Investigating Associations between Horse Hoof Conformation and Presence of Lameness.

Hoof trimming and shoeing determine the horse's hoof shape and balance. Hoof conformation plays a crucial role in limb biomechanics and can consequently prevent or predispose to injury. This study investigated the relationship between the morphometric characteristics of the horse's hoof, specifically, the dorsal hoof wall angle (DHWA), the coronet band circumference (CBC), and lameness in 73 horses categorised as undertaking either show jumping, dressage, or riding school activities. Results from logistic regression indicated that horses with either a combination of acute DHWA with large CBC, or more upright feet with larger DHWA and smaller CBC have higher probabilities of lameness. Show jumping and dressage horses showed a higher prevalence of lameness. Hoof morphometry should be monitored, and podiatric interventions should be regularly scheduled for the maintenance of correct hoof conformation to prevent injury. This study suggests that an aligned hoof-pastern axis managed by a DHWA of around 50 degrees may prevent lameness, with special emphasis on horses in dressage and show jumping activities. On the other hand, we can also speculate that the disturbed axis alignment of DHWA may be a cause of lameness.

Selenium deposition in an atypically disintegrated hoof wall in a Thoroughbred racehorse with alkali disease: Proof by energy-dispersive X-ray fluorescence analysis.

From summer 2018 to summer 2019, several Thoroughbred racehorses held at the Miho Training Centre of the Japan Racing Association inadvertently ingested excessive amounts of sodium selenite, resulting in typical chronic selenium (Se) poisoning - the so-called alkali disease. The typical abnormality was a hoof wall disorder with a circumferentially deep ring and/or transverse hoof wall cracks parallel to the coronet on all feet and appearing after excessive ingestion. One affected Thoroughbred male was unique in that all the hooves had a rough surface with a very fragile hoof wall, but no wall rings or transverse cracking. This horse was euthanized because of dysstasia due to the permanent foot pain associated with hoof wall deformities in the front feet. To detect Se deposition in the hooves, we used energy-dispersive X-ray fluorescence (EDXRF) analysis to measure the Se signal intensity of each lesion. Characteristic Se-kα signals were emitted from the areas of histologically damaged hoof wall at 33.76 ± 11.78 (mean ± SD) counts per second (cps)/mm2. In contrast, the signal from the uninjured proximal hoof wall was 1.43 ± 0.14 cps/mm2 and that from the uninjured distal hoof wall was 1.51 ± 0.23 cps/mm2. The much greater Se deposition in the injured hoof walls suggests that their disintegration was caused by alkali disease. These results indicate that atypical hoof wall abnormalities due to alkali disease can be diagnosed by EDXRF analysis.

Viscoelastic properties of the equine hoof wall.

The equine hoof wall has outstanding impact resistance, which enables high-velocity gallop over hard terrain with minimum damage. To better understand its viscoelastic behavior, complex moduli were determined using two complementary techniques: conventional (∼5 mm length scale) and nano (∼1 µm length scale) dynamic mechanical analysis (DMA). The evolution of their magnitudes was measured for two hydration conditions: fully hydrated and ambient. The storage modulus of the ambient hoof wall was approximately 400 MPa in macro-scale experiments, decreasing to ∼250 MPa with hydration. In contrast, the loss tangent decreased for both hydrated (∼0.1-0.07) and ambient (∼0.04-0.01) conditions, over the frequency range of 1-10 Hz. Nano-DMA indentation tests conducted up to 200 Hz showed little frequency dependence beyond 10 Hz. The loss tangent of tubular regions showed more hydration sensitivity than in intertubular regions, but no significant difference in storage modulus was observed. Loss tangent and effective stiffness were higher in indentations for both hydration levels. This behavior is attributed to the hoof wall's hierarchical structure, which has porosity, functionally graded aspects, and material interfaces that are not captured at the scale of indentation. The hoof wall's viscoelasticity characterized in this work has implications for the design of bioinspired impact-resistant materials and structures. STATEMENT OF SIGNIFICANCE: The outer wall of horse hooves evolved to withstand heavy impacts during gallop. While previous studies have measured the properties of the hoof wall in slowly changing conditions, we wanted to quantify its behavior using experiments that replicate the quickly changing forces of impact. Since the hoof wall's structure is complex and contributes to its overall performance, smaller scale experiments were also performed. The behavior of the hoof wall was within the range of other biological materials and polymers. When hydrated, it becomes softer and can dissipate more energy. This work improves our understanding of the hoof's function and allows for more accurate simulations that can account for different impact speeds.

Radiographic analysis of the dorsal hoof wall thickness in clinically normal draft horses.

