bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of respiratory function by impulse oscillometry in horses
Authors: Van Erck E. , Votion D. , Art T. , Lekeux P.
Published: April 2007

Reasons for performing study: Due to technical implementations and lack of sensitivity, pulmonary function tests are seldom used in clinical practice. Impulse oscillometry (IOS) could represent an alternative method.

Objectives: To define feasibility, methodology and repeatability of IOS, a forced oscillation technique that measures respiratory resistance (Rrs) and reactance (Xrs) from 5 to 35 Hz during spontaneous breathing, in horses.

Methods: Using 38 healthy horses, Rrsand Xrsreference values were defined and influence of individual biometrical parameters was investigated. In addition, IOS measurements of 6 horses showing clinical signs of heaves were compared to those of 6 healthy horses.

Results: Airtightness and minimal dead space in the facemask were prerequisites to IOS testing and standardisation of head position was necessary to avoid variations in Rrsdue to modified upper airway geometry. In both healthy and diseased animals, measurements were repeatable. In standard‐type breeds, the influence of the horse's size on IOS parameters was negligible. An increase in R5Hzgreater than 0.10 kPa/l/sec and R5Hz>R10Hz, combined with negative values of Xrsbetween 5 and 20 Hz, was indicative of heaves crisis.

Conclusions: IOS is a quick, minimally invasive and informative method for pulmonary function testing in healthy and diseased horses.

Potential relevance: IOS is a promising method for routine and/or field respiratory clinical testing in the equine species.
Is isoflurane safer than halothane in equine anaesthesia? Results from a prospective multicentre randomised controlled trial
Authors: Johnston G. M. , Eastment J. K. , Taylor P. M. , Wood J. L. N.
Published: April 2007

Reasons for performing study: Approximately 1 in 100 horses suffer unexpectedly from anaesthetic‐related death. Identification and use of the safest anaesthetic drugs should support this aim. Experimental evidence has suggested that isoflurane should be a safer maintenance agent in equine anaesthesia than halothane.

Hypothesis: The death rate would be reduced in horses being maintained with isoflurane compared to halothane.

Methods: A multicentre randomised controlled trial was undertaken to compare the effects of isoflurane and halothane for maintenance of equine anaesthesia for all types of operation. Data were analysed from 8242 horses in which anaesthesia was maintained with either halothane or isoflurane using mixed effects logistic regression models.

Results: No overall benefit of either drug was detected. However, although not part of the primary hypothesis, data showed that the overall death rate was significantly reduced in horses age 2–5 years with isoflurane and that death from cardiac arrest was also reduced with isoflurane, particularly in high risk cases.

Conclusions and potential relevance: Halothane remains an acceptable anaesthetic for maintenance of anaesthesia in horses, but isoflurane may be safer in the young horse and in high risk cases.
Radiographic evaluation of sclerosis of the third carpal bone associated with exercise and the development of lameness in Standardbred racehorses
Authors: HOPPER B. J. , STEEL C. , RICHARDSON J. L. , ALEXANDER G. R. , ROBERTSON I. D.
Published: April 2007

Reasons for performing study: Sclerosis of the third carpal bone is a common radiographic finding in both lame and sound racehorses, but there are no guidelines correlating degree of sclerosis and incidence of lameness.

Objectives: To develop a protocol for describing subchondral bone sclerosis in C3 on dorsoproximal‐dorsodistal oblique (DPr‐DDiO) radiographs of the carpus and to correlate these changes with exercise history and carpal lameness.

Methods: One hundred and six Standardbreds entering their first year of training (exercise group) and 7 age‐matched Standardbreds at pasture (controls) were examined at approximately 3 month intervals over 12‐18 months. Examinations consisted of lameness evaluation and carpal radiographs (DPr‐DDiO and flexed lateromedial projections). A grading system (very mild, mild, moderate and severe) for C3 sclerosis seen on the DPr‐DDiO radiograph was developed that utilised a combination of the criteria of trabecular thickening (trabecular score; TS) and total percent area of the C3 radial facet affected (TAA).

Results: Exercise group horses showed significant increase in TS and TAA throughout training compared to control horses. Middle carpal joint lameness developed in 32/106 (30%) exercise group horses and none of the control horses. Incidence of middle carpal joint (MCJ) lameness was lower in horses with mild (2/30, 6.7%) than moderate (10/32, 31.2%) and severe (20/44, 45.4%) sclerosis throughout training.

Conclusions: Horses with higher grades of sclerosis, as defined by this novel grading system, were more likely to develop MCJ lameness at some point of training. The proposed grading system gave a quantitative assessment of radiographic sclerosis that could then be used to correlate increasing severity of sclerosis with increasing incidences of lameness.

Potential relevance: These results serve as a basis for further investigation into determining the degree of C3 sclerosis at which pathological changes and lameness can be expected.
Relationship of foot conformation and force applied to the navicular bone of sound horses at the trot
Authors: ELIASHAR E. , McGUIGAN M. P. , WILSON A. M.
Published: April 2007

Reasons for performing study: Collapsed heels conformation has been implicated as causing radical biomechanical alterations, predisposing horses to navicular disease. However, the correlation between hoof conformation and the forces exerted on the navicular bone has not been documented.

