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The study objective was to determine the prevalence of Staphylococcus aureus colonisation in the nares and oropharynx of healthy persons and identify any risk factors associated with such S. aureus colonisation. In total 263 participants (177 adults and 86 minors) comprising 95 families were enrolled in a year-long prospective cohort study from one urban and one rural county in eastern Iowa, USA, through local newspaper advertisements and email lists and through the Keokuk Rural Health Study. Potential risk factors including demographic factors, medical history, farming and healthcare exposure were assessed. Among the participants, 25.4% of adults and 36.1% minors carried S. aureus in their nares and 37.9% of adults carried it in their oropharynx. The overall prevalence was 44.1% among adults and 36.1% for minors. Having at least one positive environmental site for S. aureus in the family home was associated with colonisation (prevalence ratio: 1.34, 95% CI: 1.07–1.66). The sensitivity of the oropharyngeal cultures was greater than that of the nares cultures (86.1% compared with 58.2%, respectively). In conclusion, the nares and oropharynx are both important colonisation sites for healthy community members and the presence of S. aureus in the home environment is associated with an increased probability of colonisation.
The importance of parasites as a selective force in host evolution is a topic of current interest. However, short-term ecological studies of host–parasite systems, on which such studies are usually based, provide only snap-shots of what may be dynamic systems. We report here on four surveys, carried out over a period of 12 years, of helminths of spiny mice (Acomys dimidiatus), the numerically dominant rodents inhabiting dry montane wadis in the Sinai Peninsula. With host age (age-dependent effects on prevalence and abundance were prominent) and sex (female bias in abundance in helminth diversity and in several taxa including Cestoda) taken into consideration, we focus on the relative importance of temporal and spatial effects on helminth infracommunities. We show that site of capture is the major determinant of prevalence and abundance of species (and higher taxa) contributing to helminth community structure, the only exceptions being Streptopharaus spp. and Dentostomella kuntzi. We provide evidence that most (notably the Spiruroidea, Protospirura muricola, Mastophorus muris and Gongylonema aegypti, but with exceptions among the Oxyuroidae, e.g. Syphacia minuta), show elements of temporal-site stability, with a rank order of measures among sites remaining similar over successive surveys. Hence, there are some elements of predictability in these systems.
The high contribution of postruminal starch digestion (>50%) to total tract starch digestion on certain energy dense diets (Mills et al. 1999) demands that limitations to small intestinal starch digestion are identified. Therefore, a dynamic mechanistic model of the small intestine was constructed and evaluated against published experimental data for abomasal carbohydrate infusions in the dairy cow. The mechanistic structure of the model allowed the current biological knowledge to be integrated into a system capable of identifying restrictions to dietary energy recovery from postruminal starch delivery.
Agriculture is one of the major sources of nitrogen (N) pollution. Dairy production causes losses of N in faeces and urine that contribute to environmental pollution with an estimated annual output of 320 kt N and 80 kt ammonia in the U.K. alone. Therefore, improving N utilization in dairy cows and especially reducing N output in excreta is desirable to reduce environmental N pollution, particularly as ammonia. Mathematical models have been used to predict potential N excretion from dairy cows. However, these models generally are empirical in nature, hence not process based and therefore there is a need to develop a model that can describe biological processes in the animal. The objective of the present study was to develop a dynamic N model to predict the amount and form of N excreted by dairy herds and seek to make appropriate recommendations that will reduce N excretion from dairy cows.
A non-invasive method is proposed for determining the extent of degradation in the rumen, based on the gas production technique and mathematical modelling. The exercise involves developing both a statistical model and a kinetic model (France et al., 2000). The statistical model shifts (or maps) the gas accumulation profile obtained using a faecal inoculum to a rumen gas profile, thus obviating the need for rumen sampling. The kinetic model determines the extent of degradation in the rumen from the shifted profile. It is presented as a generalised mathematical function, allowing any one of a number of alternative equation forms to be selected.
Raw materials used in feed manufacture are contaminated with high (>104 cfu/g) levels of enterobacteriaceae indicating the potential for contamination with pathogenic bacteria such as salmonella (Wood et al. 2001). There is urgent need to reduce the contamination of animal feed with zoonoses such as salmonella and campylobacter. During manufacture of feedingstuffs, heat and moisture are used to process and sterilise feed but this can also provide conditions for microbial growth. High temperature treatment used to sterilise feed will not protect feedingstuffs from recontamination, if residual microbial contamination remains in the feed mill. It is essential to understand the influence of feed processing and the feed mill environment on the microbial contamination of feed.