OBJECTIVE: To evaluate the radiographic thickness of the dorsal hoof wall in normal draft horse feet. ANIMALS: 33 adult draft horses with no history of laminitis, no clinically obvious lameness, and visibly unremarkable front feet were included. METHODS: This was a prospective, descriptive study of clinically normal draft horses' front feet. Lateromedial radiographs were acquired of the front feet. A ratio of the dorsal hoof wall thickness to the length of the distal phalanx (DHWP3 ratio) was calculated. RESULTS: The dorsal hoof wall thickness to length of the distal phalanx was calculated as 0.33 ± 0.03 (range of 0.28 to 0.39) in this population of draft horses. CLINICAL RELEVANCE: With very few exceptions, the heterogeneous population of draft horses evaluated in this study had a DHWP3 ratio greater than previously published values in lighter breeds (< 0.30).

Evaluating the immediate effects of hoof trimming on dairy goat hoof conformation and joint positions.

Hoof overgrowth in commercial housed dairy goats is a major health and welfare concern; thus, it is important to better understand hoof trimming, a priority practice which addresses hoof growth. We evaluated the immediate effects of trimming on external conformation, internal joint positions, and hoof wall overgrowth of front and hind hooves. Eighty female goats were enrolled. Pre and post hoof trimming data were collected at 13, 17, 21 and 25 months of age. Overall, before trimming, a high percentage of hooves were scored as overgrown (77.8%). Trimming decreased the percentage of overgrown hooves (17.6%: P < 0.001) and other moderate/severe conformational issues: dipped heels (49.3% vs. 26.7; P < 0.001), misshaped claws (37.0% vs. 17.6%; P < 0.001), splayed claws (73.7% vs. 56.7%; P < 0.001). More hind than front hooves had dipped heels pre-trimming and (91.3% vs. 7.3%; P < 0.001) and post-trimming (52.8% vs. 0.6%; P < 0.001); over half of the hind heels were not restored to an upright position. A greater proportion of toe length was removed from the hind hooves compared to the front (0.50 vs. 0.43, P < 0.001), with the greatest proportion of hoof wall overgrowth removed from the hind hoof medial claw at the 13-month assessment (P < 0.001). Following trimming, distal interphalangeal joint angle decreased more in hind compared to front hooves (11.0° vs. 6.9°; P < 0.001); distal interphalangeal joint height decreased (0.21 cm, P < 0.001), and proximal interphalangeal joint, and heel, angles increased (7.76° and 8.93°, respectively; P < 0.001). Trimming did not restore conformation of all hooves when trimmed every 4 months, suggesting a need to investigate reasons for underlying poor conformation, including trimming frequency.

Evaluating the long-term conformation and hoof growth effects of starting hoof trimming at 5 months of age in New Zealand dairy goats.

Hoof overgrowth is associated with poor conformation, an altered weight-bearing surface, and a reduction in the hoof's anatomic and functional integrity. As a result of housing systems that promote hoof overgrowth, hoof trimming is considered a priority in dairy goats. However, there are few data on the effects of the timing of first trimming on hoof conformation and growth rate. The aims of this study were (1) to evaluate the long-term effects of 2 different hoof trimming start times and (2) to investigate the pattern of hoof growth across the first 2 yr of life. Eighty 5-mo-old female Saanen-cross commercially housed dairy goats were allocated randomly to 1 of 2 treatments: (1) early trimmed (trimming beginning at 5 mo old; hooves were trimmed every 4 mo thereafter) and (2) late trimmed (trimming beginning at 13 mo old; hooves were trimmed every 4 mo thereafter). Using a combination of photographs and radiographs, hoof conformation, joint positions, and hoof wall length were assessed before the 13- and 25-mo trimming events. Hoof growth was assessed every 12 wk using caliper measurements. Overall, starting hoof trimming earlier had minor and inconsistent effects. However, detrimental changes in conformation and joint positions occurred between trimming events, particularly in the hind hooves, regardless of trimming treatment. At both assessments, there was a high percentage of overgrown toes and dipped heels, with the hind hooves being more affected compared with the front (overgrown toes at 13 mo, 97.1 vs. 79.1 ± 5.2%; overgrown toes at 25 mo, 91.7 vs. 56.3 ± 6.7%; dipped heels at 13 mo, 98.5 vs. 19.3 ± 5.0%; dipped heels at 25 mo, 88.3 vs. 4.9 ± 4.8%). In addition, at both assessments, the distal interphalangeal joint angle was greater in the hind hooves compared with the front (13 mo, 79.5 vs. 65.2 ± 1.7°; 25 mo, 79.0 vs. 66.7 ± 0.9°), whereas heel angles were less in the hind hooves compared with the front (13 mo, 41.8 vs. 57.1 ± 1.5°; 25 mo, 44.9 vs. 55.9 ± 1.1°). On average, the front hooves grew 4.39 mm/mo and the hind hooves grew 4.20 mm/mo. Early trimming did not have consistent effects on hoof growth rate. Importantly, our results suggest that trimming every 4 mo is not sufficient to prevent hoof overgrowth, the development of poor conformation, and detrimental changes in joint positions, particularly in the hind hooves. Furthermore, the detrimental changes may have masked any long-term treatment effects. Therefore, trimming frequency and age of first trimming should be considered when devising hoof care protocols for dairy goats housed in environments that do not offer opportunities for natural hoof wear.

