Hematology and hemostasis in the horse: normal functions and common abnormalities

Changes in haematological and biochemical parameters in blood serum of horses during exposition to workload stress

Health state of animals undergoing experimental procedures is an important topic nowadays, as even the small changes can influence the outcome of entire outcomes. Main aim of the study was to evaluate the influence of horse training on variety of blood parameters including mineral profile, energy profile, hepatic profile and haematology. In the experiment, the studied group of horses underwent training programme which consisted of transportation, lounging, riding, jumping, racing, treadmill training and shoeing. Blood samples were collected and later evaluated at the beginning, in the middle and at the end of 1-year lasting process. Our results show multiple significant changes in blood parameters, including changes to multiple minerals, such as Ca, K, Na as well as significant changes of total proteins, urea and certain hepatic profile parameters. Haematology results have also been affected in individual sample collections. Based on results of our study we can state that there have been changes to the internal milieu of the horse but also that there have not been any visible changes of the health status of the animals over the duration of the experiment.

Risk factors, hematological and biochemical profile associated with colic in Delman horses in Gresik, Indonesia

Background: Horses are herd animals that have been domesticated in the last century. In several countries, an overview of risk factors and clinical evaluation in horses with colic has not been well‐described. This study aimed to evaluate risk factors and hematological profiles in horses associated with colic in Gresik, East Java, Indonesia.

Methods: A cross-sectional study was performed during April - October 2019. A total of 115 horses were diagnosed based on physical examination, clinical symptoms, and rectal examination. A questionnaire was asked to the horse-owners to analyze the risk factors while the clinical examination was performed and blood samples were collected for pre-treatment and 14 days post-treatment. Hematological profile was evaluated from a whole blood sample. Serum cortisol, plasma epinephrine, and norepinephrine concentrations were also evaluated after separating the aliquots. 

Results: Of the 115 horses, 96 were diagnosed with colic. The horses with colic showed a significant association between cases with gender (p<0.021), breed (p<0.000), wheat bran feeding (p<0.015), concentrate feeding (p<0.003), anthelmintics administration (p<0.000), gastrointestinal parasites (p<0.000), dental diseases (p<0.024), previous exposure to colic (p<0.000), body condition score (p<0.000), and access to water per day (p<0.000). Based on whole blood and serum evaluation, there were ameliorated significantly on the hematological profile (p<0.01), serum cortisol (p<0.05), and plasma epinephrine (p<0.01) at 14 days post-treatment.

Conclusion: This study has identified factors associated with colic in Delman horses. The study provides crucial information to investigate cases of colic and to contribute the development of healthcare strategies during treatment and clinical evaluation.

Age- and Sex-Related Modifications of Hematology in Spanish Purebred Horse

The purpose of this study was to test the hypothesis that age and sex significantly modulate the changes in hematological parameters of physiologically healthy Spanish Purebred horse, establishing the reference values. Blood samples were obtained on a total of 159 horses (n = 77 males and n = 82 females), classified in four age groups: group A (1-2 years; n = 39), group B (>2-3 years; n = 38), group C (>3-4 years; n = 41), and group D (>4-7 years; n = 41). By means ADVIA 2020i, red blood cell (RBC), hemoglobin concentration (HB), packed cell volume, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration, platelets (PLTs), as well as total and differential white blood cells (WBCs) were determined. Total plasma protein was determined by spectrophotometry. Results obtained showed that sex had a limited influence on these parameters, being the HB higher in males and WBC higher in females (P = .047). Age caused a reduction in RBC, with a compensatory increase of MCV and MCH, decrease in WBC, PLT, lymphocytes (LYMPs), as well as an increase of N/L ratio (P = .047). Interactions between age and sex showed higher RBC in males than in females of the group B, and higher HB and WBC in males than in females of the group D. According to hematological data, Spanish Purebred horse was classified as a warm- or cold-blooded horse. Decline of RBC, WBC, and PLT parameters is a natural condition of horse with the advance of age, indicating a decrease of the narrow bone response.

Uterine responses and equine chorionic gonadotropin concentrations after two intrauterine infusions with kerosene post early fetal loss in mares

