Middle-aged Horses Research Articles

Morphological characteristics of skin thickness in postnatal ontogenesis of karabayir horses

The characteristics of changes in the morphometric dimensions of the skin of horses belonging to the “Karabayir” breed at various physiological stages of postnatal ontogenesis were studied. It was found that the thickness of the skin of various anatomical points of the horse’s body increases rapidly in the 2-3 age stages of postnatal ontogenesis, and in old horses, this indicator decreases, the thickness of the skin of the legs increases in the distal direction in connection with the morphofunctional properties, and the skin elasticity decreases. In connection with the effect of mechanical friction on the skin, it is noted that it is thin in the inner part of the thigh, and the thickest in the soft heel of the hoof, as well as somewhat thick in the lower part of the body of horses, and the thinnest in the ventral part of the head, neck, withers and abdomen. Also, it was found that the dermis of the skin in young horses, the subcutaneous layer (subcutis) thickens in middle-aged horses, and the dermis and subcutaneous layer thins and the skin elasticity decreases in old horses.

Exercise regulates shelterin genes and microRNAs implicated in ageing in Thoroughbred horses

Ageing causes a gradual deterioration of bodily functions and telomere degradation. Excessive telomere shortening leads to cellular senescence and decreases tissue vitality. Six proteins, called shelterin, protect telomere integrity and control telomere length through telomerase-dependent mechanisms. Exercise training appears to maintain telomeres in certain somatic cells, although the underlying molecular mechanisms are incompletely understood. Here, we examined the influence of a single bout of vigorous exercise training on leukocyte telomerase reverse transcriptase (TERT) and shelterin gene expression, and the abundance of three microRNAs (miRNAs) implicated in biological ageing (miRNA-143, -223 and -486-5p) in an elite athlete and large animal model, Thoroughbred horses. Gene and miRNA expression were analysed using primer-based and TaqMan Assay qPCR. Leukocyte TRF1, TRF2 and POT1 expression were all significantly increased whilst miR-223 and miR-486-5p were decreased immediately after vigorous exercise (all p < 0.05), and tended to return to baseline levels 24 h after training. Relative to the young horses (~ 3.9 years old), middle-aged horses (~ 14.8 years old) exhibited reduced leukocyte TERT gene expression, and increased POT1 and miR-223 abundance (all p < 0.05). These data demonstrate that genes transcribing key components of the shelterin-telomere complex are influenced by ageing and dynamically regulated by a single bout of vigorous exercise in a large, athletic mammal — Thoroughbred horses. Our findings also implicate TERT and shelterin gene transcripts as potential targets of miR-223 and miR-486-5p, which are modulated by exercise and may have a role in the telomere maintenance and genomic stability associated with long-term aerobic training.

Equine enterolithiasis

Enterolithiasis is characterized by the presence of enteroliths in the large colon of horses with the ascending colon being the most common site of obstruction. Enteroliths are composed of ammonium magnesium phosphate, which is supplied both by the digestive processes intestinal bacteria and by feeds. The enteroliths typically form around a central nidus. Although enterolithiasis is seen all over the world, the most cases are reported from North America, and more specifically, California, South West Indiana and Florida. As far as breed is concerned, it affects predominantly Arab horses and rarely Quarter and Thoroughbreds. As far as age is concerned, it is usually seen in middle-aged horses. Although the pathogenesis of enterolithiasis is not fully understood, nutrition and heritability are believed to be a part in it. A rich diet in ammonium, magnesium and phosphorus predisposes to enterolith formation, as those elements are the main components of enteroliths. Clinical signs vary considerably and are rarely characteristic of the disease. Usually, the presence of the enterolith is free of symptoms unless it leads to obstruction. In most cases of enterolithiasis a small amount of faeces, air and the administered mineral oil could pass from the obstruction site. On the contrary, in complete obstructions the passage is closed, defecation is absent and no laxative can pass the obstruction site. The enterolith is rarely found by rectal examination. A history of recurrent colic might be connected to the presence of enteroliths that cause partial or temporary obstruction. The most accurate method for diagnosing enterolithiasis is abdominal radiography. The treatment of choice is the surgical removal of enteroliths, which has a favorable prognosis provided that the laparotomy is going to take place early in course of the disease, before the onset of peritonitis. Intestinal rupture, which rapidly leads to peritonitis, is the gravest and commonest complication. Other complications are colitis, leakage through the laparotomy site and peritonitis. In order to prevent reformation of enteroliths, the daily consumption of alfalfa hay has to be reduced dramatically and poor quality hay has to be administered.

