Keratinopathogenic mould fungi and dermatophytes in healthy and diseased hooves of horses

Specimens of hoof horn from 187 horses were examined for a possible relationship between clinically affected hooves and the occurrence of pathogenic fungi. Specimens were taken from the coronary band and from the stratum externum and medium of the coronary horn and transferred on to Sabouraud dextrose agar, with and without cycloheximide, and incubated at 28 degrees C. Dermatophytes and mould fungi were identified by their macroscopic and microscopic characteristics. The 732 isolates could be assigned to 26 species of moulds, two different species of the dermatophyte Microsporum and three different species of the dermatophyte Trichophyton. Depending on their pathogenic potential they were assigned to three groups: (i) fungi known to be keratinopathogenic (Acremonium blochii, Alternaria alternata, Alternaria chlamydospora, Geotrichum candidum, Microsporum ferrugineum, Microsporum gypseum, Scopulariopsis brevicaulis, Trichophyton species, Trichophyton mentagrophytes, Trichophyton sch?nleinii, 57 isolates), (ii) a group of uncertain pathogenicity (223 isolates), and (iii) a group of non-pathogenic species (452 isolates). Eighty per cent of the samples from horses with hoof horn lesions and 66.7 per cent of the samples from horses with slightly affected hoof horn contained fungi of the keratinopathogenic group, whereas only 8.9 per cent of the samples from horses with healthy hoof horn contained fungi of this group. There were no significant correlations between the clinical data and the age, sex or breed of the horses or their bedding and hygiene. Twelve species of fungi were isolated from the air in the horses' stables, but none of them belonged to the keratinopathogenic group.     

Effect of dietary biotin supplement on equine hoof horn growth rate and hardness.

Over a 10-month period, 24 randomly selected riding horses were fed various amounts of biotin. Statistically significant improvements in growth rates and hardness of hooves were produced by biotin supplementation. Greater growth rates and hardness were achieved at a daily dose of 15 mg than at 7.5 mg. Increased hoof hardness was greatest in the hoof quarters and toe. No ring formation occurred in hooves of horses fed biotin intermittently.     

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios.Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.     

Surgical reconstruction of chronic coronary band avulsions in three horses

Three adult horses were admitted with chronic coronary band avulsions of 2-, 3-, and 46-month durations, respectively. The hoof had a typical appearance in all 3 horses, with a spur of coronary band and associated horn growing at right angles to the hoof wall. Each horse was anesthetized, and the coronary band was reconstructed. Follow-up evaluation of the 3 horses (12, 15, and 23 months after surgery, respectively), revealed healing of all 3 avulsed coronary bands. Mild roughening of the hoof wall distal to the previous avulsion site was observed.     

Effects of toe angle on hoof growth and contraction in the horse

The effects of toe angle on the growth of the unshod hooves of mature horses were measured over 126 days. The hooves of 4 horses were trimmed long in the toe and short in the heel (“LT”), with toe angles of 40° for the forelimb and 50° for the hind limb hooves; 4 others were trimmed short in the toe and long in the heel (“ST”), with toe angles of 50° for the forelimb and 55° for the hind limb hooves. Growth of the hoof wall at the toe ranged between .19 and .28 mm/day, and was slowest in the forelimb hooves trimmed ST. After 126 days, the hooves trimmed LT were 7% smaller in width than they had been at day 0. Narrowing of the hoof walls and frogs was accompanied by deformation of the angles of the walls (bending outward of their weightbearing surfaces). Frog lengths and sole areas were not affected by toe angle. Regardless of trimming method, all forelimb hooves tended to return to a toe angle of 45° between trimmings, while all hind limb hooves tended toward toe angles of 52° to 53°. The soles of all hooves were basically circular in shape, although the hooves trimmed LT tended to be skewed to the left, as viewed from above, after 126 days.     

Linear hoof defects in sheep infected with foot-and-mouth disease

During the epidemic of foot-and-mouth disease (FMD) in The Netherlands in 2001, a sheep farm was identified that had been subclinically infected with the disease. The FMD virus genome was detected in 12 of 16 probang samples collected from the sheep and the virus was isolated from four of these samples. Linear defects were observed, 1 to 3 cm from the coronary band, in the hooves of several of the sheep. The defects were thought to have been caused by the FMD infection. It was thought that the distance of the defects from the coronary band might be an indication of the time since the animals had been infected. To determine the growth rate of the claws of sheep, the growth of the hoof horn of uninfected lambs and ewes was measured; in the lambs the growth rate was 0.44 mm per day and in the ewes it was 0.29 mm per day.     