Pregnancy loss during the normal lifespan of endometrial cups (∼37-120-150 days of gestation) may affect a mare's ability to conceive again in the same breeding season, as equine chorionic gonadotropin (eCG) secretion by retained endometrial cups can lead to abnormal ovulations and follicular growth. While intrauterine kerosene infusion has anecdotally been proposed as a treatment for endometrial cup retention, there are no controlled studies evaluating kerosene's ability to enhance endometrial cup regression following abortion. The objectives of this study were to assess uterine response, systemic side effects, and efficacy of intrauterine kerosene infusions after abortion. We hypothesized that kerosene infusions would hasten regression of endometrial cups without detrimental effects on the endometrium and the mare's general health. Twelve light-breed mares were enrolled in the study after an experimentally induced abortion with cloprostenol (n = 12) by 60 ± 2 days of gestation. Mares were randomly allocated to receive an intrauterine infusion with 500 mL of kerosene (n = 6) or 500 mL saline (n = 6) on days 21 and 35 after pregnancy termination. Uterine biopsies were collected at days 7, 21, 35, and 49 post-abortion to evaluate the degree of endometrial fibrosis with Picrosirius Red Stain and to be graded according to the Kenney & Doig 1986 classification. Furthermore, histomorphometry analysis of the endometrium lining, glandular epithelium and glandular density was performed. Endometrial lymphocyte B CD20⁺, lymphocyte T CD3⁺, and macrophage IBA-1⁺ cell populations were characterized by immunohistochemistry. Physical examinations, blood cell counts, and serum biochemistry were performed before, and for 2 days after each uterine infusion. Serum samples were collected for assessment of eCG concentrations. Continuous data were analyzed with MIXED procedure with repeated measures in SAS, categorical data with LOGISTIC procedure of SAS. Significance was set at p < 0.05. Kerosene infusion did not affect complete blood cell counts, serum chemistry parameters, or physical examinations. Concentrations of eCG decreased over time (p < 0.001), but there were no differences between groups or time by group interactions (p = 0.72). Histological evaluation of the uterus showed no signs of increased fibrosis or degeneration in the treatment group. In conclusion, while kerosene infusions did not appear to have detrimental effects on mare health, our findings suggest that the use of kerosene in the uterus does not enhance the regression of endometrial cups by 49 days post-abortion.

Blood hematological values of Barb horses in Algeria

The Barb horse this famous Maghreb horse, symbol of the pride of the Berber peoples It is particularly significant in the Algerian history, tradition and culture. This study consists in establishing the hematologic values specific to the Barb horse in the national stud farm "Chaou-Chaoua" in Tiaret. Algeria. Age of the study animals varied between 1 and 23 years. The effects of age and sex were analyzed by dividing animals into four groups, A (1 - 2 years, n=5), B (3-5 years, n=5), C (5-10 years, n=5) and D (11-23 years, n=5); for females and E (2 - 3 years, n=5), F (5-7, n=5), G (10, n=5) and H (11-25, n=5) for males. Animals studied were clinically healthy. A blood sampling was carried out from all study animals, the following hematologic variables have been determined: erytrocytes (RBC), hematocrit (Ht), hemoglobin (Hb), mean cell volume (MCV), mean corpuscular hemoglobin concentration (MCHC), mean hemoglobin content (MHC), white blood cells (WBC), neutrophils, eosinophils, basophils, lymphocytes, monocytes, platelets, total number of platelets (PLT) and mean platelet volume (MPV). The obtained results showed that the hematologic values are within established standards for the other breeds of hot-blooded horses; these values approached the lower limits of the standards for the RBCs, HCT, Hb, WBCs and the lymphocytes. Statically significant (P<0.05) differences were observed between females in different age groups for the MCV, MCHC, Platelets and the MPV. Groups of males showed significant differences for lymphocytes and platelets and between males and females, significant differences related to the MCV, Neutrophils, Basophils Monocytes, Platelet and the MPV. This research showed that these hematologic parameters are weak, they approach the lower limits of the standards and that neither the age, nor the sex seem to have an influence on the hematologic values of the Barb horse.

Constitutive apoptosis in equine peripheral blood neutrophils in vitro

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Equine peripheral blood neutrophils underwent spontaneous time-dependent constitutive apoptosis when aged in culture for up to 36 h.

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Equine neutrophils undergoing apoptosis develop the structural and functional features of apoptosis observed in many cell types, including human neutrophils.

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Neutrophils undergoing apoptosis had diminished zymosan activated serum-stimulated chemiluminescence, but maintained responsiveness to phorbol myristate acetate.

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The constitutive rate of neutrophil apoptosis was promoted by lipopolysaccharide, tumour necrosis factor α and phagocytosis of opsonised ovine erythrocytes, while it was inhibited by dexamethasone and ZAS (a source of C5a).

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Equine and human neutrophil apoptosis differed in terms of responses to lipopolysaccharide and in the time-dependence of the response to dexamethasone.

