967 research outputs found
Towards sustainable management of rodents in organic animal husbandry
From 26 to 28 May 2004 an international seminar was held in Wageningen, the Netherlands, about current knowledge and advice on rodent management on organic pig and poultry farms in Western Europe. This paper summarizes the discussions. Rodent management is necessary to protect the food production chain from health hazards to livestock and humans. Some organic farmers prefer biological rodent control, but since rodents can also transmit diseases this bears certain risks for the production of healthy livestock and safe food. Effective rodent management requires a thorough understanding of the biology of the pest species concerned. These can be divided into two groups: field rodents, such as voles,
and commensal rodents like house mice and rats. The objective of managing field rodents is to minimize livestock exposure to these vectors, and to regulate their populations in case their density is expected to grow dramatically. Infestation of livestock facilities with commensal rodents can be prevented, but once they are present, their eradication must be aimed for. General elements of rodent management are (1) the prevention of rodent infestations through strategic actions such as modifying the habitat or rodent proofing of the buildings, (2) monitoring their appearance and population density, and (3) rodent control measures. A number of possible management actions is described to provide a basis for examining the measures’ social acceptability, their economic and environmental impacts, and their efficacy
Optimal CMB estimators for bispectra from excited states
We propose optimal estimators for bispectra from excited states. Two common
properties of such bispectra are the enhancement in the collinear limit, and
the prediction of oscillating features. We review the physics behind excited
states and some of the choices made in the literature. We show that the
enfolded template is a good template in the collinear limit, but does poorly
elsewhere, establishing a strong case for an improved estimator. Although the
detailed scale dependence of the bispectra differs depending on various
assumptions, generally the predicted bispectra are either effectively 1 or
2-dimensional and a simple Fourier basis suffices for accurate reconstruction.
For an optimal CMB data analysis, combining all n-point functions, the choice
for the excited state needs to be the same when computing power spectrum,
bispectrum and higher order correlation functions. This has not always been the
case, which could lead to wrong conclusions. We calculate the bispectrum for
different choices previously discussed for the power spectrum, setting up a
consistent framework to search for evidence of excited states in the CMB data.Comment: 19 pages, 9 figure
Oscillations in the Primordial Bispectrum: Mode Expansion
We consider the presence of oscillations in the primordial bispectrum,
inspired by three different cosmological models; features in the primordial
potential, resonant type non-Gaussianities and deviation from the standard
Bunch Davies vacuum. In order to put constraints on their bispectra, a logical
first step is to put these into factorized form which can be achieved via the
recently proposed method of polynomial basis expansion on the tetrahedral
domain. We investigate the viability of such an expansion for the oscillatory
bispectra and find that one needs an increasing number of orthonormal mode
functions to achieve significant correlation between the expansion and the
original spectrum as a function of their frequency. To reduce the number of
modes required, we propose a basis consisting of Fourier functions
orthonormalized on the tetrahedral domain. We show that the use of Fourier mode
functions instead of polynomial mode functions can lead to the necessary
factorizability with the use of only 1/5 of the total number of modes required
to reconstruct the bispectra with polynomial mode functions. Moreover, from an
observational perspective, the expansion has unique signatures depending on the
orientation of the oscillation due to a resonance effect between the mode
functions and the original spectrum. This effect opens the possibility to
extract informa- tion about both the frequency of the bispectrum as well as its
shape while considering only a limited number of modes. The resonance effect is
independent of the phase of the reconstructed bispectrum suggesting Fourier
mode extraction could be an efficient way to detect oscillatory bispectra in
the data.Comment: 17 pages, 12 figures. Matches published versio
Characteristics of Organic Pig Production and risk analysis concerning Toxoplasma infection
A short written questionnaire was used to study certain characteristics of the organic pig production chain in The Netherlands and the circumstances on the farm that might play a role in the transmission of Toxoplasma infection to the pigs. Of the 81 certified organic slaughter pig farmers present in the Netherlands in 2006, 52 responded to the questionnaire (64 % response).
The farms could be divided into two populations. One population was represented by small organic pig farms with a mean number of 55 slaughtered pigs per year. These farms covered 40% of the total number of investigated farms, but only represented 2.5 % of the total number of slaughtered pigs. The second population had a mean annual production of 1460 animals. Almost 95% of these animals are currently slaughtered and further distributed by the Vion Food Group (de Groene Weg). A small part of the pigs (4%) is directly delivered to a slaughter company in Germany (Thönes) and 1% is sold via farm home sales.