The origin and foot condition of horses slaughtered in Australia for the human consumption market

Reasons for performing study: There are ethical concerns regarding the loss of horses from various equine industries and their corresponding slaughter. However, to date, no empirical evidence regarding the extent of this loss, nor of the condition of horses involved, exists within Australia. Objectives: To determine the approximate ages, brand type and condition of feet of horses relinquished to an export abattoir in Australia. Method: Data were collected from 340 horses processed at an Australian abattoir from November 2007‐January 2008. Foot abnormalities, injuries and hoof indicators of overgrown and untrimmed hooves were assessed together with a dental inspection. Observations of brand were used to determine horse origin. Results: The dental age of 60% of horses was ≤7 years, and 53% originated from the racing industry (40% Thoroughbred and 13% Standardbred). A total of 81% of the horses had overgrown or untrimmed hooves. Standardbred horses had fewer grass cracks and more injuries to the coronary band than Thoroughbreds, probably due to pacing and trotting activities. Conclusions: Just over half of the horses slaughtered at an Australian abattoir on 3 working days were aged ≤7 years and emanated from the racing industry. Foot problems were common. Potential relevance: Future research should identify means of reducing the number of horses slaughtered and preventative measures for foot disorders.     

Equine laminitis caused by distal displacement of the distal phalanx: 12 cases (1976-1985)

Clinical data from 12 cases of equine laminitis characterized by distal displacement of the distal phalanx (P3) were reviewed. Clinical features of horses that survived the syndrome were compared with the nonsurvivors to obtain prognostic indicators. Animals affected included 8 Quarter Horses, 2 Welsh ponies, 1 Thoroughbred, and 1 Arabian. Eight of the animals were females (67%), 2 were stallions, and 2 were geldings. The mean age of affected animals was 8.6 years (2 to 14 years), and the mean body weight was 442 kg. The survivors weighed less than the nonsurvivors (384 kg vs 473 kg, respectively), suggesting that body weight may be of prognostic value for horses affected with distal displacement of P3. Ten of the 12 animals (83%) were admitted because of a disorder other than laminitis, but subsequently developed laminitis during the treatment period. All affected animals had clinical evidence of endotoxemia and/or sepsis before the onset of laminitis. Cavitation or depression of the dorsal coronary band was detected in all animals and was the most reliable clinical indicator of distal displacement of P3. Five horses had fluid (blood or serum) ooze from their coronary bands and 2 of these sloughed one or more of their hooves. Necropsy findings of the 8 horses that were euthanatized included severe hemorrhagic, congested laminae and complete detachment of P3 from the hoof wall. Histologic examination of affected laminae revealed vascular thrombosis and multifocal areas of hemorrhage and necrosis. Radiography failed to reveal distal displacement of P3 in 8 animals, but the remaining 4 animals had an accentuation of the dorsal proximal hoof wall and cavitation of the coronary band visible on lateral radiographs.     

The effect of hoof trimming on radiographic measurements of the front feet of normal Warmblood horses

The understanding of the normal position of the third phalanx (P3) and the distal sesamoid bone in relation to the size and shape of the hoof capsule in sound horses is helpful in the diagnosis of equine foot lameness. Some measurements on radiographs used to define the position of the pedal bone within the hoof capsule are significantly influenced by hoof trimming and the height of the withers. In this study, the front hooves of 40 Warmblood horses were radiographed twice, eight weeks apart, both before and after their hooves were trimmed by an experienced farrier. Using the software programme Metron PX, 22 parameters on the lateromedial view and 16 parameters on the dorsopalmar view were measured and the effect of hoof trimming and height of the withers were calculated, respectively. Some of the hoof parameters showed mild positive correlation with the height of the withers. In 70% of the horses the left hoof capsule and P3 were significantly larger than the right. Hoof trimming had a remarkable influence on hoof conformation, especially for parameters in the toe region. Of all the measurements that describe the position of the third phalanx (P3) in relation to the hoof capsule, the distances between the distal tip of P3 to the solar surface of the foot, P3 to the tip of the toe and P3 to the point of break-over showed the greatest differences before and after trimming. The database of the present study can be used by farriers and veterinarians as a guideline for routine and corrective shoeing of Warmblood horses.     

