Whole genome sequencing identified a 16 kilobase deletion on ECA13 associated with distichiasis in Friesian horses.

BACKGROUND: Distichiasis, an ocular disorder in which aberrant cilia (eyelashes) grow from the opening of the Meibomian glands of the eyelid, has been reported in Friesian horses. These misplaced cilia can cause discomfort, chronic keratitis, and corneal ulceration, potentially impacting vision due to corneal fibrosis, or, if secondary infection occurs, may lead to loss of the eye. Friesian horses represent the vast majority of reported cases of equine distichiasis, and as the breed is known to be affected with inherited monogenic disorders, this condition was hypothesized to be a simply inherited Mendelian trait. RESULTS: A genome wide association study (GWAS) was performed using the Axiom 670 k Equine Genotyping array (MNEc670k) utilizing 14 cases and 38 controls phenotyped for distichiasis. An additive single locus mixed linear model (EMMAX) approach identified a 1.83 Mb locus on ECA5 and a 1.34 Mb locus on ECA13 that reached genome-wide significance (pcorrected = 0.016 and 0.032, respectively). Only the locus on ECA13 withstood replication testing (p = 1.6 × 10- 5, cases: n = 5 and controls: n = 37). A 371 kb run of homozygosity (ROH) on ECA13 was found in 13 of the 14 cases, providing evidence for a recessive mode of inheritance. Haplotype analysis (hapQTL) narrowed the region of association on ECA13 to 163 kb. Whole-genome sequencing data from 3 cases and 2 controls identified a 16 kb deletion within the ECA13 associated haplotype (ECA13:g.178714_195130del). Functional annotation data supports a tissue-specific regulatory role of this locus. This deletion was associated with distichiasis, as 18 of the 19 cases were homozygous (p = 4.8 × 10- 13). Genotyping the deletion in 955 horses from 54 different breeds identified the deletion in only 11 non-Friesians, all of which were carriers, suggesting that this could be causal for this Friesian disorder. CONCLUSIONS: This study identified a 16 kb deletion on ECA13 in an intergenic region that was associated with distichiasis in Friesian horses. Further functional analysis in relevant tissues from cases and controls will help to clarify the precise role of this deletion in normal and abnormal eyelash development and investigate the hypothesis of incomplete penetrance.

Improving gait classification in horses by using inertial measurement unit (IMU) generated data and machine learning.

For centuries humans have been fascinated by the natural beauty of horses in motion and their different gaits. Gait classification (GC) is commonly performed through visual assessment and reliable, automated methods for real-time objective GC in horses are warranted. In this study, we used a full body network of wireless, high sampling-rate sensors combined with machine learning to fully automatically classify gait. Using data from 120 horses of four different domestic breeds, equipped with seven motion sensors, we included 7576 strides from eight different gaits. GC was trained using several machine-learning approaches, both from feature-extracted data and from raw sensor data. Our best GC model achieved 97% accuracy. Our technique facilitated accurate, GC that enables in-depth biomechanical studies and allows for highly accurate phenotyping of gait for genetic research and breeding. Our approach lends itself for potential use in other quadrupedal species without the need for developing gait/animal specific algorithms.

Biochemical differences between distal limb extensor and flexor tendons among equine breeds selected for racing and sport.

Throughout the ages, humans have selected different horse breeds for their locomotor capacities. Consequently, the properties of equine locomotor tissues could have diversified because of the specific requirements of different disciplines. Therefore, this study aimed to compare biochemical properties of tendons in different equine breeds traditionally selected for racing or sports performance. We hypothesised that tendons in racing breeds would have biochemical properties that would increase strength, whereas those in sporting breeds would have more elastic properties. An ex vivo tendon tissue study comparing the common digital extensor tendon (CDET) and superficial digital flexor tendon (SDFT) of sports horses (Friesian horse, Warmblood horse) and racehorses (Thoroughbred horse; the oldest, reference standard breed) was performed. The SDFT and CDET from middle-aged Friesian (n = 12), Warmblood (n = 12) and Thoroughbred horses (n = 8) were harvested, and their biochemical properties were compared. The biochemical analysis demonstrated significantly higher water percentage, lower collagen concentrations/glycosaminoglycan content and higher crosslink concentrations in the SDFT of sports horses compared to racing breed horses (P < 0.05); DNA content was also significantly lower in sports horses than racehorses (P < 0.05). Racehorses had mainly extra fibrillar collagen support, whereas sports horses had mainly extra crosslink collagen support. From a functional perspective, the racing Thoroughbred relied on stronger tendons, while the sporting Friesians and Warmbloods relied on less stiff, more elastic tendons. In conclusion, there were significant biochemical differences in tendon properties between breeds, possibly related to their intended locomotor performance, although this requires further biomechanical and ultimately genetic confirmation.

