Normal Adult Horses Research Articles

Radiological measurements of the feet of normal Straight Egyptian Arabian horses in Qatar

The Arabian horse has been identified as carrying a risk locus for equine metabolic syndrome, predisposing this breed to development of laminitis. Radigraphy of the equine foot is widely considered the main diagnostic imaging technique for evaluation of the laminitic horse. Knowledge of ‘normal’ breed values allows assessment of the degree and severity of radiological changes associated with laminitis. The objective of this study was to investigate the normal values for radiological measurements of the feet of the Straight Egyptian Arabian horse in Qatar. The design was a clinical prospective study. Radiographs of the fore and hind feet of 10 clinically normal adult Straight Egyptian Arabian horses were taken. On the lateromedial views, 17 measurements were taken (13 distances and four angles). On the horizontal dorsopalmar/plantar views, two measurements were taken. On the dorsal 45 degree, proximo-palmarodistal oblique projections, four measurements were taken. Normal reference ranges were reported for radiological measurements of the feet of the Straight Egyptian Arabian horse. Several variables showed significant differences between fore and hind feet, including hoof angle, distal wall thickness, and two proximal inner layer measurements (p < 0.05). In addition, the Straight Egyptian Arabian horse was found to have a number of measurements which varied from previously published reports. The results reported within provide a useful reference for normal radiographic measurements of the Straight Egyptian Arabian horse with relevance for laminitis.

Dose effect and duration of action of liposomal bupivacaine administered as a perineural analgesic in a reversible and adjustable frog-pressure model of equine lameness.

To determine the dose effect of peri-neural liposomal bupivacaine (LB) in an induced forelimb lameness model. 12 clinically normal adult horses. A randomized cross-over design was performed with 1 limb receiving saline and the other LB: low dose (6), high dose (6). Lameness was induced in 1 forelimb using a frog-pressure model. In the lame limb, peri-neural injection of the palmar nerves at the proximal sesamoid bones was performed using saline, low dose LB (0.25 mg/kg) (LDLB), or high dose LB (0.5mg/kg) (HDLB) in random order with a 1-week washout period between treatments. Distal limb swelling, mechanical nociceptive thresholds (MNT), and objective lameness data were collected before and up to 72 hours after peri-neural anesthesia. Data analysis was performed with mixed model ANOVA, equality of medians test, and Kaplan Meier survival analysis. Compared with baseline, horses treated with LDLB and HDLB had improvements in MNT and lameness (P < .001). In the LDLB group, the median duration of analgesia was 4.5 hours (range = 3-6 hours) and the median return to lameness was 7 hours (range = 4-24 hours). In the HDLB group, the median duration of analgesia was 12 hours (range = 4-48 hours) and the median return to lameness was 9 hours (range = 3-48 hours). Mild to moderate swelling was identified in 11/12 (92%) LB limbs. Both LDLB and HDLB resulted in loss of skin sensation and improvement of lameness. There was high variability among horses in duration of action for both doses.

Comparison of Computed Tomography Assisted 3D Cephalometric Measurements in Straight Egyptian Arabian and Thoroughbred Horses.

Dental malocclusions are commonly encountered in horses. The objective of this study was to report the normal cephalometric values from skull computed tomography (CT) scans of adult Straight Egyptian Arabian (SEAR) and thoroughbred (TB) horses and to compare differences in the measurements between the two breeds. Standing skull CTs were performed on 29 clinically normal adult horses (15 SEAR; 14 TB) and cephalometric measurements were taken. All 9 cephalometric measurements, as well as the interincisal angle, were found to be significantly greater in TB than SEAR (P < 0.05). TB were found to have significantly greater facial line: mandibular length (FL/ML) ratios compared to SEAR (P = 0.002) whereas for the maxillary cheek teeth length: ethmoidal line ratio (Mxa/EtL), SEAR were found to have significantly greater values than TB (P = 0.0007). SEAR cephalometric measurements, as well as certain ratios, differ significantly from TB and could have an impact on the development of dental malocclusions in this breed. Further investigation is needed to ascertain whether these cephalometric differences between the two breeds predispose the SEAR to the development of dental malocclusions.

