Analyze Diet

Topic:Equine Research

Equine biomechanics involves the study of the mechanical principles that govern the movement and structure of horses. This field examines the anatomical and physiological aspects that contribute to locomotion, including gait patterns, joint function, and muscle dynamics. Researchers utilize advanced technologies such as motion capture and force plate analysis to assess the efficiency and performance of equine movement. Understanding biomechanics aids in optimizing training regimens, improving performance, and preventing injuries. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanics of equine movement, its applications in sports and rehabilitation, and its impact on overall equine health.
Eight Weeks of 448 kHz Radiofrequency Therapy Increases Multifidus Muscle Cross-Sectional Area and Modulates Thoracolumbar Range of Motion in Horses with Chronic Back Pain.
Animals : an open access journal from MDPI    August 6, 2026   Volume 16, Issue 15 2437 doi: 10.3390/ani16152437
Beaussart M, Perrin R, Marunova E, Moraine F, Fourteau D, Blake R.We aimed to investigate the effects of an 8-week 448 kHz radiofrequency (RF) on multifidus cross-sectional area (CSA) and thoracolumbar differential range of motion (ROM). Eight Thoroughbred horseball horses received four RF treatments (T9-L6) at 2-week intervals. Multifidus CSA (T10-L5) and differential spinal ROM between the withers (W), T13, T18, L3 and sacrum (S) were measured before treatment, immediately after the first session, 24 h after the first session, and at 8 weeks (15 days after the last session). Linear mixed models with Tukey post hoc comparisons were used. Significant effects...
Four Haylages, One Metabonome: Defining Diet Driven Metabolic Shifts in Ponies.
Journal of animal physiology and animal nutrition    August 6, 2026   doi: 10.1111/jpn.70099
Moore-Colyer M, Harris P, Daniels S.Haylage is widely fed to all categories of stabled horses across Europe and New Zealand. Haylage can vary from high energy nutrient dense forage to low energy highly fibrous fodder, yet little is known about the impact different haylages have on metabolism in horses. This study provides the first direct comparison of feeding four different haylages: early cut (Lolium multiflorum), later cut (Lolium perenne) rye grass (R1 and R2); early and late cut meadow grass (M1 and M2), on urinary and faecal metabonomics, in ponies at maintenance. Using replicated Latin Square design, eight individually ho...
Sleep architecture and lying behavior in horses across age groups and two housing systems: an overnight non-invasive EEG study.
Frontiers in veterinary science    August 6, 2026   Volume 13 1898580 doi: 10.3389/fvets.2026.1898580
Zimmer L, Schramel JP, Lyrakis M, Trachsel DS, Auer U, Leschnik M, Macho-Maschler S, Hotz M, Wahl H, Brunner S, Palme R, Cavalleri JV.Sleep is a crucial factor for the well-being of horses, yet assessing equine sleep in common housing conditions remains challenging. This study investigated the effects of changes in horses' immediate environment and the influence of age on their sleep and resting behavior using a novel, non-invasive electroencephalography (EEG) mask. Ten horses from the teaching herd at the University of Veterinary Medicine Vienna were observed over four consecutive nights in two different housing systems (a large communal stable vs. two separate, adjacent individual stalls). Data collection included EEG reco...
Clinical outcomes of a novel flowable calcium silicate cement in equine endodontic treatment.
Equine veterinary journal    August 5, 2026   doi: 10.1002/evj.70299
Jackson K, Faulkner J, Staszyk C, Ha W, Quintrell E, Kelty E.Orthograde endodontic treatment of equine cheek teeth is performed infrequently with variable success rates of obturation with calcium hydroxide paste (CHP). A novel flowable calcium silicate cement (eCSC) formulated for use as an obturation material in equine teeth has demonstrated acceptable canal filling volumes and evidence of dentinal tubule penetration. However, clinical outcomes of eCSC-obturated equine teeth have not been reported. Objective: To report the clinical outcomes of orthograde endodontic treatment using eCSC. Methods: Retrospective case series. Methods: Horses that underwent...
Cryopreserved umbilical allograft (equicenta® CTM) improves clinical outcomes compared with clinician-selected standard of care in performance horses: a pragmatic prospective controlled trial.
