Comparison of volumetric urine collection versus single-sample urine collection in horses consuming diets varying in cation-anion balance

OBJECTIVE: 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). ANIMALS: 5 Thoroughbred and 6 mixed-breed mares. PROCEDURE: 3 isocaloric diets with low, medium, and high DCAB values (85, 190, and 380 mEq/kg of dry matter, respectively) were each fed for 14 days. Daily blood samples, single urine samples collected by using a urinary catheter (5 mares), and volumetric urine collections (6 mares) were obtained during the last 72 hours of each diet. RESULTS: Urine and plasma pH values, plasma concentrations, and FE values of sodium, chloride, potassium, magnesium, phosphorus, and calcium were altered by varying the DCAB. Noticeable variation in clearance and FE values was detected within horses from day-to-day on the same diet as well as between horses. Fractional excretion values were not significantly different between single-sample and volumetric methods, except for magnesium in the high DCAB diet. Volumetric and single-sample collections revealed similar patterns of change in urinary FE values with varying DCAB, except for calcium and magnesium. CONCLUSIONS AND CLINICAL RELEVANCE: Substantial variation in clearance and FE of electrolytes and minerals are evident within horses between 24-hour periods as well as between horses fed a specific diet. Three daily urine samples provide similar information regarding dietary-induced changes in clearance and FE values (excluding calcium and magnesium) as that obtained by volumetric urine collection.     

Characterization of antimicrobial aerosols for administration to horses

A study was conducted to characterize the aerosols produced by a medical ultrasonic nebulizer using solutions containing antimicrobials appropriate for therapy of equine lower respiratory bacterial infections (gentamicin sulfate and ceftiofur sodium). Test aerosols were generated using an ultrasonic nebulizer and were analyzed using a laser diffraction aerosol particle analyzer. The aerosol was described in terms of the particle size distribution (volume median diameter), span (sample dispersion), and aerosol density (% volume). The particle size distribution and aerosol density of gentamicin and ceftiofur aerosols were affected by the antimicrobial concentration of the solution. All solutions produced aerosols appropriate for delivery of antimicrobials to the intrathoracic airways of the horse, but the gentamicin (50 mg/ml) and ceftiofur (25 mg/ml) solutions offered the optimal combinations of particle size and aerosol density.     

Management of proximal sesamoid bone fractures in the horse

The case records of 49 horses with proximal sesamoid bone fracture were studied. The population consisted of 20 Thoroughbreds, 20 Standardbreds, 5 Quarter Horses, 2 Arabians, and 2 grade horses. The fractured bones were classified into 5 categories: apical fractures, basilar fractures, abaxial fractures, middle one-third fractures, and bilateral comminuted-distracted fractures. Apical fractures occurred most frequently in the Standardbred, with the prevalence of medial fracture being equal to that of lateral fracture. Basilar fractures occurred predominantly in the Thoroughbred, with the highest prevalence in the lateral sesamoid bone of the right front fetlock. Bilateral comminuted-distracted fractures also occurred primarily in the right front fetlock. The prognosis following surgical removal of apical fractures appeared to be superior to that for stall rest alone. The prognosis for basilar fractures was poor.     

Pea mania: deranged behaviour in cattle grazing a pea crop (Pisum sativum var arvense)

Hypersensitivity to external stimuli, progressing in some animals to manic behaviour, occurred in a cattle herd that grazed a crop of field peas (Pisum sativum var arvense) in the pre-flowering stage. Haematological and biochemical analyses eliminated hypomagnesaemia and ketosis as diagnoses. Other than two steers euthanased due to injuries sustained during manic episodes, all affected animals survived, recovering over 3 days when moved to alternative pasture. No necropsies were conducted. No microbial pathogens or endophytes were found on or in the plants. A previously reported incident in Victoria in 1987 in cattle grazing peas appeared to be of a similar nature. Environmental factors leading to these incidents were not clearly identified.     

