Effects of Shortening Breakover at the Toe on Gait Kinematics at the Walk and Trot

Point of breakover, defined as the portion of the hoof last in contact with the ground during the terminal stance phase of a limb, can be influenced by many factors including craniocaudal placement of the shoe. Shortening the point of breakover has been suggested to decrease strain on the deep digital flexor tendon and navicular bone as well as to improve the alignment of the second and third phalanx. The current experiment involved eight sound horses fitted with aluminum plates adhered to their front hooves, which were drilled and tapped to allow additional aluminum plates of various lengths to be attached (the longest plate was placed flush with the toe, while the shortest plate was moved 3.81 cm caudal to the toe). Horses were recorded on video while at the walk and trot over a distance of 70 meters for six repetitions to determine differences in gait kinematics. Results of this study show significant changes in stride kinematics caused by shortening the point of breakover. Retraction of the forelimbs was greatest when breakover was moved 1.27 cm back from the toe (P < .05), and minimum height of the fetlock at the trot was higher on all treatments where the breakover point was moved caudally (P < .05). Some improvements in gait quality were observed when breakover was shortened, although extreme caudal placement of the shoe (negative placement in relation to P3) resulted in a decrease in gait quality as seen by decreased retraction of the forelimb (P < .05) coupled with hoof height occurring earlier in the stride (P < .05).     

The Effect of Training on the Jumping Parameters of Inexperienced Warmblood Horses in Free Jumping

Seven Warmblood horses without sport experience were trained and filmed four times during free jumping, with a 1-month interval between each investigation. Jumping parameters were measured on selected frames by means of video image analysis. Linear and angular parameters describing takeoff, landing, and lifting of limbs above the obstacle were studied. Statistical analysis revealed that the following parameters were affected by training: hind limbs distances at takeoff and landing, lifting of the limbs above the obstacle, and the angle of bascule.     

The Influence of Speed and Height at the Withers on the Kinematics of Sound Horses at the Hand-Led Trot

The influence of speed and height at the withers on some biokinematic stride parameters (linear, temporal and angular) was measured in 15 Spanish Thoroughbreds (Andalusian Purebred) trotted hand-led along a track; analysis was made of the correlation between speed and height at the withers and of some biokinematic parameters of equine locomotion. Both height at the withers and speed were positively and significantly correlated to the linear parameters examined. Temporal parameters did not reveal a significant correlation with the height at the withers. The correlations with the angular parameters were variable, often being significant for both height at withers and speed, although in most cases the coefficient was relatively low, probably owing to the narrow ranges of speed and height at the withers and their low variability. It was concluded that horses at the hand-led trot tend to have low variability in speed during successive trials, although the speed at which they move does have a significant influence on both linear and temporal stride parameters, and also on several angular parameters, while height at the withers has a major effect on linear parameters but less on angular parameters, and does not affect the temporal parameters.     

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.     

Horses Could Perceive Riding Differently Depending on the Way They Express Poor Welfare in the Stable

This study investigated the relationships between four behavioral and postural indicators of a compromised welfare state in loose boxes (stereotypies, aggressive behaviors toward humans, withdrawn posture reflecting unresponsiveness to the environment, and alert posture indicating hypervigilance) and the way horses perceived riding. This perception was inferred using a survey completed by the usual riding instructor and during a standardized riding session (assessment of behaviors and postures, qualitative behavior assessment (QBA) and characterization of the horses’ locomotion using an inertial measurement unit). In accordance with ear and tail positions and the QBA, stereotypic and the most hypervigilant horses in loose boxes seemed to experience a more negative affective state during the riding session compared with nonstereotypic and less hypervigilant animals (P < .02 in all cases). Horses which were aggressive toward humans in loose boxes had higher scores regarding the occurrence of discomfort and defensive behaviors on the survey than nonaggressive horses (P = .03). They also presented higher dorsoventral accelerations at a canter during the riding session (P = .03), requiring the rider to increase his spinal movement (P = .005). These results suggest that aggressive horses may be harder to ride than nonaggressive animals. The expression of unresponsiveness to the environment in loose boxes was related to more reluctance to move forward, as assessed in the survey (P = .006). This study suggests that a compromised welfare state in the stable is related to horses having a more negative perception of riding. This perception could vary depending on the expression of poor welfare.     