Biomechanical loading of the porcine femorotibial joint during maximal movements: An exploratory, ex vivo study.

Thus far, there is a lack of scientific investigation regarding the hypothesis that biomechanical factors contribute to the cross-species pathogenesis of osteochondrosis (OC). Therefore, the aim of this pilot study was to investigate whether high (peak) pressures occur in the porcine femorotibial (FT) joint. In this experimental, ex vivo study, the right hind limbs of seven weaned piglets were subjected to maximal joint excursions, as a priori radiologically estimated. Subsequently, the intra-articular pressures were measured using sensors placed in both the medial and the lateral compartments of the FT joint. The overall highest individual peak pressure was found in the lateral FT joint during maximal extension (2611 kPa; group mean ± standard deviation (SD) 982.3 ± 988.2 kPa). In the medial FT joint, the highest individual peak pressure was found during maximal adduction (1481 kPa; group mean ± SD 664.9 ± 393.2 kPa). Moreover, nearly 30% of the ex vivo peak pressures were above published thresholds for cartilage catabolism (>500 kPa/0.5 MPa), but not for interfering with cell viability (>5 MPa). In conclusion, this ex vivo study on FT joint pressures in weaned piglets showed that FT joint movements at maximal excursions are related to concomitant internal peak joint pressures. More studies should be performed to evaluate the possible biomechanical relation of these observations with osteochondrosis, which would allow the design of preventive measures in the pig industry, to avoid extreme limb movements and concomitant joint peak pressures in vivo.

Equine digital tendons show breed-specific differences in their mechanical properties that may relate to athletic ability and predisposition to injury.

BACKGROUND: Throughout the ages, human subjects have selected horse breeds for their locomotor capacities. Concurrently, tissue properties may have diversified because of specific requirements of different disciplines. OBJECTIVES: The aim of this study was to compare the biomechanical properties of tendons with different functions between equine breeds traditionally selected for racing or sport. STUDY DESIGN: This study used ex vivo tendons and compared the mechanical properties of the common digital extensor tendon (CDET) and superficial digital flexor tendon (SDFT) between racehorses (Thoroughbred [TB]) and sports horses (Friesian Horse [FH], Warmblood [WB]). METHODS: The SDFT and CDET of FH (n = 12), WBs (n = 12) and TBs (n = 8) aged 3-12 years were harvested. The cross sectional area (cm2 ), maximal load (N), ultimate strain (%), ultimate stress (MPa) and elastic modulus (MPa) were determined and tested for significant differences between the breeds (P<0.05). RESULTS: The SDFT from WB horses had a significantly lower elastic modulus than TB horses and failed at a higher strain and load than both FHs and TBs. The mechanical properties of the CDET did not differ between breeds. In agreement with previous studies, the CDET failed at a higher stress and had a higher elastic modulus than the SDFT and, for the WB group of horses only, failed at a significantly lower strain. Interestingly, the mode of failure differed between breeds, particularly with respect to the FHs. MAIN LIMITATIONS: The exercise history of horses used in this study was unknown and the age-range was relatively large; both these factors may have influenced the absolute properties reported in this study. CONCLUSIONS: This study shows for the first time that mechanical properties of the SDFT differ between breeds. These properties are likely to be related to selection for high-speed vs. an extravagant elastic gait and may be an important indicator of performance ability. The Summary is available in Spanish - see Supporting Information.

Caudal cervical vertebral morphological variation is not associated with clinical signs in Warmblood horses.