Scanning electron microscopy and fungal culture of hoof horn from horses suffering from onychomycosis

Horn samples were taken from the hooves of eight horses with clinical signs of equine onychomycosis in at least one hoof capsule. None of the horses had a documented mycological history. The predominant alterations of the horn capsules were sand cracks, white line disease, brittleness (especially around the nail holes), parakeratosis and bruising. The horn samples were stored in sterile tubes for transportation and transferred onto Sabouraud Dextrose Agar and dermatophyte test agar for mycological examination within 6 h. Fungal cultures were incubated for 30 days at room temperature. Fungal identification was based on colonial morphology and microscopic examination of conidia. Horn samples were also stored at ?80°C until used for scanning electron microscopy (SEM). The fungal culture revealed that the hoof horn from all eight horses was infected with keratinophilic fungi. The keratinopathogenic fungi Trichophyton spp and Scopulariopsis brevicaulis were also detected in six horses. SEM revealed severe alterations of the horn structure in horn samples infected with keratinopathogenic fungi compared to horn samples from a sound hoof. The most evident changes were deterioration of the tubular structure of the horn wall, disruption of the horny layers, superficial lysis of cornified cells and the presence of fungal elements. Samples without dermatophyte or Scopulariopsis infection, in contrast, were similar to healthy hoof horn.     

Platelet-rich Plasma Combined With a Sterile 3D Polylactic Acid Scaffold for Postoperative Management of Complete Hoof Wall Resection for Keratoma in Four Horses

Keratoma is a nonmalignant horse tumor that grows in the space between the horn of the hoof and the distal phalanx. Keratoma causes lameness in the horse, and surgical excision is the treatment of choice. Four horses underwent removal of a keratoma by complete hoof wall resection. The remaining wound was treated with platelet-rich plasma (PRP) combined with a sterile three-dimensional polylactic acid scaffold. The PRP was applied at 3, 6, 9, 12, 15, and 18 days postoperatively. The surgical site was cleaned with gauzes and swabs soaked in Ringer’s lactate solution before applying PRP and the foot bandage. Healthy granulation tissue developed at 6–21 days postoperatively. The hoof wall defect was completely filled with new hoof wall within 6–8 months after surgery. All horses returned to their previous exercise level, and no recurrence of lameness was reported by the owner.     

Short-term habituation of equine limb kinematics to tactile stimulation of the coronet.

A lightweight bracelet that provides tactile stimulation to the horse's pastern and coronet induces a higher flight arc of the hoof. This study addresses the pattern of habituation to these devices. OBJECTIVE: To evaluate short-term habituation to tactile stimulation of the pastern and coronet in trotting horses. METHODS: Tactile stimulation was provided by a lightweight (55 g) device consisting of a strap with seven chains that was attached loosely around the pastern. Reflective markers were fixed to the dorsal hoof wall, the forehead and over the tenth thoracic vertebra of eight sound horses. The horses trotted in hand 10 times at a consistent velocity along a 30 m runway under three conditions applied in random order at two-hour intervals: no stimulators, stimulators on both front hooves or stimulators on both hind hooves. One stride per trial was analyzed to determine peak hoof heights in the swing phase. Sequential trials with stimulators were compared with unstimulated trials using a nested ANCOVA and Bonferronni's post hoc test (P < 0.005). RESULTS: Peak hind hoof height increased significantly for all 10 trials when wearing hind stimulators, whereas peak fore hoof height increased during the first six trials only when wearing fore stimulators. The first trial with stimulators showed the greatest elevation, followed by a rapid decrease over the next three trials and then a more gradual decrease. CONCLUSIONS: If the goal is to facilitate a generalized muscular response, a short burst of tactile stimulation is likely to be most effective, whereas longer periods of stimulation will be more effective for strength training.     

Membrane-coating granules and the intercellular cementing substance (membrane-coating material) in the epidermis in different regions of the equine hoof

This study aimed to carry out a comprehensive morphological examination of the structure and ultrastructure of the membrane-coating granules (MCG) and membrane-coating material (MCM) common to all hoof segments as well as segment-specific features in the MCG and MCM regarding their synthesis, structure and biochemical composition. Tissue samples from the hooves of the left front and right hind limb of 20 adult riding horses were used. Samples were preserved and embedded for histological routine methods as well as for histochemical techniques and tracer techniques for light and electron microscopy. The MCM shows a segment-specific structure, biochemical composition and function, which were demonstrated for the different parts of the hoof. The MCM and its properties are related to the segment-specific horn quality. Besides intercellular structural factors the MCM is of major importance for the structural integrity and the biomechanical properties of the hoof horn. The physiological structure and composition of MCM provides explanation for the existence of clinically well-known sites of predilection for hoof disorders such as the White Line Disease. Alterations of the MCM play a role in dysfunction and diseases of the hoof epidermis; they are particularly involved in the pathogenesis of infectious diseases of the hoof.     

