Efficient use of animal manures within an upland organic system (OF0187)

This is the final report of Defra project OF0187. The attached report starts with a detailed Executive Summary, from which this text is a short extract. The aim of this experiment (1999-2001) was to investigate the agronomic effects of applying treated and untreated farmyard manure and slurry to an organically managed, upland clover/ryegrass pasture. Seven main treatments were imposed in a split plot, randomised complete block design, simulating inputs from organic and conventional systems at ADAS Redesdale. The main treatments were; composted (Treatment A) and uncomposted (B) FYM; aerated (C) and unaerated (D) cattle slurry; ammonium nitrate (E); and a zero nitrogen control (F). A further control treatment (G), to which slurry was applied only in 1996, was added to provide a common control treatment during an earlier phase of the experiment. Target application rates were 150 kg total N/ha for untreated slurry and FYM treatments. Following aeration, the same volume of slurry as for the unaerated slurry treatments was applied. Allowing for losses, composted FYM was applied at a rate calculated to supply 80% (120 kg/ha) of total N compared to the untreated FYM treatment. Ammonium nitrate was used as a conventional control treatment, applied at an annual rate of 240 kg/N/ha. To determine the effect of phosphate and potash, one half of the plots were supplemented when soil levels of these nutrients fell below theoretically optimum levels. Highland Slag and Seagreen K were used as organic sources of P and K, while muriate of potash and superphosphate were used on the conventionally managed plots. Application rates were based on the results of soil analysis, according to standard recommendations for organic (Glenside Organics, Ltd) and conventional (Anon. 2000) production. Overall, the results indicate that high clover swards and the return of major nutrients in slurry and FYM can support a high level of productivity from an organically managed pasture, without the requirement for exogenous fertiliser inputs. Under a conservation system of management, it was clear that soil potassium could be a major limiting factor to herbage yield. However, FYM/slurry maintained an acceptable concentration of herbage K, despite a Soil Index of 0/1. The information generated on nutrient cycling, on output and other measures of productivity raises questions as to the optimum level of soil nutrients required for organic production, the role of soil microbial activity and the potential to better exploit composted FYM. The balance of crop offtake from more modest yields, with nutrients released from the soil, may dictate that high levels of extractable nutrients in the soil may not be a prerequisite for good performance from an organic system

A review of current European research on organic farming (OF0171)

This is the final report of Defra project 0F0171. This text has been extracted from the Executive Summary at the start of the attached report. In support of its policy to expand organic farming, MAFF sponsors a programme of research and extension (through Organic Conversion Information Service) to provide information to producers on organic systems of production. The purpose of this review is to provide a comprehensive framework which sets out clearly the content and key results of current European research programmes. The overall objective was to increase the body of knowledge and information available to UK producers and extension workers, and to help direct UK research effort. The priority was to examine northern and western European research programmes i.e. those likely to have the greatest relevance for the UK. Key research institutions, major projects and individual researchers were identified. The data collected were compiled into two research directories. The first was a list of research organisations containing 137 entries. The second was a project list, containing information on 724 individual research projects, including 88 in the UK. The results enabled an overview of the range, content and organisation of organic research programmes. Of the European projects listed (excluding the UK), 40% were related to crop production or soil fertility. A further 14% were on fruit or vegetable production, while 19% were related to livestock or grassland. Results from these studies will be relevant to UK researchers planning new work. Valuable insight was also provided into research methodologies and analytical tools used by European researchers, as well as approaches to dissemination and participatory research. From priorities identified during the compilation of the research directories, three specific study tours were made, focusing on aspects of organic horticulture, arable, and fruit production: - Weed Control in Organic Horticultural and Arable systems - Sustainable Nutrient Management in Organic Field Vegetable Production - Organic Fruit Production. Two technical workshops were also attended and reported: - Designing and Testing Crop Rotations for Organic Farming - Alternatives to the Use of Copper-Based Fungicides in Organic Systems Study tour reports provide detailed information on issues relevant to the UK, results and direction of each research programme. In addition, technical information was collected for technology transfer to UK producers. The research directory and study tour reports are now widely accessible, including on the Web at http://www.adas.co.uk/organic. UK producers, processors, retailers, others in the supply chain, and ultimately the consumer will be the main beneficiaries. Key messages and findings have been provided, some for immediate incorporation into existing production systems. The results will be very valuable to MAFF, research institutes, scientists and research workers when considering current and future UK research needs. Contact with European programmes will help improve the efficiency of UK research programmes, avoid unnecessary duplication and refine research methodology. The work will facilitate further contact between European research workers, to formulate collaborative bids and develop additional sources of funding. It is proposed that the research directories produced by this review are refined and formally updated, on an annual or biennial basis