Hypothesis: The angle of the distal phalanx in relation to the ground is correlated to the degree of heel collapse and foot conformation is correlated to the compressive force exerted by the deep digital flexor tendon on the navicular bone.

Methods: Thirty‐one shod Irish Draught‐cross type horses in routine work and farriery care were trotted over a forceplate, with 3‐dimensional (3D) motion analysis system. A lateromedial radiograph of the right fore foot was obtained for each horse, and various measurements taken. Correlation coefficients were determined between hoof conformation measurements and between each of these and the force parameters at the beginning (15%) of stance phase, the middle of stance (50%) and at the beginning of breakover (86% of stance phase). Significance was defined as P<0.05.

Results: The force exerted on the navicular bone was negatively correlated (P<0.05) to the angle of the distal phalanx to the ground and to the ratio between heel and toe height. This was attributed to a smaller extending moment at the distal interphalangeal joint. There was not a significant correlation between the angle of the distal phalanx and the degree of heel collapse, and heel collapse was not significantly correlated to any of the force parameters.

Conclusions: Hoof conformation has a marked correlation to the forces applied to the equine foot. Heel collapse, as defined by the change in heel angle in relation to toe angle, appears to be an inaccurate parameter. The forces applied on the foot are well correlated to the changes in the ratio of heel to toe heights and the angles of the distal phalanx.

Potential relevance: Assessment of hoof conformation should be judged based on these parameters, as they may have clinical significance, whereas parallelism of the heel and toe is of less importance.
Whip use and race progress are associated with horse falls in hurdle and steeplechase racing in the UK
Authors: PINCHBECK G. L. , CLEGG P. D. , PROUDMAN C. J. , MORGAN K. L. , FRENCH N. P.
Published: April 2007

Reasons for performing study: Falls during racing present a risk of injury to both horse and jockey and a risk of fatality to horses.

Objectives: To use video recordings of races to describe the circumstances surrounding horse falls at hurdle and steeplechase fences and to identify and quantify within‐race risk factors for horse falls in National Hunt racing in the UK.

Methods: A retrospective, matched, nested case‐control study using video recordings of races was conducted on 6 UK racecourses. Cases and controls were matched on both race type and jump number at which the fall occurred. Conditional logistic regression analysis was used to examine the univariable and multivariable relationship between predictor variables and the risk of falling.

Results: The risk of falling was significantly associated with whip use and race progress. Horses which were being whipped and progressing through the race were at greater than 7 times the risk of falling compared to horses which were not being whipped and which had no change in position or lost position through the field.

Conclusions: This study has identified whip use and the position of the horse with respect to others in the field as potential risk factors for horse falls.

Potential relevance: If these findings are confirmed by the use of intervention trials (e.g. with whip‐free or restricted whip use races), modifications could be introduced which would reduce the frequency of horse falls, leading to improved equine welfare.
What is the likelihood that Thoroughbred foals treated for septic arthritis will race?
Authors: SMITH L. J. , MARR C. M. , PAYNE R. J. , STONEHAM S. J. , REID S. W. J.
Published: April 2007

Reasons for performing study: Septic arthritis is a serious problem in the neonate, with a poor prognosis being reported for recovery. The impact of neonatal septic arthritis on the likelihood that Thoroughbred (TB) foals will start on a racecourse is not known.

Hypothesis: The development of septic arthritis in a TB foal significantly reduces the likelihood that it will race when compared to foals from the same dam.

Methods: Medical records of 69 foals treated for septic arthritis were reviewed. The dam's foaling records were reviewed and lifetime racing records were then retrieved for both the affected foals and at least one of their siblings (controls). Outcomes that were statistically evaluated included discharge from the hospital and whether the foal eventually raced. Univariate analyses of categorical variables were conducted for each outcome. The number of affected and unaffected foals that raced at least once were compared using regression analysis. Survival analysis was used to compare age at first race between the study and comparison groups.

Results: Foals with septic arthritis were less likely to start on a racecourse compared to controls (odds ratio [OR] 0.28; 95% confidence interval [CI] 0.12‐0.62, P = 0.001), while those foals that were discharged from the hospital were also less likely to start on a racecourse compared to controls (OR 0.36; CI 0.15–0.83, P = 0.008). The presence of multisystem disease was associated with a decreased likelihood of surviving to be discharged (OR 0.13; 95% CI 0.02‐0.90; P = 0.005), but did not affect the likelihood that they would start in at least one race if discharged successfully (OR 0.45; 95% CI 0.04‐2.81; P = 0.34) compared to the other foals with septic arthritis. Log‐rank comparison of survival curves confirmed that foals discharged following treatment for septic arthritis took significantly longer to start in their first race compared to the sibling population (mean age of study group 1757 days, CI 1604‐1909; mean age of sibling group 1273 days, CI 1197‐1349; P = 0.0006).

Conclusions: The development of septic arthritis in a TB foal significantly reduces the likelihood that it will start on a racecourse when compared to controls.

Potential relevance: Accurate figures allowing a realistic assessment of the athletic future of a foal following treatment for septic arthritis are of significance for both owner and treating veterinarian.
Efficacy of oral and intravenous dexamethasone in horses with recurrent airway obstruction
Authors: CORNELISSE C. J. , ROBINSON N. E. , BERNEY C. E. A. , KOBE C. A. , BORUTA D. T. , DERKSEN F. J.
Published: April 2007

Reasons for performing study: Although the efficacy of dexamethasone for the treatment of recurrent airway obstruction (RAO) has been documented, the speed of onset of effect and duration of action are unknown, as is the efficacy of orally administered dexamethasone with or without fasting.

