Growth responses of three coexisting conifer species to climate across wide geographic and climate ranges in Yukon and British Columbia

This work aimed to compare radial growth–climate relationships among three coexisting coniferous tree species across a wide geographic and climate range from southern British Columbia (BC) to central Yukon, Canada. Tree-ring data were collected from 20 mature stands of white spruce (Picea glauca), lodgepole pine (Pinus contorta var. latifolia), and subalpine fir (Abies lasiocarpa). Linear relationships between annual growth variation and monthly and seasonal climate were quantified with correlation and regression analyses, and variation in climate–growth responses over a climatic gradient were quantified by regressing growth responses against local mean climatic conditions. Temperatures had more consistent and stronger correlations with growth for all three species than precipitation, but growth–climate responses varied among species and among sites. In particular, pine and fir populations showed different responses between BC and Yukon, whereas spruce showed a more consistent response across the study domain. Results indicate that (1) the response and sensitivity of trees to seasonal climate variables vary among species and sites and (2) winter temperatures prior to growth may have significant impacts on pine and fir growth at some sites. The capacity to adapt to climate change will likely vary among the study species and across climatic gradients, which will have implications for the future management of mixed-species forests in Yukon and BC.     

Constrictive pericarditis in a mare: attempted treatment by partial pericardiectomy.

Chronic constrictive pericarditis was diagnosed in a 6-year-old Thoroughbred mare based on the clinical findings of right congestive heart failure, hyperechoic pericardium without pericardial effusion, and a dip-and-plateau shape of the right ventricular pressure curve with equilibration of the diastolic pressures in all cardiac chambers. Treatment was attempted by partial pericardiectomy using a right lateral thoracotomy approach. Because of severe epicardial involvement recurrence of the constrictive pathology was noted 6 weeks after the surgical procedure. However, in selected cases in which the disease process is limited to the pericardium, partial pericardiectomy may offer a mode of therapy in horses suffering from constrictive pericarditis.     

Pharmacokinetics and pharmacodynamics of xylazine administered by the intravenous or intra‐osseous route in adult horses

In certain situations, an alternate route for parenteral drug administration in horses may be useful. The intra‐osseous (IO) route may provide a safe alternative to the intravenous (i.v.) route for administration of sedatives to horses when the i.v. route is inaccessible or undesirable. Six adult horses were administered xylazine i.v. or IO in a block‐randomized crossover design. For the i.v. trial, both jugular veins were catheterized, and one was used for xylazine administration, while the other was used for blood collection. For the IO trial, one jugular vein was catheterized for blood collection and an intra‐osseous device was placed in the tuber coxae using a powered driver for xylazine administration. Heart rate, respiratory rate, and head position were measured, and concentration of sedation was assessed at various times up to 90 min. Xylazine concentrations were measured using high‐performance liquid chromatography and noncompartmental analysis was performed. General linear mixed modeling and Wilcoxon signed‐rank tests were used for statistical analysis, with P ≤ 0.05. There were no significant differences in heart rate, respiratory rate, head position, concentration of sedation, C_max, T_max, half‐life, or AUC between the i.v. and the IO routes of drug administration. No complications were observed following placement of the intra‐osseous device. Intra‐osseous xylazine administration provides a useful option in emergent and other settings in which i.v. access is difficult or contraindicated.     

Towards a best practice methodology for the detection of Phytophthora species in soils

The genus Phytophthora contains species that are major pathogens worldwide, affecting a multitude of plant species across agriculture, horticulture, forestry, and natural ecosystems. Here, we concentrate on those species that are dispersed through soil and water, attacking the roots of the plants, causing them to rot and die. The intention of this study was to compare the soil baiting protocol developed by the Centre for Phytophthora Science and Management (CPSM) with two other baiting methods used in Australia. The aim was to demonstrate the effectiveness of each protocol for soil baiting Phytophthora species in different substrates. Three experiments were conducted: the first to test the sensitivity of each method to detect Phytophthora cinnamomi, the second to test the effect of substrate type (sand or loam), and the third to test the detection of species (P. cinnamomi, P. multivora, or P. pseudocryptogea). The specificity of different plant species baits was compared within and between the methods. Substrate type influenced isolation in all methods; however, the CPSM method was superior regardless of substrate, albeit slower than one of the other methods for one substrate. Comparing bait species between the three methods, Quercus ilex was the most attractive bait for P. cinnamomi, particularly in the CPSM method. The choice of protocol affected the isolation associated with each bait type. Overall, the multiple bait system used by CPSM was shown to provide the most sensitive and reliable detection of Phytophthora species from soil samples.     

Usefulness of a commercial equine IgG test and serum protein concentration as indicators of failure of transfer of passive immunity in hospitalized foals

Detection of failure of transfer of passive immunity (FTPI) is important in reducing morbidity and mortality in neonatal foals. We investigated the performance of a commercial equine IgG test (SNAP Foal IgG Test Kit) to diagnose FTPI in hospitalized foals. Furthermore, we evaluated the usefulness of serum total protein (STP) and serum globulin (SG) concentrations as indicators of FTPI. Serum IgG concentration was measured by means of the SNAP test and single radial immunodiffusion, and SG and STP concentrations were determined by means of a clinical chemistry analyzer. Subjects were 67 hospitalized foals <19 days old. The SNAP test was repeated on 37 samples from 29 foals, with identical results for 24 samples (kappa statistic, 0.64; 95% confidence interval [CI], 0.46-0.82). The sensitivity of the SNAP test to detect serum IgG concentration [IgG] < or =400 and < or =800 mg/dl was 90% (95% CI, 71-98%) and 95% (85-99%), respectively, and the specificity was 79% (71-82%) and 52% (39-57%), respectively. Sensitivity for detection of [IgG] < or =400 mg/dl was not affected (P > .05) by plasma fibrinogen concentration, sepsis score, or bacteremia. Specificity for detection of [IgG] < or = 800 mg/dl was lower (P < .05) in foals with sepsis score < or =11 (50% [31-60%] versus 100% [8-100%]) and bacteremia (25% [5-56%] versus 62% [45-62%]). Sensitivity and specificity of [STP] < or = 5.0 g/dl for [IgG] < or =800 mg/dl was 94% (83-99%) and 47% (30-56%), respectively. Performance of the SNAP test in hospitalized foals is impaired because of low specificity, but can have usefulness provided that the properties of the test and characteristics of the foal being examined are considered when interpreting the results. The STP and SG concentrations are poor sole indicators of FTPI in hospitalized foals, but may be useful adjunctive tests.     

Potential susceptibility of Australian native plant species to branch dieback and bole canker diseases caused by Phytophthora ramorum

Susceptibility to branch dieback caused by Phytophthora ramorum was tested using a detached branch assay for 66 Australian native plant species sourced from established gardens and arboreta in California. Six of these species were further tested for their susceptibility to bole cankers caused by P. ramorum using a sealed log assay. Isopogon formosus and Eucalyptus denticulata were identified as potentially highly susceptible Australian branch dieback hosts. Thirteen potentially tolerant Australian host species included Banksia attenuata, B. marginata, E. haemastoma, E. regnans, Pittosporum undulatum and Billardiera heterophylla. Eucalyptus regnans was identified as a potentially highly susceptible bole canker host, while E. diversicolor and E. viminalis were considered potentially tolerant species to bole cankers caused by P. ramorum. Phytophthora ramorum was able to infect all 66 species, as confirmed by reisolation. These results extend the known potential host range for P. ramorum, confirm it as a possible threat to Australian plant industries and ecosystems and highlight additional associated hosts that are important in the global horticultural trade, native forests and plantation forestry.