bluuebunny/crossref_metadata_2025 huggingface dataset:
Haemodynamic effects of a sixty minute infusion of dopamine hydrochloride in horses anaesthetised with halothane
Authors: YOUNG LESLEY E. , BLISSITT KAREN J. , CLUTTON R. E. , MOLONY V.
Published: April 2010

To describe the haemodynamic effects of a 60 min infusion of dopamine 4 pg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 μg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2between 4.6‐5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measured using intracardiac strain gauge transducers sited in the left and right ventricle, aorta, and pulmonary artery. Left ventricular pressure was differentiated to obtain maximal rate of increase of intraventricular pressure (LVdp/dtmax). Transoesophageal Doppler echocardiography was performed to measure maximum aortic blood flow velocity (vmax) and acceleration (dv/dtmax), left ventricular velocity time integral (vTI) and cardiac output (CO), and left ventricular pre‐ejection period (PEP) and ejection time (ET). Measurements were made during the 60 min infusion, and for 30 min after the infusion was discontinued.

Infusion of dopamine 4 μg/kg/min significantly decreased mean aortic pressure, while left and right ventricular end‐diastolic pressure and mean pulmonary artery pressure remained unchanged. There was a small, but significant, increase in heart rate during dopamine infusion. Maximum acceleration of aortic blood flow, CO andvTI were also significantly increased by dopamine infusion. Maximal rate of increase of intraventricular pressure (LVdp/dtmax) was significantly decreased 10 min after commencing infusion, but then returned to baseline for the remainder of the study. Left ventricular pre‐ejection period (PEP) decreased during dopamine infusion whilst ejection time (ET) significantly increased. All measured variables except LVET had returned to baseline values within 30 min of discontinuing the infusion.

This study demonstrated beneficial effects of dopamine infusion upon left ventricular systolic function. However, the therapeutic value of the drug is likely to be limited in clinical anaesthesia due to the simultaneous falls in arterial blood pressure which accompany its administration.
Increase in blood viscosity in the sprinting horse: can it account for the high pulmonary arterial pressure?
Authors: FEDDE M. R. , ERICKSON H. H.
Published: April 2010

Blood was taken from 49 Thoroughbred horses before and after racing at the track to determine if frusemide modified the apparent viscosity of the blood and to determine the effects of changes in shear rate and packed cell volume (PCV), associated with strenuous exercise, on apparent and relative viscosities. Small increases in apparent viscosity of the blood (at a specified PCV and shear rate) occurred in horses given frusemide compared to those receiving no frusemide; however, no differences were seen in relative viscosity. Although 2 groups of horses, those receiving frusemide before racing and those not receiving this drug were studied, the results suggest no infuence of frusemide on any red blood cell variable that might modify apparent blood viscosity. Apparent viscosity of the blood was slightly (but significantly) higher after racing than before racing at any given PCV and shear rate, but relative viscosity was lower in the post race than in the prerace blood sample. The most important contributing factor to the increase in apparent viscosity in blood during racing is the increase in PCV, because the blood becomes nearly shear rate independent at shear rates likely to exist in the cardiovascular system during exercise. With an increase in PCV from 40 to 65% at shear rates above 225/s, apparent viscosity approximately doubled. However, this increase alone cannot account for the elevated pulmonary vascular pressure in the running horse, and additional factors, especially those causing the high left atrial pressure, must be considered. The cause of the elevated pressure may be multifactorial in nature.
Acetaminophen as a marker of gastric emptying in ponies
Authors: DOHERTY T. J. , ANDREWS F. M. , PROVENZA MELANIE K. , FRAZIER DONITA L.
Published: April 2010

Gastric emptying was evaluated in ponies using the acetaminophen (AP) method. Fifteen minutes after i.v. administration of metoclopramide, erythromycin, yohimbine, atropine or saline, the ponies were given AP by stomach tube. Blood samples for AP analysis were collected at baseline and 15, 30, 45, 60, 75, 90, 105 and 120 min after AP administration. Time to reach peak serum concentration (Tmax), maximum serum concentration (Cmax) and area under the AP serum concentration vs. time curve (AUC) were determined for each treatment group.

In the control group, Tmaxwas 31 min and this decreased significantly (P<0.05) following the administration of metoclopramide. Atropine significantly increased Tmaxand decreased Cmaxand AUC. Yohimbine significantly increased AUC. Erythromycin did not significantly change any parameter.

This study indicates that acetaminophen can be used to evaluate gastric emptying in ponies. The method is easy to perform and is minimally invasive. Metoclopramide stimulated gastric emptying of liquid in healthy, fasting ponies. Atropine significantly delayed, while erythromycin had little effect on, gastric emptying. Yohimbine increased the cumulative absorption of AP.
Exercise‐induced pulmonary haemorrhage (EIPH) in horses results from locomotory impact induced trauma ‐ a novel, unifying concept
Authors: SCHROTER R. C. , MARLIN D. J. , DENNY E.
Published: April 2010

Exercise‐induced pulmonary haemorrhage (EIPH) in horses, although of major welfare and economic importance worldwide, is of uncertain cause. It is accepted that the dorsocaudal region of the lung is particularly prone to the condition, but present theories of causation cannot satisfactorily explain the mechanism or pattern of occurrence. We propose that EIPH results from locomotory impact induced trauma; the mechanism being similar to that producing lung tissue damage following thoracic impact injury.

