Abstracts / Journal of Equine Veterinary Science 31 (2011) 562-609 571

[2] De Laat MA, McGowan CM, Sillence MN, Pollitt CC. Equine laminitis:induced by 48 h hyperinsulinaemia in Standardbred horses. EquineVet J 2010;42:129-35.

[3] van Eps A, Collins SN, Pollitt CC. Supporting limb laminitis. Vet ClinNorth Am Equine Pract 2010;26:287-302.

[4] Bouley MH. Treatise on the Organisation of the Foot of the Horse,Comprising the Study of the Structure, Functions and Diseases of ThatOrgan. Paris, 1851.

[5] Visser MB, Pollitt CC. The timeline of lamellar basement membranechanges during equine laminitis development. Equine Vet J 2011;43:471-7.

[6] Milinovich GJ, Klieve AV, Pollitt CC, Trott DJ. Microbial events in thehindgut during carbohydrate-induced equine laminitis. Vet ClinNorth Am Equine Pract 2010;26:79-94.

[7] van Eps AW, Pollitt CC. Equine laminitis model: lamellar histopa-thology 7 days after induction with oligofructose. Equine Vet J 2009;41:735-40.

[8] Van Eps AW, Pollitt CC. Equine laminitis model: cryotherapy reducesthe severity of lesions evaluated 7 days after experimental inductionwith oligofructose. Equine Vet J 2009;41:741-6.

[9] Baldwin GI, Pollitt CC. Progression of venographic changes afterexperimentally induced laminitis. Vet Clin North Am Equine Pract2010;26. 135–.

Foot types in feral horses and their relevance to foot care indomestic horses

Brian HampsonSchool of Veterinary Science, The University of Queensland

Take-Home Message: No single feral-horse foot model exists.Instead, foot characteristics result from interaction with theenvironment inhabited by the horse, the foot morphology beingaffected by distance traveled and by the abrasive qualities andmechanical properties of the substrate under foot. Furthermore,foot pathology is common in feral horses, so it may be inappro-priate to use the feral-horse foot as the benchmark for equine foothealth.Introduction: Conformation of the equine hoof is an importantfactor affecting sporting performance, duration of competitivelife, and risk of injury, including catastrophic musculoskeletalinjury. Foot conformation can be altered by human intervention,such as hoof trimming and the application of podiatric devicessuch as horse shoes. As early as 1899, various models of hooftrimming and “balancing” have been debated, and there is still nouniversal agreement on the optimal model of hoof conformation.To address the supposedly deleterious effects of human inter-vention on the equine hoof, an interest in the “wild-horse hoofmodel” has emerged. The wild or feral horse's foot has beenproposed as a realistic model for all equine feet, despite limiteddocumentation and without detailed empirical investigation. Ithas also been proposed that the free-roaming lifestyle of the wildor feral horse promotes ideal foot health due to the distancestraveled, a varied natural diet, and an absence of the purportedharmful impacts of domestication, including some traditionalfarriery practices.The aim of this study was to describe the range of foot charac-teristics and foot health in several feral horse populations inAustralia. These data could then be used by the equine husbandrycommunity to make more informed decisions on the value of theferal-horse foot model in guiding foot care practices for thedomestic horse.Materials and Methods: The left forefeet (n ¼ 100) werecollected from 20 adult feral horses in each of 5 geographicallyseparate populations in Australia. Populations were selected onthe basis of substrate hardness under foot and the amount oftravel typical for the resident horses. The feet were photographed

and radiographed, and 40 morphometric measurements wereobtained for each foot. Digital images were surveyed by twoexperienced assessors blinded to each other's assessment and tothe population origin. Lamellar samples from 15 feet representing3 populations were investigated histologically for evidence oflamellar pathology.Results: Of the 40 morphometric measurements, 37 differedsignificantly between populations (p < .05). A range of footmorphologies was found that appeared to be associated with thetype of environment the horses inhabited.A total of 377 gross foot abnormalities were identified in 97 feet;in only 3 of the 100 feet examined were no abnormalitiesdetected. Each population had a comparable incidence of footabnormalities, although the type and severity of abnormalityvaried among populations. Of note, there was significantpathology identified in the foot types most closely resembling thepopular “mustang” foot.Of the 3 populations surveyed by histopathology, evidence ofchronic laminitis was common, ranging in incidence from 40% to93%. In the hard-substrate, high-travel population, the incidenceof chronic laminitis was 67%, perhaps indicating a traumaticetiology. Radiographically, ungual cartilage calcification wasfound in 70% of the hard-substrate, moderate-travel population.Together, these findings suggest that concussive changes arecommon with travel on hard substrates.Discussion: This study presents evidence of an effect of theenvironment on the conformation of the feral horse's foot, inparticular substrate hardness and abrasiveness, and distancestraveled.Wewere unable to determinewhether the foot type seenin a particular environment was the result of natural selection fora certain foot type that best suited the environment, or simplya consequence of environmental influences on the foot.Significant pathology was identified in the foot types most closelyresembling the popular “mustang” foot. Advantages have beenproposed for some of the characteristics of the popular “natural”foot, such as a thick hoof wall; a thick, hard sole; and heavily worndistal wall promoting increased sole loading. However, these char-acteristicsmay actually be associatedwith pathology, whichmakesthis model inappropriate if applied to the domestic horse's feet.There is currently no clear evidence to support the use of theextreme feral horse foot as a model for foot care. There were,however, some morphometric parameters (e.g. dorsal hoof wallangle, palmar angle of the distal phalanx) that were consistentamong all feral horses studied which may be important whenconsidering the natural form of the equine foot.Conclusions and Clinical Relevance: There is currently no clearevidence to support the use of the extreme feral horse foot asa model for equine foot care.

