Journal of Equine Science最新文献

Dental age estimation in horses is very important in the context of quality healthcare, breeding programs, and welfare management. However, information on the most suitable dental age estimation methods for Nigerian local horses is not available in the literature. We evaluated and compared dental age estimates based on six dental age estimation methods with known chronological ages of Nigerian local horses to establish the most accurate techniques for this population. A cross-sectional study of 180 Nigerian local horses was conducted in Ibadan, Nigeria. Six dental age estimation methods (eruption patterns, grinding surface, cups, dental stars, angle of incidence, and Galvayne's groove) were applied by three blinded veterinarians to independent groups of 30 horses each. Data analyses included t-tests, Pearson correlation coefficients, and Bland-Altman plots. None of the estimated ages based on the estimation methods showed significant differences from the chronological age (P>0.05). The angle of incidence method showed perfect alignment with chronological age (11.9 ± 5.4 years) and the highest correlation (r=0.988, P<0.001). The eruption pattern method showed the smallest variation in estimates (range of agreement: 2.3 years), while Galvayne's groove exhibited the largest variation (range of agreement: 9.9 years). Strong correlations were also observed for the grinding surface shape and dental stars assessments (both r=0.955, P<0.001). The angle of incidence method showed the highest correlation with chronological age for Nigerian local horses (between 5 and 30 years, r=0.988), though it provides age estimates in broad categories rather than precise years. The eruption pattern method demonstrated the highest precision for younger horses (between 3 and 5 years), with the smallest range of agreement (2.3 years). Veterinarians and horse owners in Nigeria should prioritize these methods for reliable age determination, while exercising caution when using Galvayne's groove method due to its higher variability.

A subset of single-nucleotide polymorphisms (SNPs) are associated with various phenotypes, including diseases, coat colour, and athletic performance, and are widely used in medical and veterinary fields. In this study, we developed a novel method for direct SNP genotyping from whole blood without DNA extraction. Thoroughbred blood samples were diluted 100-fold with Milli-Q water and analysed using real-time polymerase chain reaction (PCR) with hydrolysis probes. Specificity and sensitivity were improved by increasing the annealing temperature and number of PCR cycles. Genotyping results for SNPs in MSTN and LCORL showed complete concordance with conventional real-time PCR using the extracted DNA. This method is simple, low-cost, highly versatile, and applicable to other genetic targets, such as CDH13 and MAOA.

The Miyako horse is one of the eight Japanese native horse breeds and is scarce in terms of population size. Japanese native horses are believed to be descended from Mongolian horses and represent a precious lineage that has preserved its traits for over a thousand years in Japan. Genetic analysis of the endangered Miyako horse is useful for preserving its original phenotypic traits. This study analysed the genetic variation in trait-related genes for coat colour (ASIP, MC1R), body composition (MSTN, LCORL), gait (DMRT3), and temperament (HTR1A) in 46 extant Miyako horses. In addition, because numerous Miyako horses have vertical stripes on their backs, we analysed the genes associated with the dorsal stripe (TBX3), a characteristic of primitive horses. Until now, Miyako horses were believed to comprise only bays and chestnuts, but genetic analysis revealed that two individuals were black. No mutations were detected in MSTN g.66619237delinsSINE, LCORL, or DMRT3, whereas polymorphisms were observed in MSTN g.66608679T>C and HTR1A. Furthermore, TBX3 analysis suggested that the patterns observed on the backs of Miyako horses could be genetically classified as dorsal stripes. Using the information on trait-related genes obtained in this study as a foundation for breeding plans is expected to contribute significantly to the production of individuals that maintain the phenotype traditionally preserved in Miyako horses. Furthermore, genetic confirmation of the Miyako horse dorsal stripe pattern could provide significant clues regarding similar markings in other Japanese native horses.

Pathological hoof-wall cavities unrelated to nailing (so called "Gidoh" in Japan) often occur in the feet of horses. In 2001, in facilities managed by the Japan Racing Association (JRA), Gidoh was found to occur most frequently in the toe of the fore-hoof, with no gender predilection, and was more prevalent in older horses. However, it remains unclear whether this trend has continued in recent years, which pathological type of Gidoh predominates, and whether there are differences in prevalence among seasons. Therefore, in spring (April) and autumn (October) of 2020, we surveyed all racehorses stabled at the JRA training centers (TCs) regarding age, gender, lesion location, disease type, lesion severity, and prevalence of Gidoh. We reaffirmed that this foot problem occurred most frequently in horses aged 6 years or older, with no gender predilection. It occurred preferentially in the toe of the fore-hoof. White-line-fissure-type Gidoh was predominant, and about 80% of cases were mild. The prevalence was significantly lower in October than in April (P=0.02). The recent trend in the prevalence of Gidoh at the JRA TCs was similar to that in the 2001 survey, suggesting that routine hoof management at the JRA facilities has been stable for the past 19 years. In addition, the new finding of a lack of a difference in prevalence between the two JRA TCs indicated that hoof-care techniques at the two TCs have become more closely aligned over the past 19 years.

Anti-Müllerian hormone (AMH) is a stable endocrine marker of the ovarian reserve in mares and correlates positively with the follicular population. This study aimed to examine plasma AMH concentration dynamics during ovum pick-up (OPU) and evaluate their relationship with follicular responses in purebred and crossbred Hokkaido native pony mares. Ten mares underwent 26 OPU sessions, with blood collected at multiple time points ranging from 1 hr before OPU to 4 weeks after OPU. Plasma AMH concentrations were measured using a chemiluminescence immunoassay. AMH concentrations declined significantly (P<0.01) at 24 hr (1.94 ng/ml), 72 hr (1.48 ng/ml), 1 week (nadir, 1.27 ng/ml), and 2 weeks (1.54 ng/ml) post-OPU compared with the pre-OPU levels (2.25 ng/ml). The levels started to increase gradually after 2 weeks. Pre-OPU AMH positively correlated with the number of aspirated follicles (r=0.48, P<0.05). This study is the first to identify a significant reduction in plasma AMH levels after OPU, followed by recovery within 3 weeks in pure and crossbred Hokkaido native ponies.

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.