Worakij Cherdchutham

Background and Aim: Echocardiographic assessment in equines is typically performed on standing animals; however, no studies have evaluated left ventricular function in anesthetized mules using high-dose xylazine. Given the unique pharmacokinetics in mules and their higher anesthetic requirements, this study aimed to assess the effects of acepromazine-xylazine-diazepam-ketamine anesthesia, using the upper limit xylazine dose (1.6 mg/kg), on the left ventricular size and function in mules. Materials and Methods: Six healthy adult mules (18.83 ± 0.75 years; 263.83 ± 39.34 kg) were evaluated using standard two-dimensional and M-mode transthoracic echocardiography. Measurements were obtained before sedation (standing) and 13-min post-anesthetic induction (dorsal recumbency). Each mule received an intravenous injection of acepromazine (0.04 mg/kg), xylazine (1.6 mg/kg), diazepam (0.1 mg/kg), and ketamine (2.2 mg/kg). Key echocardiographic parameters included interventricular septum thickness (interventricular septum in diastole and interventricular septum in systole), left ventricular internal diameters (left ventricular internal diameter in diastole and left ventricular internal diameter in systole [LVIDs]), posterior wall thickness (left ventricular posterior wall in diastole and left ventricular posterior wall in systole), ejection fraction (EF), and fractional shortening (FS). Statistical comparisons were made using paired t-tests and Wilcoxon signed-rank tests (p < 0.05). Results: Heart rate, EF, and FS significantly decreased post-anesthesia (p < 0.01), indicating reduced systolic function. Specifically, LVIDs increased from 4.60 ± 0.65 cm to 6.26 ± 0.48 cm (p < 0.01), while no significant changes were observed in diastolic parameters or respiratory rate. Anesthetic induction was smooth and graded as good to excellent in all cases. Conclusion: High-dose xylazine significantly suppressed systolic cardiac function in anesthetized mules without causing arrhythmias or bradyarrhythmia. The combination protocol was effective and provided safe anesthesia induction, with echocardiography proving feasible under dorsal recumbency. These findings support the cautious use of upper-limit xylazine dosing in mules and suggest echocardiographic monitoring as a valuable tool during anesthesia. Keywords: anesthesia, echocardiography, ejection fraction, fractional shortening, mule, ventricular function, xylazine.

External hoof characteristics, balance, and conformation have been extensively studied in horses; however, mules remain understudied in these aspects. This study evaluated the size, shape, and symmetry of untrimmed and unshod forelimb hooves, compared the symmetry between forelimb hooves and stratified external forelimb hoof measurements based on the body condition score of mules raised in the foothill plains of northern Thailand. The forelimb hooves of 38 mules were photographed and 33 parameters, including angular and linear measurements, were analyzed. A multivariate analysis was used to explore the influence of sex, age, and body condition scores (BCS) on angular, linear, and area parameters. Additionally, one-way ANOVA followed by Tukey’s test was used to compare these parameters across different BCS groups. Despite the absence of shoeing and trimming, these mules exhibited optimal left–right forelimb hoof symmetry, with no significant (p < 0.05) differences in: outer wall length and inner wall length (OWL–IWL: Left 0.11 ± 0.66 cm; Right −0.12 ± 0.43 cm); sole length and sole width (SL^S–SW: Left 1.65 ± 0.76 cm; Right 1.46 ± 0.89 cm); dorsal hoof wall length and heel length (DHWL–HL: Left 4.00 ± 0.80 cm; Right 3.81 ± 0.72 cm); and frog length and frog width (FL–FW: Left 3.88 ± 1.13 cm; Right 3.82 ± 0.18 cm). However, significant (p < 0.05) differences were observed within each body condition score group for forelimb hoof measurements for DHWL, IWL, heel separation (HS), heel bulb distance (HBD), SW, FW, and FL, while sex and age had no significant differences across the study variables. These findings provide valuable insights into mule welfare and management, contributing to understanding of the interplay between overall health and hoof conformation in the study area.

