Equine neural angiostrongylosis

Verminous encephalomyelitis due to Angiostrongylus cantonensis larvae was diagnosed in 2 foals at necropsy. The principal clinical feature was tetraparesis, although history and neurological examination revealed progressive and multifocal neurological disease. At presentation, a tentative diagnosis of parasitic larval migration involving the central nervous system (CNS), presumably due to Strongylus vulgaris, was proposed. Dissection of the spinal cord in one case resulted in recovery of intact larvae of both sexes of A. cantonensis. In both foals, histopathology of the brain and spinal cord revealed nematode sections which were consistent with A. cantonensis larvae.     

Choosing functions for semi-variograms of soil properties and fitting them to sampling estimates

The semi-variogram is central to geostatistics and the single most important tool in geo-statistical applications to soil. Mathematical functions for semi-variograms must be conditional negative semi-definite, and there are only a few families of simple function that meet this demand. These include the transitive models with finite a priori variance deriving from moving average processes. The spherical and exponential schemes are the most often encountered members. The other major group is that of unbounded models in which the variance appears to increase without limit. The linear model is the most common in this group. If more complex models are needed they can be formed by combining two or more simple models. The usual estimator of the semi-variance is often considered inefficient and to be sensitive to departures from normality in the data. It is compared with a robust estimator and shown to be generally preferable in being unbiased and having confidence intervals that are no wider. For routine analysis, fitting models to sample semi-variograms by weighted least squares approximation, with weights proportional to the expected semi-variance, is preferred to the more elaborate and computationally demanding statistical procedures of generalized least squares and maximum likelihood. The Akaike information criterion is recommended for selecting the best model from several plausible ones to describe the observed variation in soil, though for kriging it may be desirable to validate the chosen model. Examples of models fitted to soil semi-variograms are shown and compared.     

A lysimeter study of the fate of nitrogen applied to perennial ryegrass swards: soil analyses and the final balance sheet

Labelled fertilizer nitrogen was applied at a rate of 40 g N m^?2 to grass swards growing in lysimeters containing monoliths of a sandy loam soil. After 5–7 years, during which time crop uptake and drainage losses of tracer nitrogen were measured, the soils were analysed to quantify the labelled nitrogen remaining. Approximately one-third (range 31–35%) of the applied labelled nitrogen remained, with over 70% of this residue located in the top 20 cm of soil. The rate of mineralization of immobilized tracer nitrogen declined exponentially; after four years the release rate was almost constant, and was equivalent to 2% of the residual labelled nitrogen. Total labelled nitrogen measured in crop, drainage and soil amounted to 93–98%. That unaccounted for was presumed lost by denitrification, largely in the form of dinitrogen, as measured rates of nitrous oxide emission were negligible. The recovery was greatest (and by implication, the gaseous loss smallest) when fertilizer was applied in 1975 during a particularly warm and dry summer.     

THE EFFECT OF MANUAL LUNG INFLATION VS. SPONTANEOUS INSPIRATION ON THE CARDIAC SILHOUETTE IN ANESTHETIZED DOGS

The purpose of this study was to assess radiographic heart size in anesthetized dogs, comparing radiographs made with the patient breathing spontaneously to radiographs obtained using positive pressure manual lung inflation. The hypothesis was that manual inflation would cause reduction in the cardiac size. With dogs in right recumbency a radiograph was made at peak spontaneous inspiration followed immediately a radiograph made with application of positive pressure manual inflation of the thorax. Cardiac size was assessed, both subjectively and objectively using the vertebral heart scale (VHS). Two hundred and six dogs were studied. Manual inflation resulted in a significantly greater degree of lung inflation assessed radiographically ( P <0.0001). The subjectively assessed heart size was significantly smaller in radiographs made with manual inflation, leading to different subjective categorization of heart size in 67 (32%) of dogs. The objectively measured VHS was also significantly smaller in the radiographs made using manual inflation by a mean of 0.24 of a vertebral length (95% CL of mean difference: −0.29, −0.19, P <0.0001). A statistically significant reduction in subjective heart size and in VHS occurred with manual inflation of the lungs, and these differences may be clinically significant. Thus, if serial radiographs are obtained to assess cardiac size, the radiographic technique used should be the same.     

An Overview of Low Dose Insemination in the Mare

The need for relatively high numbers of spermatozoa for artificial insemination limits our application of recently available technologies such as sex‐sorted semen. The fertility of two different methods of low dose insemination using fresh, frozen and sex‐sorted semen are compared in this overview. Satisfactory conception rates are described using very low doses of spermatozoa inseminated by either hysteroscopic or deep uterine insemination methods, proving the stallion is fully fertile. The hysteroscopic method appears to give higher conception rates when inseminating fewer than 5 × 10⁶ spermatozoa and is therefore, the preferred method of insemination for sex‐sorted spermatozoa. However, hysteroscopic deposition of low numbers of spermatozoa from infertile stallions does not appear to improve their fertility.     

Local disjunctive kriging of soil properties with change of support

Disjunctive kriging estimates from a set of measurements the conditional probability that true values of a regionalized variable such as a soil property exceed, or are less than critical thresholds. Estimates can be for sites equal in size to the supports of the samples and, by changing the support of the variogram, for larger blocks. The method also estimates the block averages and their associated variances. The underlying theory and steps in the analysis are described. They are illustrated using a case study from south-east Scotland where the aim is to estimate the likelihood of copper and cobalt deficiency over whole farms or 1 km² blocks of land using data from individual fields of 5 to 10 ha only. Maps show the conditional probabilities for 1 km² squares that the available copper in the soil is less than 1 mg kg^?1 and that cobalt is less than 0.25 mg kg^?1.