The aim of this study was to characterise constitutive apoptosis in equine peripheral blood neutrophils, including assessment of factors that potentially modulate neutrophil survival through alteration of the rate of constitutive apoptosis. Cells underwent spontaneous time-dependent constitutive apoptosis when aged in culture for up to 36 h, developing the structural and functional features of apoptosis observed in many cell types, including human neutrophils. Neutrophils undergoing apoptosis also had diminished zymosan activated serum (ZAS)-stimulated chemiluminescence, but maintained responsiveness to phorbol myristate acetate (PMA). The constitutive rate of equine neutrophil apoptosis was promoted by lipopolysaccharide (LPS), tumour necrosis factor α and phagocytosis of opsonised ovine erythrocytes, while it was inhibited by dexamethasone and ZAS (a source of C5a). Formyl-Met-Leu-Phe, leukotriene B₄, platelet activating factor and PMA had no demonstrable effect on equine neutrophil apoptosis. There was a difference between equine and human neutrophil apoptosis in response to LPS and the time-dependence of the response to dexamethasone.

Coagulopathies in horses with colic

The most common coagulopathy in horses with colic is a hypercoagulable state associated with disseminated intravascular coagulation. The intensity of this coagulopathy depends on the severity and duration of the gastrointestinal lesion, with the ischemic and inflammatory problems and peritonitis being the most frequently affected by coagulopathies. Early initiation of prophylactic therapy significantly reduces the severe hypercoagulable state in horses with intestinal conditions which are recognized to be at high risk for disseminated intravascular coagulation. In addition to the systemic coagulopathy observed in horses with colic, a peritoneal coagulopathy independent from that occurring in blood has been observed, and its recognition and assessment may have clinical usefulness in the diagnosis of the gastrointestinal diseases and outcome.

Effects of haemorrhage on thermoregulation, heart rate and blood constituents in goats (Capra hircus)

The effects of two levels of bleeding (15 and 30%) on physiological responses were evaluated in adult goats. The magnitude of haemorrhage was expressed as percentage of initial total blood volume after plasma volume determination by dye dilution. The groups subjected to haemorrhage had higher rectal temperature, respiration rate and heart rate compared to the control; the responses were more marked with the higher level of bleeding. The treated groups had lower Packed Cell Volume (PCV), haemoglobin concentration (Hb) and Total Leucocyte Count (TLC) compared to the control; they were significantly lower with high level of bleeding compared to the control. The ratio of lymphocytes decreased, whereas the neutrophil ratio increased in treated groups compared to the control. The treated groups had lower serum total protein and albumin concentrations compared to the control. The plasma glucose level was higher in treated groups compared to the control and it increased with the increase of bleeding level. The treated groups had lower serum Na, Ca and Mg concentrations compared to the control. The levels of these minerals decreased with increase of bleeding level. The 15% bleeding group returned to normal values within 2 weeks, whereas the 30% bleeding group recovered within 5 weeks.

Dietary fish oil supplementation affects serum fatty acid concentrations in horses

Thirteen horses of Thoroughbred or Standardbred breeding were used to study the effect of dietary fish oil supplementation on blood lipid characteristics. Horses were assigned to either fish oil (n = 7) or corn oil (n = 6) treatment groups for 63 d. The fish oil contained 10.8% eicosapentaenoic acid (EPA) and 8% docosahexaenoic acid (DHA). Each horse received timothy hay and a mixed-grain concentrate at rates necessary to maintain BW. Oil (corn or fish) was top-dressed on the concentrate daily at a rate of 324 mg/ kg of BW. The n-6:n-3 ratio was approximately 3.6:1 for horses receiving the corn oil diet and 1.4:1 for horses receiving the fish oil diet. Horses were exercised 5 d/wk during the study. Before supplementation, there was no difference in the concentrations of any serum fatty acids between the 2 treatment groups. The mean basal concentrations of EPA and DHA on d 0 were 0.04 and 0.01 mg/mL, respectively. After 63 d, horses receiving the fish oil treatment, but not those receiving the corn oil treatment, had increased concentrations of EPA and DHA (P <0.05). Fish oil supplementation for 63 d also increased the concentrations of C22:0, C22:1, and C22:5 fatty acids (P <0.05). Overall, horses receiving fish oil had a decreased concentration of n-6 fatty acids (P <0.05) and a greater concentration of n-3 fatty acids (P <0.01), resulting in a lower n-6:n-3 fatty acid ratio after 63 d (P <0.05). Serum cholesterol concentrations increased (P <0.05) during the supplementation period in horses receiving the corn oil but not in horses receiving the fish oil. Compared with horses receiving corn oil, horses receiving fish oil had lower serum triglycerides at d 63 (P <0.05). These results demonstrate that 63 d of fish oil supplementation at 324 mg/kg of BW was sufficient to alter the fatty acid profile and blood lipid properties of horses receiving regular exercise.

