The Effect That Induced Rider Asymmetry Has on Equine Locomotion and the Range of Motion of the Thoracolumbar Spine When Ridden in Rising Trot

There is a paucity of evidence on the effect that rider asymmetry has on equine locomotion. The aim of this study was to evaluate the effect of rider asymmetry on equine locomotion by using a novel approach to induce rider asymmetry. Ten nonlame horses were recruited for this study. Joint center markers were used to capture 2D kinematics (Quintic Biomechanics) of the horse and rider and horses were equipped with seven inertial sensors positioned at the fifth (T5) and eighteenth (T18) thoracic vertebrae, third lumbar (L3) vertebra, tubera sacrale (TS), and left and right tubera coxae. Rider asymmetry was induced by shortening the ventral aspect of one stirrup by 5 cm. Kinematic data were compared between conditions using a mixed model with the horse defined as a random factor and stirrup condition (symmetrical stirrups and asymmetrical stirrups) and direction (inside and outside) defined as fixed factors. Data from riders where the right stirrup was shortened were mirrored to reflect a left stirrup being shortened. To determine differences between conditions, a significance of P ≤ .05 was set. On the rein with the shortened stirrup on the outside: an increase in lateral bending range of motion (ROM) at T5 (P = .003), L3 (P = .04), and TS (P = .02), an increase in mediolateral displacement at T5 (P = .04), T18 (P = .04), and L3 (0.03) were found. An increase in maximum fetlock extension was apparent for both the front (P = .01) and hind limb (P = .04) on the contralateral side to the shortened stirrup; for the asymmetrical stirrup condition on the rein with the shortened stirrup on the inside: an increase in flexion-extension ROM at T5 (P = .03) and L3 (P = .04), axial rotation at T5 (P = .05), and lateral bending of T5 (P = .03), L3 (P = .04), and TS (P = .02). Asymmetric rider position appears to have an effect on the kinematics of the thoracolumbar spine. These findings warrant further investigation to understand the long-term impact this may have on equine locomotor health.     

Effects of Steel and Aluminum Shoes on Forelimb Kinematics in Stock-Type Horses as Measured at the Trot

To meet the needs of sport horses, horseshoes of various styles and materials have been implemented to enhance performance. Steel shoes are commonly used for their affordability and longevity; however, the use of aluminum horseshoes is being adopted to satisfy the various requirements of certain equestrian activities. Owing to the importance of the allure of movement in many aspects of competitive riding, the lightweight nature of aluminum horseshoes has been recognized to accentuate foreleg action. By performing a repeated-measures crossover study on nine healthy stock-type horses, the effects of these two horseshoe types on forelimb action were analyzed at the trot using two-dimensional kinematics. Horses were trotted in hand for three repetitions over a distance of 50.1 meters on days 4, 18, 32, and 46 postshoeing for two 6-week shoeing cycles. Video footage was collected and analyzed using gait analysis software (EquineTec) for each repetition. The measured stride length, fetlock extension, elbow and knee range of motion, and minimum and maximum elbow angle remained constant between treatments. However, there was a significant treatment effect on minimum carpal angle and maximum hoof height, with aluminum shoes having a larger minimum carpal angle than those in steel shoes (P < .05) and a lower maximum hoof height (P < .05). An overall 3-degree difference in minimum carpal angle and approximate 2.5-cm difference in maximum hoof height was observed between treatments. This finding is of particular importance to performance horse disciplines for which a lesser degree of knee action is desirable.     

Preliminary Results: The Advantages of Low-Density Lipoproteins for the Cryopreservation of Equine Semen

