Hoof and distal limb surface temperature in the normal pony under constant and changing ambient temperatures

The Effect of Horse Shoeing with Egg Bar Shoes and Shoes with Wedge Pads on the Results of Thermal Imaging of the Equine Distal Limb

Simple Summary

Thermography is a non-invasive and contact-free imaging method that measures temperature on the surface of the body and determines temperature distribution across the examined surface. The aim of this study was to determine the effect of horse shoeing with egg bar shoes and shoes with wedge pads on hoof temperature measured by thermography. The authors decided to use egg bar shoes and shoes with wedge pads as they are commonly used in the treatment of navicular syndrome in horses. This study was conducted on 16 client-owned warmblood horses. The horses were directed for magnetic resonance imaging (MRI) according to unilateral front limb lameness, specifically associated with the hoof. For thermographic analysis, we took into consideration only one limb that was not lame and that showed no radiological changes. After the application of egg bar shoes, the temperature decreased on the palmar surface of the hoof. After shoeing with wedge pads, the temperature decreased in the dorsal and palmar views. Thermography, despite its great usefulness, is only an indirect method of assessing the blood supply in a given area, so we cannot uncritically conclude about the harmfulness of shoeing.

Abstract

The presented manuscript provides reference for practitioners when measuring normal hoof temperature, as well as controlling the temperature after shoeing with particular shoes. The aim of this study was to determine the effect of horse shoeing with egg bar shoes and shoes with wedge pads on hoof temperature measured by thermography. This was a prospective study conducted on 16 horses. The horses were divided into two groups: horses from group 1 were shod with egg bar shoes, while horses from group 2 were shod with shoes with wedge pads. Thermographic examination was performed below the metacarpophalangeal joint before and one month after shoeing. After shoeing with egg bar shoes, there was a decrease in the median of the minimal temperature in the palmar view. After shoeing with wedge pads, thermography revealed decreased hoof temperature in the dorsal and palmar views. Horse shoes may have a negative impact on the blood circulation and metabolism within the distal part of the limb; however, our study found this only to a minor extent.

Microdamage in the equine superficial digital flexor tendon

The forelimb superficial digital flexor tendon (SDFT) is an energy-storing tendon that is highly susceptible to injury during activities such as galloping and jumping, such that it is one of the most commonly reported causes of lameness in the performance horse. This review outlines the biomechanical and biothermal effects of strain on the SDFT and how these contribute to the accumulation of microdamage. The effect of age-related alterations on strain response and subsequent injury risk is also considered. Given that tendon is a slowly healing and poorly regenerative tissue, prompt detection of early stages of pathology in vivo and timely adaptations to training protocols are likely to have a greater outcome than advances in treatment. Early screening tools and detection protocols could subsequently be of benefit in identifying subclinical signs of degeneration during the training programme. This provides an opportunity for preventative strategies to be implemented to minimise incidences of SDFT injury and reduce recovery periods in elite performance horses. Therefore, this review will focus on the modalities available to implement early screening and prevention protocols as opposed to methods to diagnose and treat injuries.

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.

Exercise-induced changes in skin temperature and blood parameters in horses

The aim of the study was to assess the effects of training on haematological and biochemical blood parameters as well as on the changes in body surface temperature in horses. In order to identify the predictive value of surface temperature measurements as a marker of animal's performance, their correlations with blood parameters were investigated. The study was carried out on nine horses divided into two groups: routinely ridden and never ridden. Infrared thermography was used to assess surface temperature changes before (BT) and just after training (JAT) on a treadmill. Seven regions of interest (ROIs) located on the neck, shoulder, elbow, back, chest, gluteus and quarter were analysed. The blood samples were taken BT, JAT and 30 min after training (30AT). Haematological parameters including white blood cells, lymphocytes (LYMs), monocytes (MONOs), granulocytes (GRAs), eosinophils (EOSs), haematocrit (HCT) and platelets (PLTs) as well as biochemical parameters such as glucose (GLUC), urea, Na+, K+ and Ca2+, and creatine phosphokinase (CPK) were analysed. Our results indicated a significant increase in surface temperature JAT (p=0.043) in the neck, shoulder, elbow, gluteus and quarter in routinely ridden horses. Significant changes in EOS (p=0.046) and HCT (p=0.043) in the case of the never-ridden and routinely ridden group, respectively, were found between the times of blood collection. In addition, there was a significant effect of the horse group and the time of blood collection on the CPK activity (p=0.025 to p=0.045) and urea concentrations (p=0.027 to p=0.045). In the routinely ridden horses, there were significant correlations between the changes in MONO (ρ=0.40), GRA (ρ=-0.40), PLT (ρ=-0.77), HCT (ρ=-0.36), GLUC (ρ=0.56) and urea (ρ=0.56) and the total ROI temperature changes. Moreover, significant correlations between the changes in MONO (ρ=-0.86), EOS (ρ=-0.65), GLUC (ρ=0.85), urea (ρ=0.85), Na+ (ρ=0.59) and K+ (ρ=-0.85) and the total ROI temperature changes were found in never-ridden horses. Different changes in body surface temperature and blood parameters in routinely ridden and never-ridden horses could be associated with different conditioning and performance. A significantly higher surface temperature in routinely ridden horses, as well as the dynamics of changes in HCT, CPK and urea after training indicate better performance of these horses. Significant correlations between MONO, GLUC, and urea and a total ROI surface temperature as well as a negative correlation between MONO and the total ROI temperature in never-ridden horses indicated poor performance.