Comparison of clinical findings and short-term survival between horses with intestinal entrapment in the gastrosplenic ligament and horses with intestinal entrapment in the epiploic foramen

OBJECTIVE To compare clinical findings and short-term outcome for horses with intestinal entrapment in the gastrosplenic ligament (GLE) with those of horses with intestinal entrapment in the epiploic foramen (EFE). DESIGN Retrospective case-control study. ANIMALS 43 horses with GLE (cases) and 73 horses with EFE (controls). PROCEDURES Medical records of horses examined because of colic at a veterinary teaching hospital between 1992 and 2012 were reviewed. Signalment was extracted from medical records for all horses with colic (colic population), and additional information regarding colic history, clinical findings, treatments, and outcome was extracted from the records of horses in which GLE or EFE was diagnosed during surgery or necropsy. Signalment was compared between the colic population and the case and control populations. Clinical findings and short-term outcome were compared between the cases and controls. RESULTS The proportions of middle-aged horses and geldings in both the case and control groups were greater than those in the colic population. Mean heart rate and blood and peritoneal fluid lactate concentrations in horses with EFE were significantly greater than those for horses with GLE. The proportion of horses that underwent surgery and were discharged from the hospital (short-term survival rate) did not differ between the GLE (22/25 [88%]) and EFE (29/34 [85%]) groups. CONCLUSIONS AND CLINICAL RELEVANCE Compared with the colic population, results suggested middle-aged geldings might be predisposed to GLE and EFE. The short-term survival rate was similar between the GLE and EFE groups even though horses with EFE had more severe systemic derangements than did horses with GLE.

Oxidative Stress Biomarkers and Erythrocytes Hemolysis in Well-Trained Equine Athletes Before and After Exercise

The chronic exposure to regular exercise training seems to increase resistance to oxidative stress and improves the antioxidant defense system. The purpose of the present study was to investigate the effect of an exercise test of moderate intensity on oxidative stress biomarkers, antioxidant enzymes activity, and osmotic resistance of erythrocytes in well-trained equine athletes. Eighteen middle-aged horses of Ukrainian warmblood (8.3 ± 1.6 years) and Holsteiner (7.4 ± 1.9 years) breeds were used in this study. All horses have been in regular training for several years. The exercise test induced a significant increase of erythrocyte values, hemoglobin concentration, and hematocrit in horses of both breeds. Regular training induces activation the antioxidant enzymes and thereby can reduce oxidative stress in athletic horses. Our results suggest that the exercise test in horses of both breeds attenuates oxidative stress and accompanied with a significant decrease of lipid peroxidation and oxidatively modified proteins in erythrocytes after exercise. The findings of the present study demonstrated the elevated level of erythrocytes' catalase and glutathione reductase in Ukrainian warmblood horses, as well as decreased level of superoxide dismutase and glutathione reductase in Holsteiner horses reporting changes in levels of exercise-induced oxidative stress biomarkers in horses of both breeds. Statistically significant differences in the percentage of hemolyzed erythrocytes between pre-exercise and postexercise tests were observed and thereby signifying an oxidative stress-dependent impairment of erythrocyte stability. Our data suggest that oxidative stress and enzymatic antioxidant defense biomarkers can be used for the monitoring of fitness level, health benefits, and performance of equine athletes.

