Erica McKenzie

Oregon State University | OSU · Department of Clinical Sciences

Selective breeding and discipline specific training has led to equine breeds adept at various athletic disciplines. Breed-specific skeletal muscle adaptations have been studied in many breeds but not Warmbloods (WB). We evaluated gluteal muscle contractile muscle fiber types and citrate synthase activity (CS), a marker for mitochondrial volume dens...

Anesthesia of adult horses and foals with preexisting muscular disorders is likely commonly practiced since clinical signs are often subtle, inhibiting recognition in advance of the procedure. Benzodiazepines likely have little to no direct effect on skeletal muscle perfusion or metabolism. The volatile anesthetic agents used most commonly in horse...

This chapter describes considerations that should be taken into account when choosing a venous catheter. It aims to list indications for the placement of a urinary catheter, and calculates the appropriate volume for a whole blood transfusion. The chapter explores the potential pitfalls and complications of nasogastric and orogastric intubation, and...

Diagnosing the cause of abdominal disease in goats can be challenging. Clinical history, physical investigation, and laboratory findings do not always allow definitive identification of intra-abdominal disease or the underlying cause. Multidetector CT (MDCT) has become more readily available and now often replaces or augments other abdominal imagin...

Case description: 2 Nigerian Dwarf goats (a doe [goat 1] and a wether [goat 2]) with coughing and nasal discharge since they were purchased at an auction 6 days prior were empirically treated for suspected pneumonia and intestinal parasitism. An ivermectin dosing error (intended dose, 0.4 mg/kg, PO; administered dose, 10 mg/kg, PO) was retrospecti...

Case description: 4 alpacas and 2 llamas (11 months to 11 years old) from 2 properties were examined for lethargy (6/6), salivation and regurgitation (4/6), and recumbency (3/6). Signs developed approximately 48 to 72 hours after accidental access to black oil sunflower seeds. Clinical findings: 3 alpacas died suddenly prior to treatment and wer...

Four, mature, client‐owned goats were presented to referral hospitals for recurrent diarrhea despite treatment for intestinal parasitism. Common clinical findings included diarrhea, poor condition, neutrophilia, and hypoalbuminemia. Testing for common infectious causes of diarrhea in goats was negative. Ultrasonography and computed tomography in 2...

Skeletal muscle citrate synthase (CS) activity serves as a marker for muscle oxidative capacity. CS activity was compared among Quarter Horses (QH), Arabians (AR), Thoroughbreds (TB), Standardbreds and Warmbloods at various ages and stages of training. Gluteus medius muscle biopsies were obtained at ages 6–23 m (n = 10), 2 y (n = 37), 3 y (n = 44)...

Skeletal muscle comprises 40% to 55% of mature body weight in horses, and its mass is determined largely by rates of muscle protein synthesis. In order to support exercise, appropriate energy sources are essential: glucose can support both anaerobic and aerobic exercise, whereas fat can only be metabolized aerobically. Following exercise, ingestion...

Ultrasonography and radiography are the most frequently used imaging techniques to evaluate abdominal pathology in domestic animals. Ultrasonography can often achieve a diagnosis in small ruminants, with ease of use and virtually no contraindications. Radiography also provides a relatively comprehensive overview, but reduced penetration of the abdo...

Ultrasound imaging is the mainstay of urinary and reproductive imaging in small ruminants, assisted by the relatively superficial location of the urinary and reproductive tracts in these species. Radiography can provide an excellent overview of the abdomen, but is often limited by a lack of adequate penetration. Computed tomography scans provide su...

Ca2+ regulation in equine muscle is important for horse performance, yet little is known about this species-specific regulation. We reported recently that horse encode unique gene and protein sequences for the sarcoplasmic reticulum (SR) Ca2+-transporting ATPase (SERCA) and the regulatory subunit sarcolipin (SLN). Here we quantified gene transcript...

Background Commercial genetic tests for type 2 polysaccharide storage myopathy (PSSM2) and myofibrillar myopathy (MFM) have not been validated by peer‐review, and formal regulation of veterinary genetic testing is lacking. Objectives To compare genotype and allele frequencies of commercial test variants (P variants) in MYOT (P2; rs1138656462), FLN...