External hoof characteristics, balance, and conformation have been extensively studied in horses; however, mules remain understudied in these aspects. This study evaluated the size, shape, and symmetry of untrimmed and unshod forelimb hooves, compared the symmetry between forelimb hooves and stratified external forelimb hoof measurements based on the body condition score of mules raised in the foothill plains of northern Thailand. The forelimb hooves of 38 mules were photographed and 33 parameters, including angular and linear measurements, were analyzed. Despite the absence of shoeing and trimming, these mules exhibited optimal left-right forelimb hoof symmetry, with no significant (p < 0.05) differences in: outer wall length and inner wall length (OWL - IWL); sole length and sole width (SLS - SW); dorsal hoof wall length and heel length (DHWL - HL); and frog length and frog width (FL - FW). However, significant (p < 0.05) differences were observed within each body condition score group for forelimb hoof measurements for DHWL, IWL, heel separation (HS), heel bulb distance (HBD), SW, FW, and FL. These findings provide valuable insights into mule welfare and management, contributing to understanding of the interplay between overall health and hoof conformation in the study area.

A mare aged 9 years underwent surgical correction of a small intestinal volvulus using a side-to-side, hand-sewn jejunocecal anastomosis. Nine months after the jejunocecostomy, the horse developed colic signs and ultrasonographic examination revealed gas in the large colon in the upper right flank region and several enlarged loops of the small intestine in the lower right flank area. The differential diagnosis was right dorsal displacement of the large colon or small intestinal strangulation. The exploratory celiotomy found epiploic foramen entrapment (EFE) of the jejunocecostomy anastomosis, including parts of the distal jejunum and cecum. Manual reduction of herniation of the bowel in the epiploic foramen (EF) was impossible and the horse was euthanized. The postmortem gross finding revealed the enlarged edematous at the distal end of the jejunum and the initial body portion of the cecum had passed into the EF in the right-to-left (antegrade) direction. To the authors’knowledge, this is the first report of the antegrade epiploic foramen entrapment of a jejunocecostomy bowel part and this may be one of the complications encountered during the long-term survival period of a surgical jejunocecostomy in horses.

Background and Aim: The medical treatment of horses with nephrosplenic entrapment (NSE) of the large colon through administrating phenylephrine and rolling during general anesthesia was effective and less expensive than surgical treatment. However, the selection of drugs for non-surgical treatment of NSE is not a usual method for clinical practice. This study aimed to identify the effects of combined drugs on the cardiac and splenic response in horses and provide information on the NSE of the large colon for clinical application. Materials and Methods: Six healthy Thai native crossbred horses were enrolled in this study. Horses received two protocols with a withdrawal period of 14 days: Group 1 received xylazine (0.5 mg/kg IV) and adrenaline (1 mcg/kg IV), and Group 2 received xylazine (0.5 mg/kg IV) and adrenaline (3 mcg/kg IV). Heart rate (HR), HR variability (HRV), heart dimensions, and the splenic response of six horses were measured before the sedation, 30 and 60 min later, and 65, 70, 75, 80, 90, and 100 min after adrenaline administration. Doppler was used to obtain systolic blood pressure. Results: The HRV low-frequency and high-frequency power ratios decreased after using xylazine. Hypertension was observed after adrenaline administration. In this study, there were only minimal differences in the HR and respiratory rate between groups. However, overall cardiac and splenic parameters were statistically higher in Group 2. Conclusion: This study suggested that xylazine and three micrograms of adrenaline preserved the cardiac autonomic activity balance and were safe to use non-surgical applicability in horses.