2D versus 3D in the kinematic analysis of the horse at the trot

The handled trot of three Lusitano Purebred stallions was analyzed by using 2D and 3D kinematical analysis methods. Using the same capture and analysis system, 2D and 3D data of some linear (stride length, maximal height of the hoof trajectories) and angular (angular range of motion, inclination of bone segments) variables were obtained. A paired Student T-test was performed in order to detect statistically significant differences between data resulting from the two methodologies With respect to the angular variables, there were significant differences in scapula inclination, shoulder angle, cannon inclination and protraction-retraction angle in the forelimb variables, but none of them were statistically different in the hind limb. Differences between the two methods were found in most of the linear variables analyzed.     

Effects of Different Bedding Materials on the Behavior of Horses Housed in Single Stalls

The effects of three different bedding materials (straw, wood shavings, and straw pellets) on the behavior of six warmblood horses (four mares, two of them with foals) housed in single stalls were analyzed. Each material was used for 2 weeks in three consecutive runs. The behavior of the horses was videotaped and analyzed on the first and last 3 days for each bedding alternative in the last of the three runs. The time budgets for the behaviors including standing, eating, lying, occupation with bedding material, and other were generated. Compared with straw pellets and wood shavings, the application of straw bedding led to a significantly higher frequency and longer duration of occupation with bedding material and in turn, shorter fractions of standing and other behaviors. The total duration of lying was significantly longer on straw than on straw pellets. Straw pellets resulted in the least mean recumbency duration per occurrence of this behavior. Because occupation is one of the important functions that bedding material is supposed to fulfill, we concluded that in regard to horse behavior, straw bedding was the best among the three materials analyzed. Further investigations with a more homogeneous group of probands are necessary to verify the observed behavioral reactions.     

Nutrition and Exercise in the Management of Horses and Ponies at High Risk for Laminitis

Obesity, insulin resistance (IR) and hyperinsulinemia are risk factors for laminitis in horses and ponies. Alterations in management, especially diet and physical activity, can be helpful in the management of these risk factors. Caloric restriction, ideally combined with increased physical activity, to promote weight loss and improve insulin sensitivity is indicated for the management of obese animals. Strict control of dietary NSC through the elimination of grains and sweet feeds and by restricted access to NSC-rich pastures is recommended for insulin-resistant animals, regardless of whether they are obese or not. Medical treatment with levothyroxine or metformin may be indicated in obese or insulin-resistant animals that do not respond to conservative management.     

Pharmacokinetics and Effects of Alkalization after Intravenous Administration of Eltenac in Horses

Eltenac (ELT) [4-(2,6-dichlorophenyl)amino-3-thiophene] is a non-steroidal anti-inflammatory drug (NSAID) that was developed for veterinary use in horses and cattle. The pharmacokinetics of ELT was evaluated in horses at 0.5 mg/kg body weight (BW) after single IV injection after 5 days of repeated IV administration and after a single IV injection in horses previously subjected to 250 mg/kg BW of sodium bicarbonate (NaHCO₃) as an alkalization treatment. The aim was to determine whether blood and subsequent urinary alkalization could modify the pharmacokinetics of ELT. Drug quantification was performed with serum and urine using high performance liquid chromatography with UV-visible detection. The results were also integrated with cyclo-oxygenase-inhibition literature data to review the dosage scheme of ELT in horses. After a single intravenous administration, ELT was characterized by rapid distribution (mean t½_λ1 = 0.18 ± 0.07 hour) and a short elimination half-life (mean t½_λ2 = 2.9 ± 0.68 hour). The volume of distribution was small (V_dss = 253.51 ± 47.55 mL/kg), which is likely because of the high percentage of drug protein binding (approximately 97%). The AUC_0-∞ and Cl_B were 6.92 ± 0.84 h*μg/mL and 73.2 ± 10 mL/h/kg, respectively. Repeated administration did not cause either accumulation or modification of the pharmacokinetic profile. The in vitro effective concentrations were maintained for a 6-hour period. The alkalization procedure appeared to accelerate drug elimination, as ELT was quantifiable only for 6 hours; however, the drug clearance was not significantly modified. Thus, the administration of alkaline compounds to accelerate the elimination of ELT is not completely confirmed.     