BACKGROUND: Variation in equine caudal cervical spine morphology at C6 and C7 has high prevalence in Warmblood horses and is suspected to be associated with pain in a large mixed-breed group of horses. At present no data exist on the relationship between radiographic phenotype and clinical presentation in Warmblood horses in a case-control study. OBJECTIVES: To establish the frequency of radiographically visible morphologic variation in a large group of Warmblood horses with clinical signs and compare this with a group without clinical signs. We hypothesised that occurrence of morphologic variation in the case group would not differ from the control group, indicating there is no association between clinical signs and morphologic variation. STUDY DESIGN: Retrospective case-control. METHODS: Radiographic presence or absence of morphologic variation of cervical vertebrae C6 and C7 was recorded in case (n = 245) and control horses (n = 132). Case and control groups were compared by univariable Pearson's Chi-square and multivariable logistic regression for measurement variables age, sex, breed, degenerative joint disease and morphologic variation at C6 and C7. Odds ratio and confidence intervals were obtained. A P≤0.05 was considered statistically significant. RESULTS: Morphologic variation at C6 and C7 (n = 108/377 = 28.6%; Cases 58/245 = 23.7%; Control 50/132 = 38%) was less frequent in horses with clinical signs in univariable testing (OR 0.48, 95% CI 0.3-0.8, P = 0.001). Age, sex, breed and degenerative joint disease were not retained in the final multivariable logistic regression step whereas morphologic variation remained significantly less present in horses with clinical signs. MAIN LIMITATIONS: Possible demographic differences between equine clinics. CONCLUSIONS: Morphologic variation in the caudal cervical spine was detected more frequently in horses without clinical signs. Therefore, radiographic presence of such variation does not necessarily implicate the presence of clinical signs.

[Acute renal failure and rare severe complication of systemic steroid treatment in a 73-year-old woman]. / Akutes Nierenversagen und seltene schwere Komplikation einer systemischen Steroidtherapie bei einer 73­Jährigen.

This article reports about a 73-year-old woman of Bosnian descent who presented with acute renal failure. A renal biopsy was diagnostic for a postinfect necrotizing and extracapillary proliferative glomerulonephritis. The patient reported a febrile infection fever 2 weeks previously. The diagnostics did not reveal any indications of an ongoing infection. The glomerulonephritis responded to treatment with systemic steroids. The patient was readmitted to hospital 6 weeeks later in a severely ill condition. A gastric biopsy revealed a Strongyloides stercoralis infestation. Due to the systemic steroid therapy the patient had developed a so-called hyperinfection syndrome and died despite treatment on the intensive care unit. This case illustrates the need for awareness of this rare parasitosis, particularly in patients from endemic areas. A likely causal relationship with the glomerulonephritis is discussed and an overview of the diagnostics, course of the disease and treatment of this parasitosis is given.

The development of hoof balance and landing preference in the post-natal period.

BACKGROUND: Foals can follow the herd within hours of birth, but it has been shown that kinetic gait parameters and static balance still have to mature. However, development of dynamic balance has not been investigated. OBJECTIVES: To objectively quantify landing and pressure pattern dynamics under the hoof during the first half year of life. STUDY DESIGN: Prospective, cohort study performed at a single stud farm. METHODS: Pressure plate measurements at walk and trot from ten Dutch warmblood foals during the first 24 weeks of life were used to quantify toe-heel and medial-lateral hoof balance asymmetry indexes and to determine preferred landing strategy. Concurrently, radiographs of the tarsocrural and femoropatellar joints were taken at 4-6 weeks and after 6 months to check for osteochondrosis. A linear mixed model was used to determine the effects of time point, limb pair (front/hind), side (left/right) and osteochondrosis status of every foal. RESULTS: At 25% of stance duration at walk, front limbs were more loaded in the heel region in weeks 6-20 (P≤0.04), the medial-lateral balance was more to the lateral side from week 6 onwards at both walk and trot (P≤0.04). Landing preference gradually changed in the same directions. Variability in pressure distribution decreased over time. (Subclinical) osteochondrosis did not influence any of the measured parameters. MAIN LIMITATIONS: This study is limited by the relatively small sample size only containing one breed from a single stud farm. CONCLUSIONS: Dynamic hoof balance in new-born foals is more variable and less oriented towards the lateral side of the hoof and to the heel than in mature horses. This pattern changes gradually during the first weeks of life. Knowledge of this process is essential for the clinician when considering interventions in this area in early life.

The use of a rein tension device to compare different training methods for neck flexion in base-level trained Warmblood horses at the walk.

