The study of blood in horses encompasses the examination of its components, functions, and its role in equine health and disease. Blood consists of various elements, including red blood cells, white blood cells, platelets, and plasma, each serving specific functions such as oxygen transport, immune response, clotting, and nutrient distribution. Analyzing blood parameters can provide insights into the physiological and pathological states of horses. Common blood tests in equine medicine assess parameters like hematocrit, hemoglobin concentration, and white cell counts to monitor health status, diagnose conditions, and guide treatment decisions. This page compiles peer-reviewed research studies and scholarly articles that explore the composition, function, and clinical applications of blood analysis in horses.
HOLTON FA.In 1941, Keilin & Mann described an optical method of studying the penetration of erythrocytes by bicarbonate ions and the intracellular activity of carbonic anhydrase. This method consists of converting the haemoglobin inside the cell to methaemoglobin and observing the transformation of the methaemoglobin from the acid to the alkaline form by the entering bicarbonate ions. During this work they noticed that this transformation did not occur if the methaemoglobin cells had been washed in acid phosphate and interpreted this as an effect on the permeability of the cells. Similar observations by...
STURGE LM, WHITTAKER VP.The research article delves into the exploration of the specificity of esterases in horse blood, particularly plasma cholinesterase and the ali-esterase, drawing a clear distinction between the two, which had […]
BAER H, KABAT EA, KNAUB V.Blood group substances have been isolated from the saliva of human beings of blood group B and from the linings of individual horse stomachs. The properties of the human B substances are similar to those of hog and human blood group substances previously isolated. The horse substances showed lower hexosamine and reducing sugar and higher total and non-hexosamine nitrogen than do the materials from the other species. Materials isolated from individual horse stomachs possess either A or B activity or both. Certain stomachs yielded products of identical analytical composition but with neither blo...
FEGLER G.1. Volume p.c. of r.b.c., hæmoglobin concentration, relative viscosity of the plasma and blood, and the sedimentation rate of the r.b.c. have been estimated on 7 healthy horses.
2. Increase in the volume p.c. of r.b.c. was found in the excited or working horse. The concentration of r.b.c. in blood from the jugular vein in horses at rest is rather low in comparison with other animals.
3. Increase in the Hb. g. p.c./r.b.c. V. p.c. ratio was found in cases with the higher volume p.c. of r.b.c. with a significant correlation coefficient.
4. Apparent relative viscosity of horse blood at h...
Friend MM, McGaffigan EM, Hall SM, Staniar WB, Smarsh DN.Early detection of inflammation using a common test could be a valuable tool for preserving horse health. Objective: This observational study aimed to identify variation in complete blood count (CBC) parameters and inflammatory indices with inflammation, and to develop reference intervals (RIs) from horses with known inflammatory states, hypothesizing that RIs developed from horses with normal acute phase protein concentrations would improve the ability to predict inflammation. Methods: Concentrations of serum amyloid A (SAA) and haptoglobin from clinically healthy horses and horses under vete...
Yamashita N, Hatazoe T, Misumi K, Hobo S.The Tokara horse is a breed of native Japanese horse, for which hematological and biochemical data are lacking. The aim of this study was to obtain current hematological and biochemical data on Tokara horses. We enrolled 90 Tokara horses kept at the Kaimon Foothills Nature Park (Kagoshima) that underwent physical examinations and blood sampling between 2022 and 2024. All horses in this study were regarded as clinically healthy, based on physical examinations. Hematological and biochemical parameters also showed no abnormal values. Based on the above results, we consider that the data from this...
Meiseberg LK, Mergani A, Delarocque J, Imker R, Köhn D, Wanes D, Bonilla MC, Veldhuizen EJA, von Köckritz-Blickwede M, Ohnesorge B, de Buhr N.Equine asthma (EA) is the most prevalent chronic lung disease in horses. Neutrophils are the main effector cells in severe EA. Neutrophil extracellular traps (NETs) have been described as contributors to severity in human asthma and chronic obstructive pulmonary disease. Thus, we aimed to investigate if NET-related factors in equine neutrophils, blood and bronchoalveolar lavage fluid (BALF) allow us to differentiate EA severities and to identify NET-related mechanistic insights in EA. We quantified NETs and NET-related factors in the blood and BALF of eight healthy horses and 18 horses with di...