In impact injury, the localised impulsive load on the chest wall is transmitted by pressure waves through the lung at a slower speed than in the chest wall. The waves are subsequently reflected from the distal chest wall and other structures, producing a complex pattern of wave motion; waves travelling from regions of large cross‐section to narrower ones are amplified in magnitude, consequently these regions can experience very high local stresses. Compression/dilation and shear waves are produced within the parenchyma and the latter particularly have been implicated as the cause of parenchymal damage and rupture with oedema and haemorrhage. This form of soft tissue damage has been shown to occur at remarkably low loads with an impact velocity greater than about 11 m/s and pressure exceeding approximately 14 kPa.

In the horse, the lung is subjected to comparable levels of locomotory derived impulsive force during moderate to high speed exercise and this is the basis of the mechanism causing EIPH. During locomotion, the force following ground‐strike of the front legs is transmitted, with some attenuation, through the forelimbs to the scapulae. The anatomical arrangement of the scapula, coupled with the direction of the force at the shoulder (scapulo humeral joint) produces an impulsive force on the rib cage, approximately just below mid height of the frontal aspect of the chest approximately over the fourth rib. As a result, pressure waves are transmitted through the lung parenchyma towards the dorsal and caudal regions; these waves are subsequently reflected at the distal chest wall, spine and diaphragm causing a complex pattern of wave interaction. The observed locations of EIPH are at the sites where wave intensity is expected to be greatest due to changes in cross section and reflection. Based on available information, it is estimated that impulsive forces of more than 100 kPa, lasting approximately 10 ms, would be applied to the chest wall by each scapula in a 500 kg horse when galloping; this level of force would be sufficient to cause oedema and haemorrhage as observed in impact induced injury.
Tapeworm infection is a significant risk factor for spasmodic colic and ileal impaction colic in the horse
Authors: PROUDMAN C. J. , FRENCH N. P. , TREES A. J.
Published: April 2010

The association between the equine intestinal tapewormAnoplocephala perfoliataand specific types of intestinal disease was investigated by matched case‐control study using coprological and serological diagnosis. We have previously shown that the host IgG(T) response to 12/13 kDa antigens ofA. perfoliatacorrelates well with infection intensity, therefore this antibody response was used to investigate the risk of colic at different levels of parasite infection intensity. One hundred and three spasmodic colic cases with an equal number of controls matched for age, breed and gender, and 20 ileal impaction cases each with 2 similarly matched controls were obtained. Cases of spasmodic colic were much more likely (odds ratio = 8.0) to be associated withA. perfoliatainfection detected coprologically than controls. Serological diagnosis revealed an increasing risk of spasmodic colic with increasing infection intensity. Calculation of an aetiological fraction suggests that 22% of spasmodic colic cases in this study were tapeworm associated. No significant association was found between colic and strongyle egg count. Conditional logistic regression analysis demonstrated that the relationship between colic and A.perfoliatainfection intensity was not confounded by strongyle egg count and there was a linear relationship between infection intensity and the log‐odds of spasmodic colic. For cases of ileal impaction, a strong association was found between colic andA. perfoliataas diagnosed by coprological means (odds ratio of 34.0). Serological diagnosis also revealed a strong association that increased with higher levels of infection intensity (odds ratio = 26.0). The aetiological fraction for the ileal impaction data suggests that 81% of the ileal impaction cases in this study were tapeworm associated. This study concludes thatA. perfoliatais a significant risk factor for spasmodic colic and ileal impaction colic in the horse; and that the risk of spasmodic colic increases with infection intensity.
Effect of copper supplementation on the copper status of pasture‐fed young Thoroughbreds
Authors: PEARCE S. G. , GRACE N. D. , FIRTH E. C. , WICHTEL J. J. , HOLLE S. A. , FENNESSY P. F.
Published: April 2010

The effect of copper supplementation of pasture fed mares and foals on the copper status of the foals, in terms of plasma, soft tissue and bone copper concentrations and caeruloplasmin activity, was investigated. Twenty‐one Thoroughbred foals from either control mares (n = 9), or copper‐supplemented mares (n = 12) were divided randomly into control (pasture only, n = 10) or supplemented (pasture and oral copper sulphate, n = 11) groups. The pasture diet was grazed by all animals, and contained 4.4–8.6 mg Cu/kg dry matter (DM). The copper supplement for the mares contained copper sulphate equivalent to 0.5 mg Cu/kg liveweight (LW)/day. This daily dose was converted to allow administration as a thrice weekly dose (i.e. multiplied by 7/3) which was given for 13–25 weeks prior to foaling. The supplemented foals, also dosed 3 times a week, received 0.2 mg Cu/kg LW/day at age 21 days, which was increased to 0.5 mg Cu/kg LW/day at 49 days and was continued at this level until euthanasia at 150 days. Foal plasma copper concentration and caeruloplasmin activity increased from birth to 21 dayspost partumand then plateaued at a concentration similar to the mare, but the rise in these indices was not affected by copper supplementation of the mare or foal. Copper supplementation of the foal increased foal liver copper concentration at 150 days (P<0.03). Copper intake of diets containing approximately 8–28 mg Cu/kg DM is well reflected by liver copper concentration, but is poorly reflected by bone, other soft tissue copper concentrations and circulating copper status indices.
Effect of copper supplementation on the evidence of developmental orthopaedic disease in pasture‐fed New Zealand Thoroughbreds
Authors: PEARCE S. G. , FIRTH E. C. , GRACE N. D. , FENNESSY P. F.
Published: April 2010