BACKGROUND: Debate surrounds the use of high rein tension for obtaining different head and neck positions in the training of sport horses on account of possible welfare issues. OBJECTIVES: To compare auxiliary rein tension in two methods (Draw Reins and Concord Leader) for obtaining a standardised head and neck position on a hard and a soft surface. STUDY DESIGN: Intervention study. METHODS: Left and right rein tensions were measured in 11 base-level trained client-owned sport horses (mean age ± s.d.; 10 ± 3.2 years) exercised in-hand with, in a random order, conventional draw reins or the newly developed Concord Leader in a standardised head and neck position. Rein tension was measured using a calibrated device operating at 10 Hz during six runs of 15 s in a straight line for each training method on both a hard and a soft surface. A linear mixed model and grouped logistic regression analysis were applied to compare the two methods (P<0.05). RESULTS: The odds of a tension of 0 N were lower with draw reins than with the Concord Leader. The rein tension (mean sum of the force applied, in N) of the draw reins was 13.8 times higher than that of the Concord Leader. MAIN LIMITATIONS: This study was performed on horses exercised in-hand; however, these auxiliary aids are normally used when lungeing. Possible redirection of rein tension towards the poll was not measured. CONCLUSIONS: We showed that when using the Concord Leader a similar head and neck position is achieved with a much lower rein tension than with the draw reins and, more importantly, with a much greater likelihood of 0 N. It is unnecessary to use high auxiliary rein tension to obtain a standard, flexed head and neck position.

Mouldable, thermoplastic, glue-on frog-supportive shoes change hoof kinetics in normal and obese Shetland ponies.

BACKGROUND: Obesity and hyperinsulinaemia are frequently encountered in the equine population and risk factors for the development of laminitis. There are many options for hoof support that claim a beneficial effect, but often the scientific evidence is scarce. OBJECTIVES: To quantify the effect of frog-supportive shoes on hoof kinetics in normal and obese ponies. STUDY DESIGN: Controlled in vivo trial. METHODS: Ten Shetland mares (n = 10) with a normal (n = 5) or obese (n = 5) body condition were led over a dynamically calibrated pressure plate before (T0), immediately after (T1) and 72 h (T2) after application of the shoes. The following locomotor variables were measured: stance duration (StDur), vertical impulse (VI), peak vertical force (PVF), time to PVF and time from PVF to lift off. The hoof print was divided into a toe and heel region and the StDur toe-heel index was calculated. The toe-heel hoof balance curves of the vertical force were plotted throughout the stance phase. RESULTS: The VI and PVF increased significantly 72 h after application of the shoes, when compared with T0 and T1. The StDur toe-heel index and toe-heel balance curves were significantly different between the normal and obese ponies. These variables became more comparable between the groups after application of the frog-supportive shoes. MAIN LIMITATIONS: It would have been interesting to measure the effect of the shoe in patients with acute laminitis. However, this would have had major welfare implications. CONCLUSIONS: The obese ponies moved more carefully than the normal group, demonstrated by a decreased loading of the toe area. The data illustrate that the ponies became more comfortable 72 h after application of the shoes, with a pronounced effect in the obese group. Thus, these results suggest that frog-supportive shoes could be beneficial, especially for obese ponies.

Quantitative and qualitative aspects of standing-up behavior and the prevalence of osteochondrosis in Warmblood foals on different farms: could there be a link?

BACKGROUND: Osteochondrosis (OC) is a common, clinically important joint disorder in which endochondral ossification is focally disturbed. Reduced blood supply to growing cartilage is considered an important cause of the condition, which has both genetic and environmental origins. Housing conditions can influence cartilage injury through peak-pressure changes during limb sliding. Additionally, circulatory perturbation can cause the avascular necrosis of cartilage. In this study, we evaluated the type and frequency of limb sliding during standing up and the occurrence of OC in foals aged up to 12 months on different farms. METHODS: Standing-up behavior was observed in 50 weaned, group-housed, Dutch Warmblood foals aged 6-9 months at five farms using black-and-white surveillance cameras, and their standing-up behavior was scored using a predetermined ethogram. OC was scored using a categorical scale between 6 and 12 months of age in 50 foals in the weanling period, and in 48 from the weanling to yearling periods because two foals died in this time. RESULTS: At both 6 and 12 months of age, the total prevalence of OC differed between the farms: the lowest prevalence was observed on a farm with no sliding, and the highest prevalence was evident on a farm with a higher sliding frequency. The mean ratio of sliding versus normal standing-up behavior was 29% (range: 0-50%); i.e., foals experienced limb sliding during around 29% of standing-up maneuvres. The frequency of sliding instead of normal standing-up behavior differed significantly between the farms (range: 0-50%; P < 0.05), but significantly decreased when foals could better prepare themselves to stand, e.g., when there was an obvious provocation such as the announced approach of another foal (P < 0.05). CONCLUSIONS: Small but significant differences exist between farms in the sliding frequency and total OC incidence in Warmblood foals, but whether environmental factors are causally related to these differences requires further elucidation.

