Journal of Equine Science最新文献

A male foal developing within a pregnant native Hokkaido mare presented with an abnormal bladder on gestational day 215 and was delivered by inducing parturition. Transabdominal ultrasonography indicated a bladder depth of >13 cm, with a wall-like structure bisecting the bladder. At 42 hr after birth, transnasal endoscopy revealed a cleft hard palate, and the foal was subsequently euthanized. A defect in the palatine process of the maxillary head and a large cyst connected to the bladder, although not continuous with the umbilicus, were identified by autopsy computed tomography and necropsy. The foal was accordingly diagnosed with a cleft median hard palate and urachal dysplasia.

Pre-exercise cooling may prevent exertional heat illness in horses. We hypothesized that pre-exercise cooling before warm-up in a hot environment would not affect performance but would mitigate reductions in body weight and increases in body temperature following exercise. Six trained Thoroughbred horses were studied using a randomized, crossover design with three pre-treatments: 30-min walk on a treadmill at 1.7 m/sec (WALK), 30 min of standing (REST), and a 10-min pre-cooling shower at 26.2 ± 0.8°C (SHOWER). All horses underwent each pre-treatment, followed by a warm-up and main exercise in a hot environment (wet-bulb globe temperature: 32-33°C). After warming up by cantering at 10.0 m/sec for 30 sec, horses exercised on a treadmill with a 6% incline and a speed eliciting exhaustion within 2 min, which was approximately 115% V̇O₂max (relative intensity; 13.5-14.3 m/sec). Run time to exhaustion was recorded, with body weight measured before pre-treatment and after main exercise to calculate weight loss. Heart rate was measured from before pre-treatment to after the main exercise. Plasma lactate concentration (Lac) and pulmonary arterial temperature (a measure of body temperature) were assessed before and after pre-treatment and after the warm-up and main exercise. Weight loss in SHOWER was significantly reduced compared with the other treatments. Pulmonary artery temperatures in WALK after pre-treatment were significantly higher than in the other treatments. No significant differences were observed in heart rate, Lac, or run time. These results suggest that pre-cooling mitigates reductions in body weight and increases in body temperature without affecting performance.

Previous studies have examined the relationship between hair characteristics and temperament traits in various animals. A partial genetic association has been suggested in humans because whorl formation and neurological development occur simultaneously during the fetal period. In the horse industry, anecdotal evidence suggests a link between the forehead whorl position and temperament. In our previous study, the heritability of forehead whorl positioning was h²=0.653, indicating significant genetic contributions in thoroughbreds. Therefore, in this study, we designed a genome-wide association study using 192 Thoroughbred horses to detect candidate genes associated with forehead whorl positioning. The results revealed 11 suggestive markers on chromosomes 2, 14, 15, 19, and 26, although no significant markers were found. Five genes, namely PTTG1, CCNH, RASA1, COX7C, and CLDN1, located near these markers had functions related to skin cell or hair follicle development and temperament. Therefore, these genes may be involved in the positioning of the forehead whorl in Thoroughbreds. The candidate genes identified in this study are expected to contribute to elucidating the genetic factors behind forehead whorl in horses and to help interpret the common process of whorl and temperament development.

The equine large intestine harbors a diverse array of symbiotic microorganisms. Disruptions in the gut microbiota can lead to various diseases in horses. Probiotics offer promising avenues for enhancing equine health and performance. However, commercial formulations lack robust scientific validation. This study aimed to isolate and identify Lactobacillaceae and Bifidobacterium spp. from horse feces to explore their potential as probiotics. Fecal samples from Thoroughbred horses were subjected to isolation procedures. Lactic acid-producing bacteria were isolated using specific media and identified. The results revealed the isolation of Lactobacillaceae strains, including Limosilactobacillus equigenerosi, Ligilactobacillus equi, Ligilactobacillus agilis, and a Bifidobacterium sp., Bifidobacterium pseudolongum. These findings contribute to the understanding of equine gut microbiota and offer insights into potential probiotic candidates.

We examined the differences in serum iron (Fe) concentrations and related variables between summer and winter in Noma horses. Blood samples were collected from 37 clinically normal horses seven consecutive times: September 2018, February 2019, October 2019, February 2020, September 2020, February 2021, and February 2022. Serum Fe concentrations ranged from 74 μg/dl to 316 μg/dl with a median of 176 μg/dl. The concentrations were lower in stallions compared with mares and geldings, tended to be low at 10-14 years of age, and then increased with age. Serum Fe concentrations were repeatedly low in summer and high in winter. Total iron-binding capacity (TIBC), Fe-saturation rate, hemoglobin (Hb), hematocrit (Ht), MCV, MCH, albumin, cholesterol, sodium (Na), potassium (K), chloride (Cl), and calcium (Ca) were lower in summer than in winter. However, creatinine, total protein, inorganic phosphorus, and Mg were higher in summer. The unsaturated iron-binding capacity, RBC count, blood urea nitrogen (BUN), glucose, and AST levels were not significantly different. Serum Fe concentrations were positively correlated with Hb, TIBC, Fe saturation rate, Ht, MCV, MCH, creatinine, albumin, glucose, cholesterol, AST, Na, Cl, and Ca, but negatively correlated with BUN and K. In Noma horses, serum Fe concentrations might be higher than the reference values for horses and consistently decrease in summer in parallel with Hb and MCV. The lowering of the serum Fe concentrations in summer may be due to a combination of the effects of Fe loss from sweating, dermatitis, insect bites, dietary composition, and/or unknown factors.