Organic beef and sheep production (OF0147)

This is the final report from Defra project OF0147 To study the potential of organic farming in the hills and uplands, a comparison of organic and conventional production systems at similar stocking rates was made at ADAS Redesdale. This was supported by additional assessments in two further organic flocks, managed at reduced stocking rates, and by data collection on 10 commercial organic farms. Data were provided on physical and financial performance, animal health and welfare, and changes in botanical composition. Specific studies were done to quantify the potential of novel crops for parasite control, the performance of treated and untreated animal manures, and the requirement for trace element supplementation in organic hill stock. The attached main report starts with a detailed executive summary of the methods and findings

Developing parasite control strategies in organic systems

This report was presented at the UK Organic Research 2002 Conference. Organic farmers have taken a lead in attempting to reduce dependence on pharmaceutical control of parasites in farmed livestock. Focussing on management and nutrition, the objective of this research is to further develop control strategies, which can support and increase the flexibility of clean grazing systems for sheep and cattle. The approach has been to combine on-farm epidemiological studies, with replicated experiments, in order to develop and demonstrate better systems of control applicable to UK organic farms. Preliminary data from the first years' epidemiological studies are presented in this paper

The effect of organic farming systems on aspects of the environment - desk study OF0123

Key Conclusions 1. The crop rotations of organic systems maintain landscape diversity and biodiversity whilst the maintenance of field boundaries on organic units produces benefits to a wide range of organisms. 2. Inorganic nitrogen fertilisation and herbicide treatments of conventionally managed grassland has reduced the floral diversity of permanent pastures and maintained the low diversity of re-seeded pastures, greatly reducing their value as wildlife habitats. 3. Pesticide use is responsible for the removal of food sourcesfor birds and mammals in the form of weeds and invertebrates, as well as removing whole populations of potentially beneficial insects. 4. The majority of water pollution incidents from farms are caused during storage and spreading of cattle and pig slurries. A higher proportion of organic cattle and virtually all organic pigs are kept on solid manure systems and therefore are les of a risk. 5. The nitrogen balance of individual 'conventional' and 'organic' systems will depend greatly on the circumstances and management practices of the individual farms. Consequently it is not possible to generalise that one system is always better than the other in terms of nitrate leaching risk. With this qualification the literature does indicate that generally, organic systems offer less risk of nitrate leaching. 6. Organic systems are less likely to cause loss of phosphate into surface and ground waters. Both leaching and loss in eroded soil are likely to be reduced. 7. Organic management practicess such as rotations, the regular use of manures and non-use of pesticides usually increase soil organic matter contents. 8. Organic practices are likely to increase earthworm numbers compared to conventional systems. The increased numbers are universally acknowledged to benefit soil fertility although such effects are difficult to quantify. 9. Soil erosion is less of a problem on organic units. 10. Accumulations of copper and zinc in soils are much reduced in organic systems because organic pig and poultry producers do not supplement feeds with these metals as growth promoters. Copper fungicides are more widely used on organic farms and their use should be carefully monitored to prevent harmful effects. 11. The practices adopted by organic farmers can reduce emissions of nitrous oxide and methane. Ammonia emissions will not necessarily be less in organic than in conventional farming. 12. Organic farmers adopt practices which benefit the landscape. They maintain and introduce features largely because they are required by the Organic Standards to do so. They introduce such management practices because they are technically necessary for successful organic production

