotactic for both polymorphonuclear and mononuclear cells in late dioestrus (before functional regression) as well as after natural and induced luteal regression. By contrast, midluteal tissue showed no chemotactic activity. This is the first report of the ability of equine luteal tissue actively to recruit inflammatory cellsin vitroand supports our earlier findings that this infiltration starts prior to functional luteolysis. We hypothesise that this early influx of inflammatory cells may play an active role in luteal regression. Further research is needed to identify the specific chemotactic factor(s).
Age‐related morphometry of equine calcified cartilage
Authors: MARTINELLI M. J. , EURELL J. , LES C. M. , FYHRIE D. , BENNETT D.
Published: April 2007

Although there are many studies in the equine literature focused on articular diseases and the aetiology of osteoarthritis, few have concentrated on normal articular structures and how they change with age.

The objective of this investigation was to study the thickness and morphology of the calcified cartilage layerof the distal metacarpus over a range of ages. A parasagittal slab of bone was sectioned from the region of sesamoid contact on the medial condyle of the metacarpi from 34 horses. The slab of bone was preserved, dehydrated and embedded, undecalcified, in methylmethacrylate and then stained with toluidine blue. Six repeatable fields of interest from the distal aspect of each metacarpus were digitised and examined to determine the morphology of the calcified cartilage layer. The thickness of the calcified cartilage, range 88–426 μm, was estimated using a method of integration.

The results indicate an age‐related influence on the thickness of the calcified cartilage layer, generally increased in older horses. While this finding is significant, perhaps more importantly a positional relationship was also identified, indicating that pressures endured by different regions within a joint may dictate morphological development of the tissues. This study has begun to lay the groundwork to determine whether the calcified layer of the hyaline cartilage could be involved in the development of osteoarthritis.
Equine oocyte maturation with epidermal growth factor
Authors: LORENZO P. L. , LIU I. K. M. , CARNEIRO G. F. , CONLEY A. J. , ENDERS A. C.
Published: April 2007

Epidermal growth factor (EGF) has been shown to have a positive effect during oocytein vitromaturation in several species. This study was performed to establish the capacity of equine oocytes to undergo nuclear maturation in the presence of EGF and to localise its receptor in the equine ovary by immunohistochemical methods. Oocytes were obtained by aspiration and subsequent scraping from equine follicles (15–25 mm diameter) and cultured in 3 different treatment groups for 36 h: control Group (modified TCM 199 with 0.003% BSA), EGF Group (TCM‐199 supplemented with 50 ng/ml EGF) and EMS Group (TCM 199 supplemented with 10% v/v oestrous mare serum). Each group was divided further into 3 treatments with tyrphostin A‐47, a specific tyrosine kinase inhibitor, at 0, 10−4and 10−6mmol/l. Maturation was determined as the percentage of oocytes reaching metaphase II stage at the end of the culture period. Immunohistochemical detection of EGF‐receptor (EGFR) was performed using a streptoavidinbiotin method. The recovery rate and oocyte retrieval were 84.6% (recovered oocytes/follicles aspirated) and 6.55 (oocytes/mare), respectively. Treatment with EGF significantly (P<0.05) increased the incidence of metaphase II stage compared with the control group (69.4 vs. 26.9% in controls, respectively). The specific‐tyrosine kinase inhibitor A‐47 was effective in suppressing EGF‐effect on EGF‐cultured oocytes; no significant differences were observed in EMS‐supplemented oocytes when cultured with A‐47. EGF‐receptor was localised in follicles, with localisation being more prominent in the cumulus than in mural granulosa cells. This finding, together with the increase of oocyte nuclear maturation rate when using EGF in culture media and the inhibition of maturation by tyrphostin A‐47, suggests a physiological role for EGF in the regulation of equine oocyte maturation. The results should help successful development of assisted reproductive technology in the horse.
Interleukin‐4 and interferon‐gamma gene expression in summer pasture‐associated obstructive pulmonary disease affected horses
Authors: BEADLE R. E. , HOROHOV D. W. , GAUNT S. D.
Published: April 2007