Density and morphologic features of primary epidermal laminae in the feet of three-year-old racing Quarter Horses

OBJECTIVE: To quantify the density of primary epidermal laminae (PELs) around the solar circumference and evaluate the relationship between regional PEL density and hoof capsule morphology in horses. SAMPLE POPULATION: Forefeet from nine 3-year-old Quarter Horse cadavers. PROCEDURES: Data pertaining to gross features of hoof morphology and PEL variables, including number, density, and distribution patterns around the perimeter of the hoof wall and number of bar PELs, were collected. Tissues of the laminar junction were examined histologically. RESULTS: No significant differences were found between left and right forefeet with respect to gross hoof morphologic measurements. Mean +/- SD number of PELs, including those at the bars of the hoof, was 551 +/- 30. Primary epidermal laminar density in the toe was significantly higher, compared with that in the quarter and heel regions, and was higher on the lateral aspect of the foot, compared with the medial aspect. Feet were significantly wider on the lateral aspect of the foot, compared with the medial aspect, as measured across the widest point of the solar surface. Histologic examination revealed atypical laminar morphology at the toe. CONCLUSIONS AND CLINICAL RELEVANCE: Variations were detected in PEL density and morphology around the solar circumference of hooves from 3-year-old racing Quarter Horses. A better understanding of relationships between laminar density, laminar morphology, and gross morphology of the hoof capsule in different populations of horses may aid practitioners in diagnosis and treatment of disease involving the hoof wall in horses.     

A Cross-Sectional Survey of Forelimb Hoof Conformation and the Prevalence of Flat Feet in a Cohort of Thoroughbred Racehorses in New Zealand

Racehorses in New Zealand predominantly train counter clockwise. This training pattern has been associated with between forelimb differences in bone mineral density profile and asymmetrical limb loading after training. At present, there is limited data on the hoof conformation of these racehorses. Distal forelimb and digital hoof conformation data were collected from 75 Thoroughbred racehorses (2–5 years old) from two training yards. Digital conformation was subjectively graded, and multiple hoof measurements were made with a modified tire gauge (sole and sulci depth) and from digital photographs. All the horses were shod by two registered master farriers within a median of 15 (interquartile range [IQR], 1–25) days before measurement. There were few distal limb conformation abnormalities scored. Most (62/75) horses presented with some deviation from normal hoof parameters, with 2 (IQR, 1–3) abnormalities reported per horse. The most common hoof abnormality was uneven sulci, which was identified in 43 horses and 59 affected hooves, followed by higher medial hoof wall height in 38 horses and 53 affected hooves. Many of the linear and hoof angle measurements and their ratios were within the bounds reported within the literature and indicative of a balanced foot. The length and width measurements increased with horse age. The dorsal hoof wall (DHW) length:heel length ratios were consistently less than 3:1, and the absolute difference between toe and heel angle was generally greater than 5°. Between limb hoof variation was identified for a number of the morphologic measurements including frog length and sole length and the ratio of sole width:sole length. Flat feet (lack of concave solar surface) were identified in 21/75 (28%) horses and in 28/150 (19%) forelimb hoofs. More horses had a flat left foot (10/75) than right foot (4/75), but seven horses had both feet classified as being flat. Flat feet had 2.4 (1.1–5.6, P = .036) greater odds of presenting with uneven sulci. These data indicate that uneven sulci depth and flatter hooves with may be a typical presentation of Thoroughbred feet. Asymmetry in measurements between limb may reflect the greater loading of the left forelimb when race training counter clockwise.     