Straight Egyptian Arabian skull morphology presents unique surgical challenges compared to the Thoroughbred: a computed tomography morphometric anatomical study

The objective of this study was to compare the skull morphology of the Straight Egyptian Arabian (SEAR) to the Thoroughbred (TB), using computed tomography (CT) in the context of surgical procedures commonly performed on the equine head. Measurements relating to surgical considerations of the equine head were taken from 29 clinically normal adult horses (15 SEAR, 14 TB). A clinical prospective study. Standing skull CTs were performed. Fourteen gross and 10 CT measurements were taken. Several variables showed a significant difference between groups, in all cases greater in TB. Head length (P < .001) and facial crest length (P < .001) were significantly shorter in SEAR than TB. The head length was shorter relative to body height in SEAR (P < .001). The lateral length of a virtual maxillary bone flap was shorter in SEAR (P < .001). SEAR had smaller craniofacial angles than TB (P = .018). SEAR skull morphology differs significantly from TB, making surgical approaches potentially more challenging. Compared with TB, the shorter facial crest in the SEAR group could contribute to poor surgical access to the maxillary sinus in SEAR due to shorter maxillary flap lengths. Significant differences in the craniofacial angles between SEAR and TB suggest similarities between SEAR and brachycephalic dog breeds, warranting further investigation.

Cerebrospinal fluid and serum proteomic profiles accurately distinguish neuroaxonal dystrophy from cervical vertebral compressive myelopathy in horses

Cervical vertebral compressive myelopathy (CVCM) and equine neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM) are leading causes of spinal ataxia in horses. The conditions can be difficult to differentiate, and there is currently no diagnostic modality that offers a definitive antemortem diagnosis. Evaluate novel proteomic techniques and machine learning algorithms to predict biomarkers that can aid in the antemortem diagnosis of noninfectious spinal ataxia in horses. Banked serum and cerebrospinal fluid (CSF) samples from necropsy-confirmed adult eNAD/EDM (n = 47) and CVCM (n = 25) horses and neurologically normal adult horses (n = 45). . A subset of serum and CSF samples from eNAD/EDM (n=5) and normal (n=5) horses was used to evaluate the proximity extension assay (PEA). All samples were assayed by PEA for 368 neurologically relevant proteins. Data were analyzed using machine learning algorithms to define potential diagnostic biomarkers. Of the 368 proteins, 84 were detected in CSF and 146 in serum. Eighteen of 84 proteins in CSF and 30/146 in serum were differentially abundant among the 3 groups, after correction for multiple testing. Modeling indicated that a 2-protein test using CSF had the highest accuracy for discriminating among all 3 groups. Cerebrospinal fluid R-spondin 1 (RSPO1) and neurofilament-light (NEFL), in parallel, predicted normal horses with an accuracy of 87.18%, CVCM with 84.62%, and eNAD/EDM with 73.5%. Cross-species platform. Uneven sample size. Proximity extension assay technology allows for rapid screening of equine biologic matrices for potential protein biomarkers. Machine learning analysis allows for unbiased selection of highly accurate biomarkers from high-dimensional data.

Comparison of two glucose-monitoring systems for use in horses.

To determine the accuracy of 2 interstitial glucose-monitoring systems (GMSs) for use in horses compared with a point-of-care (POC) glucometer and standard laboratory enzymatic chemistry method (CHEM). 8 clinically normal adult horses. One of each GMS device (Dexcom G6 and Freestyle Libre 14-day) was placed on each horse, and blood glucose concentration was measured via POC and CHEM at 33 time points and compared with simultaneous GMS readings. An oral glucose absorption test (OGAT) was performed on day 2, and glucose concentrations were measured and compared. Glucose concentrations were significantly correlated with one another between all devices on days 1 to 5. Acceptable agreement was observed between Dexcom G6 and Freestyle Libre 14-day when compared with CHEM on days 1, 3, 4, and 5 with a combined mean bias of 10.45 mg/dL and 1.53 mg/dL, respectively. During dextrose-induced hyperglycemia on day 2, mean bias values for Dexcom G6 (10.49 mg/dL) and FreeStyle Libre 14-day (0.34 mg/dL) showed good agreement with CHEM. Serial blood glucose measurements are used to diagnose or monitor a variety of conditions in equine medicine; advances in near-continuous interstitial glucose monitoring allow for minimally invasive glucose assessment, thereby reducing stress and discomfort to patients. Data from this study support the use of the Dexcom G6 and Freestyle Libre 14-day interstitial glucose-monitoring systems to estimate blood glucose concentrations in horses.

Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy.

To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. Sixty eyes of 30healthy adult horses aged 8-24years. Ultrasonic pachymetry (velocity of 1640m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pressure (IOP) was estimated using rebound tonometry, and axial globe length was measured using ultrasonographic biometry. CT (mean±SDµm) measured by UBM was 854±61 (central), 994±58 (superior), 930±57 (temporal), 979±55 (inferior), and 898±48 (nasal). CT measured by UBM was greater than that measured by ultrasonic pachymetry at all locations and was statistically significant at all locations except inferior (p=0.0006-0.048). No sex nor age effect was detected for CT at any location. The repeatability of ultrasonic pachymetry was superior to that of UBM. Mean±SD ACD was 5.74±0.41mm. A weak positive correlation was identified between central CT and IOP and between central CT and axial globe length. Normal data for CT and ACD of the adult horse obtained using UBM are provided. CT determined by UBM was greater relative to pachymetry at all corneal locations.

Incidence of superficial abdominal organ identification is similar using high‐frequency linear (transrectal) and low‐frequency curvilinear (abdominal) transducers in clinically healthy horses: A pilot study

Abdominal organ displacement is a potentially life-threatening condition in horses. Primary care veterinarians commonly make referral decisions based on a combination of clinical and ultrasonographic findings. However, published studies describing the effects of transducer on identifying abdominal organ locations in horses are currently lacking. The objective of this prospective, methods comparison, pilot study was to compare organ identification using a high-frequency linear (transrectal) transducer and a low-frequency curvilinear (abdominal) transducer for transcutaneous abdominal ultrasonography of healthy horses. Twelve clinically normal adult horses owned by the University of Calgary were enrolled in the study. Abdominal ultrasonography was performed by four practitioners, each randomly assigned to an alternating rotation of transrectal or abdominal transducer and left or right side of a horse. Using a Chi square test or Fisher's exact test, the frequency of identification for each organ was compared between both transducers. There was no significant difference in organ identification on the right side of the abdomen. On the left side, the stomach, liver, and kidney were less likely to be detected with the transrectal transducer. Compared with a low-frequency abdominal transducer, a high-frequency linear transrectal transducer delivers images that allow for organ identification in transcutaneous ultrasonography of the equine abdomen except for the left kidney, left liver, and stomach.

Can levamisole upregulate the equine cell-mediated macrophage (M1) dendritic cell (DC1) T-helper 1 (CD4 Th1) T-cytotoxic (CD8) immune response in vitro?

BackgroundEquine protozoal myeloencephalitis (EPM) is a common and devastating neurologic disease of horses in the United States. Because some EPM‐affected horses have decreased immune responses, immunomodulators such as levamisole have been proposed as supplemental treatments. However, little is known about levamisole's effects or its mechanism of action in horses.ObjectiveLevamisole in combination with another mitogen will stimulate a macrophage 1 (M1), dendritic cell 1 (DC1), T‐helper 1 (CD4 Th1), and T‐cytotoxic (CD8) immune response in equine peripheral blood mononuclear cells (PBMCs) in vitro as compared to mitogen alone.AnimalsTen neurologically normal adult horses serologically negative for Sarcocystis neurona.MethodsProspective study. Optimal conditions for levamisole were determined based on cellular proliferation. Peripheral blood mononuclear cells were then cultured using optimal conditions of mitogen and levamisole to identify the immune phenotype, based on subset‐specific activation markers, intracellular cytokine production, and cytokine concentrations in cell supernatants. Subset‐specific proliferation was determined using a vital stain.ResultsConcanavalin A (conA) with levamisole, but not levamisole alone, resulted in a significant decrease (P < .05) in PBMC proliferation compared to conA alone. Levamisole alone did not elicit a specific immune phenotype different than that induced by conA.Conclusion and Clinical ImportanceLevamisole co‐cultured with conA significantly attenuated the PBMC proliferative response as compared with conA. If the mechanisms by which levamisole modulates the immune phenotype can be further defined, levamisole may have potential use in the treatment of inflammatory diseases.