The effect of copper status on the evidence of bone and cartilage lesions was investigated in 21 Thoroughbred foals. The foals and their dams were grazed on pasture containing 4.4–8.6 mg Cu/kg dry matter (DM). Four treatment groups were created by randomly allocating mares and their foals to either copper supplemented (0.5 mg Cu/kg liveweight (LW)/day), or control (pasture only) groups. This experimental design allowed the effect of copper supplementation of mare and foal to be examined independently. Parameters of bone and cartilage development were assessed in the foals bothin vivo, and atpost mortemat approximately age 150 days. Mare copper supplementation significantly (P<0.01) decreased radiographic indices of physitis in the distal third metatarsal bone of the foals at 150 days, and the prevalence of articular cartilage lesions (P<0.05). Articular cartilage lesions were minor in all foals, with no evidence of clinical developmental orthopaedic disease (DOD)in vivo, with the exception of minor radiographic changes assessed atpost mortem.Copper supplementation of the foal had no effect on any of the bone and cartilage parameters. Copper supplementation of the mares did not abolish DOD in the growing foals, emphasising the probable multifactorial nature of this condition. However, mare supplementation may be a useful treatment regime on a farm where the incidence and severity of DOD are of concern.
Gross, histological and histomorphometric features of the navicular bone and related structures in the horse
Authors: WRIGHT I. M. , KIDD LISA , THORP B. H.
Published: April 2010

Forelimb navicular bones and associated soft tissues were collected from 3 groups of horses and subjected to pathological examinations. The groups consisted of 38 horses with clinical navicular disease (ND) and 2 control groups, with no history of forelimb lameness, consisting of 25 age‐matched mature horses (A‐MC) and 9 immature horses (IC). Histological and histomorphometric studies were performed on tissue samples from 10 ND, 10 A‐MC and 5 IC horses.

Gross changes seen only in ND horses included: full thickness defects in the palmar surface fibrocartilage, palmar cortex erosion, medullary lysis, flexor digitorum profundus tendon (FDPT) surface fibrillation, FDPT core lesions and adhesions between the FDPT and navicular bone. Palmar surface partial thickness fibrocartilage loss and distal border fragmentation were seen with a significantly greater incidence in ND than in A‐MC and not observed in IC. Remodelling of the proximal border, FDPT surface colouration, palmar surface fibrocartilage colouration and proximal border entheseous bone were identified in ND and A‐MC but not in IC. Mid‐ridge synovial fossae and horizontal depressions in the palmar surface were identified in all groups.

Histologically palmar fibrocartilage thinning and loss were associated with reduced palmar fibrocartilage cell density and chondrocyte cluster formation. Palmar fibrocartilage fibrillation, palmar cortical bone defects, fibromyxoid stromal change in the medulla, medullary pseudocyst formation and entheseous new bone formation were all seen in ND. The adjacent FDPT showed fibrillation, tag formation and degeneration of the dorsal surface. Necrotic foci were also present within the body of the tendon. Although not always present, medullary bone pseudocysts, separate mineralised foci and most changes on the dorsal surface of the FDPT were specific to ND.

Bone histomorphometric parameters were compared among groups. Cross‐sectional area reduced from the sagittal ridge to the medial and lateral margins of each navicular bone. IC navicular bones had a smaller subchondral area, subchondral bone volume and a greater osteoid volume than in the AC, indicating that these differences were age‐related. In ND the medullary area was decreased but the trabecular bone volume increased. The palmar subchondral area was increased but contained bone with an increased porosity and osteoid volume. Changes occurred from the medial to the lateral margins of the bone in horses with ND indicating remodelling of the bony elements throughout the bone in ND.

The histological and histomorphometric changes in the navicular bone and palmar fibrocartilage were considered similar of those found in articular hyaline cartilage and subchondral bone in osteoarthritis.
Ex vivoSimulation ofin vivostrain distributions in the equine metacarpus
Authors: LES C. M. , STOVER S. M. , TAYLOR K. T. , KEYAK J. H. , WILLITS N. H.
Published: April 2010

The objective of this study was to examine several simpleex vivoloading conditions for the equine metacarpus, and to evaluate their ability to reproduce the mid‐diaphyseal bone surface strain distributions previously reportedin vivoat the walk and trot. Distributed axial compressive loads, and 9 different axial compressive point loads at −7.5 kN and −15 kN were applied to metacarpal‐distal carpal bone preparations from 6 Thoroughbred horses, aged 1–5 years. The resulting dorsal, medial, palmar, and lateral mid‐diaphyseal bone surface axial and shear strains were compared with previously reportedin vivosurface strain distributions using a root mean square error (RMSE) protocol. The effects of loading condition and load magnitude on RMSE were assessed with a mixed‐model analysis of variance. There were significant differences between loading conditions, and, in most cases, between load magnitudes, in the fit of theex vivoto thein vivostrain distributions.In vivomid‐diaphyseal bone surface strain distributions at the walk can be well approximatedex vivoby a distributed axial compressive load, or by a point load positioned 0.5 cm mediad to the sagittal midline, at −7.5 kN loads.In vivomid‐diaphyseal bone surface strain distributions at the trot can be well approximated by the −15 kN loads applied to the same locations. These simplified loading conditions can be used in designing biologically relevant loading protocols forex vivomechanical testing studies, as well as in developing boundary conditions for finite element analysis.