Comparison of the Immunologic Response to Anthelmintic Treatment in Old Versus Middle-Aged Horses

The purpose of this study was to evaluate whether aged horses demonstrate statistically higher fecal egg counts (FECs) compared with middle-aged horses and to investigate systemic expression of proinflammatory cytokines in old and middle-aged horses treated with moxidectin compared with horses treated with pyrantel pamoate. Old horses (n = 21) and middle-aged horses (n = 19) were blocked by levels of inflammation and randomly allocated to one of the following treatment groups: group 1 (n = 8) old treated with moxidectin gel; group 2 (n = 9) old treated with pyrantel pamoate paste; group 3 (n = 4) old receiving no treatment; group 4 (n = 8) middle-aged treated with moxidectin gel; group 5 (n = 7) middle-aged treated with pyrantel pamoate paste, and group 6 (n = 4) middle-aged receiving no treatment. Fecal samples were collected on day 0 and again 14 days after treatment to determine FECs and presence of Strongylus vulgaris by polymerase chain reaction. Peripheral blood was also collected on day 0 and again at days 3, 5, and 14 after deworming for inflammatory cytokine analysis, along with routine hematological analyses. Results indicated that old horses have significantly higher FEC than middle-aged adults. Fecal egg counts declined significantly after anthelmintic treatment in both age groups of horses. Inflammatory markers exhibited differences between age groups and by anthelmintic treatment. In summary, this study provided evidence of different inflammatory and immunologic reactions to anthelmintic treatment in old horses. Moreover, the higher FECs found in the old horse group may have practical implications for parasite management routines on farms with representation of this age group.

13 Tumor necrosis factor-α gene expression before and after exercise in middle-aged and older horses

s / Journal of Equine Veterinary Science 35 (2015) 383e391 388 13 Tumor necrosis factor-a gene expression before and after exercise in middle-aged and older horses M.M. Darby*, S.R. Malone , D.W. Horohov , and D.E. Chappell 1 Morehead State University, Morehead, KY, USA; University of Kentucky, Lexington, KY, USA Tumor necrosis factor-a (TNF-a) is a pro-inflammatory cytokine that is expressed at different levels depending on the age of the horse. Age influences the animal's ability to launch an appropriate immune response and as horses age they exhibit a lower inflammatory response. Twenty-six adult horses (n 1⁄4 8 mares; n 1⁄4 18 geldings) were used to test the hypothesis that older horses would have higher pre-exercise TNF-a values and lower postexercise values than middle-aged horses. Horses were used in a University riding program andwere ridden for approximately one hour undergoing exercise of varying intensity. Blood samples (~4 mL) were collected via venipuncture into PAXgene tubes before exercise (pre) and 3 h after exercise (post). Blood samples were analyzed using real-time polymerase chain reaction (PCR) with equine-specific primers. Statistical significance was set at P < 0.05 and analysis was done using an ANOVA. Horses were split into age groups, middle-aged (<15 years; n 1⁄4 13; mean age 10 years; range 7e14 years) and older (1⁄4 15 years; n 1⁄4 13; mean age 17.6 years; range 15e21 years). The results are displayed as the mean ± SEM. Older horses had similar (P 1⁄4 0.24) pre-exercise TNF-a mRNA expression as middle-aged horses (middle-aged 0.075 ± 0.06; older 0.18 ± 0.07). Post-exercise there was no significant difference (P 1⁄4 0.119) between groups for TNF-a mRNA expression (middle aged 0.32 ± 0.08; older 0.14 ± 0.07). The magnitude of the response to exercise was similar in both groups of horses. Older horses had slightly, but not significantly, higher TNF-a mRNA expression pre-exercise and this could be expected due to chronic inflammation or underlying conditions. Future studies may focus on a more diverse age population with a wider gap betweenmiddle-aged and older horses andmore control over underlying medical conditions.

Ultrasonographic visualization of the liver in sites recommended for blind percutaneous liver biopsy in horses.

