bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of trilostane for the treatment of equine Cushing's syndrome
Authors: McGOWAN C. M. , NEIGER R.
Published: April 2007

Reasons for performing study: Trilostane, a competitive 3‐beta hydroxysteroid dehydrogenase inhibitor, has been used successfully to control clinical signs and cortisol excess in canine pituitary dependent hyperadrenocorticism

Objectives: Trilostane was evaluated for its efficacy in resolving clinical and clinicopathological abnormalities of equine Cushing's syndrome (ECS) and to assess its safety.

Methods: Twenty horses (mean age 21 years) diagnosed with ECS were followed for 1 or 2 years. Affected horses received 0.4–1 mg/kg (mean 0.5 mg/kg) trilostane once daily.

Results: Clinical signs assessed over 1 or 2 years, showed a reduction in lethargy in all horses post treatment. Polyuria and/or polydipsia, present in 11 horses, was reduced in all after treatment. Recurrent or chronic laminitis, present in 16 horses, improved in 13/16 (81%) of cases. There were no side effects reported. Combined dexamethasone suppression and thyrotropin releasing hormone (TRH) stimulation tests were significantly different before and 30 days following therapy. There was a significant reduction (P = 0.01) of cortisol following TRH administration before (160 ± 53.0 nmol/l) and after (130 ± 46.1 nmol/l) trilostane.

Conclusions: Trilostane caused improvement in clinical signs in horses, without side effects, and a corresponding decrease in cortisol response to TRH administration.

Potential relevance: Trilostane may be a useful therapy for the treatment of ECS. Further work comparing the effects of trilostane and pergolide is warranted.
Radiographic changes in Thoroughbred yearlings. Part 2: Associations with racing performance
Authors: KANE A. J. , McILWRAITH C. W. , PARK R. D. , RANTANEN N. W. , MOREHEAD J. P. , BRAMLAGE L. R.
Published: April 2007

Reasons for performing study: Although the radiographic examination of yearlings has become commonplace at some large Thoroughbred sales, there are few data to support the decisions facing veterinarians who are asked to evaluate future racing potential.

Objectives: To identify radiographic changes in the fetlocks, proximal sesamoid bones, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings associated with future racing performance during ages 2 and 3 years.

Methods: Radiographs from routine pre‐ and post sale examinations of 1162 yearlings were used to identify individual radiographic changes in sale yearlings. Starting a race, the percent of starts placed, money earned and earnings per start were used to assess racing performance and examined for associations with the radiographic changes observed.

Results: Overall 946 (81%) yearlings started at least one race during ages 2 or 3 years. Fourteen of 24 (58%) yearlings with moderate or extreme palmar supracondylar lysis of the third metacarpus, 8 of 14 (57%) of those with enthesophyte formation on the proximal sesamoid bones and 19 of 30 (63%) of those with dorsal medial intercarpal joint disease started a race. The oDs of starting a race when age 2 or 3 years were 3 times lower for yearlings with these changes (P<0.01) compared with yearlings that did not have these changes. Twenty‐five of 36 (69%) yearlings with proximal dorsal fragmentation of the first phalanx in the hind fetlock started a race and these yearlings were also less likely (OR = 0.51, P = 0.07) to start a race. Yearlings with enthesophyte formation on hind proximal sesamoid bones placed in a smaller percentage of starts (16%, P = 0.01) earned less money ($987 US, P = 0.02) and had lower earnings per start ($252 U S, P = 0.03) compared to starters without this change.

Conclusions: Although many of the changes observed on radiographs of sale yearlings do not appear to influence future racing performance, some are associated with reduced performance.

Potential relevance: The results of this study are best applied in parallel with the clinical impressions of veterinarians experienced in examining radiographs of sale yearlings. Some findings support those established in the literature as incidental findings and others suggest new areas for concern not previously reported as a problem in Thoroughbred sale yearlings.
Effects of alpha‐2 adrenoceptor agonists during recovery from isoflurane anaesthesia in horses
Authors: SANTOS M. , FUENTE M. , GARCIA‐ITURRALDE P. , HERRAN R. , LOPEZ‐SANROMAN J. , TENDILLO F. J.
Published: April 2007

Reasons for performing study: Recovery from inhalant anaesthesia in the horse is a critical and difficult period to manage; however, several factors could help to obtain a calm recovery period including choice of anaesthetic and analgesic procedure used and the conditions under which anaesthetic maintenance and recovery occur.

Objectives: The objective of this study was to evaluate and compare the quality of recovery in horses administered saline, xylazine, detomidine or romifidine during recovery from isoflurane anaesthesia.

Methods: Six mature and healthy horses were premedicated with i.v. xylazine and butorphanol, and anaesthesia induced using ketamine. After 2 h of inhalant anaesthesia with isoflurane vaporised in oxygen, saline solution, xylazine (0.1 mg/kg bwt), detomidine (2 μg/kg bwt) or romifidine (8 μg/kg bwt) were administered. The quality of recovery of each horse and the degree of sedation and ataxia were evaluated. Cardiovascular and respiratory parameters were recorded, and arterial blood samples obtained and analysed for pH, PO2and PCO2during recovery.

Results: Quality of recovery was better in groups treated with alpha‐2 adrenergic receptors agonists, showing less ataxia. Degree of sedation was greater in the romifidine group.

Conclusions: We concluded that the administration of alpha‐2 adrenoceptor agonists during recovery from isoflurane anaesthesia in horses prolonged and improved the quality of recovery without producing significant cardiorespiratory effects.

