The effect of Cichorium intybus and Lotus corniculatus on nematode burdens and production in grazed lambs

This report was presented at the UK Organic Research 2002 Conference. The study was designed to examine the hypothesis that chicory (Cichorium intybus) and Lotus sp. (Lotus corniculatus) have the potential to affect the naturally acquired nematode burden in grazed lambs. Organic male castrate lambs (48) with a naturally acquired parasite burden grazed replicate combination plots (0.6 ha) of chicory, Lotus corniculatus, perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Lamb performance was determined by weekly weight gain and condition score assessments. Nematode burden was assessed by individual lamb faecal egg count (FEC) before and after drenching (levamisole). The range of parasitic helminths present was assessed by faecal culture and by total worm counts performed on a proportion of the lambs at slaughter. Weekly pasture larval counts (PLCs) were conducted on the trial plots. A concurrent small plot study (6 x 1m2 replicates) of each of the forages used in the grazing trial was run to assess the potential effect of forage type on the development and survival of Teladorsagia circumcincta assessed by weekly PLCs. Preliminary data suggest that lambs grazing chicory or a combination of lotus and chicory had lower FECs than those grazing PRG/WC, however there was no significant difference in the total worm counts

Lattice study of the Silver Blaze phenomenon for a charged scalar phi-4 field

We analyze a complex scalar field with phi-4 interaction and a chemical potential mu on the lattice. An exact flux representation of the partition sum is used which avoids the complex action problem and based on a generalized worm algorithm we can run Monte Carlo simulations at arbitrary densities. We study thermodynamical quantities as a function of the chemical potential mu for zero- and finite temperature. It is shown that at zero temperature thermodynamical observables are independent of mu up to a critical value mu_c (Silver Blaze phenomenon). In a spectroscopy calculation we cross-check that mu_c agrees with the mass m of the scalar field. The Silver Blaze region ends in a second order phase transition and we show that for low temperatures the second order phase boundary persists and separates a pseudo Silver Blaze region from a condensed phase with strong mu-dependence.Comment: Two typos in the appendix fixe

Simulation strategies for the massless lattice Schwinger model in the dual formulation

The dual form of the massless Schwinger model on the lattice overcomes the complex action problems from two sources: a topological term, as well as non-zero chemical potential, making these physically interesting cases accessible to Monte Carlo simulations. The partition function is represented as a sum over fermion loops, dimers and plaquette-surfaces such that all contributions are real and positive. However, these new variables constitute a highly constrained system and suitable update strategies have to be developed. In this exploratory study we present an approach based on locally growing plaquette-surfaces surrounded by fermion loop segments combined with a worm based strategy for updating chains of dimers, as well as winding fermion loops. The update strategy is checked with conventional simulations as well as reference data from exact summation on small volumes and we discuss some physical implications of the results

New techniques and results for worldline simulations of lattice field theories

We use the complex $\phi^4$ field at finite density as a model system for developing further techniques based on worldline formulations of lattice field theories. More specifically we: 1) Discuss new variants of the worm algorithm for updating the $\phi^4$ theory and related systems with site weights. 2) Explore the possibility of canonical simulations in the worldline formulation. 3) Study the connection of 2-particle condensation at low temperature to scattering parameters of the theory.Comment: Contribution to Lattice 201

Gait modulation in <i>C. Elegans</i>: it's not a choice, it's a reflex!

A commentary on 'Shared strategies for behavioral switching: understanding how locomotor patterns are turned on and off' by Mesce, K. A., and Pierce-Shimomura, J. T. (2010). Front. Behav. Neurosci. 4:49