Cross-sectional study of the prevalence of and risk factors for hoof disorders in horses in The Netherlands.

Information is scarce on the prevalence of hoof disorders in horses. In this study, we examined the prevalence of and risk factors for hoof disorders in a population of horses in The Netherlands. In a group of 942 randomly selected horses, hoof health was scored during regular foot trimming (one horse/farm). Hooves were assessed for the occurrence of one of 12 hoof disorders by a group of 21 certified farriers in two periods i.e. winter and summer of 2015. The mean age of the group of horses was 11.2±5.6years. They were mainly used for recreation (28.2%), dressage (26.8%), other disciplines (such as carriage driving and breeding) (18.7%), showjumping (17.6%) or combinations of these activities (8.6%). The horse farms studied were evenly distributed throughout the country. The horses were housed on different types of bedding, including straw (51.0%), shavings (17.5%), flax (16.1%) or other materials (11.0%), or were kept at pasture (4.4%). In 85% of the horses, at least one hoof disorder was observed during regular foot trimming. Most of the lesions were mild. The most frequently diagnosed hoof disorders were: thrush (T; 45.0%); superficial hoof wall cracks (SHWC; 30.4%); growth rings (GR; 26.3%); and sole bruises (SB; 24.7%). Less frequently observed hoof disorders included: perforating hoof wall cracks (PHWC; 16.4%); white line disease (WLD; 17.8%); and white line widening (WLW; 11.8%). Horizontal hoof cracks (5.2%), chronic laminitis (3.9%), quarter cracks (2.7%), keratoma (1.8%) and frog cancer (1.0%) were less frequently observed. Factors significantly associated with the occurrence of thrush comprised a wet stable floor (OR 1.6 and 2.9, for somewhat wet to wet respectively, compared to dry), the use of straw as bedding (OR=1.5, compared to flax), the housing strategy (e.g. permanent housing in contrast to permanent pasturing) (OR=1.7) and poor horn quality (OR=3.4). A higher prevalence of WLD was associated with less frequent hoof picking (OR=2.1 if performed weekly instead of daily), the use of flax bedding (OR=2.1, compared to straw) and poor horn quality (OR=8.1). A higher prevalence of SB was observed in horses used for multiple disciplines (OR=3.5, compared to dressage), with white-coloured hooves (OR=5.0, compared to black hooves), with longer intervals between trimming sessions (OR=4.8 in case of 8-10 weeks compared to weekly) and with poor horn quality (OR=5.4). A higher prevalence of WLW was observed in older horses (OR=15.5 for horses >19years, compared to <5years), in those with longer intervals between trimming sessions (OR=1.8 in case of 8-10 weeks compared to weekly), and in certain breeds (OR=3.2 for Friesian horses, 2.9 for Welsh ponies and 13.1 for Shetland ponies, all compared to Dutch Warmblood). In conclusion, although most of the hoof disorders identified were only in a mild stage, still an unexpectedly high prevalence of hoof disorders was observed during regular hoof trimming. Analysis of the data showed that some parameters, such as the use of flax bedding, may be protective for certain hoof disorders but a risk factor for others. This study provides useful guidelines for monitoring hoof health, reducing lameness and optimizing equine welfare.

Validation of distal limb mounted inertial measurement unit sensors for stride detection in Warmblood horses at walk and trot.