Age-associated changes in the equine flash visual evoked potential.

To investigate age-associated changes of flash visual evoked potentials (FVEPs) in sedated horses. Twenty-eight clinically healthy Standardbred Warmblooded trotters, aged 36hours to 28years. Light-adapted FVEPs and FERGs were recorded (An-vision RETIport, Roland-consult, Germany) in response to flash stimuli. Sedation was obtained using alpha-2-agonists intravenously. Akinesia of the eyelids was induced and pupils were dilated. Reproducible FVEPs and FERGs were readily recorded from all foals and horses. The FVEP waveform included up to four positive components (P1-P5) and two negative components (N1 and N2) and FVEP waveform morphology was similar across all age groups. Some differences in peak times and amplitudes associated with increasing age were observed. FVEP amplitudes recorded from newborn foals were well above the amplitudes observed in normal adult horses and FVEP peak times were somewhat shorter. In adult horses, a significant increase in P4 peak time and a gradual decrease in amplitudes, mainly for N2P4, were seen across the life-span. The overall equine FVEP waveform was similar across the normal life-span of the horse in our cross-sectional study. We found that the visual system of the foal seems to be well developed already at birth. Furthermore, our results showed a decrease in amplitudes and increase in some peak times with increasing age. We recommend that age-matched controls should be used when evaluating foals and young horses in clinical practice, whereas horses over the age of three years can be compared to other adult horses.

Bronchoalveolar lavage fluid cytology and airway hyper-reactivity in clinically normal horses.

To characterise the relationship between bronchoalveolar lavage fluid (BALF) cytology and pulmonary function testing with histamine bronchoprovocation (HBP) methods in a population of clinically normal horses. Cross-sectional study METHODS: Clinically normal adult horses (n = 33) underwent pulmonary function testing and HBP with a commercial flowmetric plethysmography system. BAL was performed 1-5 days later. Statistical analysis was used to assess associations between BALF cell concentration, relative inflammatory cell percentages and categorisation, and airway hyper-reactivity (AHR). AHR (PC35 ≤ 8 mg/mL) was demonstrated in 17 (52%) of the horses. Using current definitions, BALF cytology was consistent with inflammatory airway disease in 14 (42%) of the horses and 7 of those demonstrated either mastocytic and/or eosinophilic responses. There was no correlation between total inflammatory cell counts or relative percentage and AHR. No statistical association was found between BALF inflammatory cell categories and AHR. A direct association between cytological evidence of airway inflammation and AHR was not identified in this population of clinically normal horses. Determining the presence and measuring inflammatory cell mediators in BALF may more accurately reflect AHR. In addition, normal values for cell proportions in BALF may vary between different populations of horses and more appropriate regional reference ranges should be established.

Ultrasonographic examination of kidneys and urinary bladder of normal adult Spiti horses and Himalayan Hill mules of India

The objective of this study was to develop baseline topographical data of landmarks for locating kidneys and urinary bladder and to generate sonographic calliper measurements along with dynamic parameters of these organs. Ultrasonography was performed on 50 native adult (Spiti horses and Himalayan hill mules) healthy unsedated equines of either sex. The thickness, character and echo-architecture of these organs were recorded. The right kidney was found from 15th (±1) intercostal space (ICS) extending upto first lumbar vertebra, both in horses as well as in mules. The height of right kidney varied from 112.7 to 118.3 mm (Mean± SE= 115.6±1.01 mm) and its thickness varied from 58.4 to 71.2 mm (Mean± SE= 64.3±2.37 mm). While in mules height of right kidney varied from 90.7 to 109.2 mm (Mean± SE= of 101.1±3.14 mm) and its thickness varied from 47.3 to 56.8 mm (Mean± SE= 52.3±1.57 mm). The left kidney in horses was found between 16th ICS to 2nd lumbar vertebra, while in mules it was found from 16th ICS to 3rd lumbar vertebra. The height of left kidney varied from 87 to 107.8 mm (Mean± SE= 99.0±3.67 mm) and its thickness varied from 49.5 to 53.8 mm (Mean± SE= 51.8±0.72 mm). In mules the height of left kidney varied from 85.5 to 111.4 mm (Mean± SE= 95.3±2.36 mm) and its thickness varied from 43.4 to 55.7 mm (Mean± SE= 50.6±2.53 mm). During transrectal ultrasonography urinary bladder was observed as an oval to round structure in the caudal ventral abdomen, the wall thickness of urinary bladder varied from 2.7 to 2.8 mm (Mean± SE= 2.74±0.02 mm), 2.4 to 2.7 mm (Mean± SE= 2.62±0.05 mm) in horses and mules respectively. Hence detailed ultrasonographic examination of these organs helped us to compile baseline data, which will be helpful in future in management of the affections of these organs.