Söderroos D, Stefánsdóttir GJ, Ragnarsson S, Gunnarsson V, Jansson A.Weight-carrying capacity is important in riding horses both for performance and welfare, yet there is no standardized method to estimate individual horses' weight-carrying capacity. This study investigated the correlation between the physiological response during a (i) standardized incremental exercise test (SET) on a treadmill and a (ii) ridden incremental weight-carrying exercise test (WET). Sixteen horses (15 ± 3 years) performed both tests, including four steps with increased speed or weight load, respectively. Body weight ratio (BWR) in the WET was 20%, 25%, 30%, and 35% in each st...
Thane K, Voth R, Klee R, Warnken T, Chukwu V, Frank N.Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are promising treatments to manage hyperinsulinemia in horses with insulin dysregulation (ID). Objective: The SGLT2i velagliflozin decreases insulin concentration in horses with ID. Methods: Privately-owned adult horses (n = 37) with laboratory-confirmed ID (low-dose oral sugar test insulin concentration > 75 μIU/mL). Methods: Double-blind randomized placebo-controlled trial. Horses received placebo (n = 19) or velagliflozin 0.3 mg/kg PO q24h (n = 18) for 20 weeks (Study Period 1, SP1) immediately followed by a 20-week ope...
Urayama S, Muko R, Muranaka M, Mita H, Ohta M, Matsuda H, Tanaka A.Systemic inflammatory response syndrome (SIRS) induced by endotoxemia is usually secondary to colitis and is a major cause of high morbidity and mortality in horses. Non-steroidal anti-inflammatory drugs (NSAIDs), such as flunixin meglumine (FM) and meloxicam (MX), are used to improve clinical outcomes in SIRS/endotoxemia. These NSAIDs suppress tumor necrosis factor-alpha (TNF-α) levels; however, the underlying mechanisms remain unclear. The aim of this study was to investigate the inhibitory effects of FM and MX on TNF-α in lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear ce...
Hobbs KJ, Ludwig EK, Martin EM, Bayless R, Bauck AG, Freeman DE, Gonzalez LM.To determine if blood and peritoneal fluid levels of syndecan-1, heparan sulfate, and hyaluronan are elevated in horses with small intestinal disease compared to healthy counterparts. Unassigned: 61 horses were categorized into control (n = 20), inflammatory (11), and strangulating (30) groups. Paired peritoneal fluid and blood samples were obtained from each group from December 2016 through December 2024 and analyzed via equine-validated ELISAs for syndecan-1, heparan sulfate, and hyaluronan concentrations. Patient survival to discharge was recorded for all groups. Immunofluorescence staining...
Rocha IA, McPeek JL, Hulverson MA, Choi R, Orr K, Sponseller BT, Kennedy T, Ojo KK, Barrett LK, Ruby R, Janes J, Reed SM, Arnold SLM, Van Voorhis WC....To determine the systemic and CNS distribution of bumped-kinase inhibitors (BKIs) in healthy horses, assess potential side effects, and identify a candidate compound for a clinical trial in equine protozoal myeloencephalitis (EPM) cases. Unassigned: 9 pharmacokinetic (PK) experiments were conducted from March 2021 through November 2024. Bumped-kinase inhibitors 1708, 1748, and 1841 were screened in Sarcocystis neurona growth assays and IV PKs, followed by investigation of a lead BKI compound by single-dose or multiday oral administration. Serial plasma collections were performed to assess syst...
Feijo LS, Ledeck J, Wolfsdorf K, Ponthier J, Parry S, Felippe MJB.Associations between the immune and endocrine systems during equine pregnancy remain poorly understood. Based on the hypothesis that distinct phases of the equine healthy gestation are characterized by specific associations between circulating immunological and hormonal parameters, contributing to pregnancy maintenance, this investigation aimed to: (i) evaluate how circulating immunological and hormonal parameters change across different phases of pregnancy; (ii) investigate associations between changes in circulating immunological and hormonal parameters; and (iii) propose potential hormonal ...