Objectives: To document the time of onset of effect and duration of action of a dexamethasone solution i.v. or orally with and without fasting.

Methods: Protocol 1used 8 RAO‐affected horses with airway obstruction in a crossover design experiment that compared the effect of i.v. saline and dexamethasone (0.1 mg/kg bwt) on pulmonary function over 4 h.Protocol 2used 6 similar horses to compare, in a crossover design, the effects of dexamethasone i.v. (0.1 mg/kg bwt), dexamethasoneper os(0.164 mg/kg bwt) with and without prior fasting, and dexamethasoneper os(0.082 mg/kg) with fasting.

Results: Dexamethasone i.v. caused significant improvement in lung function within 2 h with a peak effect at 4–6 h. Dexamethasoneper oswas effective within 6 h with peak effect at 24 h at a dose of 0.164 mg/kg bwt prior to feeding. The duration of effect was, for all dexamethasone treatments, statistically significant for 30 h when compared to saline and tended to have a longer duration of effect when used orally. Dexamethasoneper osat a dose of 0.164 mg/kg bwt to fed horses had mean effects comparable to dexamethasone at a dose of 0.082 mg/kg bwtper osgiven to fasted horses, indicating that feeding decreases bioavailability.

Conclusions: Dexamethasone administered i.v. has a rapid onset of action in RAO‐affected horses. Oral administration of a bioequivalent dose of the same solution to fasted horses is as effective as i.v. administration and tends to have longer duration of action. Fasting horses before oral administration of dexamethasone improves the efficacy of treatment.

Potential relevance: Oral administration to fasted horses of a dexamethasone solution intended for i.v. use provides an effective treatment for RAO‐affected animals.
Prevention of ischaemia‐induced small intestinal adhesions in foals
Authors: SULLINS K. E. , WHITE N. A. , LUNDIN C. S. , DABAREINER R. , GAULIN G.
Published: April 2007

Reasons for performing study: Treatments addressing variously theorised pathophysiological mechanisms of small intestinal adhesions have been reported. This study applied those classes of treatments to the most clinically relevant aetiology of post operative adhesions.

Hypothesis: Treatments addressing the pathophysiology of ischaemia‐reperfusion induced adhesions would accordingly reduce the incidence of adhesions from this model.

Methods: Four classes of treatments were administered for 72 h to 16 foals subjected to complete ischaemia followed by reperfusion to create peritoneal adhesions. These groups were: 1) FPG group ‐ flunixin meglumine (1.1 mg/kg bwt i.v., divided q.i.d.), potassium penicillin G (22,000 iu/kg bwt i.v., q.i.d.) and gentamicin (2.2 mg/kg bwt i.v., t.i.d.); 2) HEP group ‐ heparin (80 iu/kg bwt subcut., b.i.d.); 3) DMSO group ‐ dimethylsulphoxide (DMSO) (20 mg/kg bwt [diluted in 500 ml normal saline] i.v., b.i.d.); and 4) SCMC group ‐ sodium carboxymethylcellulose (500 ml 3% sterile solution intraperitoneally, administered only at the beginning of surgery).

Results: Post operative intestinal obstruction did not occur in any foal. After 10 days, necropsy revealed bowel‐to‐bowel adhesions in none of the FPG or DMSO groups, in 2/4 of the SCMC group, in 3/4 of the HEP group and 5/6 foals subjected to the procedure without treatment (UIR group).

Conclusions: Inhibition of the inflammation associated with ischaemia and reperfusion in foals treated with FPG or DMSO decreased small intestinal adhesions in foals.

Potential relevance: Although anti‐inflammatory therapy was shown to eliminate bowel‐bowel adhesions in this controlled study, it must be remembered that clinical cases are without control. These therapies are advised to improve the result but are unlikely to eliminate the problem.
Meal size and starch content affect gastric emptying in horses
Authors: MÉTAYER N. , LHǑTE M. , BAHR A. , COHEN N. D. , KIM I. , ROUSSEL A. J. , JULLIAND V.
Published: April 2007

Reasons for performing study: Feeding practices have been associated with colic in horses. If meal size and composition have an effect on gastric emptying, this could be one of the mechanisms by which feeding practices are related to the occurrence of colic.

Objectives: To evaluate the effect of meal size and starch content on solid phase gastric emptying.

Methods: Solid phase gastric emptying of 3 different radiolabelled meals, small low‐starch (SmLS), small high‐starch (SmHS) and large high‐starch (LgHS) meals, was measured in 5 horses by scintigraphy using99mTc‐disofenin. Data were compared among meals using nonlinear mixed‐effects models and pairedttests.

Results: On a percentage basis, SmHS emptied significantly faster than LgHS and SmLS emptied significantly faster than SmHS meals. However, when meals of unequal size were compared by emptying rate in g/min and Keal/min, LgHS emptied significantly faster than SmHS.

Conclusions: Meal size and composition affect gastric emptying.