Using Neutral Models to Identify Constraints on Low-severity Fire Regimes

Climate, topography, fuel loadings, and human activities all affect spatial and temporal patterns of fire occurrence. Because fire is modeled as a stochastic process, for which each fire history is only one realization, a simulation approach is necessary to understand baseline variability, thereby identifying constraints, or forcing functions, that affect fire regimes. With a suitable neutral model, characteristics of natural fire regimes estimated from fire history data can be compared to a “null hypothesis”. We generated random landscapes of fire-scarred trees via a point process with sequential spatial inhibition. Random ignition points, fire sizes, and fire years were drawn from uniform and exponential family probability distributions. We compared two characteristics of neutral fire regimes to those from five watersheds in eastern Washington that have experienced low-severity fire. Composite fire intervals (CFIs) at multiple spatial scales displayed similar monotonic decreases with increasing sample area in neutral vs. real landscapes, although patterns of residuals from statistical models differed. In contrast, parameters of the Weibull distribution associated with temporal trends in fire hazard exhibited different forms of scale dependence in real vs. simulated data. Clear patterns in neutral landscapes suggest that deviations from them in empirical data represent real constraints on fire regimes (e.g., topography, fuels). As with any null model, however, neutral fire-regime models need to be carefully tuned to avoid confounding these constraints with artifacts of modeling. Neutral models show promise for investigating low-severity fire regimes to separate intrinsic properties of stochastic processes from the effects of climate, fuel loadings, topography, and management.     

Differences in the lymphoproliferative response of cattle and sheep to bovine leucosis virus infection

Lymphoblastic leukaemia, preceded by a significantly increasing percentage of prolymphocytes in peripheral blood smears for from 12 to 68 weeks before death was a feature of sheep which developed lymphosarcoma following inoculation with the Australian strain of bovine leucosis virus (BLV). Lymphocytosis and/or the appearance of immature cells were a reliable predictor of tumour formation in sheep, but not in cattle. There was a terminal lymphoblastic leukaemia in only 43 of 84 cattle with lymphosarcoma. Differences in the morphological appearance and glycogen content of the leukaemic lymphoblasts of sheep and cattle were observed. In spite of these differences the high frequency of lymphocytosis and lymphosarcoma in experimentally infected sheep suggests that they could be a useful model for studying the pathological and immunological responses to BLV infection.     

Serum Concentrations of Lidocaine and Its Metabolites MEGX and GX During and After Prolonged Intravenous Infusion of Lidocaine in Horses after Colic Surgery

Lidocaine is the most commonly used prokinetic after gastrointestinal surgery in horses. Cardiovascular status, hepatic function, and duration of therapy are the primary determinants of lidocaine metabolism, and these factors could affect equine patients after colic surgery. This study examined the systemic concentrations of lidocaine and its active metabolites monoethylglycinexylidide (MEGX) and glycinexylidide (GX), in horses that had undergone colic surgery and subsequently received prolonged postoperative lidocaine infusions. The mean lidocaine concentration increased over the course of treatment but did not exceed the therapeutic range. Concentrations of MEGX and GX increased progressively, and concentrations exceeding 1,000 ng/ml were observed frequently after 72 hours of infusion. None of the horses in the study developed severe signs of toxicity; however, the progressively increasing concentrations of lidocaine, MEGX, and GX are cause for concern in clinically ill patients receiving prolonged lidocaine therapy. The potential contribution of MEGX and GX should be considered when evaluating adverse reactions to prolonged lidocaine infusions.     

Parasite control in Canadian companion animal shelters and a cost-comparison of anthelmintics

Animal shelters have limited resources and must accommodate large numbers of animals at unpredictable intake rates. These dogs and cats are often parasitized, which can adversely affect the health of animals and expose shelter workers and adoptive owners to zoonoses. We analyzed survey responses from rural (n = 32) and urban (n = 50) companion animal shelters across Canada, and compared the wholesale cost of commercially available anthelmintics to identify cost-effective methods of managing parasites within shelters. Almost all shelters employed nematocides (98% to 99%), but cestocides and ectoparasiticides were used less frequently. Shelters identified cost as an important consideration in choosing to perform fecal diagnostic testing and administer anthelmintics, and this motivated many shelters to selectively perform testing (66%) or never to test (32%), and to use drugs extralabel (80%).