Potential clinical relevance: Administration of alpha‐2 adrenoceptor agonists after inhalent anaesthesia could prevent complications during the recovery period.
Pregnancy rates in mares after a single fixed time hysteroscopic insemination of low numbers of frozen‐thawed spermatozoa onto the uterotubal junction
Authors: MORRIS L. H. A. , TIPLADY C. , ALLEN W. R.
Published: April 2007

Reasons for performing study: To compensate for the wide variation in the freezability of stallion spermatozoa, it has become common veterinary practice to carry out repeated ultrasonography of the ovaries of oestrous mares in order to be able to inseminate them within 6–12 h of ovulation with a minimum of 300–500 × 106 frozen‐thawed spermatozoa. Furthermore, in order to achieve satisfactory fertility, this requirement for relatively high numbers of spermatozoa currently limits our ability to exploit recently available artificial breeding technologies, such as sex‐sorted semen, for which only 5–20 × 106 spermatozoa are available for insemination.

Objectives: This study was designed to evaluate and compare the efficacy of hysteroscopic vs. conventional insemination when low numbers of spermatozoa are used at a single fixed time after administration of an ovulation‐inducing agent.

Methods: In the present study, pregnancy rates were compared in 86 mares inseminated once only with low numbers of frozen‐thawed spermatozoa (3–14 × 106) at 32 h after treatment with human chorionic gonadotrophin (hCG), either conventionally into the body of the uterus or hysteroscopically by depositing a small volume of the inseminate directly onto the uterotubal papilla ipsilateral to the ovary containing the pre‐ovulatory follicle.

Results: Pregnancy rates were similarly high in mares inseminated conventionally or hysteroscopically with 14 × 106 motile frozen‐thawed spermatozoa (67% vs. 64%). However, when the insemination dose was reduced to 3 × 106 spermatozoa, the pregnancy rate was significantly higher in the mares inseminated hysteroscopically onto the uterotubal junction compared to those inseminated into the uterine body (47 vs. 15%, P<0.05).

Conclusions: When inseminating mares with <10 × 106 frozen‐thawed stallion spermatozoa, hysteroscopic uterotubal junction deposition of the inseminate is the preferred method.

Potential clinical relevance: Satisfactory pregnancy rates are achievable after insemination of mares with frozen‐thawed semen from fertile stallions 32 h after administration of human chorionic gonadotrophin (Chorulon)1. Furthermore, these results were obtained when mares were inseminated with 14 × 106 progressively motile frozen‐thawed spermatozoa from 2 stallions of proven fertility.
Uptake of 5‐hydroxytryptamine by equine digital vein endothelial cells: inhibition by amines found in the equine caecum
Authors: BAILEY S. R. , WHEELER‐JONES C. , ELLIOTT J.
Published: April 2007

Reasons for performing study: 5‐hydroxytryptamine (5‐HT; serotonin) is a potent vasoconstrictor of equine digital blood vessels and has been implicated in the pathogenesis of acute laminitis.

Objectives: The aims of this study were firstly to examine whether cells of the digital blood vessel wall exhibited an active uptake mechanism for 5‐HT and to characterise its efficiency; and secondly, to study the potential inhibitory effect on this process of other amines, produced in the equine caecum.

Methods: Confluent monolayers of equine digital vein endothelial cells (EDVEC) and equine digital vein smooth muscle cells (EDVSMC) were incubated with [3H]5‐HT (0.1–250 μmol/l) and the total and active uptake calculated. Equine pulmonary vein endothelial cells (EPVEC) were used as a positive control.

Results: Both EDVEC and EDVSMC showed uptake of [3H]5‐HT by nonfaci litated diffusion; however, only EDVEC showed evidence of saturable facilitated uptake mechanism, with a Kmof 41.6 ± 9.3 μmol/l, which was significantly higher than that of EPVEC (9.9 ± 2.1 μmol/l). All 6 caecally‐derived amines examined (tyramine, spermine, isoamylamine, tryptamine, phenylethylamine and isobutylamine) inhibited the total uptake of [3H]5‐HT in a concentration‐dependent manner, tyramine having the lowest IC50(3.7 × 10−6mol/l).

Conclusions: These data suggest that facilitated uptake into the endothelium could play a role in moderating the vasoconstrictor response to 5‐HT in the equine digital circulation.

Potential clinical relevance: The vasoconstrictor action of 5‐HT could be potentiated by gut‐derived amines, providing a feasible link between GI disturbances and the pathophysiology of laminits.
Systemic concentrations of antioxidants and biomarkers of macromolecular oxidative damage in horses with grass sickness
Authors: McGORUM B. C. , WILSON R. , PIRIE R. S. , MAYHEW I. G. , KAUR H. , ARUOMA O. I.
Published: April 2007

Reasons for performing study: The aetiopathogenesis of equine grass sickness (EGS) is unknown. The role of free radical‐mediated neuronal damage has not previously been investigated in this condition.

Objectives: To investigate the potential contribution of oxidative damage and antioxidant status to neurodegeneration in EGS.

Methods: Systemic levels of surrogate biomarkers were determined in 10 horses with acute EGS and in 2 control populations; 10 healthy horses co‐grazing with the 10 EGS horses at the onset of clinical disease, and 10 healthy mares grazing where EGS has not been reported.