Background Selenium or alpha‐tocopherol deficiency can cause neuromuscular disease. Beta‐carotene has limited documentation in horses. Objective To evaluate the effect of owner practices on plasma beta‐carotene concentration and risk of selenium and alpha‐tocopherol deficiencies. Animals Three‐hundred and forty‐nine adult (≥1 year), university an...

Prolonged submaximal exercise relies on the steady delivery of oxidizable substrates to the working muscle, with the sources of those substrates either stored reserves or food absorbed from the gastrointestinal tract during exercise. Fat oxidation could be advantageous for this type of exercise because of potentially greater reserves, but recent st...

Supplemental Figure 1 Timeline of herd testing after cases of Theiler's disease on Property B in Kansas (A) and Property E in New Jersey (B). Cases of Theiler's disease are indicated in gray or black boxes above the timeline. The time of diagnosis of additional cases of clinical or subclinical hepatitis is indicated in red above the timeline. Predi...

Supplemental Table 1 Clinical data and virology results for each Theiler's disease case. Chemistry values in bold were outside the reference interval

Supplemental Table 2 Additional diagnostic testing on Theiler's disease cases. HPLC, high performance liquid chromatography; RI, reference interval

Supplemental Table 1 Theiler's Disease Cases.

Background A novel equine parvovirus (EqPV‐H) was recently discovered in the equine liver with Theiler's disease. Objectives To determine the prevalence of EqPV‐H infection in naturally occurring Theiler's disease cases and in‐contact horses in the absence of historical equine biologic product administration. Animals Ten cases of Theiler's diseas...

Background Three flaviviruses (equine pegivirus [EPgV]; Theiler's disease–associated virus [TDAV]; non‐primate hepacivirus [NPHV]) and equine parvovirus (EqPV‐H) are present in equine blood products; the TDAV, NPHV, and EqPV‐H have been suggested as potential causes of serum hepatitis. Objective To determine the prevalence of these viruses in hors...

Equine myofibrillar myopathy (MFM) causes exertional muscle pain and is characterized by myofibrillar disarray and ectopic desmin aggregates of unknown origin. To investigate the pathophysiology of MFM, we compared resting and 3 h post-exercise transcriptomes of gluteal muscle and the resting skeletal muscle proteome of MFM and control Arabian hors...

To define which biologic, electrophysical and other modalities are used in horses for injury or performance issues, a questionnaire regarding 38 modalities was distributed to eight veterinary groups. A total of 305 complete or partial responses were obtained from over 10 geographic regions; 75.4% from private equine practice or regional private equ...

Horses are renowned for their incredible capacity for a range of athletic activities, and participation in athletic events arguably represents the most critical strut of the equine industry. Successful performance is typically a primary focus during participation in competitive athletic events, and relies upon a variety of innate physiological and...

Muscular disorders rank among the most prevalent problems of horses competing in a broad variety of athletic disciplines, including track racing, dressage, endurance racing and Western riding disciplines. As described in this review, active scientific investigation is continuing to elucidate the different mechanisms underlying specific muscular dis...

A previous report suggests a substantial incidence of exertional rhabdomyolysis (ER) in Arabian horses performing endurance racing. This study compared formalin histopathology and clinical and metabolic responses to a standardised field exercise test (SET) between Arabians with and without ER. Arabian horses with (n = 10; age 15.4 ± 5.6 years) and...

OBJECTIVE To compare the effects of equivalent volumes of equine plasma and 6% hydroxyethyl starch (600/0.75) solution (hetastarch) administered IV on plasma colloid osmotic pressure (pCOP) and commonly monitored clinicopathologic variables in horses. ANIMALS 6 healthy mares. PROCEDURES In a randomized, crossover study, horses were administered het...

Although exertionalrhabdomyolysis (ER) is common in Arabian horses,there are no dedicated studies describing histopathologic characteristics of muscle from Arabian horses with ER. To prospectively identify distinctive histopathologic features of muscle from Arabian endurance horses with a history of ER (pro-ER) and to retrospectively determine thei...