Potential relevance: Further work needs to be performed in order to substantiate the possibility of a relationship between digestive functions and occurrence of colic and gastric ulcers.
An epidemiological study of risk factors associated with the recurrence of equine grass sickness (dysautonomia) on previously affected premises
Authors: Newton J. R. , Hedderson E. J. , Adams V. J. , Mcgorum B. C. , Proudman C. J. , Wood J. L. N.
Published: April 2007

Reasons for performing study: The reasons why equine grass sickness (EGS) recurs on premises are unknown and, consequently, practical methods for reducing the risk of recurrence are not available.

Objectives: To identify risk factors associated with recurrence of EGS on premises and to gain possible insights into the pathogenesis of the disease.

Methods: Data on disease history and risk factors were collected by postal questionnaire from premises with EGS cases between 1st January 1997 and 31st December 2001. Data on variation in rates of recurrence of EGS for different risk factors were analysed using Poisson regression analysis.

Results: Of 509 premises contacted, 305 (60%) returned useable questionnaires and 100 of these (33%) were classified as ‘recurrent’ premises. An overall median incidence rate for EGS of 2.1 EGS incidents/100 horses/premises/year was recorded. There was an increased rate of recurrence with higher numbers of horses, presence of younger animals, stud farms and livery/riding establishments, loam and sand soils, rearing of domestic birds and mechanical droppings removal. The rate of recurrence decreased with chalk soil, cograzing ruminants, grass cutting on pastures and removal of droppings by hand. Several statistically significant interactions were identified.

Conclusions: Many of the findings are consistent with the theory that EGS is a toxico‐infectious form of botulism. Several of the significant factors identified may directly or indirectly relate to soil disturbance and consequent soil contamination of grass, thereby increasing the rate of exposure of grazing horses to Clostridium botulinum, which resides in soil.

Potential relevance: Identification of potentially modifiable risk factors may, ideally following validation in appropriately designed, controlled and randomised intervention studies, lead to practical measures to reduce the incidence of EGS on previously affected premises.
Descriptive epidemiology of fractures occurring in British Thoroughbred racehorses in training
Authors: Verheyen K. L. P. , Wood J. L. N.
Published: April 2007

Reasons for performing study: Musculoskeletal injury is the major cause of days lost from training and wastage in Thoroughbred racehorses. Little scientific information is available on the majority of injuries occurring in training.

Objectives: To estimate the incidence of fractures in British racehorses in training and describe the occurrence of different fracture types and bones involved.

Methods: Thirteen UK racehorse trainers participated in a prospective study, providing data on horses in their care for 2 years. Details on horses, their daily exercise and fracture occurrence were recorded.

Results: A total of 1178 horses provided 12,893 months at risk. Nontraumatic fracture incidence was 1.15/100 horse months (95% CI = 0.98, 1.35) and 78% of fractures occurred during training. A wide variety of fracture types and bones were involved, although at least 57% were stress fractures. Pelvic and tibial stress injuries accounted for 28% of fractures diagnosed.

Conclusions: It is important to study injuries in training as well as in racing. The number of stress fractures suggests that training regimes for young Thoroughbreds could often be improved to create a more robust skeleton, able to withstand injury.

Potential relevance: Studying injuries in racehorses in training can provide a scientific basis for the design of safer training regimes.;
Collateral desmitis of the distal interphalangeal joint in 18 horses (2001–2002)
Authors: Dyson S. J. , Murray R. , Schramme M. , Branch M.
Published: April 2007

Reasons for performing study: There have been no previously published case series of horses examined using either scintigraphy or MRI to diagnose collateral ligament injuries not detectable using ultrasonography or radiography, nor have other concurrent soft tissue lesions been described.

Objectives: To describe the clinical features of horses with desmitis of the collateral ligaments of the distal interphalangeal (DIP) joint and to evaluate the results of radiographic, ultrasonographic, scintigraphic and magnetic resonance imaging (MRI) examinations.

Methods: Horses were examined between January 2001 and January 2003 and were selected for inclusion in the study if there was unequivocal evidence of collateral desmitis of the DIP joint based on ultrasonography or MRI. Subject details, case history, results of clinical examination and responses to local analgesic techniques were reviewed. The results of radiographic, ultrasonographic, scintigraphic and MRI examinations were assessed.

Results: Eighteen horses were identified with desmitis of a collateral ligament of the DIP joint, 3 horses (Group I) based on ultrasonography alone, 7 (Group II) with positive ultrasonographic and magnetic resonance images and 8 (Group III) with no lesion detectable using ultrasonography, but lesions identified using MRI. Seventeen horses had forelimb injuries and one a hindlimb injury. The medial collateral ligament was injured most frequently (13 horses). In the majority of horses, no localising clinical signs were seen. Lameness was invariably worse in circles compared with straight lines. Lameness was improved by palmar digital analgesia in 16 horses (87%), but only 6 were nonlame. Intra‐articular analgesia of the DIP joint produced improvement in lameness in 6/15 horses (40%). In 16 horses, no radiographic abnormality related to the DIP joint or collateral ligament attachments was identified. Eight of 14 horses (57%) had focal, moderately or intensely increased radiopharmaceutical uptake (IRU) at the site of insertion of the injured collateral ligament on the distal phalanx. Alteration in size and signal in the injured collateral ligament was identified using MRI. In addition, 5 horses had abnormal mineralisation and fluid in the distal phalanx at the insertion of the ligament. Eleven horses had concurrent soft tissue injuries involving the deep digital flexor tendon, distal sesamoidean impar ligament, navicular bursa or collateral ligament of the navicular bone.