Results: EGS horses had alterations in levels of several antioxidants, consistent with oxidative stress, the acute phase response and/or the secondary metabolic complications of EGS. EGS horses had elevated plasma dihydroxyphenylalanine (DOPA) levels.

Conclusions: The elevated DOPA levels probably reflected a generalised disturbance of catecholamine metabolism rather than increased DOPA production via free radical‐mediated oxidation of tyrosine. However, there was no evidence of systemic macromolecular oxidative damage.

Potential clinical relevance: Further work is required to determine whether macromolecular oxidative damage occurring at the neuronal level contributes to EGS.
Equine melanoma in a population of 296 grey Lipizzaner horses
Authors: SELTENHAMMER M. H. , SIMHOFER H. , SCHERZER S. , ZECHNER P. , CURIK I. , SÖLKNER J. , BRANDT S. M. , JANSEN B. , PEHAMBERGER H. , EISENMENGER E.
Published: April 2007

Reasons for performing study: Equine melanomas occur most commonly in grey horses at age 5 years or more. Generally, benign and malignant melanomas are distinguished by microscopy, but a more distinct classification would be helpful.

Objectives: The objectives of this study were to gain further evidence concerning the occurrence of melanotic tumours, and to evaluate the impact of heredity on melanoma development.

Methods: A clinical study was conducted on a defined population of 296 grey horses of Lipizzaner breed. Individuals were classified according to theirstage of disease using a 0–5 scale. Heritability was estimated on a sample of 296 grey horses with pedigrees traced back as far as 32 generations.

Results: Of the 296 horses, dermal melanomas were present in 148 horses (50%), 68 of which were more than age 15 years; 51 of these were melanoma‐bearing. In 75.6% of cases, melanotic tumours were detected underneath the tail. Although melanoma‐bearing grey horses were encountered up to stage 4, none of the affected individuals suffered any severe clinical effect or was handicapped in performance. Statistical analysis revealed highly significant effects of stud and age (P<0.0001), explaining 28% of the total variability.

Conclusions: In contrast to melanomas in solid‐coloured horses characterised by early metastases, melanomas in grey horses showed less malignancy. Affected individuals often had encapsulated nodules or structures similar to human blue nevi. Grey horse‐specific genetic factors inhibiting metastatic processes may be responsible for this phenomenon.

Potential clinical relevance: Although the obtained heritability estimate of 0.36 with a standard error of 0.11 indicates a strong genetic impact on the development of melanoma in ageing grey horses, a possible influence of the genes with large effects was also suggested. Therefore, further analysis is required of melanoma development in the ageing grey horse.
Tenosynovitis of the digital flexor tendon sheath and annular ligament constriction syndrome caused by longitudinal tears in the deep digital flexor tendon: a clinical and surgical report of 17 cases in Warmblood horses
Authors: WILDERJANS H. , BOUSSAUW B. , MADDER K. , SIMON O.
Published: April 2007

Reasons for performing study: Inflammation of the digital flexor tendon sheaths is a chronic and nebulous condition often unresponsive to medical and surgical treatment.

Objectives: To evaluate the incidence of longitudinal tears (LT) as the underlying cause of chronic tenosynovitis and annular ligament constriction syndrome (ALCS) in warmblood horses.

Methods: The records of 25 horses with chronic tenosynovitis and ALCS in which tenoscopical inspection of the digital flexor tendon sheath (DFTS) was performed between 1999–2000 were reviewed. Of 25 horses, 17 were diagnosed with an LT in the deep digital flexor tendon (DDFT). All horses had a history of distension of the DFTS and/or signs of an ALCS. All cases presented typical signs of a chronic inflamed DFTS on ultrasonography and 11 horses showed ultrasonographic changes (echogenic material or an irregular outlining) at the lateral or medial border of the DDFT. The diagnosis of LTs of the DDFT was established in all cases by tenoscopy. Surgical treatment consisted of removal of the torn collagen fibrils using a mechanical resector and decompressing the fetlock canal by a transection of the palmar annular ligament (PAL) using a hook knife under tenoscopic control.

Results: Ten horses became sound and resumed their previous level of work, 3 horses remained lame, 4 horses returned to previous level of work but needed intrasynovial treatment of the DFTS and reduced competition frequency to remain sound.

Conclusions: Horses presented with chronic inflamed DFTS and/or ALCS might sufferfrom LTs in the DDFT; however, the diagnosis cannot be established with absolute certainty using only ultrasonography. Longitudinal tears should be suspected if ultrasonographic changes are present lateral or medial to the border of the DDFT but tenoscopical examination of the tendon sheath is essential to establish an accurate diagnosis and an effective treatment.

Potential relevance: The presence of these LTs might explain why some cases of chronic tenosynovitis of the digital flexor tendon sheath and/or ALCS do not respond on surgical transection of the PAL alone without tenoscopy.
Spectral analysis of respiratory noise in horses with upper airway disorders
Authors: FRANKLIN S. H. , USMAR S G. , LANE J. G. , SHUTTLEWORTH J. , BURN J. F.
Published: April 2007

Reasons for performing study: It has long been recognised that the production of abnormal respiratory sounds by horses during exercise is frequently associated with upper airway obstructions. Respiratory acoustic measurements have shown promise in investigation of upper airway disorders in man and, more recently, in horses with experimentally‐induced obstructions.

Objectives: To evaluate sounds from exercising horses with naturally occurring dynamic obstructions of the upper respiratory tract and to compare these with those from normal horses in order to determine whether different obstructions produce characteristic spectral patterns.