Effect of two months whole body vibration on hoof growth rate in the horse: A pilot study

Hoof problems are commonly seen in veterinary practice and manipulation of hoof growth rate can be practical and beneficial for that matter. The purpose of this research was to evaluate the effect of whole body vibration (WBV) on hoof growth rate of front feet in the horse. The study was an experimental, single subject, repeated measure design, with all horses serving as control and treatment. Ten horses were subject to WBV, 30 min, twice daily, five days a week, for 60 days in addition to their regular exercise routine. Hoof growth was measured from the reference hairline down to a horizontal groove in both front feet at 30-day (monthly) intervals starting 30 days before the start of treatment (WBV) up until 60 days post cessation of the treatment (WBV). The data analysis was carried out, by applying several paired t-tests to the mean 30-day hoof growth before, during, and after treatment (WBV). A significant mean increase in hoof growth was seen after 30 days WBV (p < 0.001) as well as after 60 days WBV (p = 0.001) with the increase occurring mainly during the first 30 days of WBV. No prolonged effect on hoof growth rate was seen after cessation of WBV. These results indicate that whole body vibration can be used as a non-invasive, safe and non labor-intensive therapeutic modality to accelerate hoof growth in the horse.

Changes in Temperature of the Equine Skin Surface Under Boots after Exercise

Equine distal limbs have evolved to have long tendons coupled with strong, tendinous muscles positioned proximally on the leg, thus enabling the horse to achieve highly efficient locomotion. The tradeoff is, that the tendons are left unprotected and prone to injuries, therefore they are often protected by various boots and bandages, which may insulate the limbs and cause hyperthermia in the underlying tendons. The actual mechanism for the degeneration of tendons is currently unknown, but damaging temperature increases due to hysteresis in hardworking horses has been suggested as a possible cause. This study compared the skin temperature of the palmar/ plantar metacarpal/metatarsal regions of the limbs after exercise with various types of boots and bandages - primarily tendon boots, leather boots and fleece bandages. Several horses were measured before and after the completion of a standard exercise test. The boots or bandages were removed immediately after the exercise and the temperature was measured at 3 separate places with A Testo 850i infrared thermometer. The differences in temperature increases between the various kinds of boots were compared. The results showed a significantly higher average temperature increase in horses wearing boots or bandages compared to the bare limb. The fleece bandages seemed to accumulate the highest amount of heat, followed by the tendon boots.

Avaliação do efeito trombogênico da perfusão regional intravenosa com gentamicina em equinos

A extremidade distal dos equinos é frequentemente afetada por processos sépticos de difícil tratamento. A perfusão regional intravenosa de antimicrobianos é uma opção de tratamento para esses processos, pois aumenta a concentração do fármaco no local mediante pequenas doses. Entretanto, apesar de ser muito utilizada recentemente, ainda apresenta várias questões. O objetivo deste trabalho foi avaliar as possíveis complicações da técnica, com o uso da gentamicina na dose de 2,2mg/kg na veia cefálica de equinos. Utilizaram-se 15 equinos hígidos divididos aleatoriamente em três grupos de cinco animais: grupo somente com torniquete (GT), grupo que recebeu 40mL de solução fisiológica (GSF) e grupo que recebeu gentamicina na dose de 2,2mg/kg, acrescida de solução fisiológica até completar o volume de 40mL (GSG). O membro perfundido foi avaliado por termografia e ultrassonografia duplex em cores ao longo do tempo. Os dados foram submetidos à análise pelos testes de Tukey e de Dunnett, e o nível de significância adotado foi de P<0,05. Todos os grupos apresentaram escore trombótico zero, e não houve diferença significativa entre os grupos quanto ao diâmetro médio da veia e da temperatura dos membros. A antibiose intravenosa regional com 2,2mg/kg de gentamicina, em dose única, não acarretou o desenvolvimento de trombose na veia cefálica.