To ascertain the frequency of ultrasonographic identification of liver at sites recommended for blind percutaneous liver biopsy in middle-aged horses and to determine whether the liver is obscured by other organs or too thin for safe sample collection at recommended locations. Prospective case series. 36 healthy middle-aged (between 3 and 18 years old) Quarter Horses or Quarter Horse crosses [Corrected]. Blood samples were collected from each horse and submitted for evaluation of liver function. Horses with any indication of liver dysfunction on serum biochemical analysis were excluded. The region just below a line drawn between the dorsal aspect of the tuber coxae and the point of the elbow joint in the right 11th, 12th, 13th, and 14th intercostal spaces (ICSs) was imaged by ultrasonography for the presence of liver. In each ICS, liver thickness and whether there was partial obstruction in viewing the liver caused by other abdominal or thoracic organs were recorded. 39% (14/36) of horses had liver imaged on ultrasonographic examination in all of the 11th to 14th ICSs. None of the 36 horses had liver of adequate thickness (ie, liver thickness ≥ 3.5 cm) for biopsy in all of the imaged ICSs. For 22 horses in which the liver was not visible on ultrasonographic examination of an ICS, lung was imaged instead in 12 (55%) horses, intestine in 8 (36%), and both intestine and lung in 2 (9%). On the basis of the results of this study, the practice of blind percutaneous liver biopsy in horses is not recommended because of the risk of serious complications.

Equine Recurrent Airway Obstruction

Abstract Equine Recurrent Airway Obstruction (RAO), also known as heaves or broken wind, is one of the most common disease in middle-aged horses. Inflammation of the airway is inducted by organic dust exposure. This disease is characterized by neutrophilic inflammation, bronchospasm, excessive mucus production and pathologic changes in the bronchiolar walls. Clinical signs are resolved in 3-4 weeks after environmental changes. Horses suffering from RAO are susceptible to allergens throughout their lives, therefore they should be properly managed. In therapy the most importanthing is to eliminate dust exposure, administration of corticosteroids and use bronchodilators to improve pulmonary function.

Haemangiosarcoma in the horse

SummaryNeoplasms arising from vascular endothelial cells include benign haemangioma and malignant haemangiosarcoma, both of which are rare in the horse. Haemangiosarcoma can arise as a solitary mass, typically involving the eye or skin, or as disseminated tumours throughout multiple organs. There is no sex, breed or age predilection but most cases are found in middle aged horses. Clinical presentations of haemangiosarcoma in the horse include the presence of a visible mass or reflect dysfunction of the organ involved, thus making it difficult to differentiate from other neoplasms. Ante mortem diagnosis through clinicopathological findings, cytological findings of body cavity effusions or fine needle aspirates are often unrewarding. Biopsy or mass submission for histopathological examination may aid in diagnosis of haemangiosarcoma. A majority of cases are diagnosed post mortem; however, if the mass is poorly differentiated additional diagnostics such as immunohistochemical staining may be needed. Unfortunately, treatment of haemangiosarcoma is often unrewarding and limited based on the location of the mass and the aggressive nature of this neoplasm.

Differentiation of equine mesenchymal stromal cells into cells of neural lineage: potential for clinical applications.

Mesenchymal stromal cells (MSCs) are able to differentiate into extramesodermal lineages, including neurons. Positive outcomes were obtained after transplantation of neurally induced MSCs in laboratory animals after nerve injury, but this is unknown in horses. Our objectives were to test the ability of equine MSCs to differentiate into cells of neural lineage in vitro, to assess differences in morphology and lineage-specific protein expression, and to investigate if horse age and cell passage number affected the ability to achieve differentiation. Bone marrow-derived MSCs were obtained from young and adult horses. Following demonstration of stemness, MSCs were neurally induced and microscopically assessed at different time points. Results showed that commercially available nitrogen-coated tissue culture plates supported proliferation and differentiation. Morphological changes were immediate and all the cells displayed a neural crest-like cell phenotype. Expression of neural progenitor proteins, was assessed via western blot or immunofluorescence. In our study, MSCs generated from young and middle-aged horses did not show differences in their ability to undergo differentiation. The effect of cell passage number, however, is inconsistent and further experiments are needed. Ongoing work is aimed at transdifferentiating these cells into Schwann cells for transplantation into a peripheral nerve injury model in horses.

