OBJECTIVE To determine whether exercise on alternative terrain affects the development of the digital cushion and bony structures of the bovine foot. ANIMALS 20 weaned bull calves. PROCEDURES Two-month-old calves were randomly allocated to an exercise or control group. For 4 months, the control group was maintained in grass paddocks, and the exercise group was maintained in a 0.8-km lane with a mixed terrain of dirt, stones (0.32- to 0.95-cm pea gravel and 5-cm crusher run), and grass. Water and food for the exercise group were located at opposite ends of the lane; calves were fed twice daily, which ensured they walked 3.2 km/d. Pedometers were applied to all calves to measure distance traveled. All calves were slaughtered at 6 months of age. The right forefeet and hind feet were harvested for MRI and CT evaluation. RESULTS Control calves walked a mean of 1.1 km daily, whereas the exercised calves walked a mean of 3.2 km daily. Mean digital cushion volume and surface area were 25,335 mm3 and 15,647 mm2, respectively, for the exercised calves and 17,026 mm3 and 12,745 mm2, respectively, for the control calves. When weight was controlled, mean digital cushion volume and surface area for the exercise group were increased by 37.10% and 18.25%, respectively, from those for the control group. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that exercise on alternative terrain increased the volume and surface area of the digital cushion of the feet of dairy calves, which should make them less susceptible to lameness.

Objective: To compare navicular bone marrow lesion (BML) conspicuity in the feet of horses as determined via 2 fat-suppressed MRI techniques, including standard short tau inversion recovery (STIR) and inversion recovery gradient echo (IRGE). Sample: Feet (n = 150) of horses with lameness referable to the distal portion of the digit. Procedures: STIR and IRGE sequences were obtained prospectively in all feet with a standing low-field equine MRI system. Presence of a BML was ascertained by identification of a characteristic combination of marrow alterations in T1-weighted, T2*-weighted, T2-weighted, and STIR images. Signal-to-noise and contrast-to-noise ratios were calculated on STIR and IRGE sequences in 56 feet with a navicular BML. Results: Signal-to-noise and contrast-to-noise ratios of both sequences correlated linearly (r = 0.87 and r = 0.92, respectively) but were significantly higher for STIR images (mean ± SD, 22.6 ± 12.7 and 12.4 ± 11.4, respectively), compared with IRGE images (13.7 ± 8.0 and 5.9 ± 7.2, respectively). Conclusions and Clinical Relevance: Results suggested that the IRGE sequence revealed BMLs significantly less conspicuously, compared with the standard STIR sequence. The 2 techniques cannot be used interchangeably, and IRGE is therefore not recommended as the sole fat-suppressed sequence for routine equine standing MRI protocols.

Objective—To compare effects of 4 types of stimulation devices attached to the hind feet on hoof flight, joint angles, and net joint powers of trotting horses. Animals—8 clinically normal horses. Procedures—Horses were evaluated under 5 conditions in random order: no stimulators, loose straps (10 g), lightweight tactile stimulators (55 g), limb weights (700 g), and limb weights with tactile stimulators (700 g). Reflective markers on the hind limbs were tracked during the swing phase of 6 trotting trials performed at consistent speed to determine peak hoof heights and flexion angles of the hip, stifle, tarsal, and metatarsophalangeal joints. Inverse dynamic analysis was used to calculate net joint energies. Comparisons among stimulators were made. Results—Peak hoof height was lowest for no stimulators (mean ± SD, 5.42 ± 1.38 cm) and loose straps (6.72 ± 2.19 cm), intermediate for tactile stimulators (14.13 ± 7.33 cm) and limb weights (16.86 ± 15.93 cm), and highest for limb weights plus tactile stimulators (24.35 ± 13.06 cm). Compared with no stimulators, net tarsal energy generation increased for tactile stimulators, limb weights, and limb weights plus tactile stimulators, but only the weighted conditions increased net energy generation across the hip joint. Conclusions and Clinical Relevance—The type and weight of foot stimulators affected the magnitude of the kinematic and kinetic responses and the joints affected. These findings suggest that different types of foot stimulators are appropriate for rehabilitation of specific hind limb gait deficits, such as toe dragging and a short stride.