Objective: To determine the effect of dantrolene premedication on various cardiovascular and biochemical variables and recovery in isoflurane-anesthetized horses. Animals: 6 healthy horses. Procedures: Each horse was anesthetized twice with a 21- to 28-day washout period between anesthetic sessions. Food was not withheld from horses before eit...

Introduction Serum immunoglobulin fractions were evaluated in horses participating in multi‐day endurance exercise. Methods Serum IgGa, IgGb, IgG (T), IgA , and IgM were measured using horse‐specific ELISA kits in 44 trained horses prior to racing, after each day of racing 50 miles per day and in 15 untrained matched control horses. Data were anal...

Eleven healthy horses underwent 5 repeated abdominocenteses, with either a sharp-tipped spinal needle or a blunt-tipped teat cannula to investigate possible differences in success rate, sample volume, depth at which a sample was obtained, length of procedure, complications and cytological variables. Variables were analysed with a repeated-measures...

Exertional rhabdomyolysis (ER) is a reported syndrome in competing endurance horses; however the prevalence and cause of ER in this population has not been defined. To determine the prevalence of ER in a sample of endurance racing horses, and to investigate factors, including relevant genetic defects, contributing to the occurrence of rhabdomyolysi...

Endurance competition frequently provokes serum biochemistry alterations in horses racing single day events. This study assessed the effect of consecutive days of endurance racing on commonly analysed serum biochemistry variables of horses. Blood was obtained once before 54 horses commenced racing 40 km or 80 km/day, and 4-6 h after horses finished...

Chronic exercise can alter immune function. The objective of this study was to determine the effect of training and racing on serum immunoglobulin fractions (sIg) in horses participating in a multiday endurance event. Blood was obtained from 54 horses the day before a multiday race event with distance categories of 40 km (n=10) or 80 km (n=44) per...

Background The objective was to determine the effects of agility exercise on dogs of different skill levels with respect to urinary eicosanoids, urinary 15F2t-isoprostane (lipid peroxidation marker) and hematological/biochemical changes in plasma. Fifteen adult dogs had blood and urine samples obtained prior to, immediately and 4-hours following an...

To compare the effects of hetastarch and lactated Ringer's solution (LRS) on plasma colloid osmotic pressure (pCOP) and other hematologic variables in healthy llamas. Prospective crossover study. 6 healthy female llamas. Procedures-Llamas were administered LRS (45 mL/kg [20.5 mL/lb]) and, after a 3-day washout period, hetastarch (15 mL/kg [6.8 mL/l...

Recurrent exertional rhabdomyolysis (RER) occurs in fit, nervous Thoroughbreds fed high nonstructural carbohydrate (NSC) diets. Clinical signs are diminished by feeding low NSC, high fat diets; however, the mechanism is unclear. To determine if the glucose, insulin and cortisol response to isocaloric diets varying in fat and NSC availability differ...

Dantrolene sodium is used to prevent exertional rhabdomyolysis in predisposed horses. Food intake might negatively impact dantrolene bioavailability in horses; however, prolonged feed restriction might be detrimental to performance. To determine a minimum duration of feed restriction that would optimise plasma dantrolene concentrations in horses af...

3 alpaca crias and cadavers of an alpaca cria and a llama cria were evaluated for evidence of esophageal dysfunction. All 5 crias were between 3 and 5 months of age when clinical signs developed, and all had a thin body condition when examined. Clinical signs included coughing, regurgitation, and grossly visible esophageal peristaltic waves. A bari...

Introduction: Exercise induces an inflammatory response that alters eicosanoid production in humans and horses. The purpose of this study was to determine the effects of agility exercise on eicosanoid production in dogs and whether skill level has any effect. Materials and Methods: Competing agility dogs were examined and their skill level record...