Organic beef and sheep production in the uplands OF0111

The overall objective of the organic project at ADAS Redesdale is to evaluate the physical and financial implicattions of converting a hill and upland unit to an organic farming system. Conversion of 400 hectares, 600 breeding ewes (in 3 flocks) and 5 suckler cows was completed in 1993. The current evaluation (1995-1998) took place under full organic production. The assessmet is based on comparing organic and conventioanl farming systems, supported by data collected from commercial organic farms linked to the main project, and a number of replicated experiments. Grassland management on the Unit integrates three distinct types of grazing; inbye fields (3%), improved hill (17%) and unimproved native hill (80%) for sheep and cattle production. Native hill receives no inputs under organic or conventional management, so that potential differences in output are very much reduced. Low levels of fertiliser and pesticide inputs are made to conventionally managed imroved hill land, with only small differnces in output ad livestock performance. The largest potential differences occur on the more productive inbye land, which receive a high level of inputs conventially. Relying mainly on clover organically managed swards, have been able to achieve 80%, or more, of the forage output from conventional swards receiving over 200 kg N ha-1. Newcastle University undertook an assessment of botanical composition on native hill, improved native and improved hill few changes have been detected, mainly due to the maintenance of comparable stocking rates on the organic and conventional systems. However in one flock, where stocking rate was reduced by 25% there were some indications of an improvement in heather cover. Good levels of livestock performance have been achieved for a hill farming system. However at the same stocking rate, organically managed ewes were consistently lighter and leaner than those managed conventionally. Lambs in the conventional flock grew 5 to 10% and 2 to 17% faster for single and twin lambs respectively. In the organically managed suckler herd, high levels of fertility were achieved. Stocking rates were reduced by 15% and 25% in two further organic flocks, and as a consequence, individual performance remaiined at a high level for a hill system. Calf growth rates averaged 0.8kg from birth to sale, as forward stores at 16-17 months of age. Premium markets have been found for organic store labs and cattle, demonstrating th epotential for better integration of organic hill and lowland systems. The health status of organically managed stock has also been good. The main health issues were trace element nutrition and parasite control. A system of alternative sheep and cattle grazing has been implemented to give better control of stomach worms, reducing the requirement for anthelmintic use compared to the conventional flock. Observational studies using homeopathy for orf and pasteurella pneumonia have shown promising results. Payments made under the Organic Aid Scheme, a premium of approx. 10% on the sale of organic store animals, and reduced forage costs have enabled an organic system to achieve similar, or improved, Net Farm Income relative to the conventional. At lower stocking densities, the individual performance of orgaic livestock animal was improved, and in appropriate circumstances the use of agri-environmental scheme payments can offset the reduction in output where stocking rates are reduced to accomadate an organic system. The results continue to show that an organic hill and upland system can be competitive with conventional production. The unit is recognised as a valuable source of research and information on organic production. The next stage of the project will capitalise on this investment, using the resources available on the Unit to promote and further develop organic farming systems. further evaluation is planned (1998-2001) to take account of longer term trends in grassland and livestock performance, the continuing evolution of markets for organic produce and the development of production standards for organic livestock