Designing strategic support to improve circulation andstimulate hoof capsule growth

Scott Morrison DVMRood and Riddle Equine Hospital, Lexington, KY

Take-Home Message: An effective support system for thecompromised hoof involves identifying the areas of compromiseand then designing a specific strategy that addresses all the needsof that foot. Careful monitoring and adaptation of the system asneeded are also critical for success.Introduction: There are various systems and devices availablethat have the goal of providing “support” to the hoof capsule.Which system to use depends largely on the stage of the disease,as determined by physical examination and radiography.

Abstracts / Journal of Equine Veterinary Science 31 (2011) 562-609572

Specific Objectives: Hoof support systemsmay be designed to doa number of different things, including these:

� alter the angle of the hoof� recruit the frog, sole, and bars into greater weight bearing� unload or reduce weight-bearing in a particular region of thehoof

� ease resistance to movement� aid in shock absorption� increase rigidity of the hoof capsule

Altering any of these components can have either a positive ora negative effect on the compromised regions of the foot.Knowledge of the effects of heel wedges, wall casts, foot casts,shoes, boots, orthotic arch supports, easing breakover, etc. ondifferent regions of the foot is important when designing a hoofsupport plan.Designing for Stage of Disease: In the chronic stage of thedisease, the compromised regions of the hoof are readily evident

radiographically, on physical examination of the foot, and withhoof testers. In the acute phase of the disease, the most compro-mised regions of the foot can be hard to identify until they becomephysically evidentdor the disease enters the chronic phase.Foot conformation can give some indication of how the hoofcapsule is loaded. In my experience, the area of the foot under themost load structurally collapses or fails first. The acute phase oflaminitis insults the lamellar interface; in the normal horse, thecenter of pressure is located in the dorsal region of the foot. Thatmay be the reason why the laminae at the toe are a common areato experience failure. Oftentimes, support systems are used whichshift the center of pressure toward the heels in order to decreasestrain on the laminae at the toe, in the hope of preventing distalphalanx rotation.Monitoring and Adapting: A careful monitoring system andever-changing foot support system may be required to detect themost compromised regions and shift the weight distributionaccordingly. Careful palpation of the coronary band and hoofgrowth patterns can give some indication of a failing region.

Practical – Evaluating Essential Foot Condition Criteria

Hoof capsule flares: gross and microscopic examination of the“normal” hoof wall

Lisa Lancaster PhD, DVMPathobiology and Diagnostic Investigation, Michigan StateUniversity

Take-Home Message: Subtle hoof capsule asymmetries may bean early indicator of internal structural weakness in the foot. Therole of hoof care is important, but other factors under horseowner control may be equally significant.Introduction: Previous research on the hoof has documentedminor asymmetries in normal feet. For example, the medial walltends to be more upright than the lateral wall. However, markedhoof wall flares are abnormal, and farriers generally rasp awayexcessive flare. There is no objective data with which to deter-mine if subtle flares are clinically significant. Research in our labhas looked at different tissues across the hoof wall in normalappearing feet. This presentation is a commentary on the hoofwall from several points of view, including that of a rider, farrier,veterinary student, researcher, and clinician.Materials and Methods: All feet sampled for these studiesappeared healthy, with little to no detectable wall flares or otherdistortion. For the horn tubule study, hoof horn sampleswere takenfrom the solar border of 12 feet, including live and cadaveric feet. Inone forefoot from each horse, samples were cut from the toe andfrom the medial and lateral quarters, and processed for histology.For the laminar study, samples of one forefoot were collectedfrom each of 9 Quarter Horse cadaver feet. Sections were cutparallel to the solar border and histologic slides prepared from thetoe and from medial and lateral hoof wall sections, collected atmid-level hoof wall.Results: In these grossly normal hooves, the laminar and tubularhorn showed regional variations in the 3 sites studied. Tubuledensity was different between themedial and lateral quarters, butsimilar between medial quarter and toe. The laminae in some ofthe racehorse feet had histologic abnormalities. The cortical andtrabecular thickness of the distal phalanx and dermal-bonejunction morphology also showed regional variation.

Discussion: Previously published work from our lab documentedlaminar density variation around the hoof in the normal-lookingfeet of 3-year-old racehorses. During data collection for thatstudy, other tissues in the samples including tubular horn andbone showed regional variation as well. Changes to the innerstructures of the hoof may be a beneficial adaptation to stress, orthey may be early signs of disease.The hoof wall shape and surface features convey something abouthow well the hooves handle their environment. Intuitively, if thehoof capsule of a sound horse looks normal and the horse is notexposed to any laminitis triggers, then one may reasonablyconclude that the feet are not in immediate danger. However,investigation of normal-looking feet in healthy horses reveals thatthere may be more going on below the surface.Bone's response to load is well established. It is not yet know ifhorn tissue in the equine foot has similar adaptive characteristics.However, observation of hoof wall features suggests thatthis specialized epidermal tissue may indeed have some adaptivecapacity, although precise mechanisms have not yet beenreported.Conclusions and Clinical Relevance: Subclinical changes tointernal structures of the equine foot may be present even whenthe hoof capsule appears normal. Some apparently healthy feetmay be developing insidious problems despite good hoof care. Asresearch reveals more about internal hoof structures in healthand disease, equine practitioners are better equipped to discusswith horse owners the value of preventivemaintenance plans andencourage early adoption of interventions that may have a lastingimpact on hoof health.

Practical Program Speakers – The New Normal: DomesticHoof Stages and Syndromes (Panel) Part 1

Practical Program Speakers – The New Normal: DomesticHoof Stages and Syndromes (Panel) Part 2