We hypothesised that horses affected with summer pasture‐associated obstructive pulmonary disease (SPAOPD) react to an allergen or allergens in their summer environment that is either absent or present at lower levels in their winter environment; and that such allergencs stimulate SPAOPD‐affected horses to produce a different T helper lymphocyte cytokine profile from that of control horses. The primary objective of this study was to determine the cytokine mRNA profile of T helper lymphocytes obtained from summer pasture‐associated obstructive pulmonary disease (SPAOPD) affected horses when 1) the horses were showing signs of disease (summer) and 2) they were in clinical remission (winter). A further objective was to determine the differences between cytokine mRNA T helper lymphocyte profiles of control and affected horses in the summer and winterseasons. Interleukin 4 (IL‐4) and interferon‐gamma (IFN‐γ) mRNA expression levels were increased in bronchoalveolar lavage fluid (BALF) and peripheral blood mononuclear cell (PBMC) samples of affected horses during disease expression. No significant amounts of IL‐5 mRNA were detected in any of the samples. These results suggest that there is an allergic component to SPAOPD of horses and that appropriate manipulation of the immune system could offer hope for treatment and prevention of the disease in the future. Further research studies will be needed to determine the most appropriate treatments to use to alter the antigen‐stimulated cytokine profile being expressed by SPAOPD‐affected horses or to alter the effects that these cytokines produce.
Changes in physiological parameters in overtrained Standardbred racehorses
Authors: HAMLIN M. J. , SHEARMAN J. P. , HOPKINS W. G.
Published: April 2007

Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial increased by 4.0% (95% probable range of true value 1.7–5.8) and peak velocity decreased by 6.9% (4.7–8.9), indicating that overtraining had occurred. Acute overtraining coincided with an increase in blood lactate concentration after the time trial and submaximal test. There were also substantial decreases in bodyweight, plasma cortisol concentration and packed cell volume after the time trial, and in the velocity at a heart rate of 200/min (V200). Parameters that showed no clear‐cut change with overtraining included maximal and recovery heart rate, basal plasma cortisol, plasma and red cell volume, and markers of skeletal damage (plasma concentrations of creatine kinase and aspartate aminotransferase). Bodyweight, V200, postexercise blood lactate and plasma cortisol concentrations may all be useful for detecting acute overtraining in equine athletes.
Characterisation of reconstituted equine cartilage formedin vitro
Authors: SUN Y. , CHEN H. , KANDEL R. , HURTIG M.
Published: April 2007

Lesions in cartilage of equine weight bearing joints commonly result in lameness. Cell‐based resurfacing techniques are currently being developed for human and veterinary applications. Biopsies of stifle joint cartilage (1 g) were harvested aseptically and chondrocytes were isolated by sequential enzyme digestion. The cells were grownin vitroon filterinserts. Analysis of cultures 8 weeks latershowed that the cells had accumulated extracellular matrix and formed a continuous layer of cartilagenous tissue as determined histologically. The cells maintained their phenotype as they synthesisedtype IIcollagen and proteoglycans similar in size to those synthesised by chondrocytes in native cartilage, but this reconstituted tissue had more sulphated glycosaminoglycan and lower collagen content than native cartilage. This experiment tests the feasibility of growing equine cartilagenous tissuein vitro.This tissue may be useful in the management of chondral injuries in the horse in a scenario where the patient donates cells, the cells are propagated under laboratory conditions and the resulting tissue becomes the therapeutic agent.
Pharmacokinetics of marbofloxacin in horses
Authors: BOUSQUET‐MELOU A. , BERNARD S. , SCHNEIDER M. , TOUTAIN P. L.
Published: April 2007

Marbofloxacin is a fluoroquinolone antibiotic expected to be effective in the treatment of infections involving Gram‐negative and some Gram‐positive bacteria in horses. In order to design a rational dosage regimen for the substance in horses, the pharmacokinetic properties of marbofloxacin were investigated in 6 horses after i.v., subcutaneous and oral administration of a single dose of 2 mg/kg bwt and the minimal inhibitory concentrations (MIC) assessed forbacteria isolated from equine infectious pathologies. The clearance of marbofloxacin was mean ± s.d. 0.25 ± 0.05 l/kg/h and the terminal half‐life 7.56 ± 1.99 h. The marbofloxacin absolute bioavailabilities after subcutaneous and oral administration were 98 ± 11% and 62 ± 8%, respectively. The MIC required to inhibit 90% of isolates (MIC90) was 0.027 μg/ml for enterobacteriaceae and 0.21 μg/ml forStaphylococcus aureus.