A Note on the Heritability of Reactivity Assessed at Field Tests for Danish Warmblood Horses

Temperament traits in horses, especially reactivity, are an important trait in relation to human–horse accidents and the welfare of the horses. However, so far, temperament is often not included in many horse breeding programs. Most of the behavioral genetic studies in horses have been based on indirect indications of a sire effect and not on estimations of the heritability of temperament traits. Therefore, the aim of this study was to estimate the heritability of behavior reactions related to reactivity observed in a practical situation, that is, during the evaluation of the conformation of the horse at field tests. The study included 323 3-year-old Warmblood horses. Data were analyzed according to an animal model, and the estimation was based on restricted maximum likelihood. Results showed a low (0.17) heritability of reactivity. Probably because of the limited number of horses in the study, a high standard error was untainted. Nevertheless, results suggested a genetic variation of reactivity when assessed at field tests, but further research is needed before reactivity can be incorporated as a selection criteria into a breeding program.     

Use of Body-Mounted Inertial Sensors to Objectively Evaluate the Response to Perineural Analgesia of the Distal Limb and Intra-articular Analgesia of the Distal Interphalangeal Joint in Horses With Forelimb Lameness

Diagnostic analgesia of the distal interphalangeal (DIP) joint is theoretically helpful to localize the source of pain in the foot to the joint and/or navicular bursa. However, it has been suggested that potential diffusion of local anesthetic agent to nearby distal limb nerves may anesthetize other areas of the foot. The objective of this study was to compare the results of palmar digital (PD) and abaxial sesamoid (AS) nerve blocks to intra-articular anesthesia of the DIP joint in horses with distal forelimb lameness. Palmar digital nerve block (group 1) or PD and AS nerve blocks (group 2) were used to abolish digital pain in 22 horses. The following day lameness was again evaluated in all horses before and 2, 5, and 10 minutes after DIP joint anesthesia. All lameness evaluations were performed objectively with a body-mounted inertial sensor system (Lameness locator; Equinosis LLC, Columbia, MO). In group 1 horses, overall improvement in group lameness was the same after DIP joint block, but only six showed positive response after DIP joint analgesia, five after 2 minutes, and one after 5 minutes. In group 2 horses, overall improvement in lameness was less after DIP joint block, with seven showing a positive response after DIP joint analgesia, one after 2 minutes, four after 5 minutes, and two after 10 minutes. Intra-articular analgesia of the DIP joint and perineural analgesia of the digit result in overlapping but unequal areas of analgesia. In addition, a time-dependent response was observed after DIP joint block with full effect requiring 5–10 minutes.     

Effects of Large Saddle Panels on the Biomechanics of the Equine Back During Rising Trot: Preliminary Results

The saddle panels, directly in contact with the horse's back, are likely an important element to optimize the fitting of the saddle, the comfort of the horse, and subsequently, the pain management in dorsalgic horses. The aim of this study was to better understand the effect of the saddle panels on the horse's back, by evaluating a prototype saddle (comfort panels: CP) compared to a standard saddle (STD). The horse's back movements were measured using inertial measurement units (IMUs) fixed at the levels of thoracic vertebrae T6, T12, T16 (under the saddle) and lumbar vertebrae L2 and L5. The centers of mass (COMs) of the horse and the rider and limb's protraction-retraction angles, pressure between saddle and horse's back, and force on the stirrups were measured using respectively 2D motion capture, pressure mat and force sensors in the stirrup leather. Three horses were trotted at the rising trot (sitting: left diagonal-rider seated; standing: right diagonal-rider standing) by the same rider. To compare saddles, linear mixed-effects regression models were used. The estimated means (SE) were calculated. During sitting phase, pressure in the cranial and middle areas of the saddle significantly increased for CP compared to STD (+0.9 (0.2) kPa and +1.0 (0.1) kPa, respectively) whereas caudal pressure decreased (−1.8 (0.4) kPa). Concurrently, the range of motion of angles T12-T16 and T16-L2 under the saddle significantly increased (+1.8 (0.2)° and +2.3 (0.3)°, respectively). The results showed that modifications of the panels' shape not only affect the pressure distribution but also the kinematics of the thoracic and lumbar regions of the equine back.     