For each farm an arbitrary Toxoplasma risk factor analysis was performed. Factors included the type of outdoor run (concrete or soil), feeding goat or sheep whey, number of cats, access of cats to outdoor run, stables and feed, rodent control and covering roughage fed to the animals. Calculation of the total risk score (summation of chance times severity scores for several factors) showed that many farmers already used management factors that decreased the risk for Toxoplasma infection. Analysis of a possible relation between risk score and farm size showed that a poor score was often seen on small farms. Because these farms mainly sell their meat in a frozen condition via home sales, this is not considered to represent a problem for food safety.
Further research is needed to investigate whether the risk for Toxoplasma can be maintained via on farm prevention or whether a Toxoplasma monitoring program should be implemented at slaughter, possibly with post slaughter decontamination. The fact that a recent report by the RIVM on food related infections has concluded that Toxoplasmosis has a markedly higher disease burden than Campylobacter or Salmonella, emphasizes the priority this subject should be given on the research agenda
The Future of Primordial Features with 21 cm Tomography
Detecting a deviation from a featureless primordial power spectrum of
fluctuations would give profound insight into the physics of the primordial
Universe. Depending on their nature, primordial features can either provide
direct evidence for the inflation scenario or pin down details of the inflation
model. Thus far, using the cosmic microwave background (CMB) we have only been
able to put stringent constraints on the amplitude of features, but no
significant evidence has been found for such signals. Here we explore the limit
of the experimental reach in constraining such features using 21 cm tomography
at high redshift. A measurement of the 21 cm power spectrum from the Dark Ages
is generally considered as the ideal experiment for early Universe physics,
with potentially access to a large number of modes. We consider three different
categories of theoretically motivated models: the sharp feature models,
resonance models, and standard clock models. We study the improvements on
bounds on features as a function of the total number of observed modes and
identify parameter degeneracies. The detectability depends critically on the
amplitude, frequency and scale-location of the features, as well as the angular
and redshift resolution of the experiment. We quantify these effects by
considering different fiducial models. Our forecast shows that a cosmic
variance limited 21 cm experiment measuring fluctuations in the redshift range
with a 0.01-MHz bandwidth and sub-arcminute angular
resolution could potentially improve bounds by several orders of magnitude for
most features compared to current Planck bounds. At the same time, 21 cm
tomography also opens up a unique window into features that are located on very
small scales.Comment: Matches version accepted for publication. Changes made to
forecasting; using k space instead of \ell space. Forecasted constraints
significantly improved for some feature
Minimal cut-off vacuum state constraints from CMB bispectrum statistics
In this short note we translate the best available observational bounds on
the CMB bispectrum amplitudes into constraints on a specific scale-invariant
New Physics Hypersurface (NPH) model of vacuum state modifications, as first
proposed by Danielsson, in general models of single-field inflation. As
compared to the power spectrum the bispectrum constraints are less ambiguous
and provide an interesting upper bound on the cut-off scale in general models
of single-field inflation with a small speed of sound. This upper bound is
incompatible with the power spectrum constraint for most of the parameter
domain, leaving very little room for minimal cut-off vacuum state modifications
in general single-field models with a small speed of sound.Comment: 9 pages, 1 figur
Presence of Salmonella and Campylobacter spp. in Wild Small Mammals on Organic Farms
The presence of Salmonella and Campylobacter spp. in rodents and insectivores (n 282) was investigated
on organic farms. Infections were encountered in house mice (8 of 83 Campylobacter positive and 1 of 83
Salmonella sp. strain Livingstone positive) and brown rats (1 of 8 Campylobacter positive) but not in other
species. No shared Campylobacter genotypes were found between rodent and pig manure isolates. Effective
on-farm rodent management is recommended
Role of rodents in transmission of Salmonella and Campylobacter
Salmonella and Campylobacter are generally regarded as the most important food-borne pathogens in the world. Reduction or elimination of these pathogens in the first part of the food chain (on the farm) is important to prevent disease among consumers of animal products. In organic farming, elimination becomes more difficult, as food animals are allowed outdoors and have easy access to potential sources of hazardous pathogens. Whilst
rodents are often associated by organic farmers with infrastructural damage and eating or spoiling of stored feed and products, their zoonotic risks are frequently underestimated. They can amplify the number of pathogens in the environment and transfer them to food animals. Thus organic farmers should be aware of the need for rodent
control from a food safety perspective. Preferably, rodent control should form an integral part of a total package of hygiene measures to prevent transfer of food-borne pathogens. These should also include e.g. control of wild birds and flies and obligatory disinfection of boots/clothes and equipment for farm workers and visitors
- …