Methods: The audio signal, airflow and videoendoscopic images were recorded simultaneously during an incremental exercise test on a high‐speed treadmill.

Results: Spectral analysis of the audio signal showed marked differences between control and clinically afflicted horses. Dorsal displacement of the soft palate was characterised by a narrow low frequency (20–80 Hz) peak during expiration. Horses with dynamic laryngeal collapse produced inspiratory sounds characterised by a broad band high frequency spectral component in the range 1.1–2.7 kHz.

Conclusions and potential relevance: Spectral analysis of respiratory sounds in horses has potential as a diagnostic technique for field use especially when facilities for highspeed treadmill assessment are not practicable.
Management of drug‐resistant cyathostominosis on a breeding farm in central North Carolina
Authors: LITTLE D. , FLOWERS J. R. , HAMMERBERG B. H. , GARDNER S. Y.
Published: April 2007

Reasons for performing study: Possible anthelmintic resistance on a breeding farm where a rapid rotation anthelmintic programme had been implemented for 9 years was investigated. Cyathostomins resistant to fenbendazole and pyrantel were documented by faecal worm egg count reduction test (FWECRT).

Objectives: To 1) manage small strongyle transmission in a herd of horses in which resistance to both pyrantel pamoate and fenbendazole was identified and thereby reduce the risk of clinical disease in the individual animal, 2) monitor the change in resistance patterns over time and 3) monitor the efficacy of ivermectin over the study period.

Methods: Targeted ivermectin treatment of horses on the farm was instituted formature horses with faecal worm egg counts (FWEC) >200 eggs/g (epg) and for horses 100 epg.

Results: Over a 30 month period, targeted ivermectin treatment achieved acceptable control in mares, as judged by FWEC, and improved control of patent cyathostome infection in consecutive foal crops. Egg reappearance time (ERT) after treatment with ivermectin was <8 weeks in mares and foals more frequently in the second year of the study than in the first year. Numbers of anthelmintic treatments were reduced by 77.6 and 53.3% in the mare and foal group, respectively.

Conclusions: Targeted ivermect in treatment may be an economically viable method of managing multiple drug resistant cyathostominosis.

Potential relevance: Use of ivermectin should be monitored closely for development of resistance.
Are the material properties and matrix composition of equine flexor and extensor tendons determined by their functions?
Authors: BATSON E. L. , PARAMOUR R. J. , SMITH T. J. , BIRCH H. L. , PATTERSON‐KANE J. C. , GOODSHIP A. E.
Published: April 2007

Reasons for performing study: Injury to the superficial digital flexor tendon (SDFT) is common in competition horses. The SDFT contributes to locomotory efficiency by storing energy; such tendons have low safety margins. Tendons which merely position the limb, including the opposing common digital extensortendon (CDET), are rarely injured. The current failure of strategies to prevent or effectively treat injury to the SDFT indicates the importance of understanding how it differs from tendons which are not injury‐prone.

Hypothesis: That the structural and material properties and matrix composition of the SDFT and CDET differ, reflecting their specific functional requirementsin vivo.

Methods: Forelimb tendons were harvested from 26 mature horses and loaded to failure prior to matrix composition analysis of specimens.

Results: The SDFT had a significantly higher cross‐sectional area, structural stiffness, failure load and failure strain and a lower elastic modulus than the CDET(P < 0.0001).

Conclusions: The SDFT has conflicting requirements for strength and elasticity; although as a whole it is a stiffer structure than the CDET, differences in the matrix molecular composition including water and total sulphated glycosaminoglycan contents allow it to remain more elastic as a material.

Potential relevance: Further information on how the two tendons attain these different properties may be of use in the development of prevention and treatment strategies for SDFT rupture.
Medetomidine‐ketamine anaesthesia induction followed by medetomidine‐propofol in ponies: infusion rates and cardiopulmonary side effects
Authors: BETTSCHART‐WOLFENSBERGER R. , BOWEN I. M. , FREEMAN S. L. , WELLER R. , CLARKE K. W.
Published: April 2007

Reasons for performing study: To search for long‐term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia.

Objectives: To determine cardiopulmonary effects and anaesthesia quality of medetomidine‐ketamine anaesthesia induction followed by 4 h of medetomidine‐propofol anaesthesia in 6 ponies.

Methods: Sedation consisted of 7 μg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 μg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (FIO2> 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals.

Results: Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89–0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0–15.8 breaths/min; PaO229.1–37.9 kPa; PaCO26.2–6.9 kPa; heart rate 31.2–40.8 beats/min; mean arterial pressure 90.0–120.8 mmHg; cardiac index 44.1–59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8–16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts.

Conclusions: In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occurbut, despite FIO2of >0.9, minimal PaO2in one pony after 4 h anaesthesia was 8.5 kPa.

Potential relevance: The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.
The role of electromyography in clinical diagnosis of neuromuscular locomotor problems in the horse
Authors: WIJNBERG I. D. , BACK W. , DE JONG M. , ZUIDHOF M. C. , VAN DEN BELT A. J. M. , VAN DER KOLK J. H.
Published: April 2007

Reasons for performing study: Systematically performed EMG needle examination of muscles provides essential information about the functional aspects of the motor unit. However, clinical studies in which information is given on the diagnostic and discriminative values of electromyography (EMG) in the horse are scarce.

Objectives: To determine to what extent inclusion of EMG analysis in clinical examination contributes to determination of type and localisation of abnormality.