As such, these loading conditions may be considered as tools to be used as a means of replicatingin vivoloading conditions during the intial design and testing stages in the development of fracture fixation devices, as well as in the theoretical mechanical analysis of the metacarpal structure.
An objective method for evaluating the flexibility of the back of standing horses
Authors: LICKA THERESIA , PEHAM C.
Published: April 2010

The spinal movements in maximum arching, dipping and left and right lateral flexion were measured in 10 horses without signs of back pain. A system for motion analysis (Expert Vision System) was used to identify the position of the markers placed on the head, the spinous processes of T5, T10, T16, L3, and on 2 of the sacral spines. By definition, the maximum of the spinal movement was set when the T16 marker reached its maximum deviation from the start position. The difference between start position and maximum position was presented as per cent of the horse's height at the withers. At T16 the mean results for flexion (arching) of the back were 5.9% (s.d. 0.9), for extension (dipping) −2.4% (s.d. 0.7), for flexion to the left 4.2% (s.d. 1.1), and for flexion to the right 5.3% (s.d. 1.3).
Equine TIMP‐1 and TIMP‐2: Identification, activity and cellular sources
Authors: CLEGG P. D. , COUGHLAN A. R. , CARTER S. D.
Published: April 2010

Matrix metalloproteinases (MMPs) are the main enzymes involved in connective tissue turnover. Regulation of MMPs is achieved by controlling production, activation of the proenzymes together with the presence of inhibitors, such as, tissue inhibitors of metalloproteinases (TIMPS). The presence of TIMPs in equine synovial fluid was assessed by the ability of the fluid to inhibit equine MMP‐9 activity using a gelatin degradation ELISA. The cellular source of the TIMPs was determined using culture supernatants of resident articular cells (chondrocytes and synovial fibroblasts) and invading inflammatory cells (polymorph neutrophils [PMN] and peripheral blood monocytes [PBM]). The TIMPs were characterised further using reverse zymography, affinity chromatography and N‐terminal amino acid sequencing.

Synovial fluid was recovered from horses with articular sepsis and aseptic joint disease (AJD) and compared with that from normal horses (n = 4). TIMP activity was minimal in articular sepsis but significantly increased, albeit a small increase, in AJD when compared to normal (P<0.05). Cell culture supernatants from synovial fibroblasts, chondrocytes and PBMs contained TIMP activity, although supernatants from PMN cell culture did not. Reverse zymography of synovial fluid recovered from normal and AJD horses showed two protein bands, 22 and 28 kDa in size, exhibiting inhibitory activity against MMP‐9. Reverse zymography of culture supernatants of synovial fibroblasts and chondrocytes gave similar results whereas the culture supernatants from PMNs and PBMs showed the presence of only the 28 kDa protein. The N‐terminal amino acid sequence was obtained for the 22 kDa protein and revealed a 66% homology with human TIMP‐2.

The identification of TIMPs in equine synovial fluids and cell culture supernatants suggest that they may have a fundamental role in the homeostasis of the normal joint and in the excess proteolysis which occurs in articular disease in the horse.
Total and respirable airborne dust endotoxin concentrations in three equine management systems
Authors: McGORUM B. C. , ELLISON J. , CULLEN R. T.
Published: April 2010

The concentrations of total and respirable airborne endotoxin in the breathing zone of a pony in 3 different management systems, on 8 occasions, are reported. Airborne endotoxin concentrations in all 3 systems were lower than those reported for many other agricultural environments. However, total airborne endotoxin concentrations in many of the conventional stables exceeded those which can induce pulmonary inflammation and bronchial hyper‐responsiveness in normal human subjects, and exceeded those which can induce bronchoconstriction in humans with pre‐existing pulmonary inflammation. Therefore, airborne endotoxin may contribute to the development of airway inflammation and dysfunction in conventionally stabled horses. Potentially detrimental effects of airborne endotoxins on the welfare and exercise performance of stabled horses can be reduced by maintaining horses in ‘low dust’ stables or at pasture, since these environments had significantly lower airborne dust and endotoxin concentrations.
Flat, hurdle and steeple racing: risk factors for musculoskeletal injury
Authors: BAILEY C. J. , REID S. W. J. , HODGSON D. R. , BOURKE J. M. , ROSE R. J.
Published: April 2010