Controlling internal parasites without anthelmintics (a review) OF0132

1.0 Executive summary 1. Internal parasites are a major source of economic loss in grazing ruminants. To a greater or lesser degree, most farms in the UK rely on anthelmintics for control. In most situations these products continue to be highly effective, but anthelmintic resistance is increasing to the limited range of products available, raising serious concerns over the future of worm control. 2. Internal parasites are also of concern on organic farms, where the prophylactic use of anthelmintic is prohibited by the standards for organic production. Organic farms generally rely on grazing management, with restricted use of anthelmintic if required. However, also within the regulations is the absolute requirement to treat individual animals if this is necessary to avoid suffering. Organic systems should aim to eliminate the need for anthelmintic drenching, but the number of farms where this has been achieved is few. 3. This report reviews current methods of parasite control, and evaluates the potential of alternatives to the use of anthelmintic, with particular reference to organic systems. Epidemiology 4. The biology and epidemiology of the major internal parasites of sheep and cattle are well known. These form the basis of management and biological control, including strategies for clean grazing. However, less is known specifically about the complex interactions between parasite, host, climate, management and pasture factors which give rise to the occurrence of disease. 5. Useful computer simulation models have been developed, usually related to specific locations, species of parasite or conditions of management. These are becoming increasingly complex as further variables such as host resistance, sward type and grazing behaviour are included in the model. As knowledge and computing power increase, the opportunity is there for models to become more comprehensive, and more accurate. 6. Trends in the occurrence of disease can broadly be predicted, on a national or regional basis, from climatic and management data. At the present time however, there is no single comprehensive model which can be used to adequately quantify and predict the development of disease at a farm or system level. Research work is continuing on this topic. Maximising the host’s ability to fight disease 7. Host factors affecting the incidence and severity of parasitic attack include the development of acquired immunity, the effect of nutritional status and the presence of concurrent disease. 8. Under-nutrition has a general debilitating effect on an animal’s ability to fight infection. In terms of roundworms, the development of the immune response and the host’s ability to restore damaged tissue has been shown to be related to energy, and particularly protein, intake. A shortfall of specific minerals and trace elements e.g. cobalt or selenium will affect the host response to infection. Parasitic infection in it's own right can increase the requirement for specific nutrients, due to increased loss or less efficient use. 9. The underlying approach to disease control on organic farms is to promote the natural immune system and livestock health. Optimising management conditions to minimise stress, provide high quality, balanced diets and avoid concurrent disease is entirely consistent with an organic approach to animal husbandry, and a good basis for any disease control programme. Clean grazing systems 10. Management strategies which optimise health, and reduce the exposure of animals to parasitic infection are a prerequisite on organic farms. Clear benefits have been demonstrated under conventional, as well as organic systems. Clean grazing systems are the favoured and most direct method of controlling internal parasites on organic farms, and wherever possible should underpin all other methods of parasite control. 11. However, the managerial discipline and farm infrastructure are not always present to operate an effective clean grazing system. On conventional farms, the perceived conflict between efficient and flexible grassland utilisation, and the availability of effective anthelmintic products, has discriminated against greater uptake of clean grazing. On organic farms the motivation is greater, but the optimum balance of livestock and arable enterprises is not always present, making management more difficult or reducing the effectiveness of a clean grazing approach. Implementation of clean grazing systems is particularly difficult on hill farms, on single enterprise units with permanent pasture, or where the ratio of cattle to sheep livestock units is wider than 35:65. 12. It is also difficult to operate current clean grazing systems without using some anthelmintic, particularly when animals are first put onto clean pasture. This is particularly critical for freshly lambed ewes, which temporarily lose their immunity and produce a high output of worm eggs during early lactation. In this case anthelmintic drenching is often required to reduce contamination of clean grazing, and to avoid the system breaking down later in the season. Systems of alternate or mixed grazing have value, but on their own are unlikely to achieve an acceptable degree of parasite control. 13. Where clean grazing cannot be set up, for example on hill farms, there is greater reliance on the extensive nature of the grazing to reduce parasitic burden, and on the sale of lambs at weaning. By means of a carefully timed move from lambing pastures to open hill, an extensively managed hill farm could theoretically avoid the need to drench lambs at least until weaning. 