Sensitivity of commercial prothrombin time reagents to detect coagulation factor deficiencies in equine plasma

The sensitivity of commercial prothrombin time (PT) tests was assessed based on a dilution series of equine pooled plasma (EPP) (experiment 1) and on 40 equine plasma samples with reduced activity of coagulation factors II, V, VII and X (experiment 2). Two different PT reagents (reagent 1, human placental thromboplastin; reagent 2, recombinant human tissue factor) were used according to the manufacturers' instructions (standard test, PT([ST])) and compared to a modified test procedure (modified test, PT([MT])) using sample dilution and fibrinogen addition. In all samples, sensitivity was lower (P<0.01) when using PT([ST]) with reagent 2 (0.20) than when using either PT([ST]) with reagent 1 (0.65) or PT([MT]) with both reagents (reagent 1, 0.60-0.75, reagent 2, 0.58-0.70, depending on sample dilution). The highest sensitivity was found for PT([MT]) when using a 1:20 sample dilution. In those samples in which at least one coagulation factor activity was decreased (by 20%; n=18), the sensitivity of PT([ST]) with reagent 2 (0.33) was found to be inadequate, in contrast to all other test procedures (0.83-0.94). This low sensitivity corresponded to shorter time intervals between different coagulation activity levels prepared by EPP dilution. The results indicate that adequate sensitivity of PT measurements in equine plasma can be achieved using a standard test procedure as long as a suitable reagent is used.

Management of hemodynamic changes associated with removal of a large abdominal myofibroblastic tumor in a pony

A 22-year-old female Welsh-cross pony was evaluated because of intermittent colic, signs of depression, pyrexia, anorexia, muscle wasting with abdominal distention, and weight gain over the preceding 12 months. A large abdominal mass was detected and surgically removed; the hemodynamic alterations and complications caused by the dramatic fluid losses and shifts that can occur in association with removal of a large abdominal mass required extensive postoperative management. Monitoring of clinical and hematologic variables such as attitude, heart rate, mucous membrane color, mean arterial blood pressure, PCV, and plasma total protein concentration provided useful information for successful management of the patient after surgery. On removal, the tumor weighed 19% of the pony's body weight and was characterized as a myofibroblastic tumor. Myofibroblastic tumors should be considered as a differential for large internal abdominal masses in horses, and surgical removal may be feasible and life extending with appropriate postoperative care.

The Variations of White Blood Cell Count in Lipizzan Horses

Total and differential leucocyte counts (lymphocytes, neutrophils, monocytes, eosinophils and basophils) were measured in 140 stallions, 101 mares and 25 foals of Lipizzan breed. The values fell in the normal ranges for warm-blooded horses. Differences between mares and stallions were not significant with the exception of foals, having higher white blood cell, neutrophil, lymphocyte, monocyte and basophil values in females than in males. Foals exhibited an age-related increase of total leucocyte count during the first 4 months of life, accompanied by a decrease in neutrophil and increase in lymphocyte and eosinophil counts. In mares and stallions, the total number of leucocytes, lymphocytes, monocytes and basophils significantly decreased but the number of neutrophils and eosinophils remained almost unchanged with age gain.

The influence of age and gender on haematological parameters in Lipizzan horses

Haematological parameters [red blood cell count (RBC), white blood cell count (WBC), packed cell volume (PCV), haemoglobin concentration, mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC)] in resting Lipizzan horses were determined for 143 stallions, 104 mares and 25 foals. The mean RBC and WBC values in Lipizzans were in the lower part of the normal range for warm-blooded horses. The mean PCV, MCV and MCH values were higher, but the mean haemoglobin concentration and MCHC values were lower than reported for other warm-blooded horses. In foals, the mean RBC, WBC, PCV, haemoglobin concentration and MCHC values were higher, whereas MCV and MCH were lower than in older animals. Results indicating a significant decrease in WBC (P < 0.01) and an increase in MCV, MCH and MCHC (P < 0.05) with increasing age are consistent with some other reports on warm-blooded horses. The age-related variations in RBC and PCV were less marked. Contrary to some reports, RBC (P < 0.01), WBC and haemoglobin concentration (P < 0.001) were higher in Lipizzan stallions than in mares, but differences in MCHC, MCH and MCV were insignificant. The specific haematological values determined in Lipizzans are presumably a result of selection and should be taken into consideration when dealing with this race of horses.

Cardiovascular, haematological and biochemical responses after large volume blood collection in horses

To determine whether removal of 20 mL/kg of blood (approximately 25% of blood volume) resulted in adverse physiological effects in donor horses, we removed this volume of blood from five horses and selected cardiovascular, haematological and biochemical variables measured during collection and for 31 days thereafter. We found that alteration in most variables occurred, although the changes in values usually remained within published reference ranges. Also, recovery of these alterations to pre-collection values was rapid, occurring within 24--48 h in most instances. We concluded that volumes of blood less than or equal to 20 mL/kg when collected appropriately from healthy donor horses result in no adverse acute or chronic physiological changes. These results suggest that horses undergo adequate physiological compensation when approximately 25% of blood volume is removed for the purposes of blood donation or production of plasma.