Methods: EMG analysis, complete clinical examination and diagnosis of 108 horses (mean ± s.d. age 7.5 ± 3.8 years; bodyweight 548 ± 86 kg; height 1.67 ± 0.07 m) were performed, and results without and with EMG analysis compared.

Results: Without EMG, myopathy and neuropathy were diagnosed in 20 and 58 horses, respectively, and with EMG in 17 and 82 horses. EMG changed localisation in myopathy and neuropathy in 12 and 37% of cases, respectively. Lesions in the C1‐T2, T2‐L3 and L3‐S3 segments were, respectively, diagnosed without EMG in 7, 11 and 30%, and with EMG in 27, 7 and 17% of cases. Where no clinical diagnosis could be made prior to EMG, many patients appeared to be suffering from localised cervical lesions (29%) or generalised neuropathy (54%).

Conclusions and potential relevance: The assistance of EMG in discriminating between normal, neuropathy and myopathy, and in locating pathology, contributes to diagnosis of neuromuscular problems.
Influence of individual competition level on back kinematics of horses jumping a vertical fence
Authors: CASSIAT G. , POURCELOT P. , TAVERNIER L. , GEIGER D. , DENOIX J.‐M. , DEGUEURCE D.
Published: April 2007

Reasons for performing study: The costs and investments required for the purchase and training of showjumpers justify the need to find selection means for jumping horses. Use of objective kinematic criteria correlated to jumping ability could be helpful for this assessment.

Objectives: To compare back kinematics between 2 groups of horses of different competition levels (Group 1, competing at high level;Group 2competing at low level) while free jumping over a 1 m vertical fence.

Methods: Three‐dimensional recordings were performed using 2 panning cameras. Kinematic parameters of the withers andtuber sacrale(vertical displacement, vertical and horizontal velocities), backline inclination and flexion‐extension motion of the 3 main dorsal segments (thoracic, thoracolumbar and lumbosacral) were analysed.

Results:Group 2horses had a lower displacement of their withers andtuber sacralefrom the end of the last approach stride until the first departure stride (P<0.05). As a result, they increased the flexion of their thoracolumbar and lumbosacral junctions during the hindlimb swing phase before take‐off (P<0.05). However, withers andtuber sacralevelocities were slightly modified.Group 1horses pitched their backline less forward during the forelimb stance phase before take‐off and straightened it more after landing (P<0.05), probably indicating a more efficient strutting action of their forelimbs.

Conclusions and potential relevance: Because significant differences in back motion were found between good and poor jumpers when jumping a 1 m high fence, criteria based on certain back kinematics can be developed that may help in the selection of talented showjumpers.
Influence of the load of a rider or of a region with increased stiffness on the equine back: a modelling study
Authors: PEHAM C. , SCHOBESBERGER H.
Published: April 2007

Reasons for performing study: Knowledge of load effects is crucial for the understanding of the aetiology and pathogenesis of equine back problems.

Objective: To investigate different load scenarios of the equine back, such as being ridden or increased muscle tone, using biomechanical simulations.

Methods: Kinetic and kinematic data of 15 sound horses and the electromyelograph of their long back muscles were recorded. A biomechanical simulation model was used for simulations under different biomechanical scenarios (ridden/unridden, localised increased stiffness) using ADAMS.

Results: The vertical forces acting through a rider were: walk 3.83 N/kg, trot 5.18 N/kg and gallop 5.60 N/kg. No significant changes in transversal forces were found between ridden and unridden horses. Profound changes were seen in the torques at the segment following a region of increased stiffness: in walk, lateral peak torques increased from 342 to 1723 Nm, and in trot from 393 to 1004 Nm, and dorsoventral from 386 to 3705 Nm (walk) and 458 to 4340 Nm (trot).

Conclusions and potential relevance: The simulation shows that the stress of a rider is lower than that of pathological processes such as partial increased stiffness of the back. Study of revised models with improved anatomical realism might help to raise the plausibility of model results.
Three‐dimensional analysis of patterns of skin displacement over the equine radius
Authors: SHA D. H. , MULLINEAUX D. R. , CLAYTON H. M.
Published: April 2007

Reasons for performing study: Surface markers are usually used to track bone movement. However, skin movement related to the bone has a large effect on the analysis of skeletal kinematics. A 2‐dimensional (2D) skin displacement correction model has been successfully developed, but no 3D skin displacement model exists.

Objectives: To develop a 3‐dimensional (3D) skin displacement model for the equine radial segment during trot.

Methods: The 3D trajectories of 6 skin‐based markers and a bone‐fixed triad were captured at trot in 4 horses. Skin displacements in the bone‐based coordinate system were calculated using a singular‐value decomposition method. The truncated Fourier series models were developed for the skin displacements using a generalised cross‐validatory spline.

Results: Mean ± s.d. of peak skin displacement of the 3 markers on the proximal radius as percentage of radial length was 10.7 ± 0.5, 4.6 ± 1.5 and 14.5 ± 2.9% in x, y and z direction, respectively. For the 3 markers on the distal radius, the equivalent displacements were 4.7 ± 0.6, 1.7 ± 0.8 and 7.3 ± 1.8% in x, y and z direction, respectively.

Conclusions: The 3D skin displacement model for correction of skin marker motion over the equine radius relative to the bone can be established using a truncated Fourier series, which has previously been used successfully to develop 2D models.

