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.

[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.

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.

[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.

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.

Dynamics of VEGF matrix-retention in vascular network patterning.

Vascular endothelial growth factor (VEGF) is a central regulator of blood vessel morphogenesis, although its role in patterning of endothelial cells into vascular networks is not fully understood. It has been suggested that binding of soluble VEGF to extracellular matrix components causes spatially restricted cues that guide endothelial cells into network patterns. Yet, current evidence for such a mechanism remains indirect. In this study, we quantitatively analyse the dynamics of VEGF retention in a controlled in vitro situation of human umbilical vascular endothelial cells (HUVECs) in Matrigel. We show that fluorescent VEGF accumulates in pericellular areas and colocalizes with VEGF binding molecules. Analysis of fluorescence recovery after photobleaching reveals that binding/unbinding to matrix molecules dominates VEGF dynamics in the pericellular region. Computational simulations using our experimental measurements of kinetic parameters show that matrix retention of chemotactic signals can lead to the formation of reticular cellular networks on a realistic timescale. Taken together, these results show that VEGF binds to matrix molecules in proximity of HUVECs in Matrigel, and suggest that bound VEGF drives vascular network patterning.

Phenotypic characteristics of hydrocephalus in stillborn Friesian foals.

Hydrocephalus is uncommon in horses. However, in recent years, it has become clear that the prevalence of hydrocephalus is greater in Friesian horses than in other breeds probably due to their limited gene pool. Before identification of candidate genes that predispose to the development of hydrocephalus in Friesian horses can be pursued, an in-depth, phenotypic, pathological description of the condition in Friesians would be of great benefit. Our study aimed to characterize the morphology of hydrocephalus in Friesian horses, to support further investigation of the genetic background of this condition. Four stillborn Friesian foals with hydrocephalus were examined macroscopically and microscopically and compared with 2 normal stillborn Friesian foals without hydrocephalus. In all clinical cases, tetraventricular and venous dilatations were observed, together with malformation of the petrosal bone and, as a result, narrowing of the jugular foramen. These observations suggest a communicative hydrocephalus with a diminished absorption of cerebrospinal fluid into the systemic circulation at the venous sinuses due to a distorted, nonfunctional jugular foramen. This type of hydrocephalus is also recognized in humans and dogs and has been linked genetically to chondrodysplasia; this has already been recognized in dwarfism, which is another monogenetic defect in Friesian horses.

Peutz-Jeghers syndrome is caused by mutations in a novel serine threonine kinase.

Peutz-Jeghers (PJ) syndrome is an autosomal-dominant disorder characterized by melanocytic macules of the lips, multiple gastrointestinal hamartomatous polyps and an increased risk for various neoplasms, including gastrointestinal cancer. The PJ gene was recently mapped to chromosome 19p13.3 by linkage analysis, with the highest lod score at marker D19S886. In a distance of 190 kb proximal to D19S886, we identified and characterized a novel human gene encoding the serine threonine kinase STK11. In a three-generation PJ family, we found an STK11 allele with a deletion of exons 4 and 5 and an inversion of exons 6 and 7 segregating with the disease. Sequence analysis of STK11 exons in four unrelated PJ patients has identified three nonsense and one acceptor splice site mutations. All five germline mutations are predicted to disrupt the function of the kinase domain. We conclude that germline mutations in STK11, probably in conjunction with acquired genetic defects of the second allele in somatic cells, cause the manifestations of PJ syndrome.

Genome-wide SNP association-based localization of a dwarfism gene in Friesian dwarf horses.

The recent completion of the horse genome and commercial availability of an equine SNP genotyping array has facilitated the mapping of disease genes. We report putative localization of the gene responsible for dwarfism, a trait in Friesian horses that is thought to have a recessive mode of inheritance, to a 2-MB region of chromosome 14 using just 10 affected animals and 10 controls. We successfully genotyped 34,429 SNPs that were tested for association with dwarfism using chi-square tests. The most significant SNP in our study, BIEC2-239376 (P(2df)=4.54 × 10(-5), P(rec)=7.74 × 10(-6)), is located close to a gene implicated in human dwarfism. Fine-mapping and resequencing analyses did not aid in further localization of the causative variant, and replication of our findings in independent sample sets will be necessary to confirm these results.

Lateralised motor behaviour leads to increased unevenness in front feet and asymmetry in athletic performance in young mature Warmblood horses.