Bacteria belonging to the family Enterobacteriaceae enter the animal feed chain as normal contaminants of raw materials used in the manufacture of animal feeds. The family Enterobacteriaceae encompasses 30 established genera, including Salmonella spp, Escherichia spp, Shigella spp and Yersinia spp. Many of the genera exhibit pathogenicity towards man, animals, insects and plants and many of the pathogenic forms produce toxins. A number of the genera in this family occur regularly in association with animals; they are found as indigenous members of the gut microflora where they may either produce no harmful effects, or are capable of causing disease in both endothermic and ectothermic animals. There is a recognised association between the risk of isolation of salmonella and degree of Enterobacteriaceae contamination (Veldman et al. 1995). This has led to the consideration of recording Enterobacteriaceae contamination levels in feed stuffs as an indicator of feed hygiene and potential limits to the degree of contamination being set by the major retailers. This paper sets out data gathered from the routine analysis of feed raw materials examined for Enterobacteriaceae contamination.
Phosphorus (P) is a key mineral in energy metabolism and is essential in nearly every biochemical aspect of dairy cow metabolism. Therefore, P needs to be supplied in sufficient quantity to optimize animal performance. However, dairy cows only use 30 – 45% of their dietary P intake and the rest is excreted mainly in faeces. Excess faecal excretion can lead to P accumulation and saturation in the soil and filter into groundwater or remain in surface water (Tamminga, 1996), which is known to cause eutrophication. It is therefore desirable to formulate P rations according to the requirement of the animals and thereby reduce P pollution. The objective of the present study was to develop a dynamic model of P metabolism in dairy cows and use that to identify and quantify trends of P excretion as a function of P intake and investigate effects of energy supplementation on P utilisation.
Previous attempts to apply statistical models, which correlate nutrient intake with methane production, have been of limited value where predictions are obtained for nutrient intakes and diet types outside those used in model construction. Dynamic mechanistic models have proved more suitable for extrapolation, but they remain computationally expensive and are not applied easily in practical situations. The first objective of this research focussed on employing conventional techniques to generate statistical models of methane production appropriate to UK dairy systems. The second objective was to evaluate these models and a model published previously using both UK and North American datasets. Thirdly, non-linear models were considered as alternatives to the conventional linear regressions. The UK calorimetry data used to construct the linear models were also used to develop the three non-linear alternatives that were all of modified Mitscherlich (monomolecular) form.
Dietary intervention to reduce methane emissions from lactating dairy cattle is both environmentally and nutritionally desirable due to the importance of methane as a causative agent in global warming and as a significant loss of feed energy. This investigation involved the development of a dynamic mechanistic model of whole rumen function (Dijkstra et al. 1992), with the objective to simulate whole-animal methane emissions for a range of dietary inputs.
The aims of this study were to determine behavioural and heart rate responses to isolation and a novel stimulus and to investigate the relationships with scores from a questionnaire developed to assess anxiety in horses.
Agriculture in general, and dairy production in particular, has been identified as one of the major sources of greenhouse gas emissions and other environmental pollutants such as nitrogen (N) (as ammonia, N and Nitrous oxides, and N leaching). Availability of cheap sources of protein has led to increased consumption of protein supplements. However, the protein is often utilised inefficiently and excess nitrogen is excreted particularly in urine, which has much more potential to pollute the environment. One of the obvious ways of reducing pollution is by evaluating the pollution potential of diets and formulating more balanced rations. A few technical mathematical models have been published but rarely do they consider more than one pollutant at a time. The objective of the present study was to develop a decision support system (DSS) by first integrating mechanistic models of N (Kebreab et al., 2002) and methane (Mills et al., 2001) with a rumen model (Dijkstra, 1994) and then develop a graphical user interface (GUI) for ease of use and analysis of outputs.
A comparative study is presented of the chemistry and crystallography of zinc-bearing strunzites from Hagendorf Süd, Bavaria, Germany and the Sitio do Castelo mine, Folgosinho, Portugal. Electron microprobe analyses of samples from the two localities show quite different cation substitutions. The Hagendorf Süd mineral is a Zn-bearing ferristrunzite, with compositional zoning due to Zn2+ replacing predominantly Fe3+ as well as minor Mn2+, whereas the Portugese mineral is a Zn-bearing strunzite, in which Zn2+ replaces Mn2+, with minor replacement of Fe3+ by Mn3+. Zincostrunzite, with dominant Zn in the interlayer octahedrally coordinated site, is a new strunzite-group mineral that has been characterized at both locations. Analysis of single-crystal synchrotron data for zinc-bearing ferristrunzite and zincostrunzite crystals from Hagendorf Süd show that the structures of both minerals contain zeolitic water in the interlayer region. The formula for strunzite-group minerals containing the zeolitic water is MFe23+(PO4)2(OH)2·6.5H2O, M=Fe, Mn, Zn. This formulation agrees with that found for zincostrunzite from the Sitio do Castelo mine, but differs from that reported previously for strunzite, MFe2+(PO4)2(OH)2·6H2O, which has no interlayer water. Interestingly, the zincostrunzites from the two localities differ in the location of the interlayer water molecule, with a corresponding difference in the H bonding.