In vitroanalysis of equine, bone marrow‐derived mesenchymal stem cells demonstrates differences within age‐ and gender‐matched horses

Stem cell therapies are used routinely in equine practice. Most published reports characterise stem cells derived from younger horses; however, middle-aged horses are often in athletic performance, and experience degenerative medical conditions. Thus, mesenchymal stem cells (MSCs) from this group should be investigated. To describe differences in in vitro adherence, proliferation and potential for differentiation of equine bone marrow-derived MSCs (equine BMMSCs) harvested from middle-aged (10-13 years old) female donors. Descriptive study of stem cell characteristics. Equine BMMSCs from 6 horses were cultured in vitro and evaluated for viability, proliferation, osteogenesis, chondrogenesis, adipogenesis, cluster-of-differentiation markers and gene expression. Equine BMMSCs from all 6 donors demonstrated fibroblastic, cellular morphology, adherence to plastic and expression of cluster-of-differentiation markers. They varied in their rate of proliferation and trilineage differentiation. The equine BMMSCs of one of 6 donors demonstrated a higher rate of proliferation, enhanced ability for cell passaging and a more robust in vitro differentiation. Comparatively, equine BMMSCs from 2 donors demonstrated a lower rate of proliferation and lack of osteogenic and chondrogenic differentiation. The results of this study confirm that donor-to-donor variation in equine BMMSCs exists and this variation can be documented using in vitro assays. Subjective assessment suggests that the rate of proliferation tends to correlate with differentiation potential.

Effect of gluteus medius muscle sample collection depth on postprandial mammalian target of rapamycin signaling in mature Thoroughbred mares

To determine the effect of biopsy collection depth on the postprandial activation of mammalian target of rapamycin (mTOR) signaling factors, particularly protein kinase B, ribosomal protein S6 kinase, ribosomal protein S6, and eukaryotic initiation factor 4E binding protein 1 in middle-aged horses. 6 healthy Thoroughbred mares (mean ± SD age, 13.4 ± 3.4 years). Horses were fed a high-protein feed at 3 g/kg. Sixty minutes after horses were fed, the percutaneous needle biopsy technique was used to collect biopsy specimens from the gluteus medius muscle at 6, 8, and 10 cm below the surface of the skin. Muscle specimens were analyzed for the activation of upstream and downstream mTOR signaling factors, myosin heavy chain (MHC) isoform composition, and amino acid concentrations. A 21% increase in MHC IIA isoform expression and a 21% decrease in MHC IIX isoform expression were identified as biopsy depth increased from 8 to 10 cm below the surface of the skin; however, no significant change was evident in the degree of MHC I expression with muscle depth. Biopsy depth had no significant effect on the phosphorylation of any of the mTOR signaling factors evaluated. Postprandial mTOR signaling could be compared between middle-aged horses when biopsy specimens were collected between 6 and 10 cm below the surface of the skin. Optimization of muscle biopsy techniques for evaluating mTOR signaling in horses will facilitate the design of future investigations into the factors that regulate muscle mass in horses.