Diarrhea is highly prevalent in racing sled dogs, although the underlying causes are poorly understood. Hypothesis: Clostridium perfringens enterotoxin (CPE) and Clostridium difficile Toxin A and B are associated with diarrhea in racing sled dogs. One hundred and thirty-five sled dogs. Freshly voided feces were obtained from 55 dogs before racing a...

Serum immunoglobulin dynamics have not been studied in racing sled dogs, despite hypoglobulinemia having been reported during racing events. Hypoglobulinemia in racing sled dogs is associated with decreases in serum IgA, IgE, IgG, and IgM concentrations during prolonged exercise. One hundred and fifty-seven Alaskan sled dogs that successfully compl...

Chronic exertional rhabdomyolysis represents a syndrome of recurrent exercise-associated muscle damage in horses that arises from a variety of etiologies. Major advances have been made in the understanding of the pathophysiology of this disease, and causative genetic defects have been recently identified for two conditions-polysaccharide storage my...

To assess changes in muscle glycogen (MG) and triglyceride (MT) concentrations in aerobically conditioned sled dogs during prolonged exercise. 54 Alaskan sled dogs fed a high-fat diet. 48 dogs ran 140-km distances on 4 consecutive days (cumulative distance, up to 560 km); 6 dogs remained as nonexercising control animals. Muscle biopsies were perfor...

20 alpaca crias (13 females and 7 males) were examined for diarrhea (n=20), weight loss (15), and poor appetite (5). Fourteen crias were between 8 and 18 days of age at time of admission. Cryptosporidiosis was diagnosed in all crias. Common biochemical abnormalities included acidemia, hyperlactemia, azotemia, and hyperglycemia and increases in aspa...

To determine the effects of SC administration of filgrastim on cell counts in venous blood and bone marrow of healthy adult alpacas. 10 healthy alpacas. Alpacas were randomly assigned to receive treatment with filgrastim (5 microg/kg, SC; n=5) or an equivalent volume of physiologic saline (0.9% NaCl) solution (5) once a day for 3 days. Blood sample...

To determine serum antibody titers against canine distemper virus (CDV), canine adenovirus type II (CAV-2), and canine parvovirus (CPV) in trained sled dogs prior to and after completion of a long-distance race. Prospective cohort study. 195 Alaskan sled dogs (from 18 kennels) that participated in the 2006 Iditarod Trail Race. All 1,323 dogs partic...

A description of the clinical signs and necropsy findings in 10 alpacas with thrombotic endocarditis. Clinical cases admitted to 2 veterinary referral hospitals between May 1998 and December 2006. A retrospective study was performed by searching hospital records to identify alpacas diagnosed with endocarditis. Common clinical findings included ster...

Polyuria and polydipsia provide a diagnostic challenge for the equine clinician. This article describes the various known causes of polyuria and polydipsia in horses and provides a description of a systematic diagnostic approach for assessing horses with polyuria and polydipsia to delineate the underlying cause. Treatment and management strategies...

Omeprazole reduces the severity of exercise-induced gastritis but not the prevalence of gastric lesions in sled dogs. The frequent feeding of sled dogs during competition likely results in decreased absorption of omeprazole and, thereby, decreased efficacy. Famotidine, a histamine-2 blocker with good bioavailability in the presence of food, would r...

To determine the impact of successive days of endurance exercise on select serum chemistry values in conditioned Alaskan sled dogs. Prospective cohort study. 10 conditioned Alaskan sled dogs. All dogs ran 160 km/d for 5 consecutive days. Serum was obtained prior to exercise and immediately after each exercise run; all samples were obtained before d...

To determine effects of exercise performed while breathing cold air on expression of cytokines and influx of neutrophils in airways of horses. 9 adult horses. In a crossover study, bronchoalveolar lavage fluid (BALF) was obtained 24 and 48 hours after each of 2 submaximal exercise sessions performed by horses while breathing warm (25 degrees C) or...

15 llamas and 34 alpacas between 3 weeks and 18 years old with fecal oocysts or intestinal coccidial stages morphologically consistent with Eimeria macusaniensis were examined. Nineteen of the camelids were admitted dead, and 30 were admitted alive. Camelids admitted alive accounted for 5.5% of all camelid admissions during this period. Many severe...

