A 17-year-old Thoroughbred stallion died suddenly after grazing. Necropsy revealedmassive hemorrhage in the pericardial sac, suggesting cardiac tamponade. Aorticperforation was observed at the aortic origin, and hemorrhage was observed in and aroundthe epicardium. Superficial observation of the aortic lumen revealed a transverse tear ofthe 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 ofthe rupture. A nodular goiter was observed in the left thyroid gland. The horse did notengage in strenuous exercise or activity likely to significantly elevate blood pressureduring grazing. These results suggest that sudden death was caused by cardiac tamponadedue to bone metaplasia and transverse aortic rupture with calcification, potentiallytriggered by a mild increase in blood pressure associated with normal activity duringgrazing.

Osteoarthritis (OA) is a prevalent condition in horses, leading to changes in trabecular bone structure and radiographic texture. Although fractal dimension (FD) and lacunarity have been applied to quantify these changes in humans, their application in horses remains nascent. This study evaluated the use of FD, bone area fraction (BA/TA), and lacunarity in quantifying trabecular bone differences in the proximal phalanx (P1) in 50 radiographic examinations of equine metacarpophalangeal joints with varying OA degrees. In the dorsopalmar view, regions of interest were defined in the trabecular bone of the proximal epiphysis, medial and lateral to the sagittal groove of P1. Lower BA/TA values were observed medially in horses with severe OA (P=0.003). No significant differences in FD and lacunarity were found across OA degrees (P>0.1). FD, BA/TA, and lacunarity were not effective in identifying radiographic texture changes in the P1 trabecular bone in horses with different metacarpophalangeal OA degrees.

Individual identification and paternity testing are important for avoiding inbreeding inthe management of small populations of wild and domestic animals. In horse racingindustries, they are extremely important for identifying and registering individuals anddoping control to ensure fair competition. In this study, we constructed an individualidentification panel for horses by using insertion and deletion (INDEL) markers. The panelincluded 39 INDEL markers selected from a whole-genome INDEL database. Genotyping of 89Thoroughbreds showed polymorphisms with minor allele frequencies (MAFs) of 0.180–0.489 inall markers. The total probability of exclusion for paternity testing, power ofdiscrimination, and probability of identity were 0.9994271269, >0.9999999999, and0.9999999987, respectively. The panel was applied to 13 trios (sires, dams, and foals),and no contradictions were observed in genetic inheritance among the trios. When thispanel was applied to the trios (52 trios) containing false fathers, an average of 7.3markers excluded parentage relationships. In addition, genomic DNA extracted from theurine of six horses was partially genotyped for 39 markers, and 6–28 markers weresuccessfully genotyped. The newly constructed panel has two advantages: a low markermutation rate compared with short tandem repeats and a genotyping procedure that is assimple as short tandem repeat typing compared with single nucleotide variant typing. Thispanel can be applied for individual identification, paternity determination, andurine-sample identification in Thoroughbred horses.

Gene doping, which is prohibited in horseracing and equestrian sports, can be performed by introducing exogenous genes, known as transgenes, into the bodies of postnatal animals. To detect exogenous genes, a method utilizing quantitative polymerase chain reaction (qPCR) with a hydrolysis probe was developed to test whole blood and plasma samples, thereby protecting the fairness of competition and the rights of stakeholders in horseracing and equestrian sports. Therefore, we aimed to develop sample storage methods suitable for A and B samples in gene doping tests using blood. For sample A, sufficient qPCR detection was demonstrated after refrigeration for 1 to 2 weeks post collection. For sample B, the following procedures were confirmed to be suitable for storage: 1) centrifugation after sample receipt, 2) frozen storage, 3) natural thawing at room temperature, and 4) centrifugation without mixing blood cell components. Our results indicated that long-term cryopreservation yielded good plasma components from frozen blood samples even though it destroyed blood cells, indicating its applicability to the gene doping test using sample B, which can be stored for later use. Sample storage procedures are as important as detection methods in doping tests. Therefore, the series of procedures that we evaluated in this study will contribute to the efficient performance of gene doping tests through qPCR using blood samples.

ABSTRACTThe Taishu horse in Tsushima is one of eight Japanese native breeds. The breed is on theverge of extinction due to a rapid decrease in numbers since the 1960s owing tomotorization in Japan. In this study, we aimed to confirm the pedigree information of 52horses by genotyping 31 microsatellites in order to avoid inbreeding. Parentageverification failed to identify genetic contradictions among trios (sires, dams, andfoals) registered with the Japan Equine Affairs Association (JEAA). Pedigree informationregistered at the JEAA was obtained and adequately understood. Additionally, the geneticdiversity of the Taishu horses was evaluated and compared with those of other Japanesenative breeds. The average values for the number of alleles, observed heterozygosity,expected heterozygosity, and inbreeding coefficient were 4.7, 0.643, 0.632, and −0.02,respectively. Using the Structure software, the 52 horses were classified into threesubgroups based on the individuals with more than 50% of specific genetic components. Thephylogenetic trees created based on neighbor-joining classification tended to beconsistent among the stallions. The effective population size was 27.5 and lower than thatrequired for maintaining 90% genetic variation in the source population over a period of100 years (47.5). Compared with the other Japanese breeds, the Taishu horse populationincluded in the current study exhibited moderate genetic diversity. Our study willcontribute to reconsideration of the breeding strategy of Taishu horses.