Potential relevance: This method of determining 3D skin displacement correction needs to be extended to the entire fore‐ and hindlimbs to provide a more sensitive measure of kinematic analysis. Accurate descriptions of the 3D motions of the limb segments and interactions between adjacent segments at the joints are necessary for understanding of the mechanics of different gaits and the gait aberrations that manifest as lameness.
Effects of athletic taping of the fetlock on distal limb mechanics
Authors: RAMÓN T. , PRADES M. , ARMENGOU L. , LANOVAZ J. L. , MULLINEAUX D. R. , CLAYTON H. M.
Published: April 2007

Reasons for performing study: Athletic taping is used frequently by human athletes to stabilise, maintain or strengthen soft tissue structures, but empirical evidence supporting any changes in equine kinematics is lacking.

Objectives: To assess the effects of athletic taping of the fetlock applied by an experienced athletic trainer on forelimb mechanics in healthy horses.

Hypotheses: That athletic taping of the distal forelimb reduces

hyperextension of the fetlock joint during stance,

flexion of the fetlock joint during swing and 3) ground reaction forces during stance.

Methods: Ground reaction force and kinematic data were obtained for 6 healthy horses trotting at 3 m/sec for 4 sequential conditions (baseline, untaped; pre‐exercise, taped; post exercise, taped post 30 mins trotting exercise; transfer, 4 h after tape removal). Data were analysed using 2‐way mixed ANOVAs (condition; joint).

Results: A statistically significant interaction was identified for the fetlock during the swing phase (mean ± s.d. peak flexion at baseline 157 ± 4°, reduced with taping to 172 ± 4°; P<0.05) compared with no differences across conditions for the other joints. Peak vertical force reduced significantly (P<0.05) with taping.

Conclusions: Athletic taping of the fetlock does not alter the kinematics of the forelimb during stance, but does limit flexion of the fetlock during the swing phase. The decreased peak vertical force may be due to an increased proprioceptive effect.

Potential relevance: Reduced peak vertical forces may be of benefit in preventing or reducing injury. Further investigation remains necessary before it can be concluded that taping should be applied for tendinous or ligamentous rehabilitation in equine patients.
Relationships between fore‐ and hindlimb ground reaction force and hoof deceleration patterns in trotting horses
Authors: GUSTÅS P. , JOHNSTON C. , ROEPSTORFF L. , DREVEMO S. , LANSHAMMAR H.
Published: April 2007

Reasons for performing study: The transmission of shockwaves following hoof impact is proposed to be one major source of stress to the limb. In the forelimb, there are indications that the period of horizontal deceleration of the hoof is related to the attenuation of shockwaves. In the hindlimb, information about the hoof deceleration has been lacking.

Objective: To compare hoof deceleration patterns between the fore‐ and hindlimbs.

Methods: Seven Standardbreds were trotted by hand over a force plate covered with sand, with triaxial accelerometers mounted on the fore and hind hooves. Variables representative of decelerations (first 2 main vertical deceleration peaks; characteristic minimum and maximum values in the craniocaudal deceleration; hoof braking time) and ground reaction forces (vertical loading rates; maximum and the following local minimum of the craniocaudal force) of the initial part of the stance phase, and the differences between individual fore‐ and hindlimb time and amplitude variables were used for statistical analyses.

Results: Force plate data showed significantly greater vertical loading rate (mean ± s.d. 6.5 ± 5.9 N/sec) and horizontal loads (190.4 ± 110.2 N) in the forelimb than the hindlimb, but the parameters from accelerometer data showed no significant differences.

Conclusions: No significant difference was found in the hoof deceleration, but the deceleration curves displayed a common pattern that described in detail the kinematics of the fore and hind hooves during the initial period of hoof braking.

Potential relevance: These results contribute to further knowledge about the characteristics of these potential risk factors in the development of subchondral bone damage in the horse. Further studies are required on the influence of hoof braking pattern at higher speed, different shoeing and ground surfaces with different properties.
In vitromeasurement of internal hoof strain
Authors: HOBBS S. J. , MATHER J. , ROLPH C. , BOWER J. A. , MATUSZEWSKI B.
Published: April 2007

Reasons for performing study: Strains during stance on the hoof wall surface have been measured by a number of authorsin vitroandin vivo. Histological structure and mechanical properties vary through the wall thickness (radially); radial strain measurements may therefore aid the understanding of mechanical function of the capsule and adjacent tissues.

Objectives: To develop instrumentation capable of measuring internal hoof strain, and to carry out a preliminary comparison of normal and laminitic hooves.

Methods: Six forelimbs from 4 horses, including 2 with laminitis from the same horse, were tested using an Instron test rig designed to simulate the walk at impact, midstance and breakover. Internal strains were measured at a dorsal site using strain gauges moulded into a plug made of 007 fast‐set structural adhesive. In addition, kinetic and kinematic data were collected from each specimen.

Results: When simulating the walk, a significant (P<0.0001) increase in gradient of radial tensile strain was found in a normal hoof wall, from 5.6 ± 73.9 με at the outer gauge to 418.5 ± 170.6 με at the inner gauge. However, radial strains measured at the inner gauge site in limbs with laminitis were found to be significantly (P<0.0001) compressive, with values of ‐406.7 ± 156.3 and ‐109.9 ± 72.4 με forSpecimens 1and2, respectively.