New Parvovirus Associated with Serum Hepatitis in Horses after Inoculation of Common Biological Product.

Equine serum hepatitis (i.e., Theiler’s disease) is a serious and often life-threatening disease of unknown etiology that affects horses. A horse in Nebraska, USA, with serum hepatitis died 65 days after treatment with equine-origin tetanus antitoxin. We identified an unknown parvovirus in serum and liver of the dead horse and in the administered antitoxin. The equine parvovirus-hepatitis (EqPV-H) shares <50% protein identity with its phylogenetic relatives of the genus Copiparvovirus. Next, we experimentally infected 2 horses using a tetanus antitoxin contaminated with EqPV-H. Viremia developed, the horses seroconverted, and acute hepatitis developed that was confirmed by clinical, biochemical, and histopathologic testing. We also determined that EqPV-H is an endemic infection because, in a cohort of 100 clinically normal adult horses, 13 were viremic and 15 were seropositive. We identified a new virus associated with equine serum hepatitis and confirmed its pathogenicity and transmissibility through contaminated biological products.

Ultrasonographic examination of liver and spleen of normal adult spiti horses and Himalayan Hill mules of India

The main objective of this study was to develop baseline topographical data of landmarks for locating liver and spleen and to generate sonographic calliper measurements along with dynamic parameters of these organs. Abdominal ultrasonography was performed on 50 native adult (Spiti horses and Himalayan hill mules) healthy unsedated equines of either sex. The thickness, character and echo-architecture of liver and spleen were recorded. In horses, the right lobe of liver was found from 8th to 15th intercostal space (ICS) and left lobe from 6th to 11th (±1) ICS, while in mules the right liver lobe was found between 6th to 15th (±1) ICS and left lobe between 6th to 9th (±1) ICS. The liver was recognized by its branching vasculature and architecture was found relatively homogenous. In addition ventral edges were distinctly sharp. Spleen was found from 8th to 17th ICS both in horses as well as in mules. The splenic parenchyma was homogenously granular in appearance with few blood vessels and most echogenic organ in the abdominal cavity of equines. The only measurement that was reliably obtained was the central thickness or depth of the spleen, which varied from 41.4 to 68.4 mm (Mean± SE= 50.84±4.61 mm) in horses and 37.9 to 51.6 mm (Mean± SE = 42.76±2.34 mm) in mules. Therefore detailed ultrasonographic examination of liver and spleen helped us to compile baseline data, which will be helpful in management of the affections of liver and spleen in future.

Ultrasonographic examination of the stomach, duodenum and jejunum of normal adult spiti horses and Himalayan hill mules of India

The study was conducted on equids of high altitude to develop baseline topographical data of landmarks, sonographic calliper measurements and dynamic parameters of abdominal organs. Ultrasonography was performed on healthy adult spiti horses and Himalayan mules of either sex. The wall thickness, contractility, character and echo-architecture of these organs were recorded for standardization. The stomach was found between 8th-15th and 8th-14th Inter-Costal Space (ICS) with wall thickness of 4.92 ± 0.23 and 4.24 ± 0.06 mm in horses and mules, respectively. Ascending duodenum was found between 11th-13th and 10th-13th ICS with a wall thickness of 2.0 ± 0.00 and 1.96 ± 0.04 mm in horses and mules, respectively. Descending duodenum was found from 16th and 15th ICS to just caudal to the last rib in horses and mules, respectively. Jejunum was found from 12th (±1) to 17th ICS with wall thickness of 2.04 ± 0.04 and 2.02 ± 0.02 mm in horses and mules, respectively. Detailed ultrasonographic examination of these organs helped to compile baseline data, which will be useful in future in management of the affections of stomach, duodenum and jejunum.