Prevalence and genetic diversity of equine piroplasms in Tov province, Mongolia

Equine piroplasmosis represents a serious problem in horse industry. Although, researchers suggested the possible use of sub-unit vaccines to control equine piroplasmosis, the genetic diversity of vaccine candidate antigens was not properly investigated. In the present study, we screened 250 horses reared in three different districts of Tov province, Mongolia, for Babesia caballi and Theileria equi using ELISA and nested PCR (nPCR) assays. Among these animals, piroplasms were detected in 128 (51.2%) horses by nPCR assays (B. caballi, 42.4%; T. equi, 6.4%; and mixed infections, 2.4%), while 204 (81.6%) were positive by ELISA (B. caballi, 51.6%; T. equi, 19.6%; and mixed infections, 10.4%). Male and middle-aged horses showed higher positive rates than female and younger or older horses. The findings also suggested that a combination of nPCR and ELISA techniques might be useful to detect horses that were chronically or subclinically infected with piroplasms. B. caballi-BC48 and T. equi-EMA-1 gene sequences, in addition to 18S rRNA, were subjected to phylogenetic analyses, and the findings suggested the presence of genetically diverse populations of equine piroplasms in Mongolia. BC48 sequences were separated into four clades in phylogram, and all the Mongolian sequences determined in the present study were found in a single clade. However, a single BC48 sequence previously isolated from a tick in Mongolia formed a separate branch. Similarly, EMA-1 sequences formed four clades, and Mongolian sequences were observed in two different clades, one of which was formed only of Mongolian sequences and is suggested as a new clade. This is the first report that describes the genotypes of equine piroplasms in Mongolia. The findings also emphasized the need for further investigations to study the effect of genetic diversity observed among BC48 as well as EMA-1 sequences on host’s immune responses.

Effects of training on potassium homeostasis during exercise and skeletal muscle Na+,K+-ATPase concentration in young adult and middle-aged Dutch Warmblood horses

To investigate the effects of moderate short-term training on K+ regulation in plasma and erythrocytes during exercise and on skeletal muscle Na+,K(+)-ATPase concentration in young adult and middle-aged horses. Four 4- to 6-year-old and four 10- to 16-year-old Dutch Warmblood horses. The horses underwent a 6-minute exercise trial before and after 12 days of training. Skeletal muscle Na+,K(+)-ATPase concentration was analyzed in gluteus medius and semitendinosus muscle specimens before and after the 12-day training period. Blood samples were collected before and immediately after the trials and at 3, 5, 7, and 10 minutes after cessation of exercise for assessment of several hematologic variables and analysis of plasma and whole-blood K+ concentrations. After training, Na+,K(+)-ATPase concentration in the gluteus medius, but not semitendinosus, muscle of middle-aged horses increased (32%), compared with pretraining values; this did not affect the degree of hyperkalemia that developed during exercise. The development of hyperkalemia during exercise in young adult horses was blunted (albeit not significantly) without any change in the concentration of Na+,K(+)-ATPase in either of the muscles. After training, the erythrocyte K+ concentration increased (7% to 10%) significantly in both groups of horses but did not change during the exercise trials. In horses, the activation of skeletal muscle Na+,K(+)-ATPase during exercise is likely to decrease with age. Training appears to result in an increase in Na+,K(+)-ATPase activity in skeletal muscle with subsequent upregulation of Na+,K(+)-ATPase concentration if the existing Na+,K(+)-ATPase capacity cannot meet requirements.

Microanatomic characteristics of the insertion of the distal sesamoidean impar ligament and deep digital flexor tendon on the distal phalanx in healthy feet obtained from horses.

To describe microanatomic characteristics of the insertion of the aistal sesamoidean impar ligament (DSIL) and deep digital flexor tendon (DDFT) on the distal phalanx in horses. Healthy feet obtained from 62 horses of various breeds. Feet from 23 horses were used to histologically examine the insertion of the DSIL and DDFT (n = 7), its vasculature (10), and neural elements (6). In 39 other horses, the insertion zone was examined for proteoglycan. The insertion of the DSIL and dorsal half of the DDFT contained bundles of collagen fibers with intervening loose connective tissue septa with arteriovenous complexes (AVC) and nerve fibers. Microscopic examination revealed adaptive changes in the insertion with regard to proteoglycan content. In young adult horses, little or no staining for proteoglycans was evident, whereas in middle-aged horses, moderate proteoglycan staining was seen. Six older horses had slight proteoglycan staining at the insertion. The study revealed that this region contained a rich neurovascular complex between the collagen bundles. A gradual increase in production of proteoglycan, evident at the insertion of the DSIL and DDFT on the distal phalanx, indicates that adaptive responses to stress rather than age alone may be the primary determining factor. These observations indicate that this insertion site may be susceptible to stress during stance and impact loading, because this region appears to be strategically situated to regulate important neurovascular functions of the foot.