Aim: The objective of this study was to assess a new lead system method to improve electrocardiographic measurement in horses. Materials and Methods: Twenty-two horses with an average age of 8.8±0.8 years were enrolled in this study. Horses were divided into two groups, consisting of a control group (n=11) and athlete group (n=11). Electrocardiography (ECG) and echocardiography were performed to provide information on the structure and function of the heart. Two lead systems, base apex and modified precordial leads, were used for the electrocardiogram to assess the cardiac electrophysiological functions. Results: PR interval, QT interval, and QRS-T angle presented significant differences between the control and athlete groups when the modified precordial lead system was used. However, significant variations in the mean electrical axis were found when the base apex lead system was used. The modified precordial lead system resulted in more significant differences in cardiac electrophysiological parameters than the base apex lead system. In the athlete group, echocardiography showed cardiac adaptations such as increases in the left atrial and left ventricular dimensions and stroke volume and a decrease in heart rate in response to exercise and training. The observed differences in cardiac morphology and function between groups suggested differences in health performance in the athlete group. Conclusion: These data provided the first evidence that the modified precordial lead system improved statistical variation in ECG recording and provided the most reliable method for health screening in horses.

The match play patterns in equestrian polo are unique and require specific training programs to ensure sport performance. The effect of commonly used exercise training regimens on the adaptation of skeletal muscle is unclear. The present study investigated the modulating effects of the classic training regimen, comprised of aerobic exercise training with increasing exercise intensities and varying duration combined with match play, on the properties of muscle in polo ponies. Nine healthy adult female polo ponies were subjected to four consecutive subsets of 1 year classic training regimen including basal activity (B), low intensity (L), low to moderate intensity (LM), and low to moderate intensity training plus match play during polo tournament (LMP), respectively. At the end of each training period, gluteus medius muscle samples were taken for determination of muscle fiber type distribution, muscle metabolic capacity, capillary density, and lipid and glycogen content. The expression profile of metabolic genes including succinate dehydrogenase (SDH), phosphofructokinase (PFK), glycogen phosphorylase (PYG), and glycogen synthase (GYS) were also measured. Among all exercise training subsets, only LMP exercise period caused an increase in the number of oxidative fibers (type IIa), along with increases in properties related to oxidative metabolism including high capillary density, intramuscular lipid content, and expression of SDH and PYG genes, with a corresponding decrease in the number of type IIx muscle fibers. The combination of low to moderate and high intensity training in LMP are only sufficient to induce changes in oxidative characteristics. As the first scientific evidence providing such insight about the classic polo training regimen, the data forms a basis for further consideration in training program design.

To evaluate a novel tendon biopsy technique for use in the horse and to assess the effect of different exercise levels on the healing process of minimally damaged superficial digital flexor tendons (SDFT), 24 Dutch Warmblood foals were randomly divided into 3 equally sized groups one week after birth. One group was box rested, one group got box rest with additional enforced exercise, and one group got free pasture exercise. Biopsies from the peripheral region of the SDFT were taken at age 2 months using a new micro-biopsy technique. At age 5 months the foals were euthanized and samples from the biopsy site and a control site were harvested. Collagen fibrillar index (CFI, the total amount of collagen as a percentage of the measured area), mass-average diameter (MAvD, mean of the diameter versus area distribution) and collagen fibrillar diameter frequency (the distribution of collagen fibril sizes expressed as a percentage of the number of collagen fibrils) were calculated. The CFI, MAvD values were significantly lower in the wound samples. It is concluded that the biopsy technique may be a useful tool for research applications. The absence of exercise-induced effects on the collagen fibril population in the wound samples suggests that the first phase of the process of tendon healing in immature equine SDFT’s sustaining a minor surgically-induced wound, is not exercise-dependent. However, findings may be different in mature horses sustaining accidental trauma. A novel technique to take biopsies from immature equine flexor tendons was developed and used to evaluate the effect of various levels of exercise on the development of the collagen fibril diameter distribution in the resulting wounds. The technique appeared to be minimally invasive, but complication rate was deemed too high for clinical use. There was no effect of exercise on mass average diameter of collagen fibrils, suggesting that the repair process, at least in its initial stage, is exercise-independent. ³ Present address: Dr. C. K. Becker, Bogen- straBe 58, D-22869 Schenefeld, Germany