An oasis of fertility on a barren island: Earthworms at Papadil, Isle of Rum

The Isle of Rum, Inner Hebrides, has an impoverished earthworm fauna as the soils are generally acidic and nutrient-poor. Species associated with human habitation are found around deserted crofting settlements subjected to “clearances” in the mid-19th century and at Kinloch, where a large volume of fertile soil was imported from the mainland around 1900. Earthworms, and the dew worm Lumbricus terrestris L. in particular, were investigated at Papadil, an abandoned settlement and one of the few locations on Rum where a naturally developed brown earth soil is present. The small (1.5 ha), fertile location is isolated, so was also suitable for field experimentation. Visits over six years allowed dew worm distribution to be assessed within low lying grassland and woodland and also within an adjacent sloping broadleaved woodland. The factors limiting dew worm distribution at the site were investigated with associated translocation to adjacent uninhabited areas. Small scale spatial dynamics were studied with density manipulation and containment experiments where Visual Implant Elastomer marking of individuals was utilised. Translocations from streamside woodland to adjacent grassland was successful over a short period (5 months), but the colonies did not persist over a longer term (5-6 years). Field trials with earthworm tagging were successful, but highest tag recovery rate was 25%. Where adults/sub-adults were removed, recruitment of juveniles was notable. Exceptionally large (>12 g live mass) individuals were found in soils of terraces on wooded slopes, suggesting that dew worms may be long lived at this location, where food is abundant and relatively few terrestrial predators are present

Control of internal parasites in organic livestock without the use of pharmaceutical anthelminthics

Organic systems seek to reduce reliance on external inputs, and develop sustainable methods of production which balance output with high standards of animal welfare. The standards for organic production emphasise preventive control strategies based on grazing management, appropriate breeding and good nutrition. The ultimate goal is to eliminate dependence on anti-parasitic drugs, however this is rarely achieved in practice. The overall objective of this research was to develop organic farming systems, which do not rely on pharmaceutical control of roundworm parasites. Focussing on management and nutrition, the approach was to combine on-farm epidemiological studies, with replicated experiments, in order to develop and demonstrate better systems of control applicable to UK organic farms. The project was a collaborative study involving ADAS, Institute of Rural Science (IRS), Moredun Research Institute (MRI) and Scottish Agriculture Colleges (SAC). Specific objectives: 1. To study the epidemiology of parasitic gastro-enteritis (PGE) on selected 'focus' farms, representing a range of organic systems 2. To quantify the effect of dietary manipulation, novel crops, and drenching with tannins, on the development of PGE in organic sheep and cattle systems 3. To evaluate the role of crop type and pasture larval ecology on the development of PGE 4. To develop the application of alternative approaches on 'focus' farms, under best management practice 5. To ensure effective technology transfer Five commercial organic farms, reflecting a range of production systems (specialist hill sheep, upland beef and sheep, lowland specialist sheep, specialist dairying, and lowland mixed arable / livestock) were selected for detailed epidemiological study. The aim was to assess the level and pattern of parasite challenge, critical points for disease control, and the degree of success achieved with current management practices. The study combined the use of standard epidemiological techniques, with close collaboration of the researchers, participating farmers and their veterinary advisers. Comprehensive epidemiological data were collected over two contrasting seasons (2002 and 2003). Without recourse to routine anthelmintic, control was generally underpinned by grazing management, within the constraints of land/crop resources and diversity of enterprises available for each farm. Role of nutrition: Previous studies, using tightly controlled nutritional protocols and a known parasite challenge, developed a nutritional hypothesis for understanding nutritional influences on the host response to parasites. A replicated experiment was set up to test whether this framework could be extended to organically managed ewes carrying a mixed naturally-acquired infection. Novel crops: A series of experiments were undertaken to determine the potential of several novel crops for parasite control. Parasite pasture ecology: Nematode larvae populations have also been shown to differ between herbage species, potentially due to differences in crop morphology or microclimate beneath the sward (which may affect larval development and survival, or the number of coprophagous or nematophagous organisms at soil level). Several small plot and pot experiments were undertaken to assess the effect of crop type on larval survival, rates of faecal degradation, and soil dwelling invertebrates. Overall, the results from this study indicate that with sufficient diversity of cropping and stocking, it is possible to virtually eliminate anthelmintic usage. However, many farms still face significant difficulties, particularly those systems dominated by sheep. The extent to which control can be achieved by management alone, depends on the farming system, with the greatest opportunity for control in the more mixed, or very extensive production systems. Many of the issues faced by the organic sector are increasingly relevant to conventional farmers where anthelmintic resistance is becoming increasingly prevalent. More integrated strategies are required, not only for organic producers, but also to prolong the life of drenches currently used in conventional farming. Practical recommendations have been derived from this research, and promoted to organic and conventional farmers, based around key messages of system planning, parasite monitoring and maintaining biosecurity