The values of surrogate markers of antimicrobial efficacy (AUIC, Cmax/MIC ratio, time above MIC90) were calculated and the marbofloxacin concentration profiles simulated for repeated administrations. These data were used to determine rational dosage regimens for target bacteria. Considering the breakpoint values of efficacy indices for fluoroquinolones, a marbofloxacin dosage regimen of 2 mg/kg bwt/24 h by i.v., subcutaneous or oral routes was more appropriate for enterobacteriaceae than forS. aureus.
Molecular characterisation of carbohydrate digestion and absorption in equine small intestine
Authors: DYER J. , MEREDIZ E. FERNANDEZ‐CASTAÑO , SALMON K. S. H. , PROUDMAN C. J. , EDWARDS G. B. , SHIRAZI‐BEECHEY S. P.
Published: April 2007

Dietary carbohydrates, when digested and absorbed in the small intestine of the horse, provide a substantial fraction of metabolisable energy. However, if levels in diets exceed the capacity of the equine small intestine to digest and absorb them, they reach the hindgut, cause alterations in microbial populations and the metabolite products and predispose the horse to gastrointestinal diseases. We set out to determine, at the molecular level, the mechanisms, properties and the site of expression of carbohydrate digestive and absorptive functions of the equine small intestinal brush‐border membrane. We have demonstrated that the disaccharidases sucrase, lactase and maltase are expressed diversely along the length of the intestine and D‐glucose is transported across the equine intestinal brush‐border membrane by a high affinity, low capacity, Na+/glucose cotransporter type 1 isoform (SGLT1). The highest rate of transport is in duodenum > jejunum > ileum. We have cloned and sequenced the cDNA encoding equine SGLT1 and alignment with SGLT1 of other species indicates 85–89% homology at the nucleotide and 84–87% identity at the amino acid levels. We have shown that there is a good correlation between levels of functional SGLT1 protein and SGLT1 mRNA abundance along the length of the small intestine. This indicates that the major site of glucose absorption in horses maintained on conventional grass‐based diets is in the proximal intestine, and the expression of equine intestinal SGLT1 along the proximal to distal axis of the intestine is regulated at the level of mRNA abundance. The data presented in this paper are the first to provide information on the capacity of the equine intestine to digest and absorb soluble carbohydrates and has implications for a better feed management, pharmaceutical intervention and for dietary supplementation in horses following intestinal resection.
Detection of cold‐adapted vaccine‐strain influenza virus using two commercial assays
Authors: ADAM E. N. , MORLEY P. S. , CHMIELEWSKI K. E. , CARMAN J. , GONZALES G.
Published: April 2007

Because of the contagious nature of influenza virus it is necessary to identify infected individuals after the virus is introduced into a population. The aim of this study was to characterise influenza virus detection with commercially available assays after intranasal vaccinating horses with cold‐adapted influenza virus. Seven horses were vaccinated and placed with 3 unvaccinated horses. Nasal secretion samples were evaluated using 2 antigen detection assays. All 10 horses were positive in the Flu OIA assay during the study period, but only one horse was positive on one sample using the Directigen Flu A assay. Horses were most likely to be positive during the first 3 days following vaccination, and several horses were intermittently positive for several days after this. Obtaining positive test results from nonvaccinated, incontact horses suggests they became infected with vaccine‐strain virus that was shed by vaccinated horses. These results are important for the correct interpretation of influenza antigen detection tests in situations when this modified‐live intranasal vaccine has been used.
Evaluation of a combined laser Doppler flowmetry and iontophoresis technique for the assessment of equine cutaneous microvascular function
Authors: McGORUM B. C. , MILNE A. J. , TREMAINE W. H. , STURGEON B. P. R. , McLAREN M. , KHAN F.
Published: April 2007