BACKGROUND: Inertial measurement unit (IMU) sensor-based techniques are becoming more popular in horses as a tool for objective locomotor assessment. OBJECTIVES: To describe, evaluate and validate a method of stride detection and quantification at walk and trot using distal limb mounted IMU sensors. STUDY DESIGN: Prospective validation study comparing IMU sensors and motion capture with force plate data. METHODS: A total of seven Warmblood horses equipped with metacarpal/metatarsal IMU sensors and reflective markers for motion capture were hand walked and trotted over a force plate. Using four custom built algorithms hoof-on/hoof-off timing over the force plate were calculated for each trial from the IMU data. Accuracy of the computed parameters was calculated as the mean difference in milliseconds between the IMU or motion capture generated data and the data from the force plate, precision as the s.d. of these differences and percentage of error with accuracy of the calculated parameter as a percentage of the force plate stance duration. RESULTS: Accuracy, precision and percentage of error of the best performing IMU algorithm for stance duration at walk were 28.5, 31.6 ms and 3.7% for the forelimbs and -5.5, 20.1 ms and -0.8% for the hindlimbs, respectively. At trot the best performing algorithm achieved accuracy, precision and percentage of error of -27.6/8.8 ms/-8.4% for the forelimbs and 6.3/33.5 ms/9.1% for the hindlimbs. MAIN LIMITATIONS: The described algorithms have not been assessed on different surfaces. CONCLUSIONS: Inertial measurement unit technology can be used to determine temporal kinematic stride variables at walk and trot justifying its use in gait and performance analysis. However, precision of the method may not be sufficient to detect all possible lameness-related changes. These data seem promising enough to warrant further research to evaluate whether this approach will be useful for appraising the majority of clinically relevant gait changes encountered in practice.

The development of locomotor kinetics in the foal and the effect of osteochondrosis.

REASON FOR PERFORMING STUDY: Foals stand and walk immediately after birth, but insight into the subsequent longitudinal development of their gait kinetics in the early juvenile phase and the possible influence of osteochondrosis thereon is lacking. OBJECTIVES: To quantify gait kinetics in foals during the first half year of life, taking into account their osteochondrosis status. STUDY DESIGN: Prospective, cohort study performed at a single stud farm. METHODS: Pressure plate measurements at walk and trot from 11 Dutch Warmblood foals during the first 24 weeks of life were used to determine body mass normalised peak vertical force, normalised vertical impulse and stance duration. Coefficients of variation of peak vertical force and stance duration were used as measures for gait maturity. Radiographs of tarsocrural and femoropatellar joints were taken at age 4-6 weeks and after 6 months to check for osteochondrosis. A linear mixed model was used to determine the effects of age, limb, presence of osteochondrosis and speed on gait parameters. RESULTS: Mean walking and trotting velocity increased over time as did stance duration and normalised vertical impulse, normalised peak vertical force values however remained relatively constant. During the first weeks of their life only the coefficient of variation of stance duration decreased significantly, while the coefficient of variation of peak vertical force did not. None of the foals was visibly lame, but the presence of osteochondrosis resulted in a temporarily but significantly reduced normalised peak vertical force. MAIN LIMITATIONS: This study is a relatively small sample size of one breed from a single stud farm. A stand-alone pressure plate was used and body mass was estimated rather than measured. CONCLUSIONS: Despite being precocious, foals need time to mature their gait. During growth, velocity at walk and trot increases, but normalised peak vertical force remains relatively constant. Although not visibly lame, a temporary reduction in normalised peak vertical force was detected in osteochondrosis positive foals using a pressure plate.

[Subcutaneous panniculitis-like T-cell lymphoma : Two case reports]. / Subkutanes pannikulitisartiges T-Zell-Lymphom : Zwei Kasuistiken.

Histopathology, immunohistochemical, and molecular genetic findings revealed the diagnosis of subcutaneous panniculitis-like T-cell-lymphoma in two patients, aged 44 and 70 years. The clinical morphology of the lymphoma manifestations showed varied significantly. One patient presented with a singular erythematous nodule in the chin region. The other patient suffered from extended plate-like resistances and atrophy of the face, upper arms and left breast. Hemophagocytic syndrome was not present in either patient. Prognosis of subcutaneous panniculitis-like T-cell lymphoma without associated hemophagocytic syndrome is reported to be favorable. Radiotherapy of the singular lesion on the chin and systemic corticosteroids of the extended plaques induced complete remission in both patients.

The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses.

BACKGROUND: In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking. OBJECTIVES: The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA). ANIMALS AND METHODS: The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 ± 217 kg (mean ± SD) and aged 10 ± 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 ± 178 kg, aged 13 ± 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means. RESULTS: The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29-2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82-1.45). CONCLUSION AND CLINICAL RELEVANCE: In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