Ultrasonographic examination of caecum and colon of normal Adult Spiti horses and Himalayan Hill mules of India.

The objective of this study was to develop baseline topographical data of landmarks for locating and generating sonographic calliper measurements along with dynamic parameters of caecum and colon in 50 native adult healthy unsedated Spiti horses and Himalayan Hill mules of either sex. The wall thickness, contractility, character and echo-architecture of caecum and colon were recorded. Caecum was found from 15th to 17th inter costal space (ICS). Right dorsal colon (RDC), right ventral colon (RVC), left ventral colon (LVC) and left dorsal colon (LDC) were found from 6th to 14th, 9th to 17th, 9th to 14th and 6th to 15th ICS, respectively. Descending colon was found in the left paralumbar fossa upto tuber-coxae in both horses as well as mules. The corresponding values of horses and mules for wall thickness (in mm) was 2.1±0.05 and 1.4±0.05 for the caecum, 2.16±0.05 and 1.32±0.02 for the right dorsal colon, 2.1±0.03 and 1.32 ±0.02 for the right ventral colon, 2.12±0.03 and 1.32±0.02 for the left dorsal colon, 2.1±0.03 and 1.32±0.02 for the right dorsal colon and 2.04±0.02 for the descending colon. Prominent sacculations were observed on ventral colon and absent on dorsal colon. Detailed ultrasonographic examination of caecum and colon generated baseline data, which will be useful for management of the affections of caecum and colon.

Effects of anesthesia with isoflurane on plasma concentrations of adrenocorticotropic hormone in samples obtained from the cavernous sinus and jugular vein of horses.

OBJECTIVE To determine effects of anesthesia on plasma concentrations and pulsatility of ACTH in samples obtained from the cavernous sinus and jugular vein of horses. ANIMALS 6 clinically normal adult horses. PROCEDURES Catheters were placed in a jugular vein and into the cavernous sinus via a superficial facial vein. The following morning (day 1), cavernous sinus blood samples were collected every 5 minutes for 1 hour (collection of first sample = time 0) and jugular venous blood samples were collected at 0, 30, and 60 minutes. On day 2, horses were sedated with xylazine hydrochloride and anesthesia was induced with propofol mixed with ketamine hydrochloride. Horses were positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen and a continuous rate infusion of butorphanol tartrate. One hour after anesthesia was induced, the blood sample protocol was repeated. Plasma ACTH concentrations were quantified by use of a commercially available sandwich assay. Generalized estimating equations that controlled for horse and an expressly automated deconvolution algorithm were used to determine effects of anesthesia on plasma ACTH concentrations and pulsatility, respectively. RESULTS Anesthesia significantly reduced the plasma ACTH concentration in blood samples collected from the cavernous sinus. CONCLUSIONS AND CLINICAL RELEVANCE Mean plasma ACTH concentrations in samples collected from the cavernous sinus of anesthetized horses were reduced. Determining the success of partial ablation of the pituitary gland in situ for treatment of pituitary pars intermedia dysfunction may require that effects of anesthesia be included in interpretation of plasma ACTH concentrations in cavernous sinus blood.

Evaluation of a Hyaluronic Acid-Based Biomaterial to Enhance Wound Healing in the Equine Distal Limb

The objective of this study was to evaluate the ability of a cross-linked hyaluronic acid-based biomaterial (CMHA) to promote healing in an equine distal limb wound model. Three 6.25 cm2 full thickness skin wounds were surgically created on the dorsomedial metacarpus and metatarsus of each of four limbs of eight normal adult horses under general anesthesia. Three days after surgery, wounds were photographed and one of four treatments was applied to all three wounds on a single limb: control (no CMHA), single application of CMHA gel, multiple applications of CMHA gel, and multiple applications of CMHA film. Wounds were assessed for quality of repair tissue and photographed for image analysis at bandage changes every 4 days throughout the 47-day study. Exuberant granulation tissue was excised as needed and weighed. Size of granulating wounds was analyzed by repeated measures analysis of covariance and rate of wound healing assessed using a logistic decay model fitted to the data by nonlinear least-squares regression. Significance was set at P < .05. No adverse effects of CMHA were noted. There was a significant day by treatment interaction; however, overall, there were no significant differences among treatment groups (P = .09). Wounds treated with CMHA films decreased to half their original size significantly faster, were significantly smaller on day 31, and healed with higher quality, less fragile epithelium than wounds in other treatment groups. Treatment of distal limb wounds in horses may benefit from use of CMHA films to improve healing.