OBJECTIVE To examine the equine foot for the presence of sensory receptors including Merkel cells and small lamellated Pacinian-like corpuscles (SLPCs). SAMPLE Forefeet obtained from 7 horses following euthanasia for reasons other than foot disease. PROCEDURES Disarticulated feet were cut into either sagittal sections or cross sections and immersed in neutral-buffered 4% formalin. Following fixation, samples were obtained from the midline of the dorsal aspect of the hoof wall and from the frog (cuneus ungulae) between the apex and central sulcus. The formalin-fixed, paraffin-embedded hoof wall and frog sections were routinely processed for peroxidase immunohistochemistry and stained with H&E, Alcian blue, and Masson trichrome stains for histologic evaluation. RESULTS Sensory myelinated nerves and specific receptors were identified within the epidermal and dermal tissues of the equine foot including the hoof wall laminae, coronet, and frog. Merkel cells were identified with specific antisera to villin, cytokeratin 20, and protein gene product 9.5 in coronet epidermis and hoof wall. These cells were interspersed among basilar keratinocytes within the frog, coronary epidermis, and secondary epidermal laminae. The SLPCs were present within the superficial dermis associated with the central ridge of the frog (ie, frog stay). Numerous S100 protein and protein gene product 9.5 immunoreactive sensory nerves in close proximity to these receptors were present throughout the dermal tissues within both the frog and hoof wall. CONCLUSIONS AND CLINICAL RELEVANCE The presence of Merkel cells and SLPCs that are known to detect tactile and vibrational stimuli, respectively, further defined the diverse range of neural elements within the equine foot.

Objective-To determine cellular changes associated with secondary epidermal laminae (SEL) in forefeet and hind feet of ponies with insulin-induced laminitis. Animals-8 ponies. Procedures-Laminitis was induced in 4 ponies by IV administration of insulin and glucose; 4 control ponies received saline (0.9% NaCl) solution IV. Laminar tissue samples obtained from the dorsal aspects of the hooves were histologically evaluated. Primary epidermal lamina (PEL) length and width and SEL length, width, and angle were determined. Numbers of epidermal cell nuclei per micrometer and per total length of SEL and numbers of apoptotic and proliferative cells in axial, middle, and abaxial laminar regions were determined. Results-SEL in treatment group ponies were significantly longer, were significantly narrower, and had a smaller angle relative to PEL in all laminar regions versus control ponies. In treatment group ponies, the number of epidermal cell nuclei per SEL was typically higher and the number of cells per micrometer of SEL was lower in laminar regions, apoptotic cell numbers were higher in abaxial and middle regions in forefeet and hind feet, and proliferating cell numbers were higher in axial laminar regions in forefeet and all laminar regions in hind feet, versus control ponies. Conclusions and Clinical Relevance-Results indicated SEL elongation, narrowing, and alteration in orientation developed in all feet of ponies with insulin-induced laminitis. This was primarily attributable to cell stretching that developed at the same time as an accelerated cell death-proliferation cycle; differences in cell cycle responses among laminar regions between forefeet and hind feet may have been attributable to differences in load bearing.

Objective: To establish and validate an objective method of radiographic diagnosis of anatomic changes in laminitic forefeet of donkeys on the basis of data from a comprehensive series of radiographic measurements. Animals: 5 donkeys with and 85 without forelimb laminitis for baseline data determination; a cohort of 44 donkeys with and 18 without forelimb laminitis was used for validation analyses. Procedures: For each donkey, lateromedial radiographic views of 1 weight-bearing forelimb were obtained; images from 11 laminitic and 2 nonlaminitic donkeys were excluded (motion artifact) from baseline data determination. Data from an a priori selection of 19 measurements of anatomic features of laminitic and nonlaminitic donkey feet were analyzed by use of a novel application of multivariate statistical techniques. The resultant diagnostic models were validated in a blinded manner with data from the separate cohort of laminitic and nonlaminitic donkeys. Results: Data were modeled, and robust statistical rules were established for the diagnosis of anatomic changes within laminitic donkey forefeet. Component 1 scores ≤ −3.5 were indicative of extreme anatomic change, and scores from −2.0 to 0.0 denoted modest change. Nonlaminitic donkeys with a score from 0.5 to 1.0 should be considered as at risk for laminitis. Conclusions and Clinical Relevance: Results indicated that the radiographic procedures evaluated can be used for the identification, assessment, and monitoring of anatomic changes associated with laminitis. Screening assessments by use of this method may enable early detection of mild anatomic change and identification of at-risk donkeys.