REASONS FOR PERFORMING STUDY: In cases of laminitis, an increased muscle force or contracture of the deep digital flexor muscle (DDFM) is suggested, but evidence-based research is lacking. OBJECTIVES: To test if the DDFM of laminitic equines shows an increased muscle force detectable by needle-EMG including Interference Pattern Analysis (IPA). STUDY DESIGN: Cross-sectional study. METHODS: Three groups consisted of Group 0 (control): 6 Royal Dutch Sport horses, 3 Shetland ponies and one Welsh pony (healthy, sound adults, mean ± s.d. weight 411 ± 217 kg). Group 1: 3 Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, 2 Welsh ponies, one miniature Appaloosa and 6 Shetland ponies (adults, mean ± s.d. weight 310 ± 172 kg) suffering from acute or chronic laminitis. EMG measurements including firing frequency (F) and IPA parameters Turns/Second (T), Amplitude/Turn (M) and Ratio M/T (R) were performed. ANOVA was used to analyse data. P values of P<0.05 were considered significant. RESULTS: Mean ± s.d. F of Group 0 and Group 1 was 53 ± 11 and 72 ± 21 Hz, mean ± s.d. T was 112 ± 57 and 106 ± 42, mean ± s.d. M was 284 ± 51 and 254 ± 38 µV and mean ± s.d. R was 0.39 ± 0.17 and 0.42 ± 0.16%, respectively. The firing frequency of Group 1 was significantly higher compared to Group 0 (P = 0.02), whereas other differences were not significant. CONCLUSIONS: In human medicine, an increased firing frequency is a characteristic of increased muscle force [1,2]. Thus, the increased firing frequency of the DDFM in case of laminitis suggests an elevated muscle force. As all parameters show a high variance, a repeated study including a larger test group is advised. Ethical animal research: Data collection from controls was approved by the Animal Welfare Committee of Utrecht University, approval number 2008.III.07.061 and 2013.III.01.012. Clinical cases were privately owned and written owner consent was obtained. SOURCE OF FUNDING: None. Competing interests: None declared.

Thoracic aortic rupture and aortopulmonary fistulation in the Friesian horse: histomorphologic characterization.

Aortic rupture in horses is a rare condition. Although it is relatively common in the Friesian breed, only limited histopathologic information is available. Twenty Friesian horses (1-10 years old) were diagnosed with aortic rupture by postmortem examination. Ruptured aortic walls were analyzed with histology and immunohistochemistry. Based on the histologic and immunohistochemical findings, these cases were divided into 3 groups: acute (n = 4, 20%), subacute (n = 8, 40%), and chronic (n = 8, 40%). Features common to samples from horses in all groups included accumulation of mucoid material; disorganization and fragmentation of the elastic laminae; aortic medial smooth muscle hypertrophy; and medial necrosis of varying degrees, ranging from mild and patchy in the acute cases to severe midzonal necrosis in the chronic cases. Inflammation, most likely secondary to medial necrosis, varied from predominantly neutrophilic infiltrates in the media and periadventitial tissue in the acute group to the presence of mainly hemosiderophages in the periadventitial tissue in the chronic group. Medial fibrosis with aberrant collagen morphology was seen in the subacute group and, more commonly, in the chronic group. Only minimal changes were seen in the aortic vasa vasorum. Smooth muscle hypertrophy and accumulation of mucoid material were not related to the age of the lesions. The findings of this study suggest that a connective tissue disorder affecting elastin or collagen in the aortic media is potentially the underlying cause of aortic rupture in Friesian horses.

Esophageal Dysfunction in Friesian Horses: Morphological Features.

Megaesophagus appears to be more common in Friesian horses than in other breeds. A prevalence of approximately 2% was observed among Friesian horses presented to the Wolvega Equine Clinic and the Utrecht University Equine Clinic. In this study, morphologic changes in the esophagi of Friesian horses with megaesophagus were compared with those of 6 control horses. Of 18 horses with clinically observed megaesophagus, only 12 animals had esophageal dilation at necropsy, usually involving the thoracic portion. Muscular hypertrophy of the distal esophagus was present in only one-third of the affected horses, indicating that this change is not the most relevant cause of megaesophagus in Friesians. Increased deposition of clumped and disorganized collagen was present in these clinically affected horses mainly in the non-dilated portion of the esophagus. At necropsy, a decrease in neural elements and elastin was present principally in horses with megaesophagus. Mild degeneration and necrosis of the tunica muscularis along the entire length of the esophagus were present in clinically affected horses and encountered only rarely in control animals. There were no significant differences among affected and control horses with respect to inflammation, mineralization, or the number of cells of Cajal. The increased occurrence of megaesophagus in the Friesian breed compared with other horse breeds, together with the presence of abnormal collagen in very young foals, supports the hypothesis that megaesophagus is hereditary in Friesians.