Frontiers in veterinary science    August 4, 2026   Volume 13 1833933 doi: 10.3389/fvets.2026.1833933
Bertone AL, Davern AJ, Sutter WW, Mesch H, Beinlich C, Smith A, Ramstrom C, White S, Dubynsky B, Cantrell K, Hay BP, Davis W, Mazzarelli L.This multicenter, prospective, controlled clinical study and client survey evaluated the safety and effectiveness of an equine umbilical tissue suspension (equicenta® CTM; eCTM, 2:1) compared with clinician-selected standard of care (SOC) for treating lame performance horses. Unassigned: This pragmatic, real-world, open-label study enrolled horses diagnosed with appendicular musculoskeletal conditions affecting the joints, tendons, or ligaments under owner consent and an intention-to-treat design with an optional crossover after no improvement at 12 weeks and per-protocol analyses at 26 ...
Health assessment of Tokara horses on Nakanoshima island: potential chronic hepatic dysfunction induced by Leopard plant (Farfugium japonicum) ingestion.
The Journal of veterinary medical science    August 3, 2026   doi: 10.1292/jvms.26-0275
Yamashita N, Yoshihara T, Hatazoe T, Misumi K, Hobo S.We investigated the health of Tokara horses (n=34) on Nakanoshima as part of conservation efforts for this breed. Although the horses were clinically healthy, elevated white blood cell count, neutrophil count and gamma-glutamyl transferase (GGT) levels were observed, leading to suspicion of chronic hepatic dysfunction and infectious disease. A survey revealed that the caretakers had been feeding the horses Leopard plant, which contains toxic pyrrolizidine alkaloids (PAs). The abnormal GGT levels observed in these horses may suggest the possibility of chronic PA poisoning resulting from the con...
Advanced 3D Horse Reconstruction: Integrating Image-to-3D Modelling and Non-Rigid Registration for On-Barn Body Measurements.
Animals : an open access journal from MDPI    August 3, 2026   Volume 16, Issue 15 2397 doi: 10.3390/ani16152397
Yuan X, Wang S, Zhu Q, Wang Y, Ruchay A, Pezzuolo A, Wang Q, Li J, Guo H.Precision livestock farming (PLF) relies on high-precision three-dimensional (3D) horse reconstruction and automatic body measurement to support refined breeding management and health surveillance. However, data collection is restricted by building environment noise and hardware layout constraints; complex equine body shapes and large individual variations induce local geometric distortions in reconstructed models, limiting field deployment. Drawing on generative 3D reconstruction, this study develops the first image-to-3D pipeline that leverages three consumer depth cameras to reconstruct hig...
Technical note on cervical epidural catheterization in two adult horses: Injectate distribution and epidural space effects.
Veterinary surgery : VS    July 30, 2026   doi: 10.1111/vsu.70140
O'Scanaill O, Moorman VJ, Perlini M, Reed RA.To determine the caudalmost extent of diffusion of contrast media administered through a cervical epidural catheter (CEC) and to describe pathologic changes associated with maintaining an indwelling CEC for up to 17 days. Methods: Pilot study. Methods: Two mature horses. Methods: CECs were placed under ultrasound guidance in two horses. Both horses were injected with 5 mL 50% Iohexol contrast solution, followed by radiographs of catheter insertion site to confirm placement. A total volume of 15 mL contrast solution was injected in 5 mL aliquots up to 25 min post-initial injection. La...
Species-specific effects of spinal stiffness on gait and actuation-cost proxy in simulated cheetah and horse galloping.
Journal of biomechanics    July 30, 2026   Volume 206 113495 doi: 10.1016/j.jbiomech.2026.113495
Schütz D, Shield S, Patel A.Cursorial quadrupeds employ distinct mechanical strategies for high-speed locomotion, with felids relying more strongly on axial motion than equids. The biomechanical role of spinal stiffness, however, is difficult to isolate experimentally because it is coupled to limb mechanics, morphology, and coordination. Here, we used comparative three-dimensional trajectory optimization to test how spinal stiffness influences gait mechanics and actuation-demand proxies in simulated cheetah-like and horse-like galloping. Homologous cheetah and horse models were evaluated across spinal-stiffness values, p...