Pharmacokinetics and Effects of Alkalization During Oral and Intravenous Administration of Naproxen in Horses

The use of suitable therapeutic protocols is particularly important when extra-label drugs are used or when physiological parameters are modified, as in the case of the administration of alkaline substances to racehorses. The pharmacokinetics of naproxen (NAP), after both intravenous (iv) and oral administration of 10 mg/kg body weight (BW), was investigated in horses under normal metabolic conditions and in horses whose conditions were modified by the iv administration of 250 mg/kg BW of sodium bicarbonate (NaHCO₃). The hypothesis that blood and consequent urinary alkalization could modify NAP pharmacokinetics was evaluated. Drug quantification was performed on serum and urine using High Performance Liquid Chromatography (HPLC) with ultraviolet-visible detection. Results were also integrated with cycloxygenase (COX)-inhibition published data to suggest an appropriate schedule for NAP dosage in horses. After iv administration, NAP was rapidly distributed (t_1/2α: 0.71 ± 0.43 iv NaHCO₃ and 0.55 ± 0.62 hours No NaHCO₃), whereas its elimination was quite slow (t_1/2β: 6.74 ± 0.41 hours), particularly in iv NaHCO₃ animals (t_1/2β: 8.95 ± 1.37 hours). After oral treatments, NAP was more rapidly absorbed and elimination was slower in iv NaHCO₃ animals (t_1/2λ_z: 17.50 ± 6.66 vs. 7.17 ± 0.91 hours). The oral bioavailability of NAP was approximately 87% and 77% in No NaHCO₃ and iv NaHCO₃, respectively. Urinary excretion of the drug as a parent compound was low. The alkalization procedure did not anticipate the elimination of the acidic drug as expected, but it also influenced the absorption of the drug that was administered orally. The dosage scheme of 10 mg/kg BW iv or orally seems to be appropriate to produce an anti-inflammatory effect for 12 to 24 hours.     

Effects of Bit Chewing on Right Upper Quadrant Intestinal Sound Frequency in Adult Horses

Many therapies have been proposed to prevent and treat postoperative ileus (POI) in horses, but to date none is considered fully effective. Various methods have been considered in the prevention of POI in humans too, and among these, gum chewing is gaining a role, reducing time from surgery to first fecal passage and hospitalization time. The aim of the present study is to produce a method to consistently induce horses at chewing without ingesting food and to evaluate its effects on gut sounds in healthy horses. Animals used in this study were 10 adult horses of both genders. A digital phonendoscope was positioned on the right upper flank. A first registration was started and lasted for five consecutive minutes. Then a snaffle bit with toggles was applied to the horse, and a second registration was obtained in the following 15 minutes. Recording sessions were cut into 5-minute subsessions and blindly assessed by two operators that calculated the number of borborygmi per minute in each session. Application of a bit produced consistent mastication and swallowing in all horses for a period of 20 minutes or more. There was a significantly different increase in short (<3 seconds) gut sounds in the first 5 minutes after application of the bit. In conclusion, mastication of a bit consistently caused an increase in gut sounds on the right upper quadrant. Bit chewing can be easily obtained in horses at rest, and further evaluation as an adjunctive element in the management of POI is warranted.     