Conclusions and potential relevance: Collateral desmitis of the DIP joint should be considered as a cause of foot lameness. Although some injuries are detectable ultrasonographically, false negative results occur. Focal IRU at the ligament insertion on the distal phalanx may be indicative of injury in some horses. MRI is useful for both characterisation of the injury and identification of any concurrent injuries. Further follow‐up information is required to determine factors influencing prognosis.;
Equine laminitis: loss of hemidesmosomes in hoof secondary epidermal lamellae correlates to dose in an oligofructose induction model: an ultrastructural study
Authors: French K. R. , Pollitt C. C.
Published: April 2007

Reasons for performing study: Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal‐epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention.

Objectives: To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage.

Methods: Three pairs of normal horses, dosed with OF at 7.5, 10 and 12.5 g/kg bwt via nasogastric intubation, developed laminitis 48 h later. Following euthanasia, their forefeet were processed for transmission electron microscopy. Lamellar basal cell hemidesmosome (HD) numbers and the distance between the basal cell plasmalemma and the lamina densa of the basement membrane were estimated and compared to control tissue.

Results: Increasing OF dosage caused greater HD loss and more severe laminitis. The characteristic separation of the basement membrane, cytoskeleton failure and rounded basal cell nuclei results from combined HD dysassembly and anchoring filament failure.

Conclusions: Without properly assembled HDs, dysadhesion between the lamina densa of the basement membrane (BM) and epidermal basal cells occurs, emphasising the fundamental importance of HDs in maintaining attachment at the lamellar interface. Medical conditions that trigger lamellar matrix metalloproteinase (MMP) activation and/or compromise entry of glucose into lamellar basal cells appear to promote loss and failure of HDs and, therefore, laminitis development.

Potential relevance: A correlation between lameness severity and escalating loss of lamellar HDs now exists. Therapy aimed at protecting the lamellar environment from haematogenous delivery of MMP activators or from glucose deprivation may control laminitis development.
Hoof wall wound repair
Authors: Pollitt C. C. , Daradka M.
Published: April 2007

Reasons for performing study: Surgical stripping of the hoof wall results in a wound that heals remarkabley well. In contrast, lamellae recovering from laminitis are often deformed. Investigating lamellar wound healing may aid understanding of laminitis.

Objectives: To document temporal changes in the lamellar basement membrane (BM), dermis and epidermis after surgery.

Methods: Wall strips were made in the dorsal hoof wall midline of 6 mature horses. Immunohistochemistry was used to document changes in the basement membrane (BM) and detect proliferation of epidermal cells in lamellar tissues harvested at intervals. A conforming metal plate was screwed to the hoof wall to maintain alignment of the wound edges.

Results: Wall stripping caused lamellar tips to snap and remain behind in the dermis along with the majority of the lamellar BM and some lamellar basal cells. Three days later the BM was intact and new lamellae had been reconstructed by proliferation of surviving epidermal cells. By 5 days the surface of the stripped zone was covered with yellow epidermis that subsequently thickened and hardened. Eventually the hoof wall deficit was replaced by new wall growing down from the coronet. The conforming metal plate and post operative analgesic ensured minimal lameness.

Conclusions and potential relevance: In wall stripped lamellae the BM survives virtually intact and is used as a template for proliferating cells, from snapped‐off lamellar tips, to migrate and quickly achieve repair to near normality. In laminitis epidermal dysadhesion and lamellar BM destruction occurs and lack of a functional BM template may explain the prolonged and abnormal repair of affected lamellae.
Epidermal cell proliferation in the equine hoof wall
Authors: Daradka M. , Pollitt C. C.
Published: April 2007

Reasons for performing study: Current theories explaining how the hoof wall ‘grows’ and moves past the stationary distal phalanx are speculative and based on incomplete evidence. Movement in the lamellar region could occur by cell proliferation or an enzyme‐based remodelling process. Since laminitis pathogenesis appears to involve increased transcription and activation of enzymes normally involved in tissue remodelling, it is important to know precisely which process dominates the lamellar region of the hoof.

Objectives: T o investigate epidermal cell proliferation in the equine hoof wall and calculate a proliferative index (PI) for the coronet, lamellae and toe.

Methods: An analogue of thymidine, 5‐bromo‐2′‐deoxyuridine (BRdU), was infused i.v. into 5 ponies. After tissue harvesting, BRdU (and therefore basal cell proliferation) was detected immunohistochemically using mouse anti‐BRdU. PIs were calculated for the coronet and 10 levels of the dorsal hoof wall lamellae.

Results: The highest PIs (mean ± s.e.) were in the coronet; 12.04%± 1.59 and proximal lamellae (7.13%± 1.92) and are therefore growth zones of the proximal hoof wall. PIs of more distal lamellae were 0.11%± 0.04 to 0.97%± 0.29; significantly lower (P = 0.05) than the lamellar growth zone.