REASON FOR PERFORMING STUDY: Foot stance in grazing significantly influences hoof conformation and development from foal to yearling age. OBJECTIVES: To conduct a longitudinal study to establish if the relationship between motor laterality and uneven front feet persisted in 3-year-old horses at the time of studbook selection and to investigate if such laterality and unevenness might influence the horses' ability to perform symmetrically while trotting, cantering and free jumping. METHODS: Seventeen clinically sound but untrained (with only minimal experience of handling) and sound Warmblood horses that had participated in a previous study were assessed as per the protocol reported. Laterality was tested in a preference test (PT) and z-values were calculated for analysis purposes. Laterality and hoof unevenness were related to both relative limb length and relative head size, while the ability to perform symmetrically was tested in free trot-canter transitions and free jumping exercises. Differences in performance between horses with and without a limb preference in the PT and those with 'uneven' and 'even' feet were tested for differences in performance metrics using Students' t test, while linearity was tested using a regression analysis (P<0.05). RESULTS: Significant laterality was still present in 24% of the 3-year-old horses and the relationship between laterality and uneven feet pairs was stronger than at foal and yearling stages. Horses with significant motor laterality had almost 4 times more unevenness, a smaller head and longer limbs and the relationship between body conformation and laterality was still present. There was a strong linear relation between unevenness, laterality and a bias or side preference for trot-canter transitions. However, this relationship was not significant during the free jumping exercise. CONCLUSION: Motor laterality and uneven feet pairs were still present and significantly related in the 3-year-old horses and both variables were also strongly related to sidedness in trot-canter transitions. POTENTIAL RELEVANCE: Warmblood studbooks should include quantitative data on laterality at the time of studbook admission as part of the selection criteria.

Intra-articular opioid analgesia is effective in reducing pain and inflammation in an equine LPS induced synovitis model.

REASONS FOR PERFORMING STUDY: Intra-articular administration of morphine as a local analgesic and anti-inflammatory drug is widely used in human medicine. In equids, little is known about its clinical analgesic and anti-inflammatory efficacy. OBJECTIVES: To use an inflammatory orthopaedic pain model to investigate the analgesic and anti-inflammatory effects of intra-articularly administered morphine as a new treatment modality in horses with acute arthritis. METHODS: In a crossover study design, synovitis was induced in the left or right talocrural joint by means of intra-articular injection of 0.5 ng lipopolyssacharide (LPS). The effect of 120 mg morphine, intra-articularly administered at 1 h after induction of synovitis, was evaluated using both physiological and behavioural pain variables. Synovial fluid was sampled at 0, 4, 8, 28 and 52 h after induction of synovitis and analysed for total protein concentration, leucocyte count and for prostaglandin E(2), bradykinin and substance P concentrations by ELISA. Ranges of motion of metatarsophalangeal and talocrural joints were measured as kinematic variables with the horses walking and trotting on a treadmill under sound and lame conditions. Clinical lameness scores and several behavioural variables related to the perception of pain were obtained. RESULTS: LPS injection caused marked transient synovitis, resulting in increased concentrations of inflammatory synovial fluid markers, clinical lameness, joint effusion and several behavioural changes, such as increased time spent recumbent, decreased limb loading at rest and decreased time spent eating silage. Intra-articular morphine resulted in a significant decrease in synovial white blood cell count, prostaglandin E(2) and bradykinin levels and improvement in clinical lameness, kinematic and behavioural parameters, compared to placebo treatment. CONCLUSIONS: Intra-articular morphine offers potent analgesic and anti-inflammatory effects in horses suffering from acute synovitis. POTENTIAL RELEVANCE: Local administration of opioids may be useful for horses with acute inflammatory joint pain and offers possibilities for multimodal analgesic therapies without opioid-related systemic side effects.

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.

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.

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.

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.

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.

Heritability of foot conformation and its relationship to sports performance in a Dutch Warmblood horse population.