A retrospective case‐control study was conducted to identify and quantify risk factors for serious musculoskeletal injury sustained at 4 Australian metropolitan racetracks. During the period of study (August 1988‐July 1995) there were 196 cases from flat racing, 52 cases from hurdle racing and 53 cases from steeplechases. The incidences of fatal musculoskeletal injuries per start for flat, hurdle and steeple races were 0.06, 0.63 and 1.43% respectively. Logistic regression identified harder track surfaces, horses being older than age 3 years, one racecourse (Flemington) and jumping races as significant risk factors which increased the risk of musculoskeletal breakdown. The incidence of fatal musculoskeletal injuries for flat races at the 4 study tracks was similar to that reported in the UK but less than the USA. Death rates for hurdle and steeple races in the study population were higher than in the UK. Strategies to reduce the incidence of serious musculoskeletal injuries may include avoidance of excessively hard track surfaces through closer regulation of track moisture content; implementation of more rigorous prerace lameness examinations of horses, particularly older horses; and altering the design and number of jumps in hurdle and steeple races. The quantification of risk, as we have reported here, is the first step towards addressing the causes of musculoskeletal breakdown and should help in applying a reasoned approach to intervention measures that may be effective in reducing racing injuries.
The effect of foot imbalance on point of force application in the horse
Authors: WILSON A. M. , SEELIG T. J. , SHIELD R. A. , SILVERMAN B. W.
Published: April 2010

Foot imbalance is believed to be a common cause of musculoskeletal injury in the horse; its biomechanical effects are, however, poorly understood. Wedges (angle 3.7 and 5°) were attached to modified shoes to elevate one aspect of both front feet of Thoroughbred‐type horses. The point of force application during weightbearing was determined at trot using a forceplate system. A total of 8 horses were studied with a minimum of 4 providing data for each wedge condition. The results demonstrated that application of a standard steel horse shoe to a balanced foot has minimal effect on the point of force trace through stance. Alteration of mediolateral hoof balance resulted in a displacement of point of force application by about 10 mm in the direction of the wedge throughout stance. Elevation of the heels delayed unloading of the heels and elevation of the toe advanced unloading. Reassessment 24 h after shoeing showed minimal change in the point of force trace. This work demonstrates that a horse is unable to compensate for an acute foot imbalance by redistributing the load under the foot. The higher loads in the elevated region are likely to have a detrimental effect on the hoof structure and horn growth in that part of the hoof.
The role of prostanoids and nitric oxide in endotoxin‐induced hyporesponsiveness of equine digital blood vessels
Authors: BAILEY S. R. , ELLIOTT J.
Published: April 2010

Endotoxin has been implicated in the pathophysiology of acute laminitis. The aim of this study was to examine the direct effects of endotoxin on isolated equine digital blood vessels. Equine digital veins (EDV), incubated in Krebs‐Henseleit solution containing lipopolysaccharide (LPS) (1 μg/ml) became hyporesponsive to 5‐HT after 16 h. Cycloheximide and ibuprofen blocked this effect of LPS and increased the maximum response obtained to 5‐HT when compared to control vessels. L‐nitroarginine methyl ester (L‐NAME) reversed the hyporesponsiveness caused by LPS. Vessels maintained in culture medium containing LPS also became hyporesponsive to 5‐HT, an effect which was completely prevented by ibuprofen but only partially reversed by L‐NAME.

Measurements were made of 6‐keto PGF1αand nitrite production by segments of equine digital artery and vein in culture medium alone or co‐cultured with peripheral blood leucocytes. LPS did not stimulate nitrite production from vessel segments but increased nitrite release from leucocytes, an effect which was inhibited by cycloheximide and L‐NAME. Lipopolysaccharide increased 6‐keto PGF1αproduction by blood vessels, an effect which was inhibited by cycloheximide and ibuprofen but not L‐NAME. No synergistic effect on release of nitrite or 6‐keto PGF1αwas noted in co‐cultures of blood vessels and leucocytes.

These data suggest that induction of cyclo‐oxygenase by LPS was a major cause of hyporesponsiveness of digital blood vessels to 5‐HT. Release of nitric oxide was not detectable in LPS‐stimulated blood vessels maintained in culture even in the presence of activated leucocytes yet L‐NAME did protect against LPS‐induced hyporesponsiveness indicating nitric oxide synthase induction may play some role in the effect of LPS. These findings are important in furthering our understanding of the pathophysiological mechanisms underlying the vascular changes which occur in acute laminitis.
Endoscopic examination of the tarsal sheath of the lateral digital flexor tendon in horses
Authors: CAUVIN E. R. J. , TAPPREST JACKIE , MUNROE G. A. , MAY S. A. , SCHRAMME M. C.
Published: April 2010

This study was designed to develop a reliable technique for endoscopic examination of the tarsal sheath of the lateral digital flexor tendon of horses. The anatomy of the tendon sheath and associated structures was studied in detail in cadavers before determining portals for the insertion of an arthroscope into the sheath. Approaches into the sheath through the proximal pouch and through theflexor retinaculum, at the level of thesustentaculum tali, were performed and compared in cadavers. The proximal pouch portal permitted visualisation only of the proximal half of the sheath, while the approach through theretinaculumallowed examination of the entire sheath. The normal endoscopic appearance of the tarsal sheath was studied. The endoscopic approach was subsequently used to examine and treat 5 horses with tarsal sheath tenosynovitis, including 2 cases of chronic, traumatic tenosynovitis and 3 of subacute septic tenosynovitis. Four of these horses had fragmentation of thesustentaculum tali. The technique allowed adequate examination of the sheath and debridement of adhesions and lesions within the lumen of the sheath. Fragments dorsal to the medioplantar edge of thesustentaculum talicould not be visualised endoscopically and had to be removed after widening of the wound. All 5 horses survived. Follow‐up enquiries (8–31 months) revealed that the horses were all reported to be sound. Four were performing at their previous level of activity, 1 was used for hacking. The 2 cases presented with chronic tenosynovitis had residual sheath distension with no associated loss of function. A prospective study, including longer term follow‐up investigation, is currently being performed.
The effect of low level laser therapy (LLLT) on wound healing in horses
Authors: PETERSEN S. L. , BOTES C. , OLIVIER A. , GUTHRIE A. J.
Published: April 2010