The Forelimb and Hoof Conformation in a Population of Mongolian Horses

This article describes the lower limb and hoof conformation of a population of semi-feral Mongolian horses living on an open tundra/steppe environment. Data were collected from a convenience sample of 120 Mongolian horses used in the 2011 Mongolian Derby. Digital images of the hooves were obtained, and the lower limb conformation was assessed by four veterinarians involved in the screening of the horses offered for the derby. The horses were predominantly geldings (96%, 100/104), approximately 8.6 ± 2.5 years old, and 137 ± 8 cm at the withers. None of the horses were subjected to routine hoof trimming. Based on a 7-point linear score, lower limb conformation was normal, with a trend (>1 linear score deviation) slightly toward carpal valgus, mildly offset cannon (third metacarpal), and valgus at the matacarpophalangeal joint. Hoof measurements were within the norm for horses of this size. Fetlock valgus was associated with a smaller hoof width:length ratio (P = .016). None of the other hoof measurements were significantly associated with abnormal conformation scores. Overall, few conformation abnormalities were observed, and hoof shape and size was within the normal expected range for horses of this size. The hoof conformation in this population of Mongolian horses represented the natural interaction of the hoof with the environment.     

Do hoof cracks represent a superficial hoof-problem?

Fifty-four horses with hoof cracks were referred to the Equine Hospital of the University of Zurich, for treatment. The horses were admitted because of lameness or other symptoms caused by the cracks. Deep or complicated quarter cracks were the most common type of cracks diagnosed. Poor conformation and abnormal hoof shape were the most important causes of hoof crack development, whereas injury to the coronary band was a less frequently encountered cause. Effective treatment of this problem includes corrective shoeing, removing horn from the weight-bearing surface as well as from the crack with a Dremel tool and immobilization of the borders of the crack. However, even with such a therapy, the recurrence rate of hoof cracks was with 20% very high.     

Morphological spectrum of primary epidermal laminae in the forehoof of Thoroughbred horses

Reasons for performing the study: Hoof health is a major concern of horse owners as well as the equine industry. However, many questions remain concerning regional variations of laminar junction and its potential to remodel. Hypothesis: To examine regional variations in the morphology of the laminar junction and thickness of the hoof wall in Thoroughbred horses. Methods: The forefeet of 25 Thoroughbred cadavers were examined. Each hoof was divided into 20 blocks through 4 proximodistal slices (below the coronary band, each 1 cm apart) and 5 circumferential positions (toe, medial and lateral quarters and heels). In each block, 25 central primary epidermal laminae (PEL) were considered. Orientation of each lamina in relation to the hoof wall (LO), degree of bending (IA) and the spaces between the adjacent laminae (LS) were measured. Thickness of the hoof wall and number of branched PEL were also measured. Data were analysed using a split‐block design in ANOVA. Results: There were significant differences between the 2 proximal and 2 distal slices in LO and IA data, but not in LS data. Circumferentially, toe blocks were different from heel and quarters blocks. Lateral and medial heels as well as the quarters were mostly different. The hoof wall was slightly thicker laterally than medially. There were more branched PEL on the lateral side of the left hooves and on the medial side of the right hooves. Conclusions: These data add to the circumstantial evidence supporting the hypothesis of adaptive remodelling in the laminar junction. Results of this study signify the capability of PEL to remodel in response to applied stress to the regions of the hoof. Potential relevance: A deeper understanding of the gross and cellular processes of laminar remodelling may well prove to be complementary to an understanding of their failure in laminitis.     

Effect of prolonged water immersion on equine hoof epidermis in vitro

OBJECTIVE: To evaluate the effect of prolonged water exposure on tissue mass and solutes of outer and inner layers of the stratum medium, sole, frog, and the stratum medium (SMZA) zona alba layer of horses' hooves. SPECIMEN POPULATION: 10 hooves from 10 horses without foot abnormalities. PROCEDURES: Hoof wall tissue specimens were obtained and immersed for 10 days in distilled deionized water. Serial changes in mass were recorded during the immersion period. Subsequently, osmolarity and Na+, K, Cl-, and protein concentrations of the immersion solution were quantified. RESULTS: Fully cornified outer hoof wall, sole, and frog epidermal structures increased in mass, whereas the SMZA lost mass when immersed in water. All hoof structures had a variable loss of crystalloids during immersion, but none of the specimens lost proteins. The frog epidermis was distinct in that total solute lost during immersion could not be ascribed to N+, K+, and Cl-. CONCLUSIONS AND CLINICAL RELEVANCE: Data support a 2-compartment model for the fully cornified outer stratum medium, frog, and sole that permits the exchange of crystalloids, but not proteins, across the cell membrane and infers that topical agents containing proteins cannot benefit the hoof. The unique osmotic behavior of the SMZA relative to other hoof structures suggests the hypothesis that it is composed of transitional epithelial cells. The solutes lost from frog epithelium are interpreted to reflect its unique lipid composition.