Hierarchical modeling of elastic moduli of equine hoof wall.

This study predicts analytically effective elastic moduli of substructures within an equine hoof wall. The hoof wall is represented as a composite material with a hierarchical structure comprised of a sequence of length scales. A bottom-up approach is employed. Thus, the outputs from a lower spatial scale serve as the inputs for the following scale. The models include the Halpin-Tsai model, composite cylinders model, a sutured interface model, and classical laminate theory. The length scales span macroscale, mesoscale, sub-mesoscale, microscale, sub-microscale, and nanoscale. The macroscale represents the hoof wall, consisting of tubules within a matrix at the mesoscale. At the sub-mesoscale, a single hollow tubule is reinforced by a tubule wall made of lamellae; the surrounding intertubular material also has a lamellar structure. The lamellae contain sutured and layered cells at the microscale. A single cell is made of crystalline macrofibrils arranged in an amorphous matrix at the sub-microscale. A macrofibril contains aligned crystalline rod-like intermediate filaments at the nanoscale. Experimentally obtained parameters are used in the modeling as inputs for geometry and nanoscale properties. The predicted properties of the hoof wall material agree with experimental measurements at the mesoscale and macroscale. We observe that the hierarchical structure of the hoof wall leads to a decrease in the elastic modulus with increasing scale, from the nanoscale to the macroscale. Such behavior is an intrinsic characteristic of hierarchical biological materials. This study can serve as a framework for designing impact-resistant hoof-inspired materials and structures.

The Effect of Lunging with Three Aids on the Thermographically Determined Temperatures of the Distal Portion of Horse Limbs.

The regulation of head and neck position during physical exercise may be obtained using lunging aids (LAs): Chambon (CH), rubber band (RB), or triangle side reins (TR). The use of LAs would shift the center of horse mass caudally, thereby change the limb load. The aim is to evaluate the pattern of superficial temperatures (PST) of hoof wall (HW), the coronary band (CB), and the dorsal aspect of the fetlock joint (FJ) obtained before and after lunging with LAs and freely moving head (FMH). Sixteen horses were imaged using an infrared camera. The temperatures of HW, CB, and FJ were measured, and differences between images obtained before and after lunging were evaluated. The correlations between HW, CB, and FJ were then described using respective coefficients (r, rho). Before lunging PST was similar (P < .05) in FMH, CH, RB, and TR, with the strong positive correlations for forelimbs (HW/CB:rho = 0.9022; HW/FJ:rho = 0.7064; CB/FJ:rho = 0.8010) and hindlimbs (HW/CB:rho = 0.7287; HW/FJ:r = 0.7831; CB/FJ:r = 0.7233). After lunging, PST and correlations changed (P > .05) depending on LAs application. No correlations for FMH and CH, and positive correlations for RB and TR were noted: HW/CB for forelimbs (RB:r = 0.6813; TR:r = 0.8396), CB/FJ for hindlimbs (RB:r = 0.5621; TR:rho = 0.4579). The PST of the distal portion of limbs and relations between measured temperatures change depending on used LAs.

Effect of shoeing conditions on hoof dimensions in Icelandic and Warmblood horses.