Temporary Turnout for Free Exercise in Groups: Effects on the Behavior of Competition Horses Housed in Single Stalls

In Germany, most competition horses are housed in single stalls and free exercise is not permitted in many cases. The reason for not allowing free exercise is mostly the risk of injury. Additionally, opinions exist that the horses’ demand for exercise is fulfilled by training and that the horses’ willingness to perform is negatively influenced by free exercise. In the present study, three turnout practices were investigated with regard to their effect on the behavior of four horses: daily training without free exercise (no turnout), 2-hour turnout (for free exercise) before training, and 2-hour turnout after training. The aim of this study was to determine any differences in the horses’ behavior between the three treatments. The horses’ behavior in the stable was observed through video recordings. The behavior during turnout was observed directly and during training was evaluated by the riders with the aid of a questionnaire. Additionally, the distance covered during turnout was measured by Global Positioning System devices. The behavior within the stall was more restless in the treatment without turnout—which became apparent in significantly more frequent changes between behaviors as compared with the treatments with turnout. The results of Global Positioning System measurement during turnout showed a significantly shorter distance covered when horses were trained before they were turned out compared with turnout before training. If the horses were turned out after training, they also showed less trotting and cantering and more dozing. The horses’ willingness to perform was not significantly different between the three treatments.     

Effects of Intravenous Detomidine on Schirmer Tear Test Results in Clinically Normal Horses

This study was conducted to determine the effects of intravenous detomidine on Schirmer tear test (STT) results in clinically normal horses. Eighteen adult horses were randomly divided into two groups of nine horses each. The treatment group was sedated with intravenous detomidine alone (20 μg/kg), and the control group received only intravenous saline (0.2 mL/100 kg). Schirmer tear test was performed just before intravenous administration of detomidine or saline in treatment and control groups, respectively. Schirmer tear tests were repeated 5, 20, 60, and 120 minutes later. Horses enrolled in this study consisted of nine males and nine females. Breeds were Arabian and Hanoverian, ranging from 3 to 6 years in age. In the treatment group, the pretreatment and subsequent posttreatment mean ± standard deviation values were 17.0 ± 6.9 (0 minutes), 11.8 ± 2.9 (5 minutes), 12.1 ± 2.0 (20 minutes), 12.1 ± 3.1 (60 minutes), and 15.0 ± 2.8 (120 minutes) mm wetting/min. In this group of horses, a significant reduction was observed in STT values at 5, 20, and 60 minutes after treatment with detomidine hydrochloride in comparison to the pretreatment values (analysis of variance with post hoc testing; P₅ = 0.004, P₂₀ = 0.007, P₆₀ = 0.006). There was no significant difference between baseline values and posttreatment values in the control saline group (P ≥ .08). We conclude that intravenous detomidine causes a significant reduction in STT values in clinically normal horses. In horses, practitioners should measure STT values before intravenous administration of detomidine to accurately assess the results.     

Modifying the Height of Horseshoes: Effects of Wedge Shoes,Studs, and Rocker Shoes on the Phalangeal Alignment,Pressure Distribution,and Hoof-Ground Contact During Motion

This study was designed as a comparative study with the intention to accumulate fundamental data on a wide variety of farriery methods. Twenty-five warmblood/crossbred horses, allocated into five groups (n = 5), underwent radiological and kinetic examination of the barefoot hoof, the shod hoof with a standard horseshoe, and finally a modified horseshoe. For radiographic measurements, a special podoblock with embedded reference points and changeable ground surfaces was used. Kinetic examinations were performed by placing one sensor between the shoe and the hoof and the second sensor between the shoe and the ground and then walking the horses on four different ground surfaces. When wedges were applied, the palmar angle increased by approximately 5° on all surfaces. However, this effect was only seen on firm surfaces combined with studs. Using a rocker shoe, the palmar angle increased on a firm surface (0.6 ± 0.3°) and decreased on a deformable surface (0.8 ± 0.3°). No consistent data were noted for the orientation of the proximal and middle phalanx in relation to the palmar angle. Pressure distribution showed wedges and studs to cause an increased pressure load on both the toe and the heels on a firm surface. Rocker shoes led to pressure peaks at the inner section of the toe, and high pressure was exerted on the quarters. In conclusion, all modified horseshoes showed unintended side effects and their influence on biomechanical parameters varied depending on the ground surface.