Computed tomography (CT) offers high-resolution, three-dimensional imaging, making it particularly valuable for assessing complex structures, such as the head, especially when conventional radiography and endoscopy are insufficient for a definitive diagnosis. Herein, we present two cases of equine cranial disorders resulting from congenital malformations. In case 1, which had a dentigerous cyst, CT images confirmed the location of the ectopic tooth within the skull and a detailed fistula tube. In case 2, which had temporohyoid osteoarthropathy, CT examination revealed that the stylohyoid bone was malformed, and the inner ear was presumed to be filled with soft tissue with calcification. The information obtained by CT was invaluable, as it allowed for accurate diagnosis and precise surgical planning.

We investigated the changes in inbreeding levels in Japanese Thoroughbred horses over the past 46 years. Our results show a significant increase in inbreeding over the past 30 years, primarily due to the influence of two sires, Northern Dancer and Sunday Silence. Northern Dancer's bloodline spread gradually through descendants like Northern Taste, leading to a slower increase in the inbreeding coefficient. In contrast, Sunday Silence was directly imported and became a leading sire, causing a rapid increase in his blood proportion and inbreeding coefficient. Our findings suggest that monitoring the trajectories of successful sires and considering historical factors can help predict and control potential inbreeding depression in the future.

Including Internet of Things (IoT) technology in horse-rearing management can potentially mitigate problems such as human resource shortages and time limitations in performing daily behavior monitoring. In this study, a small and inexpensive activity meter used to monitor dogs and cats (PLUS CYCLE^®, JARMeC, Kanagawa, Japan) was used to monitor the daily behavior of horses. A study was performed to examine the suitability of the PLUS CYCLE^® device for monitoring horses and to determine whether it could estimate horse behavior. The device was equipped with an accelerometer and was used to monitor Kiso horses in horse stalls and pastures after installing the devices at specific locations on headcollars and girths. The amount of activity from the accelerometer showed differences among the horses' behavioral types (lying, standing, walking, and feeding) in the stall, suggesting that it functions in horses. In the pasture, the amount of activity was correlated with GPS movement speed. Then, we tried to establish restricted cubic spline regression models to predict the locomotion speed in the pasture based on the amount of activity, but the prediction accuracy was low. This study showed that PLUS CYCLE^® can be used to monitor horse activity amount during the daily management of individual horses. However, to achieve higher precision in monitoring detailed behaviors, additional investigation and data pertaining to the amount of activity for each horse during rearing in different environments are needed.

A two-year-old male Japanese draft horse (known as a "Ban'ei horse") excreted eight cestodes. Based on their morphological features, they were identified as Anoplocephala perfoliata. The partial mitochondrial cytochrome c oxidase subunit 1 (COI) sequences of the worms were nearly identical to A. perfoliata isolated from horses in Europe. The results of phylogenetic analyses of COI revealed that our samples and the European isolates formed the same clade, which was separate from Chinese and Australian isolates. Ban'ei horses were developed by crossbreeding draft horses imported from European countries in the 1900s. Our results suggest that A. perfoliata was transported to Hokkaido with horses from Europe. To our knowledge, this is the first report of A. perfoliata infection in a Japanese draft horse.

We evaluated the clinical efficacy of total intravenous anesthesia (TIVA) with propofol-ketamine-xylazine (PKX) with or without remifentanil for castration in horses. Twenty-four Thoroughbred horses were premedicated with intravenous (IV) xylazine (1.0 mg/kg) and midazolam (0.02 mg/kg) and anesthetized with IV ketamine (1.5 mg/kg) and propofol (1.0 mg/kg). Surgical anesthesia was maintained with constant infusion of propofol (3.0 mg/kg/hr)-ketamine (3.0 mg/kg/hr)-xylazine (1.0 mg/kg/hr) (group PKX: n=8), PKX combined with remifentanil (3.0 µg/kg/hr) (group PKXR3: n=8), or PKX combined with remifentanil (6.0 µg/kg/hr) (group PKXR6: n=8). During anesthesia, none of the horses showed any limb movements, but five, two, and two horses in the PKX, PKXR3, and PKXR6 groups, respectively, showed cremaster muscle contractions. One horse in the PKX group required doubling the PKX infusion rate to continue surgery. Adverse effects of remifentanil (trembling of the nose tip or tongue) were observed in one and three horses in the PKXR3 and PKXR6 groups, respectively. Heart rate and arterial blood pressure were well maintained in all groups. Ventilation was assisted in four, five, and six horses in the PKX, PKXR3, and PKXR6 groups, respectively. Recovery scores in the PKX group were fair in one horse, good in three horses, and excellent in four horses, whereas recovery in all horses in the PKXR3 and PKXR6 groups was judged to be excellent. TIVA with PKX combined with remifentanil 3.0 µg/kg/hr could provide more sufficient anesthetic depth than PKX with fewer clinically significant adverse effects than that with remifentanil 6.0 µg/kg/hr.