Evaluation of Microvascular Flow Imaging and Power Doppler Ultrasonography in an Equine Model of Induced Superficial Digital Flexor Tendonitis. Garcia-Collao MR, Ortved K, Stefanovski D, Christensen JL, Underwood C.Superficial digital flexor tendon (SDFT) injuries are common in athletic horses and are associated with prolonged healing and high reinjury rates. Conventional ultrasonography provides structural information but limited physiologic assessment. This study compared microvascular imaging (MVI) and Power Doppler (PD) for evaluating vascular changes in a collagenase-induced equine SDFT injury model and assessed the effect of scanning technique on vascular signal detection. Eight adult Thoroughbred horses underwent bilateral collagenase-induced SDFT injury, with one forelimb randomly assigned to int...
Approaches to Thoroughbred Horse Identification in Diverse Sample Types Using Multiplexed SNP-PCR Sequencing Panels.
Animal genetics    July 29, 2026   Volume 57, Issue 4 e70170 doi: 10.1002/age.70170
Maniego J, Harding C, Hincks P, Habershon-Butcher J, Ryder E.The ability to determine the identity of equine samples would be highly advantageous in cases of ambiguous sample source, as individual-specific controls for gene editing detection, or forensic examination of suspect biological materials in potential doping cases. To this end, a SNP-PCR sequencing-based panel comprising 93 markers in one reaction was designed and investigated for use in Thoroughbred horses. Marker amplification performance and discriminating power were calculated against a population survey of 264 Thoroughbred whole blood samples from routine doping testing. The sensitivity of...
Differences between horses (Equus caballus) displaying oral and locomotor stereotypies in their responses to a stable mirror.
Behavioural processes    July 28, 2026   105415 doi: 10.1016/j.beproc.2026.105415
Lewis K, McBride SD, Parker MO, Faithfull R, Proops L.Recent cross-species analyses suggest that the different forms of stereotypic behaviour have heterogeneous causal mechanisms. In ungulates, there are indications that some forms of locomotor stereotypy may be linked to social factors. Using the domestic horse as a model species within this clade, we investigated whether individuals displaying the locomotor stereotypy box-walking (n=6) demonstrated greater responses to a stable mirror, intended to mimic presence of a conspecific, than horses displaying the oral stereotypy crib-biting (n=5) and non-stereotypic horses (n=5). After a 24hr baseline...
Somatic cell nuclear transfer as a complementary tool for genetic conservation of the Peruvian Paso horse.
The Journal of reproduction and development    July 28, 2026   doi: 10.1262/jrd.2026-068
Cortez JV, Segura Portocarrero GT, Murga Valderrama NL, Bardales Escalante W, Encina Ruiz R, Velásquez Castillo CL, Grupen CG, Maicelo Quintana JL.The Peruvian Paso horse, a breed of national significance in Peru known for its unique gait, has been selectively bred for nearly 500 years and now faces potential risks due to reduced genetic diversity. To investigate the potential of somatic cell nuclear transfer to enhance genetic conservation strategies, a program was initiated to produce cloned Peruvian Paso foals. Skin biopsies from a highly awarded stallion with exceptional breed-defining traits were used as the source of donor somatic cells. Of the 15 cloned embryos reconstructed, seven blastocysts were produced, and five were transfer...
Risk factors for horse falls in British jump racing (2010-2023).
Equine veterinary journal    July 27, 2026   doi: 10.1002/evj.70215
Allen SE, Taylor S, Given J, Verheyen KLP.Horse falls are an important safety and welfare concern in jump racing, as they are associated with an increased risk of equine fatality and injury, as well as jockey injury. Objective: To identify risk factors for horse falls in British jump racing. Methods: Retrospective cohort. Methods: All jump race starts made on British racecourses between January 2010 and April 2023 were considered. Available horse, race, racecourse, trainer and jockey data were collated and combined with faller data recorded in official databases. Horses that were 'brought down' by another horse were not considered a f...
Perineural dexamethasone does not prolong bupivacaine sensory blockade in equine palmar digital nerve blocks: a randomized crossover trial.
American journal of veterinary research    July 27, 2026   1-6 doi: 10.2460/ajvr.26.05.0207
Larriva DS, Lopez JS, Garcia-Collao M, Farnsworth K, Villarino NF, Hall NP.To determine whether dexamethasone sodium phosphate (dexamethasone SP) prolongs the sensory blockade produced by perineural bupivacaine during medial and lateral palmar digital nerve blocks in horses. Unassigned: 8 healthy adult horses were enrolled in a blinded, randomized 4 X 4 crossover trial. Each horse received 1 of 4 perineural treatments over the palmar digital nerves of the left forelimb: bupivacaine, bupivacaine + dexamethasone SP, dexamethasone SP alone, or saline. A minimum 7-day washout was used between treatments. Mechanical nociceptive threshold (MNT) was measured at baseline and...