Effect of a bandage or tendon boot on skin temperature of the metacarpus at rest and after exercise in horses

OBJECTIVE

To determine the skin temperature of the metacarpus in horses associated with the use of bandages and tendon boots, compared with the bare limb, at rest and after 20 minutes of lunging.

ANIMALS

10 adult horses.

PROCEDURES

Skin temperature on the bare metacarpus of both forelimbs was measured at rest and after lunging. Subsequently, a bandage was applied to the left metacarpus and a tendon boot to the right metacarpus and skin temperature was measured at rest and after lunging. Skin temperature was measured with fixed sensors and thermographically.

RESULTS

Mean ± SD skin temperatures of the bare metacarpi were 14.1 ± 2.4°C (left) and 14.1 ± 3.4°C (right) at rest, and 14.4 ± 1.8°C (left) and 13.6 ± 2.6°C (right) after exercise. Skin temperatures under the bandage were 15.3 ± 1.6°C at rest and 24.8 ± 3.6°C after exercise. Skin temperatures under the tendon boot were 15.3 ± 2.6°C at rest and 20.6 ± 2.9°C after exercise. Skin temperatures under the bandage and tendon boot were significantly higher after exercise than at rest. Skin temperatures at rest were not significantly different with a bare limb, bandage, or tendon boot.

CONCLUSIONS AND CLINICAL RELEVANCE

Skin temperature of the metacarpus in horses increased significantly during exercise but not at rest when a bandage or tendon boot was used. The authors speculate that both a bandage and a tendon boot accelerate the warm up phase of exercise. Further research should focus on the effects of warm up and maximum exercise on the temperature of other anatomic structures such as tendons.

The influence of temperature and age on the T1 relaxation time of the equine distal limb

The extent of fat suppression using short tau inversion recovery (STIR) imaging is variable between horses. Our aim was to determine if patient's age and/or hoof temperature have an influence on the T(1) relaxation time of bone marrow in the equine distal limb, thereby affecting the suppression of fat signal. Magnetic resonance imaging was conducted on standing horses and cadaver samples using a low-field magnet (0.27 T). The hoof temperature was measured at the lateral side of the coronary band. A modified inversion recovery fast spin-echo (IR-FSE) sequence was used to measure the signal intensity for a range of inversion times (TIs) at six different regions of interest (ROI): (1) distal aspect of the proximal phalanx, (2) proximal aspect of the middle phalanx, (3) distal aspect of the middle phalanx, (4) navicular bone, (5) proximal aspect of the distal phalanx, and (6) distal aspect of the distal phalanx. The T(1) of the bone marrow in the equine distal limb was calculated from the results and was found to increase by 3.13 ± 0.08 (SE) ms/°C. There was no significant effect of age (2-16 years) but the T(1) values measured from the limbs of young (< 1 year) animals were considerably longer (32.6 ± 1.7 (SE) ms). Similar effects of temperature and age were found for all measured ROIs but there were significant differences in the mean values of T(1) , ranging from +7.7 (distal aspect of the distal phalanx) to -13.2 ms (distal aspect of the proximal phalanx).

The effect of cooling on the contractility of equine digital small lamellar arteries: modulating role of the endothelium

The equine hoof displays thermoregulatory functions, and the blood vessels lying under the hoof wall are temperature sensitive. The aim of this study was to investigate the effect of cooling on the contractile responses to α-adrenoceptor and 5-HT receptor stimulation in equine small lamellar arteries using wire myography. The role of the endothelium in the response mediated by 5-HT was also evaluated. Moderate cooling caused a reduction of the contraction induced by depolarizing Krebs solution (DKS, containing 118 mm KCl) and the maximal contraction caused by UK-14304 (α(2)-adrenoceptor agonist). The potency of methoxamine (α(1)-adrenoceptor agonist) was reduced by cooling [pD(2) (-log EC(50)) at 22°C, 5.7 (5.5-6.0) versus 30°C, 5.9 (5.7-6.1)]; however, the efficacy was maintained. The contractions evoked by sumatripan and α-methyl 5-HT (5-HT receptor agonists) were not modified by moderate cooling. In contrast, a cooling-enhanced contraction was observed in response to 5-HT [maximum response (E(max)) at 22°C, 213.2 ± 13% DKS versus 30°C, 179.9 ± 11% DKS]. Furthermore, this effect was more evident in endothelium-denuded lamellar arteries (E(max) at 22°C, 270.2 ± 26% DKS versus 30°C, 172.2 ± 20% DKS), suggesting a potential modulating role of the endothelium. The L-NAME/ibuprofen-resistant relaxation in response to carbachol was reduced by cooling in small lamellar arteries precontracted with 5-HT but not phenylephrine. Therefore, a moderate reduction of temperature modulates the reactivity of small lamellar arteries by enhancing the 5-HT-mediated contraction, but inhibits the α-adrenoceptor-mediated response. Furthermore, the endothelium of these blood vessels may play an important role in preventing excessive vasoconstriction in response to 5-HT and maintaining digital blood flow in cool environmental temperatures.