Photogrammetric processing of archival stereo imagery offers the opportunity to reconstruct glacier volume changes for regions where no such data exist, and to better constrain the contribution to sea-level rise from small glaciers and ice caps. The ability to derive digital elevation model (DEM) measurements of glacier volume from photogrammetry relies on good-quality, well-distributed ground reference data, which may be difficult to acquire. This study shows that ground-control points (GCPs) can be identified and extracted from point-cloud airborne lidar data and used to control photogrammetric glacier models. The technique is applied to midtre Lovénbreen, a small valley glacier in northwest Svalbard. We show that the amount of ground control measured and the elevation accuracy of GCP coordinates (based on known and theoretical error considerations) has a significant effect on photogrammetric model statistics, DEM accuracy and the subsequent geodetic measurement of glacier volume change. Models controlled with fewer than 20 lidar control points or GCPs from sub-optimal areas within the swath footprint overestimated volume change by 14–53% over a 2 year period. DEMs derived from models utilizing 20–25 or more GCPs, however, gave volume change estimates within ∼4% of those from repeat lidar data (−0.51 m a−1 between 2003 and 2005). Our results have important implications for the measurement of glacier volume change from archival stereo-imagery sources.
The Central Molecular Zone (CMZ), the inner 450 pc of our Galaxy, is an exceptional region where the volume and column densities, gas temperatures, velocity dispersions, etc. are much higher than in the Galactic plane. It has been suggested that the formation of stars and clusters in this area is related to the orbital dynamics of the gas. The complex kinematic structure of the molecular gas was revealed by spectral line observations. However, these results are limited to the line-of-sight-velocities. To fully understand the motions of the gas within the CMZ, we have to know its location in 6D space (3D location + 3D motion). Recent orbital models have tried to explain the inflow of gas towards and its kinematics within this region. With parallax and proper motion measurements of masers in the CMZ we can discriminate among these models and constrain how our Galactic Center is fed with gas.
Leaf cuticle micromorphology has been cited as an important set of taxonomic characters in gymnosperms, but previous studies have largely been based on small sample sizes. The premise of this study was to understand whether external factors affect cuticular micromorphology of Podocarpaceae. Two example species, Prumnopitys andina and Podocarpus salignus, were studied. Of 21 sampled characters, nine (c.43% of the total) were visually assessed as being moderately reliable or highly reliable for taxonomic discrimination for both species, with an additional six (c.29%) being moderately reliable or highly reliable for only one or other of the example species, and six characters (c.29%) unreliable for both. Seven of the most variable stomatal characters were selected for further analysis to establish whether environmental factors affect them. The relationship between these seven stomatal characters, the environment and climate was analysed using the R ‘vegan’ package and climate data gathered from WorldClim. Our results showed that both species had larger stomata in moist and shady conditions, and a higher density of (smaller) stomata in sunny and drier conditions. An additional novel finding was the presence of stomata on the adaxial leaf surface in 46% of samples of Prumnopitys andina: the first record of adaxial stomata in this species, highlighting the necessity of studying multiple samples of a given species. In conclusion, these results indicate that larger sample sizes than have hitherto been employed in cuticle micromorphological studies are necessary to fully document the amount of phenotypic variation that exists.
Cryofracture of living material and fracture at room temperature of herbarium material were used to obtain cross-sections of the stomatal complexes of four species of Podocarpus (Podocarpaceae) for scanning electron microscopy. Cross-sections of the stomata of one species in Podocarpus subgenus Foliolatus section Foliolatus (Podocarpus rubens), one in Podocarpus section Globulus (Podocarpus beecherae), one in Podocarpus subgenus Foliolatus section Longifoliolatus (Podocarpus insularis) and one in subgenus Podocarpus section Australis (Podocarpus nivalis) were studied. The architecture of the stomatal complex, including the wax plug, is described. It was found that the wax plug sits high in the stomatal antechamber in Podocarpus rubens, P. beecherae and Podocarpus decipiens and about halfway up the chamber in P. nivalis. A ridge, which appears to correspond to the crease where the guard cells meet, exists on the underside of the wax plug in Podocarpus beecherae, P. decipiens and P. rubens; its presence in P. nivalis requires confirmation. In addition, ridges within the stomatal antechamber were observed when viewing the cross-sections of Podocarpus decipiens and P. rubens, the internal surface of the cuticle of P. decipiens, Podocarpus teysmannii, P. insularis and Podocarpus milanjianus, and the external surface of the cuticle of Podocarpus chinensis, Podocarpus macrophyllus and Podocarpus pilgeri. These ridges may consist of wax and be a result of epitaxis.