Diagnostic findings and prognosis following arthroscopic treatment of subtle osteochondral lesions in the shoulder joint of horses: 15 cases (1996-1999).

To determine clinical, scintigraphic, radiographic, and arthroscopic findings and results of treatment in horses with lameness attributable to subtle osteochondral lesions of the shoulder joint. Retrospective study. 15 horses. Medical records were reviewed, and results of physical examination, scintigraphy, radiography, arthroscopy, and treatment were recorded. Severity of lameness ranged from grade 1 to 4. Response to shoulder flexion or extension was variable. Twelve horses had a narrow upright foot. Intra-articular anesthesia of the shoulder joint localized the cause of the lameness to the shoulder joint in 9 of 10 horses. Scintigraphic abnormalities were detected in 4 of 6 horses. Radiographic lesions were subtle and included glenoid sclerosis, focal glenoid lysis, small glenoid cysts, and alterations in the humeral head contour. Arthroscopic evaluation confirmed clefts in the glenoid cartilage, glenoid cysts, a humeral head cyst, fibrillation of the humeral head cartilage, cartilage fragmentation, or a nondisplaced fracture of the humeral head. After treatment, 12 horses returned to their previous level of performance, 1 was sound for light riding, 1 remained lame, and 1 was euthanatized because of chronic lameness. Results suggest that a combination of physical examination, scintigraphy, and radiography is necessary to diagnose subtle osteochondral lesions of the shoulder joint in horses. Arthroscopy can be used to confirm the diagnosis and treat cartilage and subchondral bone lesions. Young and middle-aged horses with subtle osteochondral lesions of the shoulder joints have a good prognosis for return to performance following arthroscopic treatment.

Disseminated hemangiosarcoma in the horse: 35 cases.

Thirty-five cases of disseminated hemangiosarcoma (21 clinical cases and 14 previously reported cases) were reviewed to describe the disease in horses. Hemangiosarcoma occurred in mature, particularly middle-aged horses, with no apparent sex predilection. Thoroughbreds seemed to be overrepresented (13 cases) but a true breed predilection could not be established. The respiratory and musculoskeletal systems were most commonly affected and presenting complaints included dyspnea (26%), subcutaneous or muscular swelling (24%), epistaxis (17%), and lameness (12%). Heart and respiratory rates were usually increased and mucous membrane color was frequently pale or icteric. Capillary refill time and rectal temperature were often normal. Anemia (88%), neutrophilic leukocytosis (62%), and thrombocytopenia (48%) were common. Examination of tissue samples collected by fine-needle aspirate or biopsy established an antemortem diagnosis in 4 horses. The diagnosis was made during postmortem examination in the remaining 31 horses. The lung and pleura (77%), skeletal muscle (46%), and spleen (43%) were most commonly affected. A primary site of tumor involvement could be identified in 22 horses. Hemangiosarcoma should be included as a differential diagnosis for horses with evidence of hemorrhage into body cavities, skeletal muscle, or subcutaneous locations.

Chronic glomerulonephritis in two horses

Two middle-aged horses with chronic glomerulonephritis and renal insufficiency are described. Both horses had a history of dullness, inappetence, lethargy and weight loss during the monthprior to presentation. Physical examination revealed thin horses with pale mucus membranes and generalized subcutaneous edema. Routine hematology and serum biochemistry detected anemia, hypoalbuminemia, hypercalcemia, hyperkalemia and profound azotemia in both horses. Urinalyses revealed low urine specific gravities and proteinuria. The diagnosis of chronic glomerulonephritis was confirmed by microscopic examination and both horses had kidneys with prominent glomeruli which wherethickened by an amorphous, eosinophilic material.