ABSTRACTIndisputably, the use of antivenoms for the treatment of snakebite envenoming isbeneficial for the victims. However, there are few studies addressing the effect oflong-term hyperimmunization in inoculated horses. It is known that the injection of snakevenoms and adjuvants leads to local and systemic reactions in horses, but little is knownabout the response of inflammatory proteins. The aim of this study was to evaluate serumproteins and the electrophoretic profile of horses undergoing crotalid venomhyperimmunization. Twenty horses were divided into two groups: an inoculated group,comprising ten horses that were already being used for production of a Crotalus sp.antivenom, and a control group, comprising ten animals that had never been used forhyperimmunization. All animals were clinically healthy and without laboratoryabnormalities. Total protein and albumin concentrations were measured in serum. Serumglobulins were obtained by calculation. Plasma fibrinogen estimates were determined by theheat precipitation method. Serum proteinograms were obtained using agarose gelelectrophoresis. The results revealed a significant increase in the concentrations oftotal serum proteins, globulins, and β-globulins in the inoculated group, exceeding thereference values. There were slight increases in the α-1- and α-2-globulin subfractions inserum-producing horses, with no statistical significance. We also observed that horsesused to produce hyperimmune plasma developed hypoalbuminemia, although the decrease inalbumin production was not statistically significant. Our findings suggest that thecontinuous use of horses to produce crotalid antivenom may lead to a chronic inflammatorystimulus, with changes in plasma levels of inflammatory proteins.

ABSTRACTThe secretion of prolactin and growth hormone in response to exercise and emotionalstresses was investigated in Thoroughbreds. Two experiments were performed: one withloading of only exercise stress and one with simultaneous loading of exercise andemotional stresses. Exercise stress was loaded in 4 steps using a treadmill for horses:pre-exercise period (5 min), walking period (6.5 min), galloping period (3 min), andcooling down period (10 min). Emotional stress was loaded by showing a loud video of anaudience at a racetrack during the walking period. The results clearly demonstrated thatexercise stress rapidly increased the secretion of prolactin and growth hormone and thatsecretion of them persisted for a specific period after the exercise. In addition,emotional stress promoted prolactin secretion.

ABSTRACTErythrocyte alloantigen frequencies of draft horses in Japan were investigated to assessblood donor suitability for transfusion. Here, 148 Japanese draft, 69 Percheron, and 65Breton horses were blood-typed and subjected to an indirect antiglobulin test. Regardingthe major immunogenic factors, the rates of Aa- and Qa-negative horses ranged from 0.35 to0.49 and from 0.82 to 1.00, respectively. The rate of alloantibody-positive horses rangedfrom 0.12 to 0.35. Although the prevalence of alloantibodies in these horses was higherthan that expected naturally, the rates of Aa- and Qa-negative horses were higher thanthose of some breeds reported previously. The current draft horse population could providepotential candidates for donors, and the obtained information may contribute to theselection of a safe donor for transfusion.

ABSTRACTThis review briefly describes the virus classification, clinical signs, epidemiology, diagnosis, disinfection, and vaccines related equine group A rotavirus (RVA) infection. Equine RVA is one of the most important pathogens causing diarrhoea in foals. The main transmission route is faecal–oral, and the clinical signs are diarrhoea, fever, lethargy, and anorexia (decreased suckling). Some human RVA rapid antigen detection kits based on the principles of the immunochromatographic assay are useful for the diagnosis of equine RVA infection. The kits are used in daily clinical practice because of their rapidity and ease of handling. Equine RVA is a non-enveloped virus and is more resistant to disinfectants than enveloped viruses such as equine influenza virus and equine herpesvirus. Although amphoteric soaps and quaternary ammonium compounds are commonly used in veterinary hygiene, they are generally ineffective against equine RVA. Alcohol products, aldehydes, and chlorine- and iodine-based compounds are effective against equine RVA. Inactivated vaccines have been used for equine RVA infection in some countries. Pregnant mares are intramuscularly inoculated with a vaccine, and thus their colostrum has abundant antibodies against RVA at the time of birth. According to G and P classification defined in accordance with the VP7 and VP4 genes, respectively, the predominant equine RVAs circulating in horse populations globally are G3P[12] and G14P[12] equine RVAs, but the vaccines contain only the G3P[12] equine RVA strain. Ideally, a G14P[12] equine RVA should be added as a vaccine strain to obtain a better vaccine effect.

ABSTRACTThe purpose of this study was to elucidate the colostral and foal serum immunoglobulin G(IgG) concentration values in heavy draft horses in Japan and to examine the effects ofperipartum mare condition on colostral immunity. Colostrum was obtained 1 hr after foaling(pre-suckling; n=178). Blood was collected from the jugular vein of the foals (n=147) at24 to 48 hr after birth. The foaling statuses of 73 mares were recorded. The averagecolostral IgG concentration was 10,540 ± 3,190 mg/dl (median=10,928; range 1,434−17,514mg/dl). The average serum IgG concentration obtained from neonatal foals 24 to 48 hr afterbirth was 1,750 ± 919 mg/dl (median=1,890; range 0−3,510 mg/dl). Although colostral IgGdid not differ between the normal foaling mare (n=59) and dystocial mare (n=14), foalserum IgG was lower in foals born in dystocia than in foals in normal foaling (P<0.05).This study demonstrates reference values for colostral and foal serum IgG specific toheavy draft horses in Japan and suggests that dystocia may interfere with the acquisitionof colostral immunity in neonatal foals.