REASONS FOR PERFORMING STUDY: Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future performance, but reduce the risk of injuries and lameness. Negative conformational traits, such as asymmetrical or 'uneven' forefeet would possibly diminish performance. OBJECTIVES: To assess the prevalence and heritability of uneven feet and its genetic relationship to other conformation traits as well as to sporting performance later in life in Warmblood riding horses. METHODS: The databases of the Royal Dutch Warmblood Studbook (KWPN, n = 44,840 horses) and Royal Dutch Equestrian Sports Federation (KNHS, n = 33,459 horses in dressage and n = 30,474 horses in showjumping) were linked through the unique number of each registered horse. Therefore, heritabilities and genetic and phenotypic correlations could be estimated from the scores of the jury at studbook admission and the sports performance of that population in dressage and jumping over the period 1990-2002. RESULTS: The prevalence of uneven feet was 53% on average, and increased from under 4.5% during the first 3 years of recording to over 8% in the years from 2000 onwards. Heritability estimates of foot conformation traits were moderate and ranged from 0.16 for heel height to 0.27 for hoof shape. The genetic correlation between the trait of uneven feet and performance in competition was negative but weak: -0.09 with dressage and -0.12 with showjumping. CONCLUSIONS: Predisposition to uneven feet can be reduced by selection. Because of weak genetic correlations, the increased prevalence is not directly associated with selection for better sports performance or higher conformation grade. If the trait 'uneven feet' arises from a disproportionate relationship between height at the withers and neck length, then selection on conformation grade might result in development of uneven feet. In general, limb conformation has a moderate genetic relationship to conformation grade and foot conformation traits have a genetic relationship to sporting performance. Reducing occurrence of uneven feet by selection is possible, without limiting progress in sport performance.

Influence of foot conformation on duration of competitive life in a Dutch Warmblood horse population.

REASONS FOR PERFORMING STUDY: Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future sports performance, but reduce the risk of early retirement due to lameness. Negative conformational traits, such as asymmetrical or 'uneven' forefeet may possibly shorten the career of sporthorses. OBJECTIVES: To investigate the significance of foot conformation at young age to duration of the career of sporthorses. METHODS: Databases of the Royal Dutch Warmblood Studbook (KWPN) and of the Royal Dutch Equestrian Sports Federation (KNHS) were matched and resulted in a dataset comprising 23,116 records of horses for which their conformation scores and duration of their sports career were available. Survival analysis was used to determine which of the conformation traits had a significant effect on duration of sports career in dressage and jumping at basic and elite level. RESULTS: Duration of competitive life was shorter for jumping than for dressage. A different set of risk factors was found for each level and discipline. The trait 'uneven feet' tended to shorten the competitive life in dressage, but was a significant risk factor at the elite level of jumping. CONCLUSIONS: Limb conformation and, in particular, the conformation of the distal limb, are important for duration of competitive life. From the prevalence of uneven feet in sports disciplines, it may be concluded that this is an undesirable trait, particularly at the elite level of jumping, since uneven feet have a detrimental effect on the duration of competitive life in a sporthorse population. POTENTIAL RELEVANCE: This study provided evidence that the conformation trait uneven feet has a negative effect on Warmblood jumping performance and, therefore, breeders should be encouraged to avoid this phenomenon at foal age.

In vitro evaluation of metacarpophalangeal joint loading during simulated walk.

REASONS FOR PERFORMING STUDY: Insight into the loading pattern of the articular cartilage surface during the complete stride is important as biomechanical factors play a pivotal role in the pathogenesis of joint trauma and osteoarthritis (OA). OBJECTIVES: To determine the loading pattern in the equine MCP articulation in vitro during simulated walk. METHODS: Eight cadaveric limbs from mature Dutch Warmblood horses were loaded in a pneumatic loading device in 6 different positions (A1-A6). The pressure distribution on the articular surface of the proximal phalanx (P1) was measured at 7 sites (S1-7) using intra-articularly placed pressure sensitive films, which were analysed by scanning and densitometry. RESULTS: Pressures recorded after mid-stance (A4, 5, 6) were significantly (P < 0.05) higher than those before (A1, 2, 3) and showed the biphasic loading pattern of the walk at all sites, except for the site halfway along the sagittal groove (S7). At S7, there was a linear increase in pressure during the progress of the stance phase of the stride in most horses. Medially (S4, 5, 6) the pressure was significantly higher than laterally (S1, 2, 3) (P < 0.05). CONCLUSIONS AND POTENTIAL RELEVANCE: The heavier medial loading coincides with the location where articular cartilage degeneration in the process of OA in the equine MCP joint is known to start. The discrepancy between the loading of the central groove and the other parts of the joint may result in large stress differences at the end of the stance phase, which might be related to the pathogenesis of stress fractures in the first phalanx and distal third metacarpal bone.