A combined laser Doppler flowmetry and iontophoresis (LDFI) technique, used routinely to assess human microvascular function, was evaluated as a noninvasive technique for assessment of equine microvascular function, to facilitate the study of diseases such as laminitis. Baseline and vasoactive agonist‐induced (acetylcholine and nitroprusside) microvascular flux was quantified at 2 sites (on the dorsal pastern adjacent to the coronary band and over the gluteals) in 6 clinically normal horses on 5 or 6 separate occasions under standardised conditions. Both agonists significantly increased microvascular flux. Skin pigmentation significantly attenuated the baseline flux, but not the magnitude of the agonist‐mediated vasodilatory response. While LDFI was simple to perform, its value as a clinical and research tool for assessing the equine cutaneous microcirculation is limited by its poor reliability, as indicated by the marked intra‐ and intersubject variability in baseline and agonist‐mediated microvascularflux.
Plasma adrenocorticotropin (ACTH) concentrations and clinical response in horses treated for equine Cushing's disease with cyproheptadine or pergolide
Authors: PERKINS G. A. , LAMB S. , ERB H. N. , SCHANBACHER B. , NYDAM D. V. , DIVERS T. J.
Published: April 2007

Plasma ACTH levels have been variable in horses with a positive clinical response for therapy for equine Cushing's Disease (ECD). Therefore, our purpose was to determine the value of monitoring plasma adrenocorticotropin (ACTH) levels during treatment of equine Cushing's disease (ECD) with either cyproheptadine (n = 32) or pergolide (n = 10). First, we validated the chemiluminescent ACTH assay (specificity, precision, accuracy, intra‐assay and interassay variations) and tested methods of handling the whole blood from the time of collection to when the ACTH was assayed. The sensitivity and specificity of high plasma ACTH levels for detecting ECD was determined in a retrospective study on hospitalised horses (n = 68). Surveys were sent to veterinarians who submitted equine ACTH levels that were high initially and had at least 2 ACTH samples to determine the value of monitoring ACTH levels during therapy of ECD.

The ACTH chemiluminescent assay was valid. The ACTH was stable when whole blood was collected and held in plastic tubes for 8h before separating the plasma. The sensitivity and specificity of plasma ACTH levels for detecting ECD were 84% (n = 19, 95% CI 60, 97) and 78% (n = 49, 95% CI 63, 88), respectively. Treated horses generally showed a decrease in plasma ACTH. Plasma ACTH levels may be helpful when monitoring therapy of ECD, although improvement in clinical signs should be considered most important. There were no differences between cyproheptadine and pergolide in terms of improvements in any of the clinical signs.
Calcium homeostasis and intact plasma parathyroid hormone during exercise and training in young Standardbred horses
Authors: VERVUERT I. , COENEN M. , WEDEMEYER U. , CHROBOK C. , HARMEYER J. , SPORLEDER H. ‐P.
Published: April 2007

Physical exercise is known to affect calcium homeostasis in horses, but there is little information on the hormonal regulation of calcium metabolism during exercise. In order to evaluate the effects of exercise and training on calcium homeostasis and intact plasma parathyroid hormone, 7 untrained Standardbred horses were studied in a 6 week training programme. These horses were accustomed to running on the treadmill 3 weeks before onset of training and were exercised on a high‐speed treadmill with an initial incremental standardised exercise test (SET 1: 6 incremental steps of 5 min duration each; first step 5 m/s, increase 1 m/s). SET 1 was followed by a lactate‐guided training programme (6 weeks in total) with 2 types of exercise in alternating order with a day of rest after each work day: high‐speed exercise (HSE) of 15 min duration, starting at VLa4, continuous increase in speed every 60 s by 0.3 m/s (14 incremental steps); and low‐speed exercise (LSE) at a constant velocity at VLa2.5, duration ˜60–90 min. The whole training programme consisted of 8 HSE and 8 LSE sessions. HSE and LSE were calculated to require the same energy expenditure. A final SET (SET 2) finished the training programme. Blood samples for lactate, plasma total calcium [Ca], blood ionised calcium [Ca2+], blood pH, plasma inorganic phosphorus [Pi] and plasma intact parathyroid hormone [PTH] were collected before, during and after SETs 1 and 2, before and after the first and eighth HSE and LSE. During SETs 1 and 2, HSEs 1 and 8 there was a decrease in ionised Ca2+and pH and a rise in lactate, intact PTH and Pi. LSEs 1 and 8 resulted in an increase in pH, whereas lactate, ionised Ca2+, total Ca, Piand intact PTH were not affected. No changes in calcium metabolism were detected during training. Results of this study suggest that intact PTH is a mediator in counter‐regulation of exercise‐induced hypocalcaemia.