Conclusions and potential relevance: These preliminary data indicate that a marked redistribution may well occur in the wall of laminitic hooves. With a larger sample size, the results should have relevance to the treatment and management of laminitis.
The role of conformation in musculoskeletal problems in the racing Thoroughbred
Authors: ANDERSON T. M. , McILWRAITH C. W. , DOUAY P.
Published: April 2007

Reasons for performing study: The relationship of conformation to future potential injury is a standard approach in practise but, at present, is largely based on subjective observations.

Objective: To measure conformation in 3‐year‐old Thoroughbreds and objectively test its relationship with the occurrence of musculoskeletal problems.

Methods: Conformation measurements were taken from photographs using specific reference points marked on the horses and processed on the computer. Clinical observations were recorded for each horse on a regular basis. Stepwise (forward) logistic regression analysis was performed to investigate the relationship between the binary response of the clinical outcomes probability and the conformation variables by the method of maximum likelihood.

Results: Clinical outcomes significantly (P<0.05) associated with conformational variables included effusion of the front fetlock, effusion of the right carpus, effusion of the carpus, effusion of the hind fetlock, fracture of the left or right carpus, right front fetlock problem and hind fetlock problem.

Conclusions: Offset knees (offset ratio) contributed to fetlock problems. Long pasterns increased the odds of a fracture in the front limb. An increase in the carpal angle as viewed from the front (carpal valgus) may serve as a protective mechanism, as the odds for a carpal fracture and carpal effusion decreased with an increase in the carpal angle.

Potential relevance: This study demonstrates relationships between conformation and musculoskeletal disease in the racehorse. The information may be useful in selection and management of the racing Thoroughbred.
Ultrasonographic examination of the equine sacroiliac region
Authors: KERSTEN A. A. M. , EDINGER J.
Published: April 2007

Reasons for performing study: Little information exists about the normal ultrasonographic appearance of the equine sacroiliac region, but knowledge of the ultrasonographic anatomy is necessary to understand the possible pathological changes in sacroiliac diseases.

Objectives: The normal ultrasonographic appearance of soft tissues and bony structures of the sacroiliac region in horses was studied in order to establish clinically relevant reference parameters.

Methods: Thirteen cadaver specimens were examined using a transcutaneous approach above thetubera sacraleto image the dorsal sacroiliac ligament and the tendon of thelongissimus dorsimuscle. A rectal approach was used to outline the sacroiliac joint and its adjacent structures. Thirteen sound horses with no history of back pain were examined following the same protocol as for thepost mortemexaminations.

Results: The tendon of thelongissimus dorsimuscle can clearly be distinguished from the dorsal sacroiliac ligament, especially in longitudinal images. Transrectal examination of the sacroiliac joint consists of evaluation of the bony surfaces of the sacrum and ilium in comparison with the contralateral side.

Conclusions: Ultrasonographic examination of the sacroiliac region provided clear images of the caudomedial border of the sacroiliac joint and its adjacent structures and is a useful aid in the diagnosis of sacroiliac joint diseases and adjacent lesions. The study has shown ultrasonography to be a useful method for examining and differentiating thelongissimus dorsimuscle and the dorsal sacroiliac ligament at the level of thetubera sacrale.

Potential relevance: Diagnostic ultrasound is available to most practitioners. These reference ultrasound parameters may help to improve the diagnosis of sacroiliac diseases.
Immunological response to long‐term transport stress in mature horses and effects of adaptogenic dietary supplementation as an immunomodulator
Authors: STULL C. L. , SPIER S. J. , ALDRIDGE B. M. , BLANCHARD M. , STOTT J. L.
Published: April 2007

Reasons for performing study: Little information exists on the immunological effects of transport or the use of supplements to minimise transport stress.

Objectives: To establish baseline ranges and evaluate immunophenotypic and functional changes associated with transport and a nutritional ‘adaptogen’ supplement.

Methods: Horses received either supplement (n = 10) or placebos (n = 9) during the 30 day study. After 28 days in stalls, 12 horses (6 supplement; 6 placebo) were transported for 24 h, then unloaded and recovered. Venous blood samples were collected on Days 1, 14 and 28 to establish baselines, and on Days 28, 29 and 30 to examine changes during transport and recovery.

Results: Transport prompted elevations (P<0.05) in cortisol concentration, neutrophil count and white blood cell counts, while lymphocyte subpopulation counts (CD3+, CD4+, CD8+, CD21+) decreased (P<0.05). Normal phenotypic lymphocyte profiles returned within 24 h of recovery. Supplement effects on immunophenotype (CD21+and CD8+) were observed in stabled horses (P<0.05), but not in transported horses.

Conclusions: These results provide insights into the immunological mechanisms associated with long‐term transport.

Potential relevance: The existence of a small window of immunological uncertainty follows long‐term transportation, enhancing the potential risk of infectious disease in susceptible individuals.
Effects of manipulating intrauterine growth on post natal adrenocortical development and other parameters of maturity in neonatal foals
Authors: OUSEY J. C. , ROSSDALE P. D. , FOWDEN A. L. , PALMER L. , TURNBULL C. , ALLEN W. R.
Published: April 2007

Reasons for performing study: Intrauterine growth retardation (IUGR) impairs post natal adaptive responses and is associated with increased adrenocortical activity in many species.

Objectives: To determine whether a restricted or enhanced intrauterine environment affects neonatal adaptation and adrenocortical function in horses.