Conclusions: A 20‐fold PI decrease between proximal and more distal lamellae suggests that the majority of the normal lamellae are nonproliferative and their main function is to suspend the distal phalanx within the hoof capsule. Remodelling within the hoof wall epidermal lamellae, which must occur as the hoof wall moves past the stationary distal phalanx, is a process not requiring epidermal cell proliferation.

Potential relevance: A hoof lamellar epidermis that remodels using the same MMPs involved in laminitis pathogenesis implies that laminitis is a normal process out of control. Understanding MMP control and how the normal lamellar epidermis achieves this will help in the development of better laminitis preventative and treatment strategies.
Horse‐level risk factors for fatal distal limb fracture in racing Thoroughbreds in the UK
Authors: PARKIN T. D. H. , CLEGG P. D. , FRENCH N. P. , PROUDMAN C. J. , RIGGS C. M. , SINGER E. R. , WEBBON P. M. , MORGAN K. L.
Published: April 2007

Reasons for performing study: Fractures below the level of the radius or tibia (distal limb fractures) are the most common cause of equine fatality on UK racecourses; however, little is known about their epidemiology or aetiology. Identification of risk factors could enable intervention strategies to be designed to reduce the number of fatalities.

Objectives: To identify horse‐level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses.

Methods: A case‐control study design was used. Fractures in case horses were confirmed bypost mortemexamination and 3 matched uninjured controls were selected from the race in which the case horse was running. One hundred and nine cases were included and information was collected about previous racing history, horse characteristics and training schedules. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture.

Results: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have trained on a sand gallop, i.e. a gallop described by trainers as being primarily composed of sand.

Conclusions: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal distal limb fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 805‐2012 m (4‐10 furlongs)/week.

Potential relevance: The information from this study can be used to alter training schedules in an attempt to reduce the incidence of fatal distal limb fracture in Thoroughbred racehorses. Training should include some gallop work, and further studies, recording the exact level of work, will help to identify an optimum range of training speeds and distances which will reduce the liklihood of catastrophic fracture on the racecourse.
Clinical anatomy of the equine sphenopalatine sinus
Authors: McCANN J. L. , DIXON P. M. , MAYHEW I. G.
Published: April 2007

Reasons for performing study: Disorders of the equine sphenopalatine sinus, including empyema and neoplasia, have been reported to cause damage to cranial nerves II and V. However, the clinical anatomy of these sinuses is not well described in horses.

Objective: To examine the anatomy of the sphenopalatine sinuses in a range of equidae and, in particular, to examine the relationship of these sinuses to adjacent major nerves and vessels.

Methods: The anatomy of the sphenoidal and palatine paranasal sinuses was examined in 16 equidae, primarily using transverse skull sections. Relevant structures were documented and photographed.

Results: There was much variation between individual horses in sphenopalatine sinus anatomy. The sphenoidal sinuses were small in young horses and appeared to become larger and more complex with age. Variation was present in the extent that the sphenopalatine sinus extended into the basisphenoid bone. The septum dividing left and right sphenoidal sinuses was frequently not midline, but was intact in all cases. The sphenoidal and palatine sinuses communicated in most horses. In such cases, what could accurately be termed the (combined) sphenopalatine sinuses usually drained directly into the caudal maxillary sinuses. Additionally, in 5 out of 16 cases, some compartments of the sphenoidal sinus also drained into the ethmoidal sinus. The dorsal and lateral walls of the sphenoidal sinus were very thin and directly adjacent to cranial nerves II, III, IV, V and VI and major blood vessels.

Conclusions: The equine sphenoidal and palatine sinuses are very variable in their anatomy, but are always in close proximity to multiple cranial nerves and major blood vessels.

Potential relevance: Many cranial nerves and blood vessels could be damaged with disorders involving the sphenopalatine sinus, potentially causing major and variable neurological syndromes, haemorrhage and extension of sepsis.
Onset of puberty in pasture‐raised Thoroughbreds born in southern hemisphere spring and autumn
Authors: BROWN‐DOUGLAS C. G. , FIRTH E. C. , PARKINSON T. J. , FENNESSY P. F.
Published: April 2007

Reasons for performing study: There is little information on age, weight and time of year of puberty in Thoroughbred horses, and the interpretation of such data is difficult due to the wide variety of descriptions of the onset of puberty.

Objectives: To examine the age, bodyweight and date of onset of puberty in Thoroughbreds born in spring and autumn.

Methods: Bodyweight data and blood samples were collected in 59 pasture‐raised Thoroughbred horses. Five autumn‐born and 18 spring‐born colts and 3 autumn‐born and 33 spring‐born fillies were examined from birth to age 13 and 17 months. A testosterone concentration >2 s.d. above the baseline concentration was indicative of onset of puberty in colts; and progesterone concentration >2 ng/ml and at least 3 times greater than the previous progesterone concentration was indicative of a first ovulation in fillies.

Results: Spring‐born fillies and colts were older and heavier than autumn‐born fillies and colts at puberty. The age at onset of puberty in spring‐ and autumn‐born foals was 291‐408 days and 212‐270 days, respectively. The weight at puberty in spring‐born foals was 302‐409 kg, and in autumn‐born foals was 277‐344 kg. However, the mean date at onset of puberty was not significantly different between spring‐ and autumn‐born horses, with puberty occurring in October (New Zealand spring).