Acute laminitis: medical and supportive therapy

Acute laminitis is a serious complication of many primary conditions in the horse. This article summarizes the most appropriate approach to management of the horse with acute laminitis, based on current information.

Therapeutic hypothermia (cryotherapy) to prevent and treat acute laminitis

Digital hypothermia successfully reduces the severity of experimentally induced laminitis. Continuous-distal limb cryotherapy may be a useful technique in clinical cases that are at risk of developing laminitis. This article examines the effects of hypothermia on tissue as well as the rationale, and suggested protocols for the usage of distal limb cryotherapy in the prevention and treatment of laminitis.

Equine laminitis model: cryotherapy reduces the severity of lesions evaluated seven days after induction with oligofructose

REASONS FOR PERFORMING STUDY

A previous preliminary study demonstrated the potential of distal limb cryotherapy (DLC) for preventing laminitis. Clinically, DLC must be effective for periods longer than 48 h and the preventive effect must extend beyond its discontinuation.

OBJECTIVES

To evaluate the effect of DLC, applied during the developmental phase of induced laminitis, on the severity of clinical laminitis and lamellar histopathology 7 days after dosing.

METHODS

Eighteen normal Standardbred horses were divided into 3 groups of 6. Continuous cryotherapy was applied for 72 h to the distal limbs of the first group. The second and third groups were administered laminitis inducing doses of oligofructose and 72 h of cryotherapy applied (immediately after dosing) to the second group. After clinical assessment all horses were subjected to euthanasia 7 days after dosing and hoof lamellar tissues were harvested and analysed.

RESULTS

In the laminitis induced horses clinical lameness and laminitis histopathology was significantly reduced in horses that underwent 72 h of DLC compared with untreated controls. Cryotherapy alone produced no significant lameness or other ill effect.

CONCLUSIONS

Continuous, medium- to long-term (72 h) cryotherapy applied to the distal limbs of horses safely and effectively ameliorates the clinical signs and pathology of acute laminitis.

POTENTIAL RELEVANCE

Pre-emptive distal limb cryotherapy is a practical method of ameliorating laminitis in ill horses at risk of developing the disease.

The effects of vasoactive amines found in the equine hindgut on digital blood flow in the normal horse

REASONS FOR PERFORMING STUDY

Disturbances of digital blood flow are thought to be fundamental to the pathophysiology of acute laminitis. However, factors linking the initiating events in the equine hindgut with these disturbances in the foot remain to be determined.

HYPOTHESIS

Amine compounds, formed by bacteria in the equine hindgut, have digital vasoconstrictor effects in vivo.

METHODS

Tryptamine (1.6 microg/kg/min) and phenylethylamine (2.13 microg/kg/min) were infused i.v. into standing nonsedated horses. Digital blood flow was measured by Doppler ultrasound and foot surface temperature was monitored. Plasma 5-hydroxytryptamine (5-HT) concentrations were measured by HPLC.

RESULTS

Tryptamine and phenylethylamine infusions had no effect on systemic arterial blood pressure or heart rate, but caused significant decreases in digital arterial blood flow (mean +/- s.e. 29.2 +/- 8.5 and 18.4 +/- 6.8%, respectively). Both amines also caused decreases in dorsal hoof wall temperature (0.6 +/- 0.1 and 0.5 +/- 0.1 degrees C for tryptamine and phenylethylamine, respectively) and concomitant increases in plasma 5-HT concentration.

CONCLUSIONS

Tryptamine and phenylethylamine caused reduction of digital blood flow, effects which may have been mediated, in part, via displacement of 5-HT from platelets.

POTENTIAL RELEVANCE

Amine compounds occurring in the equine hindgut, if released into the circulation following carbohydrate overload, could contribute to selective digital vasoconstriction. Further work in ponies and horses, with naturally occurring laminitis, is necessary to determine whether amines represent a therapeutic target in this disease.