A Global Structural Variation Map Reveals Novel Variants for Body Conformation and Racing Ability in Horses.
Genomics, proteomics & bioinformatics    July 27, 2026   qzag071 doi: 10.1093/gpbjnl/qzag071
Gong Y, Liu X, Zheng Z, Zeng S, Zhang Y, Pu Y, Pan J, Ma Y, Jiang L.The selection of horses has been instrumental in shaping long-range mobility, advancing warfare strategies, and diversifying equine phenotypes. However, the structural variants (SVs) favored by this process remain largely unexplored. Utilizing high-fidelity Pacific Biosciences sequencing, we assembled three high-quality horse genomes, incorporating 237 Mb (9.48%) of novel sequences relative to the existing reference genome. These assemblies achieved an average Benchmarking Universal Single-Copy Orthologs completeness of 95.1%. By employing a graph-based approach, we genotyped 23,163 high-con...
Efficiency of transvaginal oocyte aspiration (TVA), post-mortem ovary harvest (OH), and Intracytoplasmic Sperm Injection (ICSI) in a Quarter Horse mare population in North America.
Theriogenology    July 27, 2026   Volume 265 118111 doi: 10.1016/j.theriogenology.2026.118111
Ramírez-Agámez L, Love CC, Hernández-Avilés C.In a clinical setting, Intracytoplasmic Sperm Injection (ICSI)-derived equine blastocysts can be obtained either by transvaginal oocyte aspiration (TVA) or post-mortem ovary harvest (OH). Most peer-reviewed retrospective reports have described the suitability of these techniques for obtaining blastocysts, pregnancies, and live foals, particularly in Warmblood horse populations in Europe. In this study, retrospective data from Quarter Horse client-owned mares subjected to TVA-ICSI (n = 105; 151 cycles) or OH-ICSI (n = 42) at an academic institution in North America between 2023 and 2025...
Environmental and genetic effects on measured hock bone proportions in young Polish Warmblood horses undergoing performance test training for breeding horses.
Veterinary journal (London, England : 1997)    July 25, 2026   106795 doi: 10.1016/j.tvjl.2026.106795
Buczkowska R, Hecold M, Verwilghen D, Lewczuk D.The hock bone proportions in young Polish Warmblood horses (69) were studied based on x-ray image measurements done during official breeding horse performance testing. Six measurements were used to identify 4 width and length proportion indices. The radiological examinations were done before and after horse training, which consists of work with or without the rider at walk, trot and canter (40-50min) with some light class (< 100cm) jumping (<12 jumps) 6 days a week. The training effect was investigated using analysis of variance (procedure MIXED, Statistical Analysis System). The statist...
Compartmentalization of DHCR7 links 7-DHC metabolism to B-ring unsaturated steroid synthesis in the equine fetal gonad.
Endocrinology    July 25, 2026   Volume 167, Issue 9 bqag083 doi: 10.1210/endocr/bqag083
Malin K, Conley AJ, Verstraete M, Norris J, Hsu YC, Holl W, van Heule M, Vieira F, Scoggin KE, Ball B, Takahashi K, de la Fuente A, Newman JW....The endocrinology of equine pregnancy is unique, but many of its unusual phenomena closely resemble pregnancy in women. Placental estrone synthesis uses fetal adrenal androgen precursors in women, but from the fetal gonads in mares, peaking midway through the 11-month gestation. Unique to equine pregnancies, other estrogens like equilin, typified by an unsaturated B-ring sterol structure, are synthesized from 7-dehydrocholesterol (7-DHC), the immediate precursor to cholesterol, without cholesterol formation, peaking later in gestation. Currently, the spatial and temporal regulation underlying ...
Effects of equine sperm incubation under capacitation-supporting conditions on homologous and heterologous ICSI outcomes.