Conclusions and potential relevance: Seasonal changes in photoperiod affect the timing of onset of puberty, provided a minimum threshold bodyweight has been reached. Springborn horses reached this threshold weight during the winter months and remained reproductively inactive until after the stimulus of increasing day‐length occurred. The autumn‐born horses reached the threshold weight to support puberty at the same time as stimulatory photoperiod and, therefore, reached puberty significantly younger and lighter than the spring‐born horses.
Routine castration in 568 draught colts: incidence of evisceration and omental herniation
Authors: SHOEMAKER R. , BAILEY J. , JANZEN E. , WILSON D. G.
Published: April 2007

Reasons for performing study: Castration is one of the most common routine surgical procedures performed in the horse, from which a number of potential complications can arise. We undertook a prospective evaluation of short‐term complications associated with castration of draught colts over a 3‐year period (1998–2000).

Objectives: To compare castration complications in a large number of draught foals with previously published literature.

Methods: Five hundred and sixty‐eight draught colts, age 4 or 5 months, were castrated in field conditions. Foals were observed for complications for 24 h post operatively.

Results: There was no significant difference in complication rates between open and closed surgical techniques. Inguinal/scrotal hernia rate was 4.6% (26/568) prior to surgery, and evisceration of the small intestine occurred in 4.8% (27/568). Foals observed to eviscerate underwent immediate surgical correction with an overall survival rate of 72.2% (13/18). Omental herniation was seen in 2.8% (16/568) of colts.

Conclusions: This study showed no difference between the closed and open techniques of castration and the rate of omental herniation or evisceration. The evisceration rate in combination with the omental and presurgical herniation rates approached 12.2%, which is high enough to warrant further examination.

Potential relevance: Future investigation should help to assess predisposing factors for evisceration. Regardless of the technique employed, herniation appears to pose a significant risk to draught foals undergoing castration.
Osteoarthritis of the talocalcaneal joint in 18 horses
Authors: SMITH R. K. W. , DYSON S. J. , SCHRAMME M. C. , HEAD M. J. , PAYNE R. J. , PLATT D. , WALMSLEY J.
Published: April 2007

Reasons for performing study: Talocalcaneal osteoarthritis (TO) is an uncommon cause of moderate to severe hindlimb lameness, on which only isolated case reports have been published to date.

Objectives: To review the clinical features of TO and determine optimal methods for diagnosis, management and prognosis.

Methods: The case records from 4 referral centres of 18 horses showing hindlimb lameness considered, as a result of clinical investigation, to be caused by TO, were reviewed.

Results: TO affected mature sports and pleasure horses (age 7‐16 years) and caused moderate to severe lameness, usually of sudden onset with no obvious inciting cause. There were few localising signs, other than worsening of lameness by hock flexion. Tarsocrural joint analgesia produced improvement in lameness in 6/11 horses (55%) and perineural analgesia of the tibial and fibular nerves complete soundness in 6/14 horses (43%) in which it was performed; 7/14 horses (50%) showed a further substantial improvement. Radiological findings included subchondral bone lysis and sclerosis and irregular joint space width, seen most obviously in a lateromedial view. Nuclear scintigraphy revealed marked uptake of radiopharmaceutical predominantly plantaromedially in the region of the talus in the 7 horses in which it was performed. Fourteen horses were treated conservatively with box‐ or pasture‐rest, with or without intra‐articular corticosteroids, hyaluronic acid or polysulphated glycosaminoglycan, and all remained lame. Intra‐articular corticosteroids appeared to have no effect in any horse. Of 10 horses receiving conservative management only, 6 were subjected to euthanasia, 3 were retired and 1 remained in light work, but was still lame. Two horses treated by either partial tibial and fibular neurectomy or subchondral forage failed to regain soundness and were retired. Six horses were treated by surgical arthrodesis of the talocalcaneal joint with 2 or three 5.5 mm AO screws introduced obliquely across the joint from the plantarolateral aspect of the calcaneus, which resulted in improvement in lameness in all cases.

Conclusions: Osteoarthritis of the talocalcaneal joint causes acute onset severe lameness, but clinical findings and diagnostic analgesia often fail to identify precisely the site of pain. Consistent radiographic changes suggested TO was contributing to the lameness and this diagnosis was supported by nuclear scintigraphy. The poor success of conservative treatment (including intra‐articular medication) suggests that surgical arthrodesis is the treatment of choice, although the prognosis is still poor for a return to full soundness. Potential relevance: The clinical features described should facilitate more accurate diagnosis and prognosis. A novel surgical treatment is described which appears to offer significant improvement in the lameness. Further work is necessary to determine the causes of this condition and more effective management.
Cardiopulmonary effects and pharmacokinetics of i.v. dexmedetomidine in ponies
Authors: BETTSCHART‐WOLFENSBERGER R. , FREEMAN S. L. , BOWEN I. M. , ALIABADI F. S. , WELLER R. , HUHTINEN M. , CLARKE K. W.
Published: April 2007

Reasons for performing study: Currently available sedatives depress cardiopulmonary function considerably; therefore, it is important to search for new, less depressive sedatives. The study was performed to assess duration and intensity of cardiopulmonary side effects of a new sedative, dexmedetomidine (DEX), in horses.

Objectives: To study pharmacokinetics and cardiopulmonary effects of i.v. DEX.