Laser therapy is used in many countries, including South Africa, for the treatment of skin wounds. Low level galium aluminium arsenide (GaAlAs) laser was administered to full thickness skin wounds (3times3 cm) induced surgically on the dorsal aspect of the metacarpophalangeal joints of 6 crossbred horses in a randomised, blind, controlled study. Treated wounds that received a daily laser dosage of 2 J/cm2were compared with nontreated control wounds on the opposite leg. There were no wound complications. Both groups of wounds were cleaned daily using tap water. Wound contraction and epithelialisation were evaluated using photoplanimetry. There were no significant differences in wound contraction or epithelialisation between the laser treated and the control wounds. It was therefore concluded that laser therapy had no clinically significant effect on second intention wound healing in this study.
A method for determination of equine hoof strain patterns using photoelasticity: anin vitrostudy
Authors: DEJARDIN L. M. , ARNOCZKY S. P. , CLOUD G. L.
Published: April 2010

During impact, equine hooves undergo viscoelastic deformations which may result in potentially harmful strains. Previous hoof strain studies using strain guages have been inconclusive due to arbitrary guage placement. Photoelastic stress analysis (PSA) is a full‐field technique which visually displays strains over entire loaded surfaces. Thisin vitrostudy identifies normal hoof strain patterns using PSA.

Custom‐made photoelastic plastic sheets were applied to the hoof surface. The hooves were axially loaded (225 kg) under level and varus/valgus conditions. Strain patterns were video‐recorded through a polariscope. Strains were concentrated between middle and distal thirds of the hoof wall regardless of the loading conditions. This strain distribution appears to result from the differential expansion of the hoof wall under load. Increasing load resulted in higher strains and asymmetric loading resulted in an ipsilateral increase in strain magnitudes without altering strain locations.

This study shows that PSA is a reliable method with which to evaluate hoof strains invitroand is sensitive enough to reflect subtle load‐related strain alterations.
Distribution of substance P binding sites in equine airways
Authors: SONEA IOANA M. , BOWKER R. M. , ROBINSON N. E.
Published: April 2010

Autoradiography with [125I]‐Bolton Hunter substance P ([I]‐BHSP) was used to detect substance P binding sites in the equine lung. Specific [I]‐BHSP binding sites were very dense over small bronchial vessels, tracheobronchial glands and airway epithelium in large and small airways. The density of [I]‐BHSP binding sites over airway smooth muscle was much lower than in the preceding tissues. Competition with an excess of either a specific neurokinin 1 receptor agonist, or a specific neurokinin 2 receptor agonist indicated that most specific [I]‐BHSP binding sites in the equine lung represent neurokinin 1 receptors. The receptor‐mediated effects of substance P in the equine lung are most likely to involve regulation of vascular tone and airway secretions based upon the density of specific [I]‐BHSP binding sites in these tissues. Activation of intrapulmonary afferent nerves containing Substance P by noxious stimuli such as inhaled allergens or irritants may lead to increased mucus secretion and decreased airway diameter due to vascular congestion.
Prediction of first season stallion fertility of 3‐year‐old Dutch Warmbloods with prebreeding assessment of percentage of morphologically normal live sperm
Authors: PARLEVLIET JOYCE M. , COLENBRANDER B.
Published: April 2010

In the selection procedure to acquire a breeding licence, 3‐year‐old Dutch Warmblood stallions have to undergo a breeding soundness test It is questioned whether this evaluation is predictive of the stallion's fertility results in the first breeding season. Therefore, semen parameters at the beginning of their first breeding season were evaluated and correlated to nonreturn at first cycle and foaling rate of mares bred by stallions (n = 13). The total number of mares inseminated with chilled semen from those stallions was 1055.

Semen parameters were recorded on 2 ejaculates, collected 1 h apart. Percentage progressive sperm motility, % morphologically normal from unstained spermatozoa (MNA), % sperm cells with abnormal acrosomes and the total number of spermatozoa were correlated with first cycle nonreturn rate and foaling rate. Mean motility at evaluation was 72 ± 6%. Mean MNA was 62 ± 13%. Mean first cycle nonreturn rate and foaling rate were 58 ± 15% and 69 ± 12%, respectively. A significantly positive correlation (P<0.05) was found between the MNA and first cycle nonreturn rates. Foaling rates were not significantly correlated with semen characteristics and first cycle nonreturn rates. In conclusion, the breeding soundness test is of predictive value for the breeding results in the breeding season following the test. First cycle nonreturn rates reflect fertilising capacity better than foaling rates.
Effects of inhaled dry powder ipratropium bromide on recovery from exercise of horses with COPD
Authors: DUVIVIER DOMINIQUE H. , BAYLY W. M. , VOTION DOMINIQUE , VANDENPUT SANDRINE , ART TANIA , FARNIR F. , LEKEUX P.
Published: April 2010

The present study evaluated ventilatory, cardiovascular and metabolic parameters during recovery from strenuous exercise in horses suffering from a crisis of chronic obstructive pulmonary disease (COPD) and to determine whether ipratropium dry powder inhalation (DPI) before exercise has an effect on these parameters.