To determine whether prolonged exercise by conditioned sled dogs affects urine concentrations of homovanillic acid (a metabolite of dopamine), vanillylmandelic acid (a metabolite of norepinephrine and epinephrine), and cortisol. 24 conditioned Alaskan sled dogs (2 to 8.5 years old) that were in training for a multiday endurance race. Voided urine s...

Inspired air is warmed to body temperature and fully humidified by the upper airway mucosa under normal resting conditions. This conditioning process may not be completed by the upper airways during conditions of increased minute ventilation or when the inspired air is unusually cold, resulting in cooling and desiccation of lower respiratory surfac...

Alterations in the appearance and function of gastrointestinal mucosa are common after strenuous exercise. However, the duration of exercise required to alter the gastrointestinal mucosa has not been reported. We used 42 sled dogs to test the hypothesis that the magnitude of exercise-induced gastrointestinal mucosal dysfunction is related to exerci...

Humans undergoing intense exercise exhibit transient microalbuminuria. Previous studies have shown that swimming, but not running, induces microalbuminuria in dogs. In this study, urine samples were collected from nineteen well-conditioned Alaskan sled dogs and analysed by the Heska ERD-Screen Test for microalbuminuria. None of the dogs has microal...

To develop a diagnostic test for recurrent exertional rhabdomyolysis (RER) in Thoroughbreds that relied on in vitro contracture of muscle biopsy specimens and determine whether the inheritance pattern of RER diagnosed on the basis of this contracture test was consistent with an autosomal dominant trait. Clinical trial. 8 adult horses with RER and 1...

To determine the depletion of muscle glycogen during five consecutive days of endurance exercise in Alaskan sled dogs consuming a high-fat, low-carbohydrate diet. Forty-two fit Alaskan sled dogs were used in the study, of which six dogs served as nonexercising control animals. The remaining 36 dogs ran 160 km x d(-1) for up to 5 d while consuming a...

Athletes who perform repeated exercise while breathing cold air have a high prevalence of asthmalike chronic airway disease, but the mechanism linking such activity to airway inflammation is unknown. We used a novel animal model (exercising horses) to test the hypothesis that exercise-induced chronic airway disease is caused by exposure of intrapul...

Racing Alaskan sled dogs develop exercise-induced airway inflammation, similar to that reported for elite human athletes participating in cold-weather sports. These human athletes also have airway hyperresponsiveness, but airway function in sled dogs has not been measured. To compare respiratory mechanical properties in trained, rested Alaskan sled...

To determine the effect of oral administration of dantrolene sodium on serum creatine kinase (CK) activity after exercise in horses with recurrent exertional rhabdomyolysis (RER). 2 healthy horses and 5 Thoroughbreds with RER. 3 horses received 2 doses of dantrolene (4, 6, or 8 mg/kg, p.o., with and without withdrawal of food) 2 days apart; 90 minu...

To determine the effect of dietary starch, bicarbonate, and fat content on metabolic responses and serum creatine kinase (CK) activity in exercising Thoroughbreds with recurrent exertional rhabdomyolysis (RER), 5 RER horses were fed 3 isocaloric diets (28.8 Mcal/d [120.5 MJ/d]) for 3 weeks in a crossover design and exercised for 30 minutes on a tre...

To determine daily variation in urinary clearance and fractional excretion (FE) of electrolytes and minerals within and between horses and to compare volumetric and single-sample urine collection for determining FE values of diets with a range of dietary cation-anion balance (DCAB). 5 Thoroughbred and 6 mixed-breed mares. 3 isocaloric diets with lo...

To determine whether plasma, urine, and fecal electrolyte and mineral concentrations differ between clinically normal horses and Thoroughbreds with recurrent exertional rhabdomyolysis (RER) after consumption of diets varying in cation-anion balance. 5 Thoroughbred mares with RER and 6 clinically normal mixed-breed mares. Each of 3 isocaloric diets...

Thesis (Ph. D.)--University of Minnesota, 2003. Includes bibliographical references.