Hammack SM, Moshage SG, Kersh ME, McCoy AM.To quantify circulating levels of myokines with a known role in bone remodeling (receptor activator of nuclear factor κ B ligand [RANK-L], matrix metalloproteinase 2 [MMP-2], and irisin) in foals in response to exercise and over the first year of life. Unassigned: 12 foals were enrolled in the study; 6 underwent an 8-week exercise program, and 6 were nonexercised controls. Blood samples were collected between 2 and 11 months of age. Receptor activator of nuclear factor κ B ligand, MMP-2, and irisin were quantified using equine-specific ELISAs. Unassigned: RANK-L, MMP-2, and irisin did not ch...
Huang Q, Ren W, Shan D, Su Y, Li Z, Li L, Wang R, Ma S, Wang J.This study aimed to compare blood samples from Yili horses with outstanding and average performance in 5000 m races through transcriptome sequencing, identify key differentially expressed genes, lncRNAs, and circRNAs, as well as related enriched pathways, and elucidate their regulatory networks. This study used six healthy four-year-old Yili stallions as subjects, divided into an excellent group (E group, = 3) and an ordinary group (O group, = 3) based on their 5000-m race performance. Blood RNA-Seq technology was used to analyze differentially expressed mRNAs, lncRNAs, and circRNAs. A total...
Wang T, Yang X, Wang C, Wang J, Meng J, Yao X, Zeng Y, Ren W.Studying the genetic characteristics and molecular mechanisms of immune regulation in horses is of great significance for protecting their genetic resources, improving breeding strategies, and enhancing their disease resistance, thereby ensuring their healthy performance in both sports and production. Objective: This study investigates the genetic characteristics and molecular mechanisms underlying immune regulation in Yili horses, comparing them with Thoroughbreds and Kazakh horses. Methods: Blood samples from each breed were analyzed for physiological, biochemical, and immune indices alongsi...
Hanousek K, O'Hara V, Riddell DO, Piercy RJ.In Thoroughbred horses, a highly prevalent short interspersed nuclear element (SINE) mutation in the myostatin gene (MSTN) promoter influences circulating myostatin concentration and is associated with muscle morphology, fracture risk and optimal race distance. Our prior data reveal that within horses there is substantial variation in serum myostatin concentration, particularly in MSTN heterozygotes and wild type horses but it was unclear whether such variation relates to within-horse differences or to environmental or temporal effects. Here we report the intra-horse consistency of circulating...
The aim of the study was to identify proteomic signatures from the serum of horses affected by simple obstructive intestinal colic to characterize the pathological process and to assess potential biomarkers for early diagnosis. Seven horses with obstructive colic received venous blood samples for determination of standard hematobiochemical, inflammatory, and lipid profiles at the time of initial clinical examination and after conservative therapy upon recovery. Proteomic profiling was also performed on all samples by means of a within-group analysis (sick horses at discharge vs. sick horses at...
Alsultan A, Karim SM, Al-Saadi M, Alsallami D, Ben Said M, Belkahia H.Equine piroplasmosis (EP), caused by the intracellular protozoa Theileria equi, Babesia caballi, and Theileria haneyi, represents a major health and economic threat to the equine industry worldwide. Existing diagnostic methods, including PCR, serology, and microscopy, are constrained by their dependence on specialized equipment, lengthy protocols, and the requirement for skilled personnel. Objective: This study aimed to develop a rapid, accurate, and field-deployable molecular diagnostic assay for T. equi. Methods: A nucleic acid-based diagnostic platform combining recombinase polymerase ampli...
Kranenburg LC, Reinke KS, van den Broek J, Zaal EA, van den Boom R, van Doorn DA.Hydrolysed collagen is used as a supplement for horses with osteoarthritis, hoof horn growth problems, and gastric ulcers. To determine the oral availability of a specific hydrolysed collagen supplement and the appropriate dose, six Warmblood mares were fed two different concentrations of the supplement: 100 g HC (C), 50 g HC (C), and a control of 0 g HC (C) during one week in a randomised cross-over design. On day 7, 14 and 21, blood sampling for amino acid (AA) analysis was performed, just prior to feeding the supplement (t = 0) and every hour after feeding for 8 h (t = 1-8). Statistical ana...