Histopathologic findings in the sacrocaudalis dorsalis medialis muscle of horses with vitamin E–responsive muscle atrophy and weakness

To characterize clinical findings, outcomes, muscle characteristics, and serum or muscle concentrations of α-tocopherol for horses with vitamin E-responsive signs of muscle atrophy and weakness consistent with signs of equine motor neuron disease (EMND). Retrospective case-control study. 8 affected (case) adult horses with acute (n = 3) or chronic (5) gross muscle atrophy that improved with vitamin E treatment and 14 clinically normal (control) adult horses with adequate (within reference range; 8) or low (6) muscle concentrations of α-tocopherol. Medical records were reviewed, serum and muscle concentrations of α-tocopherol were measured, and frozen biopsy specimens of sacrocaudalis dorsalis medialis muscle and gluteal muscle were histologically evaluated for pathological changes. Fiber type composition and fiber diameters were assessed in gluteal muscle specimens. A myopathy that was histologically characterized by redistribution of mitochondrial enzyme stain (moth-eaten appearance) and anguloid atrophy of myofibers was evident in sacrocaudalis dorsalis medialis muscle fibers of the 8 affected horses that had low serum (6/8) or skeletal muscle (5/5) concentrations of α-tocopherol; these histopathologic changes were not found in muscle specimens of control horses with low or adequate muscle concentrations of α-tocopherol. All affected horses regained strength and muscle mass within 3 months after initiation of vitamin E treatment and dietary changes. A vitamin E-deficient myopathy characterized histologically by a moth-eaten appearance in the mitochondria and anguloid myofiber atrophy in frozen sections of sacrocaudalis dorsalis medialis muscle biopsy specimens was found in horses with clinical signs of EMND that were highly responsive to vitamin E treatment. This myopathy may be a specific syndrome or possibly precede the development of neurogenic muscle fiber atrophy typical of EMND.

Effects of action of proparacaine and tetracaine topical ophthalmic formulations on corneal sensitivity in horses

To compare the corneal anesthetic effects and duration of action of 2 ophthalmic anesthetic agents in horses. Prospective, randomized masked crossover study. 8 clinically normal adult horses. Corneal sensitivity was determined by measuring each eye's corneal touch threshold (CTT) with a Cochet-Bonnet esthesiometer. Each eye's baseline CTT was recorded prior to anesthetic instillation at 0 minutes and every 10 minutes thereafter for 60 minutes. Each eye was randomly assigned to receive 2 of 4 treatments: 0.5% aqueous proparacaine ophthalmic solution (aqueous proparacaine; 8 eyes); 0.5% aqueous tetracaine ophthalmic solution (aqueous tetracaine; 8 eyes); 0.5% viscous tetracaine ophthalmic solution (viscous tetracaine; 8 eyes); and saline (0.9% NaCl) eyewash solution (8 eyes) as a negative control. There was a 48-hour washout period. Every horse received all treatments. Median baseline CTT of eyes was 4.5 cm (range, 0.5 to 6 cm). Median CTT for saline solution-treated eyes never differed significantly from baseline. The maximum anesthetic effect with the other 3 treatments occurred at 10 minutes. Median CTT of eyes at 10 minutes was 0.5 cm (range, 0 to 2.5 cm) with aqueous proparacaine treatment, 0.25 cm (range, 0 to 2.0 cm) with aqueous tetracaine treatment, and 0 cm (range, 0 to 0.5 cm) with viscous tetracaine treatment. Maximum anesthetic duration was 20 minutes with aqueous proparacaine and aqueous tetracaine treatments and 30 minutes with viscous tetracaine treatments. Treatment of eyes with viscous tetracaine resulted in the greatest decrease in CTT and the longest duration of action, compared with treatment with aqueous proparacaine or aqueous tetracaine.