The aim of this study was to determine the best concentration of low-density lipoproteins (LDL) in a semen extender to improve the percentage of motile spermatozoa in equine sperm after freezing and thawing in comparison with standard extenders. Ten extenders were compared: 1 with 2% egg yolk (EY), 8 with different concentrations of LDL (0.25%, 0.50%, 0.75%, 1%, 2%, 3%, 4%, and 5%), and INRA 96; all of the extenders contained 2.5% glycerol. Fourteen ejaculates were collected from four different stallions. The first dilution was made with equal parts at +37°C, centrifuged (600 × g/10 min), and resuspended in the corresponding extenders to obtain a final concentration of 100 × 10⁶ spermatozoa/ml. The resulting mixture was cooled to 4°C over 1 hour, packed into four 0.5-ml straws, and left for a further 30 minutes at +4°C. Finally, the straws were frozen in nitrogen vapors 4 cm over liquid nitrogen for 10 minutes before being immersed in liquid nitrogen at −196°C and stored. Two straws per extender and per ejaculate were thawed in a water bath at +37°C for 30 seconds. The contents of each straw were recovered into a cryotube and placed in a water bath at +37°C for 10 minutes before being examined with an image analyzer. The best post-thaw motility results were obtained with the extenders made with 0.5%, 2%, and 3% LDL and with the control extender made with egg yolk; no significant difference was observed between these extenders. The last two straws were thawed to perform four sperm function tests. The hypo-osmotic test was used to assess the integrity of the plasma membrane; the 2% and 3% LDL treatments were the most suitable and were comparable to that with whole egg yolk for protecting stallion sperm during cryopreservation (32.3%, 32.4%, and 31.3%, respectively). The Pisum sativum agglutinin-fluorescein isothiocyanate test was used to verify the integrity of the acrosomes; the best results were obtained with the 0.5%, 0.75%, and 3% LDL and INRA96 extenders; no significant differences were observed among the 85.8%, 85.0%, 84.7%, and 84.8% extenders. The acridine orange test was used to assess DNA integrity; there were no significant differences among the various extenders: the DNA was preserved in 98% of the spermatozoa. Finally, spermatozoal morphology was examined using Spermac stain; 78% of the spermatozoa did not present any anomalies in the 0.25% and 2% LDL extenders. In conclusion, the 2% LDL extender gave the best post-thaw percentage of motile spermatozoa. The results of the sperm function test were also superior for this extender.     

Characterization of Equine Phospholipase C Zeta: A Review and Preliminary Results on Expression Defects in Subfertile Stallions

In all mammalian species studied thus far, fertilization results in a series of intracellular Ca²⁺ ([Ca²⁺]_i) increases, referred to as oscillations, responsible for driving oocyte activation and embryonic development. Current evidence supports the notion that sperm-borne phospholipase C zeta (PLCZ) is responsible for the initiation of these [Ca²⁺]_i oscillations. Although this appears to be a highly conserved mechanism for oocyte activation, differences in PLCZ sequence, activity, and expression do exist among different species. Herein, we summarize the information supporting PLCZ as the oocyte-activating factor in mammals and present our current knowledge regarding the characterization of this protein in the horse. The equine sequence yielded a protein of high relative [Ca²⁺]_i-releasing activity. Equine PLCZ was expressed over the head region overlying the acrosome, equatorial segment, connecting piece between the head and midpiece, and on the principal piece of the flagellum of stallion sperm. Equine PLCZ expressed both over the head and tail sperm regions was catalytically active, with the latter representing a characteristic unique to the horse. We also present preliminary data in subfertile stallions displaying PLCZ expression defects, although further research is required to establish a clear association between these defects and fertility problems in the horse. In summary, the information presented raises the questions of whether equine PLCZ could play diverse roles in sperm physiology and/or become a marker for the evaluation of stallion fertility, both of which are worthy of further investigation.     

Tramadol Effects on Lameness Score After Inhibition of P-GP by Ivermectin Administration in Horses: Preliminary Results

This study aimed to evaluate the effects and lameness degree in horses administered tramadol after the P-glycoprotein (P-gp) enteric inhibitor ivermectin. Six horses were randomly distributed into three groups, which received two different doses of tramadol by a nasogastric tube: 1 mg/kg (tramadol group 1(GT1)), 4 mg/kg (tramadol group 4 (GT4)), and tramadol 1 mg/kg combined with ivermectin 0.2 mg/kg PO (ivermectin tramadol group (GT1 + Ive)), with one-week washout interval. Heart rate (HR), respiratory rate (RR), intestinal motility, body temperature, and the degree of lameness were evaluated for 360 minutes. The blood gas parameters were evaluated at 0, 60 minutes, and 120 minutes. There were no differences in HR and the degree of lameness. Hypomotility occurred in GT1 and GT4 only at the end of the evaluation period, and RR increased in all groups. We conclude that inhibition of enteric P-gp by ivermectin did not alter the effects of tramadol, suggesting that tramadol is not a substrate for P-gp. However, future studies should be conducted to assess the interaction between P-gp inhibitors on the pharmacokinetics of tramadol.     

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.