Training on deep sand is commonly employed in endurance horses, but its physiological adaptation remains poorly characterized. This study aimed to characterize locomotor adaptations during a 7 km controlled-speed canter on deep sand in eighteen endurance horses, to identify heart rate variability (HRV) components, and to investigate changes in hematological variables before and after exercise. Stride frequency (SF) and stride length (SL), HRV, and hematological profiles were recorded during exercise and recovery with a fitness tracker. Associations between maximum speed and locomotor parameter...
Mitlyng N, Hobbs KJ, Cooper BL, Sheats MK.Lipopolysaccharide (LPS) is frequently used in equine research to model clinical endotoxemia; however, there is no standardized protocol for inducing cytokine production in equine whole blood. To address this knowledge gap, the goal of this study was to compare the cytokine responses elicited by three different LPS stimulation protocols. Whole blood was collected from six healthy horses (aged 5-30 years; mixed breeds and genders) from the North Carolina State University teaching herd (IACUC #23-412). Sixty milliliters of heparinized blood were aseptically drawn and divided into 15 mL aliquots....
Zuluaga-Cabrera AM, Barbosa da Costa G, Martinez ID, Arias MP.Colombian Paso horses (CPs) excel in gait competitions due to their endurance, speed, and precision, which demand a high level of cardiorespiratory fitness. However, their training regimes often lack scientific support, and few studies have linked physiological parameters to optimal training zones. This study aimed to estimate the aerobic lactate threshold (LTaer) using mathematical methods and to correlate it with heart rate (HR) zones and blood lactate. Eighteen CPs were evaluated and classified into trained (GT) and untrained (GD) groups. All animals underwent a field-based incremental exer...
Meng C, Wang J, Zeng Y, Yao X, Meng J.This study investigated the effects of varying proline supplementation doses in weaned foals. Twenty-eight weaned foals (approximately 5 months of age; body weight: 54.45 ± 11.33 kg; with an equal number of males and females) were randomly assigned to one of four groups-a control group, a low-dose group (20 mg/kg·d), a medium-dose group (40 mg/kg·d), and a high-dose group (60 mg/kg·d)- receiving continuous supplementation for 60 days. Blood samples were collected periodically for the analysis of hormones, antioxidants, immune parameters, and plasma amino acids. Concurrently, fecal 16S rRNA...
Fresa K, Catandi GD, Gonzalez-Castro R, Omar A, Whitcomb LA, Cheng MH, Chen TW, Carnevale EM, Chicco AJ.Advancing age is associated with a decline in fertility and functional capacity, which may result in part from suboptimal nutrition and impaired mitochondrial function. Dietary essential polyunsaturated fatty acids (PUFA) are broadly recommended to mitigate weight loss and reduce risk of chronic disease in aged populations, but their effects on mitochondrial function are less clear. The present study investigated the impacts of dietary supplementation with essential omega-3 PUFA (flaxseed oil; N3) or omega-6 PUFA (corn oil, N6) on blood, muscle and follicular cell fatty acid composition and mi...
Aiche S, Chikhaoui M, Smail F, Benamor N, Benia AR.Pregnancy causes increased oxidative stress in mares, possibly harming both the mare and the foal, whereas the effects of different exercise levels on oxidative stress and lipid metabolism during pregnancy remain unclear. Objective: For this reason, the aim of this research was to explore the impacts of different training intensities on oxidative stress and lipid metabolism during pregnancy. Methods: The study comprised 22 clinically normal Purebred Arabian mares from Algeria, which were divided into three groups according to age and exercise frequency. Blood samples were collected during both...
Brito G, Damián JP, Trigo P, Ruprechter G.The Raid Hípico Uruguayo (RHU) is the oldest equestrian endurance sport in Uruguay. A high percentage of horses fail to complete RHU rides. Therefore, the aim of this study was to investigate whether weather conditions (comfort index [CI]), horse experience, and ride distance affect horse performance (finishing ride [FR] or nonfinishing ride [NFR]) in the RHU. An additional objective was to determine whether finishing the ride affects the hematological and biochemical parameters of the horses. This study involved 17 RHU rides over distances of 60-90 km and 284 horses. Blood samples were tak...