Theriogenology    July 24, 2026   Volume 265 118109 doi: 10.1016/j.theriogenology.2026.118109
Arroyo-Salvo C, Cabrera P, Treulen F, Gambini A, Arias ME, Felmer R, Perez-Martinez S, Aguila L.Intracytoplasmic sperm injection (ICSI) in horses has become sufficiently efficient to be considered for clinical and commercial application; however, several factors influencing its efficiency remain poorly understood. This study evaluated whether incubating equine sperm under capacitating conditions induces capacitation-associated changes and affects embryo development following homologous equine ICSI, as well as oocyte activation, early cleavage, and 5-methylcytosine (5 mC) and 5-hydroxymethylcytosine (5hmC) levels following heterologous ICSI using bovine oocytes. Equine spermatozoa were ...
First experience with radiofrequency catheter ablation in horses with recurrent, persistent naturally occurring atrial fibrillation.
Equine veterinary journal    July 24, 2026   doi: 10.1002/evj.70286
Buschmann E, Van Steenkiste G, Vernemmen I, Schauvliege S, Decloedt A, Duytschaever M, van Loon G.Myocardial sleeves in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial fibrillation (AF) in horses. Objective: Isolation of myocardial sleeves in the caudal vena cava or pulmonary veins might reduce the risk for AF recurrence. Methods: Case series. Methods: Records from seven horses with persistent, recurrent, naturally-occurring AF that were treated with three-dimensional electro-anatomical mapping and radiofrequency catheter ablation (RFCA) in order to reduce recurrence risk were reviewed. Mapping of the caudal vena cava was performed...
Effects of TECAR Therapy on Body Surface Temperature and Longissimus Dorsi Muscle Tone in Thoroughbred Racehorses: A Pilot Study.
Animals : an open access journal from MDPI    July 24, 2026   Volume 16, Issue 15 2300 doi: 10.3390/ani16152300
Grzegorczyk W, Soroko-Dubrovina M, Dobrowolski M, Grabska D, Dudek KD.Capacitive and resistive electric transfer (TECAR) therapy is increasingly used in equine physiotherapy; however, objective evidence regarding its immediate effects on equine back muscles remains limited. This pilot study aimed to evaluate the effects of TECAR therapy on body surface temperature and muscle tone of the longissimus dorsi muscle in Thoroughbred racehorses. A randomized, single-blinded experimental study was conducted in 20 clinically healthy Thoroughbred racehorses aged 2-3 years. Horses were randomly assigned to either a TECAR treatment group ( = 10) or a sham-treatment control ...
Development and validation of a liquid chromatography-tandem mass spectrometry method for the quantification of twenty-five steroids in equine serum.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences    July 24, 2026   Volume 1282 125222 doi: 10.1016/j.jchromb.2026.125222
Ledeck J, Dubrowski T, Peeters S, Le Goff C, Deleuze S, Ponthier J, Cavalier E.Steroids are potential biomarkers for monitoring equine pregnancy. However, immunoassays currently used for their quantification suffer from cross-reactivity and limited specificity, thus requiring more accurate methods. This study reports the development and validation of a robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of 25 steroids covering the main biosynthetic pathways of progestogens, corticosteroids, androgens, and estrogens. Steroids were extracted by protein precipitation followed by evaporation, derivatization, and reconstitut...
Phenotypic Definition Influences Genetic Inference and Predictive Ability for Reining Performance in Quarter Horses Using Random Regression Models.
Animal science journal = Nihon chikusan Gakkaiho    July 23, 2026   Volume 97, Issue 1 e70223 doi: 10.1111/asj.70223
Santana ML, Bignardi AB.Reining performance is influenced by subjectivity and competition structure, challenging genetic evaluation. This study estimated genetic parameters for reining performance in Brazilian Quarter Horses using random regression models (RRM) and evaluated how alternative phenotypic definitions affect genetic inference and predictive ability. A dataset comprising 21,165 longitudinal records from 1603 horses was analyzed, comparing within-group rank (RANK) and Blom-transformed rank (BLOM). Model comparison indicated that cubic RRM provided the best fit for both phenotypes. Heritability estimates wer...
Effects of IGF1 Knockdown and Overexpression on the Phenotype and Function of Equine Primary Skeletal Muscle Cells.
Biology    July 23, 2026   Volume 15, Issue 15 1225 doi: 10.3390/biology15151225
Su Y, Ren W, Zeng Y, Meng J, Yao X, Wang J.Skeletal muscle serves as the direct executor of movement, and the proliferation and migration capacities of its constituent cells represent the key physiological foundation determining equine endurance and speed. Previous whole-transcriptome analysis has shown that Insulin-like Growth Factor 1 () is significantly upregulated in following racing and is involved in the PI3K-Akt signaling pathway; however, its specific regulatory mechanism in equine skeletal muscle cells remains unclear. This study utilized primary equine skeletal muscle cells as a model. By constructing an overexpression plas...