When 6 saddle horses, affected with COPD, developed airway obstruction, they inhaled placebo and ipratropium (2400 μg/horse), the order being randomly chosen. Pulmonary function tests were then recorded 15 min after inhalation. Following these tests, the horses underwent a strenuous treadmill exercise, followed by a recovery period that consisted of a 10 min walk. Measurements were made at the first and tenth min of recovery. Respiratory flow, O2 and CO2 fractions in the respired gas, pleural pressure changes and heart rate were recorded. Arterial and mixed venous blood samples were analysed for gas tensions, haemoglobin and plasma lactate concentrations. Oxygen consumption (VO2), CO2 production, tidal volume, alveolar oxygen tension (PAO2), alveolar ventilation, the alveolar‐pulmonary capillary oxygen difference ((A‐a)dO2) and total pulmonary resistance (RL) were measured.

The PAO2 was the only parameter significantly improved during recovery following ipratropium DPI. This improvement was not accompanied by evidence of improvement of other ventilatory or cardiorespiratory parameters.

The results showed that in horses suffering from a crisis of COPD, recovery is characterised by an exercise‐induced bronchodilation. Secondly, ipratropium DPI at a dose of 2400 μg/horse is an effective bronchodilator in these horses at rest but it has little effect on the airway calibre during the recovery period. It is suggested that the short term recovery period is still influenced by exercise‐induced adjustments that may exceed the bronchodilatory effect of inhaled ipratropium that are observed before exercise.
Skeletal muscle metabolic response to exercise in horses with ‘tying‐up’ due to polysaccharide storage myopathy
Authors: VALBERG STEPHANIE J. , MACLEAY JENNIFER M. , BILLSTROM JESSICA A. , HOWER‐MORITZ MELISSA A. , MICKELSON J. R.
Published: April 2010

Polysaccharide storage myopathy (PSSM) is a distinct cause of exertional rhabdomyolysis in Quarter Horses that results in glycogen and abnormal polysaccharide accumulation. The purpose of this study was to determine if excessive glycogen storage in PSSM is due to a glycolytic defect that impairs utilisation of this substrate during exercise. Muscle biopsies, blood lactates and serum CK were obtained 1) at rest from 5 PSSM Quarter Horses, 4 normal Quarter Horses (QH controls) and 6 Thoroughbreds with recurrent exertional rhabdomyolysis (TB RER) and 2) after a maximal treadmill exercise test in PSSM and QH controls. In addition, 3 PSSM horses performed a submaximal exercise test. At rest, muscle glycogen concentrations were 2.4x and 1.9x higher in PSSM vs. QH controls or TB RER, respectively. Muscle lactates at rest were similar between PSSM and QH controls but significantly higher in PSSM vs. TB RER. Muscle glucose‐6‐phosphate concentrations were also higher in PSSM horses than controls combined. During maximal exercise, mean muscle glycogen concentrations declined 2.7x more and mean lactate increased 2x more in PSSM vs. QH controls; however, differences were not statistically significant. Blood lactate concentrations after maximal exercise did not reflect generally higher muscle lactate in PSSM vs. QH controls. No change in blood lactate concentrations occurred in PSSM horses with submaximal exercise. Serum CK activity increased significantly 4 h after maximal and submaximal exercise and was significantly higher in PSSM vs. QH controls. These results show that during maximal exercise, PSSM horses utilised muscle glycogen and produce lactic acid via a functional glycolytic pathway and that during submaximal exercise oxidative metabolism was unimpaired. The excessive glycogen storage and formation of abnormal polysaccharide in PSSM horses therefore appear to reflect increased glycogen synthesis rather than decreased utilisation. The specific subset of horses with exertional rhabdomyolysis due to PSSM would likely benefit clinically from a diet low in soluble carbohydrates like grain with fat added as well as gradually increasing daily exercise to reduce excessive glycogen accumulation and enhance utilisation.
Differences in second‐intention wound healing between horses and ponies: histological aspects
Authors: WILMINK JACINTHA M. , VAN WEEREN P. R. , STOLK P. W. TH. , VAN MIL F. N. , BARNEVELD A.
Published: April 2010

The histological aspects of second‐intention healing were studied in 5 horses and 5 ponies. Biopsies were taken weekly from standardised wounds on the metatarsus and femoral biceps muscle of one horse and one pony. Sections were stained to enable cell counting and the detection of DNA synthesis, fibrin, smooth muscle actin (SMA), collagen, and bacteria.