Parker M, Arnade H, Parker JL, Gordon J, Peroni JF.Investigation of alternative antibiotic therapies is critical for the future of medicine. Platelet lysate (PL) is a blood product that has shown antibiotic potential, which could be used to augment or replace current antibiotics. Objective: To compare the effects of equine PL versus antibiotics on growth of clinically isolated antibiotic resistant bacteria. We hypothesized that PL would exert an antimicrobial effect on equine bacterial isolates resistant to antibiotics. Methods: In vitro experimental study. Platelets were collected via apheresis from nine donor horses and underwent two freeze-...
Decoster C, Lefère L, Raes E, van Loon G, Dufourni A.Leptospirosis is a widespread zoonotic, infectious disease associated with abortion, stillbirth, as well as liver and kidney failure. Leptospiral Pulmonary Haemorrhage Syndrome (LPHS) has increasingly been reported in human and canine patients infected by Leptospira and is associated with a high fatality rate. In equine medicine, pulmonary haemorrhage has mainly been described in foals with leptospiral infections, but rarely in adult horses. Objective: To characterise the clinicopathological features of pulmonary haemorrhage as a distinct disease entity in adult horses with leptospirosis, term...
Crossland WL, Aviles-Rosa EO, Perry EB, Crowell C, Webberson E, Brown J, Fassbender J.Our objective was to evaluate the effect of transdermal melatonin on physiological stress biomarkers in horses, with some subjected to transport stress. Sixteen horses were assigned to a 2 × 2 factorial design assessing treatment (melatonin vs. no melatonin) and transport status (transported vs. non-transported), creating four groups: Control (CON), Transport only (TRS), Melatonin only (MEL), and Melatonin plus Transport (MELTRS). Horses in melatonin groups received 24 mg/day transdermally for 21 days and transported groups underwent a 3-hour trailer ride on day 21. Day 21 blood samples were ...
Eskandari G, Ahmadi Sheikhsarmast S, Ghasemi S, Mohri M.Neutrophil gelatinase-associated lipocalin (NGAL) is a glycoprotein involved in immune responses and inflammation, with established diagnostic utility in acute kidney injury (AKI) and systemic diseases. However, reference values for NGAL in healthy horses, particularly the Turkmen breed, remain poorly defined. Objective: This study aimed to establish reference values for serum NGAL concentrations in healthy Turkmen horses and to evaluate the influence of age, sex, pregnancy status and physical activity on its levels, as well as its correlations with haematological and serum biochemical variabl...
Deniz Ö, Erol HS, van den Hoven R, Onmaz AC, Aragona F, Fazio F.Weaning represents a major developmental milestone for foals, especially when 4- to 7-month-old foals are abruptly separated from their dams. Studies have shown that the post-weaning period is associated with physiological and psychological stress, which may affect immune function. The present study aimed to describe and analyze the pattern of blood inflammatory biomarkers related to the innate immune system. A gradual foal-dam separation procedure was chosen, which included post-weaning social buffering by a familiar adult horse. Twelve Thoroughbred foals (six fillies, six colts) aged 4-6 mon...
James C, Sheahan J, Arthur P.Thoroughbred race performance is influenced by genetics, training, recovery, and management, but decisions about race readiness are often subjective and lack validated physiological markers. This study evaluated thiol-oxidised albumin, a blood-based indicator of oxidative stress, as a potential biomarker of pre-race fitness in Australian Thoroughbreds. Seventy-five clinically healthy racehorses from seven stables were monitored across 216 competitive events (150 races, 66 trials). Blood samples were collected from the jugular at baseline, 48 h pre-race, and for each day up to 8 days post-race ...
Reemtsma FP, Giers J, Horstmann S, Stoeckle SD, Gehlen H.Amino acid (AA) metabolism and the adaptation of muscles to increased physical performance are interdependent. This field study examined changes in plasma amino acid (PAA) concentrations and two metabolites (ammonia and urea) before and after cross-country (CC) competitions throughout an entire eventing season and their associations with performance outcomes in eventing horses. Twenty horses from nine different Warmblood breeds were evaluated between two and seven times across 14 international eventing competitions over a 23-week period. A total of 55 rides were sampled. Blood samples were col...