In Icelandic horses (ICE), high, long hooves with added weights are often used to improve gait quality in competitions. From a biomechanical point of view, excessively long hooves can be problematic as they increase forces acting on the distal limb. The study aimed to determine if hoof capsule size and angle of ICE at competitions are comparable to those of Warmblood horses (WB) requiring shoeing. Hoof dimensions and balance were quantified in 13 horses of each breed at the beginning of a shoeing period (BSP), allowing a baseline comparison between breeds, as well as for WB at the end of a shoeing period (ESP) and for ICE when shod for competition (COMP). Left front and hind hoof capsules and bony structures of the hooves were measured on lateromedial and dorsopalmar/dorsoplantar radiographs at BSP (ICE, WB), ESP (WB) and COMP (ICE), respectively, using the software Metron-Hoof-Pro. Compared to WBBSP, ICEBSP had larger hoof capsules relative to the size of P3 and, when controlled for withers height, longer dorsal hoof wall lengths. The comparison of ICECOMP to WBESP indicated that the relative increase in hoof length and volume was greater in ICECOMP compared to WBESP. Hoof balance was closer to previously published values in WBs, while hoof angles in ICE (particularly palmar/plantar angle of P3) were generally larger and thus less problematic. In conclusion, hooves of ICECOMP were relatively larger and less balanced than WBESP, but hoof angles in WB were smaller than in ICE.

Microstructure and mechanical properties of an alpha keratin bovine hoof wall.

Bovine hoof wall with an alpha keratin structure, as the interface between the ground and the body, can protect the bony skeleton from the impact and the destruction. Microstructure and mechanical properties of the bovine hoof wall are investigated by scanning electron microscope (SEM), transmission electron microscope (TEM) and quasi-static mechanical tests. Mechanical results show that the mean J-integral values of the LD specimens parallel to the tubular axis are higher than those of the TD specimens normal to the tubular axis, and the fracture toughness reaches the peak values (21 kJ/m2, 33 kJ/m2 for the TD and the LD specimens, respectively) at 16.5% moisture content. The morphology results show that the laminated keratin structure can form the extensive strain-transition interfaces and the tubules played an important role in twisting crack propagation. Angles of the laminated structures within the inter-tubular materials are not a uniform distribution varying from 0° to 90° against to the tubular axis. The interlocking interface in the tubular structure can provide increased the contact area and contribute to the bonding strength between the layers. We also propose models to illustrate the morphological structure and the crack propagation mechanism of the bovine hoof wall. This structure with the strong fracture resistance ability will provide a new inspiration for design of structural materials and architectures.

The influence of trimming of the hoof wall on the damage of laminar tissue after loading: An in vitro study.

Laminitis is associated with failure of the suspensory apparatus of the distal phalanx (SADP) connecting the distal phalanx to the hoof wall. The specific aim of this study was to examine in vitro whether thinning of the hoof wall leading to increased deformability influences the damage of the laminar tissue created by loading of the hoof. Paired cadaver forelimbs from twelve horses were used. For each pair, the hoof wall from one hoof was thinned by 25%; this was ascertained by radiography. The contralateral hooves were used as controls. In a material testing machine, hooves were loaded in a proximodistal direction at 0.5mm/s until a cut-off value of 8kN or 14mm was reached. Afterwards, samples of the SADP were taken for histology. Image-based evaluation of the destruction of the SADP was performed using quantitative histogram analysis. Additionally, three examiners masked to treatment (trimmed/untrimmed) qualitatively evaluated SADP destruction. During hoof loading with forces from 0.5 to 1.8 times the body mass of the donor horses, hooves with thinned hoof wall underwent significantly more deformation (P<0.05). Quantitative histogram analysis detected a shift to higher brightness values and a higher pixel intensity in control hooves, representing disruption in the histologic analysis. Qualitative evaluation of histology sections showed significantly more disruption of the SADP in untrimmed hooves (P=0.03). These results confirm the hypothesis that reduced hoof wall thickness can decrease disruption of laminar tissue in vitro, thus supporting the evaluation of hoof wall reduction as a prophylactic measure in horses at imminent risk of SADP failure.

RADIOGRAPHIC AND ANATOMIC CHARACTERISTICS OF DORSAL HOOF WALL LAYERS IN NONLAMINITIC HORSES.

Early radiographic diagnosis of acute laminitis is important for treatment planning and prognosis in horses. While four histopathologic layers make up the hoof wall, only two layers are distinguished on digital radiographs of horses' hooves. Objectives of this descriptive study were to determine which macroscopic layers correspond to the two radiographically visible layers, and to describe radiographic layer measurements in a group of clinically sound Warmblood horses. Twelve ex vivo equine hooves were examined at three different levels of the dorsal hoof wall. The four macroscopic layers were variably grouped and compared with radiographic layers. Stratum externum and stratum medium represented the superficial radiographic layer while stratum internum and dermis parietis represented the deep layer. In 27 clinically sound horses (54 thoracic feet), the superficial radiographic layer represented 64.3% ± 3.6% of the total dorsal hoof wall. Findings from this study provided baseline information for future studies of horses with acute laminitis.