In the ponies, the number of polymorphonuclear leucocytes (PMNs) was high during the first 3 weeks and subsequently decreased rapidly. In the horses, the initial number of PMNs was lower, but remained persistently elevated during the evaluation period. PMNs were found mainly in the superficial zones. Significantly more fibrin was present in the wounds of the horses. No significant differences were observed in the number of fibroblasts, the amounts of SMA and collagen. However, myofibroblasts were significantly less regularly organised in the wounds of the horses, particularly in the metatarsal wounds. The mitotic activity of the epithelium was temporally reduced in week 3. The mitotic activity of the granulation tissue was initially high but declined rapidly from week 1 onwards, with the exception of the metatarsal wounds of the horses, in which mitotic activity remained significantly higher.

Histology confirmed and explained the macroscopical differences in wound healing between horses and ponies by the strict organisation of the myofibroblasts and the more effective acute inflammation in the ponies. Stimulation of the organisation of myofibroblasts and improvement of the efficacy of the inflammatory response in horses may therefore result in better second‐intention wound healing in horses in clinical practice.
Galloping exercise induces regional changes in bone density within the third and radial carpal bones of Thoroughbred horses
Authors: FIRTH E. C. , DELAHUNT J. , WICHTEL J. W. , BIRCH H. L. , GOODSHIP A. E.
Published: April 2010

This study was performed to test the hypothesis that a localised bone hypertrophy could occur within the subchondral cancellous architecture of the third and radial carpal bones. Using 2 levels of controlled and defined exercise, it was observed that a high intensity treadmill exercise protocol resulted in functional adaptation of the carpal bones. The increase in trabecular thickening and density was seen to be localised to those regions underlying common sites of cartilage degradation, the interface of the thickened trabeculae with the normal architecture in the third carpal bone was coincident with a common site of clinical fractures. The bone changes were determined both qualitatively on examination of slab radiographs and quantified by dual energy x‐ray absorptiometry.

The findings from this study are relevant to mechanical factors involved in the pathophysiology of joint degeneration. The potential clinical implications of this study are in relation to changes in the type and duration of exercise regimens used in training of equine athletes. The rapid response of bone to mechanical stimulation has implications in the longer term for localised cartilage degradation. Imaging techniques could be developed to monitor these early bone changes in the specific areas identified in this study and thus allow appropriate changes in training intensity to minimise subsequent damage to the articular surface.
Thoracic trauma in newborn foals
Authors: JEAN D. , LAVERTY S. , HALLEY J. , HANNIGAN D. , LÉVEILLÉ R.
Published: April 2010

In a report describing life ending fractures (255 horses) from the Livestock Disease Diagnostic Center, Kentucky (1993 and 1994), 32 foals had rib fractures. The purpose of our study was to examine the incidence of rib fractures in newborn foals on a Thoroughbred studfarm by physical and radiographic examination, to determine factors which may contribute to the problem and to document any clinical consequences. All foals (263) included were examined within 3 days of birth. The thoracic cage was palpated externally for abnormalities and all foals were placed in dorsal recumbency to evaluate thoracic cage symmetry. Radiographs were used to diagnose foals with thoracic cage asymmetry (TCA) and rib fracture (RF). A diagnosis of costochondral dislocation (CD) was made when no radiographic evidence of fracture was present but there was severe TCA. Fifty‐five foals (20.1%) had TCA (9 RF). One to 5 ribs were fractured on 9 of 40 radiographic studies. No consequences of the thoracic trauma was detected clinically, radiographically or ultrasonographically in this group of foals or at a 2‐ and 4‐week follow‐up examination. The percentage of foals with a history of abnormal parturition was higher in the TCA foals (15%) compared to the normal foals (6.8%). There were more primiparous dams in the TCA group than in the normal foal group. Fillies (56.6%) had a higher incidence of birth trauma than colts (43.4%). This study demonstrates that thoracic trauma is often present in newborn foals and may not always be of clinical significance. Dystocia foals and foals from primiparous mares should be considered high risk for thoracic trauma.
Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co‐dominant genetic condition
Authors: NAYLOR J. M. , NICKEL D. D. , TRIMINO G. , CARD C. , LIGHTFOOT K. , ADAMS G.
Published: April 2010

Historical, clinical and experimental data were collected from 9 horses homozygous for HYPP (H/H). All showed episodes of respiratory stertor, described as a rattling or honking sound, usually within the first weekpost partum.Five horses had one or more episodes of dysphagia, in 3 horses this was accompanied by drooling and in 3 by weight loss. In comparison, only one of 35 contemporaneous half siblings (of which approximately half would be expected to be of the H/N genotype and half N/N) was observed to have respiratory stertor prior to weaning and none had problems with dysphagia.

One mature homozygous stallion was infertile secondary to urospermia. Six homozygous horses died or were subjected to euthanasia; 4 age less than a year, one age 20 months and one age 5 years. The remaining 3 cases were still alive at the end of the study.

A comparison of homozygous and heterozygous horses using standardised potassium chloride challenge testing indicated that during attacks homozygotes showed significantly more frequent signs of drooling, prolapse of the third eyelid, respiratory stridor and weakness than heterozygous horses. Homozygotes also had significantly more total abnormalities (including myotonic discharges, high frequency repetitive discharges, and spontaneous activity) on electromyographic examination than heterozygotes.

These data imply that HYPP is inherited as a co‐dominant genetic defect, because the homozygotes showed more severe clinical signs of disease than heterozygotes. Homozygous foals would be expected to be produced in 25% of matings in which both parents are heterozygous. Owners and veterinarians should be aware of the risks of this mating.