High-Throughput Equine Plasma Profiling Using Laser-Assisted Rapid Evaporative Ionisation Mass Spectrometry.
Journal of mass spectrometry : JMS    July 23, 2026   Volume 61, Issue 8 e70077 doi: 10.1002/jms.70077
Molnár A, Arko M, Troha K, Marton A, Tauber B, Iglič A, Balogh GT, Balog J, Hočevar M, Kos VK, Battelino S, Kralj-Iglič V, Schlosser G.Remnants of erythrocyte removal from blood constitute therapeutic plasma-a water-based solution containing mainly platelets, extracellular vesicles (EVs), protein and lipid complexes and ions. Plasma-based therapies, including their use to accelerate wound healing in human and animal patients, are increasingly gaining prominence in regenerative medicine; however, methods for the optimal preparation of individual plasma are still under development. Rapid and accurate analysis of plasma composition is essential for the development of therapeutic applications and for ensuring the quality of plasm...
Growth Performance, Milk Productivity, Productive Longevity, and Milk Composition of Mugalzhar Horses.
Animals : an open access journal from MDPI    July 22, 2026   Volume 16, Issue 14 2272 doi: 10.3390/ani16142272
Toishimanov M, Alikhanov O, Aubakirov K, Karibayeva D, Kargaeva M, Sapakhova Z, Begaliyeva D, Kanat R, Tugunova Y, Daurov D, Daurova A, Zhambakin K....The Mugalzhar horse is an important native breed of Kazakhstan, valued for its adaptability, milk production, and meat productivity under extensive pasture-based management. This study evaluated the relationships among first-lactation milk yield, productive longevity, lifetime milk production, growth, morphometric traits, and milk composition in the Mugalzhar horse breed using data from 100 mares with complete lifetime production records, 108 adult mares and 12 stallions for morphometric evaluation, and 68 foals (35 colts and 33 fillies) for growth analysis. The study was conducted on Mugalzha...
Evaluation of an Immunoturbidometric Assay for Measurement of Total Adiponectin Concentration in Equine Serum Samples.
Veterinary clinical pathology    July 22, 2026   doi: 10.1111/vcp.70118
Nolen-Walston RD, Lowndes CR, Kulp JC, Luethy D, Stefanovski D, Van Eps AW.Total adiponectin (TA) is a marker of metabolic health in equids, with values below a critical decision point of < 7.9 μg/mL conferring increased risk of laminitis. Objective: To evaluate an IT assay to measure serum [TA] in equids and to assess its correlation with [high molecular weight adiponectin] (HMWA) measured by ELISA. Methods: Total serum adiponectin concentrations from 207 adult horses were measured using both an IT assay for TA and HMWA using a previously validated ELISA assay. Data were analyzed using Spearman correlation and Passing-Bablok regression. Intra- and inter-assa...
Correction: Review: Genomic insights into the adaptive traits and stress resistance in modern horses.
Stress biology    July 20, 2026   Volume 6, Issue 1 50 doi: 10.1007/s44154-026-00327-z
Jafari H, Abebe BK, Cong L, Ahmed Z, Zhaofei W, Sun M, Muhatai G, Chuzhao L, Dang R.No abstract available
Morphological investigation of myocardial sleeves with potential relevance to atrial fibrillation in Norwegian-Swedish Coldblooded Trotters.
Veterinary journal (London, England : 1997)    July 19, 2026   Volume 318 106784 doi: 10.1016/j.tvjl.2026.106784
Kallmyr-Mack A, Hellings IR, Press CM, Ibrahim L, van Loon G, Fintl C.Myocardial sleeves (MSs) are thin layers of cardiac muscle that extend from the atria into the caval and pulmonary veins. They are recognised as important structures in both initiating and maintaining atrial tachycardia, and especially atrial fibrillation (AF), which is the most clinically important cardiac arrhythmia in horses with a reported prevalence of 1.3-2% in Standardbred racehorses. In contrast, the Norwegian-Swedish Coldblooded Trotter (NSCT) has a much lower prevalence of AF despite experiencing similar physical demands. The purpose of this study was to describe the macro-, and micr...