Methods: Embryos from large (577 kg) Thoroughbred (TB) mares were transferred to smaller (343 kg) pony (P) mares and vice versa, to create a restricted (TB‐in‐P, n = 11) or enhanced (P‐in‐TB, n = 8) intrauterine environment. Control groups (TB‐in‐TB, n = 8; P‐in‐P, n = 7) were also included.

Results: Thirty foals were born live at full term (range 314‐348 days) and 4 (3 TB‐in‐P, 1 P‐in‐TB) were stillborn between 275 and 335 days. TB‐in‐P foals were significantly (P<0.05) lighter than TB‐in‐TB, but heavier than P‐in‐P foals. TB‐in‐P foals took longer to first stand and suck and some had fetlock hyperextension and low (<4 g/l) plasma immunoglobulin G concentrations. Other foal groups showed normal behavioural responses. Haematological parameters were normal in all 4 groups of foals. Plasma ACTH levels were high at birth and plasma cortisol concentrations increased after delivery and returned to baseline within 6 h post partum in all but the TB‐in‐P foals, which had elevated levels until 48 h post partum. Plasma cortisol concentrations increased in all groups following exogenous ACTH administered on Days 1 and 5 post partum.

Conclusions: The TB‐in‐P foals showed IUGR and impaired post natal adaptive responses with basal hypercortisolaemia.

Potential relevance: Foals born following IUGR may require clinical assistance in the early post natal period, but appear mature with respect to adrenocortical function.
Transcranial magnetic stimulation: normal values of magnetic motor evoked potentials in 84 normal horses and influence of height, weight, age and sex
Authors: Nollet H. , Deprez P. , Van Ham L. , Dewulf J. , Decleir A. , Vanderstraeten G.
Published: April 2007

Reasons for performing study: Cervical spinal cord dysfunction is a common problem in equine medicine and the currently available tests give no objective information about the functionality of the nervous tracts. Therefore, transcranial magnetic stimulation (TMS) was performed in 84 healthy horses of different height in order to have an objective measure for the integrity of the descending motor tracts in normal horses.

Objectives: To obtain reference values for onset latency and peak‐to‐peak amplitude of magnetic motor evoked potentials (MMEPs) and to evaluate the possible effect of height, age and gender on the neurophysiological measures.

Methods: All horses were sedated and stimulated transcranially by using a magnetic coil placed on the forehead. The stimulator triggered the sweep of an electromyogram machine that recorded MMEPs bilaterally from needle electrodes in theextensor carpi radialisand cranial tibial muscles. In that way, it was possible to measure latency between stimulus and onset of response.

Results: A significant difference was found between recordings made in the fore‐ and hindlimbs; MMEPs recorded in the front legs had a shorter onset latency and higher peak‐to‐peak amplitude. Mean ± s.d. normal values for onset latency of 19.32 ± 2.50 and 30.54 ± 5.28 msecs and peak‐to‐peak amplitude values of 9.54 ± 3.73 and 6.62 ± 3.62 mV were obtained forextensor carpi radialisand cranial tibial muscles, respectively. The left‐to‐right difference in onset latency and peak‐to‐peak amplitude was not significant. In the same horse, differences up to 0.82 and 1.53 msecs for theextensor carpi radialisand cranial tibial muscles, respectively, lie within the 95% confidence limit and are considered normal. In contrast to onset latency, peak‐to‐peak amplitude showed a very large intra‐ and interindividual variability, even in the same muscle. To reduce the variability and predict normal values of new individual cases, influence of height, weight, age and sex on the MMEPs were determined. No significant effects of sex were observed on onset latency and peak‐to‐peak amplitude. The age of the horse had only a small but significant effect on peak‐to‐peak amplitude, with larger responses in older horses. Height at the withers and weight of the horse, parameters that strongly correlate with the size of the horse, had an important significant influence on onset latency but not on peak‐to‐peak amplitude.

The age of the horse and height at the withers were used to predict peak‐to‐peak amplitude and onset latency, respectively, in normal horses.

Conclusions and potential relevance: TMS is an excellent addition to the few tools we have for noninvasive imaging of the equine nervous system. Magnetically evoked potentials are highly reproducible and recent advances suggest that the applications of TMS in horses will continue to grow rapidly.
Idiopathic muscular hypertrophy of the oesophagus in the horse: a retrospective study of 31 cases
Authors: Benders N. A. , Kroeze E. J. B. Veldhuis , Van Der Kolk J. H.
Published: April 2007

Reasons for performing study: To present the first report of a case series concerning equine idiopathic muscular hypertrophy of the oesophagus (IMHO).

Objectives: To investigate the clinical and pathological features of the disorder.

Methods: The medical records of 31 horses suffering from the disorder were reviewed retrospectively. In all these animals the diagnosis was confirmed atpost mortemexamination.

Results: The median age of the affected horses was 12.5 ± 5.6 years (range 1–26) without sex or breed predilection. Only 2 out of 31 horses showed clinical signs associated with oesophageal dysfunction, indicating that the muscular hypertrophy was rather a coincidentalpost mortemfinding. Histology revealed thickening of the distal portion of the oesophagus mainly involving the circular layer of thetunica musculariswithout fibrosis or inflammation. In 8 cases, the disorder was seen in concurrence with idiopathic hypertrophy of thetunica muscularisof various other parts of the gastrointestinal tract.

Conclusions: In the majority of patients, IMHO was a coincidental finding atpost mortemexamination usually confined to the smooth, circular muscle layer of thetunica muscularis externa.

Potential relevance: Further research is necessary to study the precise effect of IMHO on oesophageal function.