Methods: Pharmacokinetics of 3.5 μg/kg bwt i.v. DEX were studied in a group of 8 mature (mean age 4.4 years) and 6 old ponies (mean age 20 years). Cardiopulmonary data were recorded in mature ponies before and 5, 10, 20, 30, 45 and 60 mins after administration of DEX 3.5 μg/kg bwt i.v. Data were analysed using ANOVA for repeated measures, and where appropriate Dunnett'sttest was used to detect differences from resting values (P<0.05).

Results: Within 2 h after DEX administration, plasma levels were beyond limits of quantification (0.05 ng/ml). Mean values for kinetic parameters for mature and old ponies were: Cmax (ng/ml) 4.6 and 3.8, t1/2(min) 19.8 and 28.9 and AUC (ng.min/ml) 34.5 and 44.3, respectively. Heart rate, central venous pressure, pulmonary artery pressure and pulmonary capillary wedge pressure did not change significantly compared to presedation values throughout the 60 min observation period. Compared to presedation values, stroke volume and mixed venous PO2were reduced for the first 5 mins, paralleled by an increase in systemic and pulmonary vascular resistance. Cardiac index was reduced for the first 10 mins, arterial blood pressures at 20, 30 and 45 mins and respiratory rate throughout the 60 min observation period, but no change in arterial PO2or PCO2occurred.

Conclusions: DEX administration i.v. causes similar cardiopulmonary changes to those caused by other alpha‐2adrenoceptor agonists, but of very short duration. DEX is redistributed particularly rapidly.

Potential relevance: DEX might be safer for sedation of horses because of its very short‐lasting cardiopulmonary side effects. For long duration sedation, its kinetics favour its use as a continuous infusion.
Age‐related changes in serum insulin‐like growth factor‐I, insulin‐like growth factor‐I binding protein‐3 and articular cartilage structure in Thoroughbred horses
Authors: FORTIER L. A. , KORNATOWSKI M. A. , MOHAMMED H. O. , JORDAN M. T. , O'CAIN L. C. , STEVENS W. B.
Published: April 2007

Reasons for performing study: Structural changes in articular cartilage associated with the ageing process require definition for investigators performing developmental and age‐related studies, for which information is lacking.

Objectives: To 1) determine the onset and end of puberty as defined by serum insulin like growth factor (IGF‐I) and IGF‐binding protein‐3 (IGFBP‐3) concentrations and 2) correlate articular‐epiphyseal cartilage complex structural changes with the onset and end of puberty.

Methods: IGF‐1 and IGFBP‐3 were measured in serum samples from normal female and male horses age 9‐715 days to determine peak and steady‐state values for horses transitioning through puberty. Osteochondral tissue sections were obtained from horses age 120‐840 days (4‐28 months) and examined histologically for cartilage canals and tidemark formation.

Results: In male and female horses, serum IGF‐1/IGFBP‐3 concentrations peaked at approximately 225 days, defining the onset of puberty. Cartilage canals were absent from articular cartilage just prior to this time point. IGF‐1/IGFBP‐3 concentrations declined to steady‐state levels at approximately age 450 days, signalling exit from puberty and therefore the beginning of ageing. This time point correlated to initial formation of a tidemark in the osteochondral tissue sections.

Conclusions: Horses may be considered pubescent at age 225‐450 days, and post pubescent and ageing after age 450 days.

Potential relevance: Defining the normal post natal to post pubescent concentrations for serum IGF‐I and serum IGFBP‐3 establishes subsets of animals for age‐related studies and may be used to monitor horses for abnormally high IGF‐1 concentrations due to natural disease or subsequent to systemic growth hormone administration.
Arterial lactate concentration, hospital survival, sepsis and SIRS in critically ill neonatal foals
Authors: CORLEY K. T. T. , DONALDSON L. L. , FURR M. O.
Published: April 2007

Reasons for performing study: Blood lactate concentration has been shown to be a useful clinical indicator in human patients, but has not been formally investigated in critically ill foals.

Objective: To investigate the association of blood lactate with hospital survival, markers of cardiovascular status, metabolic acid base status, sepsis and systemic inflammatory response syndrome (SIRS).

Methods: A database containing clinical, haematological, plasma biochemical and hospital outcome data on neonatal foals referred to an intensive care unit in 2000‐2001 was analysed. Seventy‐two foals for which arterial lactate was measured at admission were included in the study.

Results: Sixty‐one foals had an admission lactate concentration >2.5 mmol/1. Admission lactate was statistically associated with hospital survival, mean arterial pressure, blood creatinine concentration, bacteraemia, anion gap, lactate concentration at 18‐36 h after admission and evidence of SIRS, but not with packed cell volume or heart rate. Lactate at 18‐36 h was also associated with survival and evidence of SIRS. Anion gap, base excess, base excess due to unidentified anions (BEua), simplified strong ion gap or bicarbonate correctly classified foals for presence of hyperlactaemia (>5 mmol/1) in 80% of animals.

Conclusions: Admission blood lactate gives important prognostic information. Lactate should be measured rather than assumed from the anion gap, base excess, BEua, simplified strong ion gap or bicarbonate.

Potential relevance: Blood lactate concentrations at admission are clinically relevant in neonatal foals and warrant further investigation. This should include the clinical value of measuring changes in lactate in response to treatment.