Measuring the Heat Loss in Horses in Different Seasons by Infrared Thermography

It is necessary to consider breed and cold tolerance in the housing and caring of horses. This study demonstrates differences in heat loss between horse types at low temperatures and examines rate of loss in different types during different seasons. Eighteen horses participated. Groups by type were light (L), warmblood (W), coldblood (C), and pony (P). A camera filmed thermographic images at 15 degrees C, 2 degrees C (all types), -8 degrees C (L, W, C), and -12 degrees C (P). The study calculated loss from the neck, trunk, and inner surfaces of front and hind legs. Loss was similar in all types at 15 degrees C. L, W, and C dissipated more heat at 2 degrees C than at 15 degrees C (p < .001) and from neck and trunk at -8 degrees C than at 2 degrees C (p < .05). P dissipated heat similarly at 2 degrees C and -12 degrees C. At 2 degrees C, loss was less from neck and trunk in C and P compared with L (p < .05). At -8 degrees C, loss in L and W was greater than in C (p < .05).

Current research and theories on the pathogenesis of acute laminitis in the horse

A large number of studies have been undertaken in recent years aimed at furthering our understanding of the complex mechanisms underlying the common and debilitating condition of acute laminitis in the horse. Many of these studies have either reinforced or cast doubt on previously held theories on the pathogenesis of this disease, while others have suggested new mechanisms which may play a key role in its development. This review seeks to put the current hypotheses into the context of this recent body of evidence. While a unifying theory may not yet seem to be achievable, this review demonstrates that most of the current theories are not mutually exclusive. Studies utilising in vitro and in vivo models of the disease, particularly addressing the areas of inflammation, haemodynamic disturbances and enzyme activation in the hoof, as well as the preceding events occurring in the hindgut, have helped to explain many clinical observations of the disease and may possibly lead to more effective therapies and means of prevention in the future.

Evaluation of hoof wall surface temperature as an index of digital vascular perfusion during the prodromal and acute phases of carbohydrate-induced laminitis in horses

OBJECTIVE

To evaluate the use of hoof wall surface temperature (HWST) as an indirect indicator of digital perfusion and to describe HWST patterns during the prodromal and acute phases of carbohydrate-induced laminitis in horses.

ANIMALS

30 adult horses without foot abnormalities.

PROCEDURES

Three experiments were performed. In the first, HWST was measured in 2 groups of horses acclimatized to hot (n = 6), or cold (6) environments and exposed to cold (15 C) ambient temperature. In the second experiment, HWST were measured in both forefeet of 6 horses before and after application of a tourniquet to 1 forefoot to induce vascular occlusion. In the third experiment, HWST were recorded in 12 horses before and during the prodromal and acute phases of carbohydrate-induced laminitis.

RESULTS

Mean HWST of hot-acclimatized cold-challenged horses was significantly less than that of cold-acclimatized cold-challenged horses at all times. Transient episodes of high HWST were observed during prolonged cold-induced vasoconstriction. Hoof wall surface temperature significantly decreased during arterial occlusion and increased during reperfusion. Digital hypothermia was observed during the prodromal phase of carbohydrate-induced laminitis.

CONCLUSIONS AND CLINICAL RELEVANCE

Determination of HWST is a valid technique to evaluate digital perfusion under appropriate controlled conditions in horses. Digital hypothermia detected during the prodromal phase of laminitis is consistent with decreased digital vascular perfusion or metabolic activity. If administered to horses during the prodromal phase, agents that enhance digital perfusion may prevent development of laminitis.

Exploring the possible functions of equine hoof wall tubules

Possible functions of equine hoof wall tubules were investigated in this study. Hydration tests were conducted on blocks of hoof wall tissue in order to test the hypothesis that hollow tubules facilitate the conduction of water vapour distally. Although water loss or gain was inhibited through the outer wall surface, the increase in surface area provided by medullary spaces was ineffective in facilitating hydration through the face with exposed tubule ends. Rather, hollow tubules appear to allow for a higher dehydration rate through their exposed ends. Analysis of medullary space indicates that the presence of these voids does not provide either a significant increase in flexural stiffness, or a decrease in thermal conductivity. These findings suggest that nonmechanical roles of hoof wall tubules are unlikely and, therefore, the hollow nature of tubules may be a reflection of manufacturing constraints in producing keratin fibres at steep angles to the coronary border.

Diagnostic techniques for identification and documentation of tendon and ligament injuries

Conventional clinical examination remains of medical and economic value for diagnosis of soft tissue injuries in the equine athlete. This procedure requires concentration and rigor to establish the diagnosis, and, if possible, some experience to better evaluate the prognosis. None of the new imaging techniques can replace the physical examination, but each may provide additional information. These sophisticated methods are bringing considerable progress in the knowledge of locomotor injuries in the horse and a tremendous improvement in our ability to diagnose precisely lamenesses and limitations of performance.