Increasing species and trophic diversity of mesofauna affects fungal biomass,mesofauna community structure and organic matter decomposition processes

A laboratory mesocosm experiment was set up to study the effects of five mesofauna model communities on litter fungal biomass (ergosterol content) and litter decomposition parameters (litter mass remaining, N concentration) for 4 months. The five treatments were: (1) no soil mesofauna, (2) the collembolan Folsomia fimetaria, (3) an assemblage of the collembolan species Isotomurus prasinus, Hypogastrura assimilis, F. fimetaria, Mesaphorura macrochaeta and Protaphorura armata, (4) the same collembolan assemblage plus the enchytraeid Enchytraeus crypticus, and (5) the six species plus the predaceous mite Hypoaspis aculeifer. After 30, 60, 90 and 120 days of incubation, six mesocosms of each treatment were sacrificed and biomass, species richness and dominance were measured. Changes occurred during the study with an increase in total detritivore biomass and a decrease in species richness with strong dominance by a few species in multispecies mesocosms. A vertical stratification of species was also observed in the mesocosms. Litter mass loss and N mineralisation were reduced with the introduction of fauna and showed the largest effects in the multispecies detritivore treatments. Ergosterol production was only temporary reduced in the multispecies treatments reflecting an effect of mesofauna on fungal biomass related to diversity rather than the biomass of mesofauna. An inhibitory predator effect was observed on functional decomposition parameters and indicated top-down control of decomposition via detritivorous mesofauna.     

Evaluation of effects of transgenic Bt maize on microarthropods in a European multi-site experiment

The effects of maize expressing the Bacillus thuringiensis Cry1Ab protein (Bt maize) on soil microarthropods were assessed in the field at four European locations (two in Denmark and two in France) that differ in their climatic conditions or soil properties. Each site was considered as a separate experiment, with separate statistical comparison. Effects of farming practices using Bt maize were compared with conventional farming practices using near-isogenic non-Bt maize and also (at some of the sites) other conventional varieties. Furthermore, at one field site (Foulum, Denmark), the effects of Bt crops were studied in both conventional tillage and reduced tillage contexts. At another field site (Askov, Denmark), Bt maize effects were also compared to the effects of the chemical insecticide dimethoate. Moreover, at three of the field sites (all except Narbons, France), the possibility of a localised Bt effect around the rhizosphere compared to the bulk soil was assessed by sampling within and between maize rows. There were some significant negative effects of Bt maize on microarthropods in soils with a high clay content. Significant differences of the same magnitude also occurred between different conventional varieties of maize, but the effect of dimethoate appeared clearly greater than Bt effects. It is thus debatable if the Bt maize effect is an effect of the Bt toxin or just an effect of the maize variety. Based on the results, it can be concluded that the effect of Bt maize on soil microarthropods was small and within the normal variation expected in conventional agricultural systems.     

Biological nitrogen fixation in a grazed perennial grass/clover ley and correlation with herbage and soil variables

In a grazed grass/clover pasture, biological nitrogen fixation (BNF) is a source of nitrogen (N). The determination of this N input and how it is influenced by N, phosphorus (P) and potassium (K) in the soil, is complicated by grazing animals, which cause variation in defoliation and soil mineral content in both space and time. In a perennial grass/clover ley on a commercial Danish organic farm, exclusively grazed by dairy cows, we investigated BNF, clover proportion of the herbage, accumulated dry matter of clover and N, P and K concentrations in separates of clover and grass in relation to inorganic concentrations of N, P and K in the soil. The ¹⁵N natural abundance technique was used to determine the proportion of clover N derived from the atmosphere (pNdfa) using grass as a non-fixing reference. In September 1997, soil and biomass sampling was carried out on 81 randomly selected plots. The value of pNdfa was on average 0.6, ranging from 0.12 to 0.96 and BNF exhibited a significant but weak correlation (r=0.432) with accumulation of dry matter in clover. For the significant correlations, r varied between −0.403 and 0.648. The proportion of clover in the sampled herbage averaged 48%, ranging between 18 and 78%, but varied independently of BNF. Due to a high concentration of P and moderate to high concentration of K in the soil, clover and grass were well supplied with P and K, which was confirmed by the concentrations of K and P in shoot material.     

Epidemiological enquiries in two Q fever outbreaks in a community of Baden-Württemberg during 2008 and 2009

In 2008 and 2009, two consecutive outbreaks of Q fever in humans were recorded in the district of Freudenstadt, northern Black Forrest, Baden-Württemberg, Germany. In 2008, a total of 41 persons from a single local community fell ill and were found infected with Coxiella burnetii. Although comprehensive diagnostic and epidemiological outbreak investigations were conducted and control measures taken which included vaccination of ruminants at risk in three parts of the affected community, re-occurrence of the disease in 2009 with further 29 confirmed human Q fever cases could not be prevented. While the origin of infection of the first outbreak was probably a flock of 550 sheep moved in the surrounding of the affected villages, the source of infection for the consecutive outbreak in 2009 could not be identified. It seems possible that meadows contaminated with infectious placenta or birth fluids represented the sources of infection.     

