Journal of Equine Science最新文献

The endemic situation of respiratory disease caused by equine herpesvirus type-1 (EHV-1) and type-4 (EHV-4) was investigated in a training facility for Thoroughbred yearlings in Japan. Vaccination typically starts in mid-September or early October-only after all yearlings have arrived-leaving those introduced earlier unprotected. To bridge this immunity gap, a revised vaccination program that started earlier was implemented. In 2021-2022 and 2022-2023, yearlings were allocated to three groups according to their introduction dates. Each group received a live EHV-1 vaccine (Equi N Tect ERP, Nisseiken, Tokyo, Japan) as early as possible after arrival, with a second dose administered two months later. Virus-neutralizing titers to EHV-1 rose significantly after the first vaccination in each group as anticipated. Virus type-specific enzyme-linked immunosorbent assays showed that, in 2018-2019 to 2020-2021, pyretic horses (≥38.5°C) infected with EHV-1/4 occurred more frequently between August and September than in other months: 15 cases with EHV-1, 9 cases with EHV-4, and 5 cases with both viruses across the three years. In 2021-2022 and in 2022-2023, only three pyretic horses with EHV-1 infection were confirmed in the corresponding period. The infection rates for EHV-1/4 in the entire population peaked between August and September in 2018-2019 to 2020-2021 (6.8‰-10.9‰). Under the new program, infection rates were much lower, at 2.6‰-3.8‰ in 2021-2022 and 1.2‰-1.7‰ in 2022-2023 (P<0.05). The reduction in these parameters was likely associated with the efficacy of the updated vaccination program.

We evaluated metabolic abnormalities in six neonatal Noma foals (Nos. 54-57, 62, and 66) that died shortly after birth, using laboratory tests, pathological examinations, serum amino acid (AA) analyses, gas chromatography/mass spectrometry (GC/MS), and genetic analyses. Nonspecific clinical symptoms, such as poor suckling and weakness, were commonly observed at birth. Sepsis caused by various bacterial infections was detected in foal Nos. 54, 62, and 66, while a heart malformation was identified in foal No. 57. Laboratory tests showed high aspartate transaminase, lactate dehydrogenase, and creatine kinase levels and low globulin and glucose levels in dead foals. The AA and GC/MS analyses revealed elevated levels of ammonia, orotic acid, and uracil in foal Nos. 54 and 55, while citrulline, arginine, and ornithine levels were low or within normal ranges, suggesting accelerated pyrimidine synthesis and suppressed urea cycle activity. Foal No. 56 had high uric acid and tyrosine levels, hypoglycemia, and liver dysfunction, suggesting glycogen storage disease. In foal No. 57, hypertyrosinemia was suggested because of high phenylalanine and tyrosine levels. We conducted a sequencing analysis of the ornithine transcarbamylase, argininosuccinatelyase, argininosuccinate synthase 1, uridine monophosphate synthase, G6PC1, and G6PT1/SLC37A4 genes associated with metabolic disorders. However, no mutations were detected. In conclusion, although metabolic pathways abnormalities resembling certain hereditary metabolic disorders were observed in neonatal foals that died in Noma horses, no specific mutations were identified in candidate genes, making hereditary disorders less likely.

A 17-year-old Thoroughbred stallion died suddenly after grazing. Necropsy revealed massive hemorrhage in the pericardial sac, suggesting cardiac tamponade. Aortic perforation was observed at the aortic origin, and hemorrhage was observed in and around the epicardium. Superficial observation of the aortic lumen revealed a transverse tear of the aortic wall at the bases of the right semilunar valve and septal semilunar valve. Fibro-osseous changes with calcification were histopathologically observed at the site of the rupture. A nodular goiter was observed in the left thyroid gland. The horse did not engage in strenuous exercise or activity likely to significantly elevate blood pressure during grazing. These results suggest that sudden death was caused by cardiac tamponade due to bone metaplasia and transverse aortic rupture with calcification, potentially triggered by a mild increase in blood pressure associated with normal activity during grazing.

Sixty-one horses were included in this study and classified into three groups based on the severity of colic, assessed by heart rate, oral mucous membrane color, and abdominal distension. The groups consisted of a strangulating colic (SC) group (n=21), a non-strangulating colic (NC) group (n=20), and a control group (n=20) of randomly selected healthy horses without colic. Serum concentrations of tumor necrosis factor α (TNFα), haptoglobin (Hp), nitric oxide (NO), malondialdehyde (MDA), zinc, iron, and copper were measured in all horses. Receiver operating characteristic (ROC) analysis was conducted to assess and compare the diagnostic performance of the analytes in terms of sensitivity, specificity, and area under the curve (AUC). TNFα demonstrated the highest diagnostic accuracy for non-strangulating colic at a cutoff value of >24 mg/l, with 100% sensitivity, 95% specificity, and an AUC of 0.996. For strangulating colic, TNFα also exhibited the best diagnostic performance at a cutoff value of >33 mg/l, achieving 100% sensitivity and specificity with an AUC of 1.00. Haptoglobin followed with a cutoff value of >52 µg/l, showing 95% sensitivity, 75% specificity, and an AUC of 0.898. This study provides new insights into the diagnostic performance of TNFα for detecting non-strangulating colic and TNFα and haptoglobin for diagnosing strangulating intestinal conditions in horses with colic.

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.

Dareshuri horses are the predominant breed in Fars Province, Iran. Although disorders affecting their maxillary cheek teeth and maxillary sinuses are relatively common, limited fundamental data are available on the dimensions and relationships of these structures at different ages. Given the significant anatomical changes in the heads of young horses as they mature, this study aimed to evaluate age-related changes in the position and anatomical relationships of individual maxillary cheek teeth within the rostral and caudal maxillary sinuses (RMS and CMS, respectively), as well as changes in the lengths and heights of individual sinus compartments during their growth. Radiographs were performed on 29 heads of live, healthy horses aged between 4 months and 5 years and were analyzed using the EConsole1 Radiography Viewer software (V.3, 2017, DRTECH Europe GmbH, Schwalbach am Taunus, Germany). Statistical analyses revealed that the only significant change throughout the study was an increase in the length of the CMS (4.075 ± 0.99 cm; SE), which was more significant in horses up to three years old. At less than 1 year old, the only tooth present in the maxillary sinus was M1. At 1-2 years old, M2 was observed entering the maxillary compartments; PM4 entered the RMS at 2-3 years old, and M3 entered the CMS at 3-4 years old. Eventually at 4-5 years old, PM3, M1, and M2 were present in the RMS, and M2 and M3 were present in the CMS. This information should be of value in the diagnosis and treatment of Dareshuri maxillofacial disorders and used as a reference for further anatomical investigations.

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.