Objective—To investigate the density of the primary epidermal lamellae (PEL) around the solar circumference of the forefeet of near-term fetal feral and nonferal (ie, domesticated) horses. Sample—Left forefeet from near-term Australian feral (n = 14) and domesticated (4) horse fetuses. Procedures—Near-term feral horse fetuses were obtained from culled mares within 10 minutes of death; fetuses that had died in utero 2 weeks prior to anticipated birth date and were delivered from live Thoroughbred mares were also obtained. Following disarticulation at the carpus, the left forefoot of each fetus was frozen during dissection and data collection. In a standard section of each hoof, the stratum internum PEL density was calculated at the midline center (12 o'clock) and the medial and lateral break-over points (11 and 1 o'clock), toe quarters (10 and 2 o'clock), and quarters (4 and 6 o'clock). Values for matching lateral and medial zones were averaged and expressed as 1 density. Density differences at the 4 locations between the feral and domesticated horse feet were assessed by use of imaging software analysis. Results—In fetal domesticated horse feet, PEL density did not differ among the 4 locations. In fetal feral horse feet, PEL density differed significantly among locations, with a pattern of gradual reduction from the dorsal to the palmar aspect of the foot. The PEL density distribution differed significantly between fetal domesticated and feral horse feet. Conclusions and Clinical Relevance—Results indicated that PEL density distribution differs between fetal feral and domesticated horse feet, suggestive of an adaptation of feral horses to environment challenges.

After removal of 1 metatarsal pad and formation of a granulation tissue bed, free segmental 6- X 8-mm grafts from digital pads were sutured into recessed same-size recipient sites in the granulation tissue. In 5 dogs, the grafted area had been denervated by excision of a segment of the tibial nerve at the level of the tarsus. The grafted area was not denervated in the remaining 5 dogs. In both groups of dogs, the grafts placed around the periphery of the wound healed, blocked ingrowth of delicate epithelium from the surrounding skin, and provided a tough keratinized epithelium that covered the wound's center. As healing progressed, the grafts coalesced as the wounds contracted. Weight bearing resulted in graft expansion to provide functional weight-bearing tissue. Dogs of the denervated group had clinical and histologic evidence of collateral sensory reinnervation of the denervated area. However, with the exception of 1 dog, results of sensory nerve action potential tests indicated that reinnervation may not have been by way of regeneration across the excisional gap in the nerve. Evaluation of reinnervation of the tibial autonomous zone in 2 additional dogs revealed clinical evidence that collateral reinnervation began between 19 and 28 days after nerve excision and progressed proximad to distad. Results of sensory nerve action potential tests indicated that reinnervation may not have been via regeneration across the excision site. Results of fluorescent tracer studies did not have positive findings regarding the route of collateral reinnervation. Segmental paw pad grafts can be used effectively to provide weight-bearing tissue on a dog's limb. With local nerve damage on the distal portion of the limb, collateral innervation can grow into the area to reinnervate tissues, including pad grafts.

Two types of sensory receptors were located in the equine foot, using anatomic techniques. Histologic examination of stained hoof sections revealed lamellated corpuscles in the hoof dermis, which had many of the morphologic characteristics of Pacinian corpuscles. These sensory receptors were restricted to the palmar (caudal) aspects of the solar dermis of the heel. A second type of receptor was detected by use of immunocytochemistry, indicating apparently naked nerve endings containing the neuropeptide calcitonin gene-related peptide-like immunoreactivity in skin, solar dermal tubules, and the digital cushion. This peptide is an example of a sensory neurotransmitter contained in dorsal root ganglion cells and is believed to exist only in unmyelinated sensory nerve fibers. These 2 morphologic structures may be used for detection of sensory stimuli, such as pressure (or vibratory senses) and pain, respectively, in horses during various locomotory gaits.