Electroencephalographic recordings in dogs: Prevention of muscle artifacts and evaluation of two activation techniques in healthy individuals

This study was performed to improve a standard anesthetic protocol for electroencephalography (EEG) in dogs and to evaluate the effect of photic stimulation and hyperventilation on the EEG of healthy dogs. Ten clinically and neurologically normal beagle dogs were anesthetized with propofol given intravenously with average doses of 7.5 mg/kg for induction and 0.37 mg/kg/min constant rate infusion for maintenance. Rocuronium bromide (0.4 mg/kg IV) was used as a peripheral muscle relaxant in order to prevent muscle artifacts. EEGs were recorded digitally using five subdermal needle electrodes. Photic stimulation and hyperventilation were performed to evaluate two activation techniques commonly used in human EEG recording methods. Monopolar and bipolar montages were analyzed visually and quantitatively. The use of rocuronium produced muscle artifact-free EEG recordings during the given recording procedure which indicates that rocuronium is a valuable adjunct to anesthesia during EEG recording. Photic stimulation and hyperventilation did not provoke paroxysmal discharges in the EEG of healthy dogs. Analysis of quantitative EEG data showed that background activity did not differ significantly between periods with and without stimulation. This data are important basic values and will further help to compare the effects of photic stimulation and hyperventilation of healthy dogs and those suffering from epilepsy.     

Fecal microbiota of calves in the clinical setting: effect of penicillin treatment

The effect of parenteral penicillin treatment on the intestinal microbiota was determined by monitoring the phenotypic antimicrobial resistance among Escherichia coli in 19 calves (15 calves received treatment and four calves were healthy controls) and by examining changes in the fecal microbial community structure using molecular fingerprinting techniques in a subset of eight calves (five treated calves and three control calves). After five days of penicillin treatment an increased resistance to multiple unrelated antimicrobial agents, including non-β-lactams, was seen in E. coli from treated calves, and this was not seen in the controls. Automated ribosomal intergenic spacer analysis (ARISA) and terminal restriction fragment length polymorphism (TRFLP) revealed that penicillin treatment causes a significant variation in the microbial structure within an individual calf. The study shows that parenteral administration of penicillin has an impact on the composition of the fecal microbiota in calves, and on the antimicrobial resistance pattern of their fecal E. coli.     

Rennet-induced aggregation of heated pH-adjusted skim milk

Heated (20-100 °C/0-30 min) skim milks (pH 6.5-7.1) were diluted in buffer (pH 7.0). Rennet was added, and the particle size with time was measured. For all samples, the size initially decreased (lag phase) and then increased (aggregation phase). Milks heated at ≤60 °C had short lag phases and rapid aggregation phases regardless of pH. Milks heated at >60 °C at pH 6.5 had long lag phases and slow aggregation phases. As the pH increased, the lag phase shortened and the aggregation phase accelerated. The aggregation time was correlated with the level of whey protein associated with the casein micelles and with the level of κ-casein dissociated from the micelles. Heated milks formed weak gels when renneted. It is proposed that the milks heated at low pH have whey proteins associated with the casein micelles and that these denatured whey proteins stabilize the micelles to aggregation by rennet and therefore inhibit gelation. In the milks heated at higher pH, the whey proteins associate with κ-casein in the serum and, on rennet treatment, the κ-casein-depleted micelles and the serum-phase whey protein/κ-casein complexes aggregate; however, the denatured whey proteins stabilize the aggregates so that gelation is still inhibited.     

Effects of isoflurane upon minimum alveolar concentration and cerebral cortex depression in pigs and goats: An interspecies comparison

This study compared the effects of isoflurane in pigs (n = 10 Yorkshire–Landrace cross) and dairy goats (n = 10) by evaluation of electroencephalographic (EEG) burst suppression thresholds (BST) in the cerebral cortex and minimum alveolar concentration (MAC) values in the spinal cord. The study also investigated whether individual MAC values can predict the effects of isoflurane on the cerebral cortex. MAC values and BST/MAC ratios were significantly different between species. Inhibition of movement by isoflurane may be less effective in pigs than in goats. No significant correlation was found between individual MAC and BST values, indicating that in single animals the individual MAC poorly reflects the cerebrocortical depressant effect of isoflurane in pigs and goats.