14. However, for organic farms in the hills/uplands trying to finish lambs after weaning, parasitic gastro-enteritis will remain a hazard, and the limited use of anthelmintic is almost inevitable for individuals, or whole groups, depending on the season. Even where lambs are sold at weaning, all or a proportion of lambs may require drenching on arrival at their new destination, particularly if going onto clean pasture. 15. On lowland organic farms supporting ‘commercial’ stocking rates, current practice is to support clean grazing by the strategic use of anthelmintic, often a single drench to ewes around lambing time, before entry to clean pastures, or as a ‘salvage drench’ should parasitic burden become too great. Genetically resistant animals 16. Trials have shown that 10% of lambs in a given flock may contribute 50% to total faecal egg output.Ironically, one method of reducing total anthelmintic use is to target those individual lambs within the flock which, in terms of faecal egg output, appear to be the worst offenders. At a practical level this is done by drenching scouring lambs. However, scouring in not necessarily indicative of a high faecal egg output. 17. Eliminating the most contaminating individuals from a flock, can have a very significant impact on the overall level of parasitic challenge. The existence of genetically linked resistance to roundworms is well recognised in the UK and abroad. Several experimental flocks have been established in Australia and New Zealand, with high and low responder lines differing in faecal egg output for a particular parasite, usually Haemonchus contortus or Ostertagia circumcinta. 18. These traits are low to moderately heritable, and therefore can be used to increase the frequency of resistant genes in a particular flock or population. Neither does selection for increased parasite resistance necessarily reduce performance in economically traits, especially in a heavily parasitised environment. 19. Genetically resistant animals have traditionally been selected on the basis of nematode egg output in the faeces, after dosing with a known challenge of infective larvae, or from naturally acquired worm burdens. This the most direct and cheapest form of selection. Indirect methods have been sought on the basis of host physiology and blood biochemistry. So far the results have not been conclusive. 20. Some progress has been made in the identification of genes associated with the sheep Major Histocompatibility Complex (MHC) which may be involved in conferring increased resistance to internal parasites. However, there are other non-MHC genes also involved in the regulation of host responses. 21. A recent development by Glasgow University Veterinary School has been the identification of a genetic marker for increased resistance to O. circumcinta in Scottish Blackface sheep. This test is currently being validated on commercial farms where single sire mating is practised in pure-bred flocks. With continuing improvement in genetic mapping and biotechnology techniques, this type of test is likely to be used increasingly in genetic selection. 22. One of the difficulties in extrapolating from an experimental flock of genetically resistant animals, is in determining how representative this sub-group is of the sheep population as a whole. Nevertheless, commercial breed improvement programmes are now in operation in Australia and New Zealand which incorporate resistance to worms in the selection index. 23. On an individual organic farm which breeds its own replacements, selection for parasite resistance is possible. Selecting future breeding stock by the extent of dagginess (as currently practised on some organic farms) may in fact be selecting for resilience against parasite attack, rather than for resistance. Fortuitously, resilience and resistance traits are positively correlated. The accuracy of selection for resistance could be greatly improved by carrying out egg counts in samples of faeces taken over a period. Just as importantly, this strategy could be used to eliminate from the breeding flock animals inclined to have persistently high faecal egg output, thereby reducing pasture contamination and parasitic challenge to the flock as a whole. Manipulating sward structure and composition 24. Sward structure has been shown to affect the concentration of infective larvae on the upper horizon of the sward, through effects on the micro-climate within the sward or due to the morphology of the plants themselves. These effects have been shown to modify parasite burden in the grazing animal; Yorkshire Fog for example, has been shown to result in lower rates of infection than Ryegrass swards. 25. Most of the data derives from studies in Australia and New Zealand, often with H. contortus. Significant effects remain to be demonstrated at a strategic or applied level under UK conditions. Conclusive relationships have yet to be established, which would allow this factor to be used in a management system. 26. New Zealand studies have shown that the species of plant present in the sward can also affect the worm burden acquired by grazing stock. Some of the most interesting work relates to certain plants, in particular, Lotus corniculatus and sulla (Hedysarium coronarium) which contain condensed tannins (CT’s). Several experiments have shown that CT’s can reduce the parasite load and improve the performance of parasitised lambs due, at least in part, to their protective effect on dietary protein which increases protein supply at the duodenum. Control by vaccination 27. The host parasite relationship is very complex. A lack of detailed knowledge of the immune response is the main factor which currently limits the ability of molecular biologists to develop suitable vaccines. Initial successes against blood sucking and mucosal parasites provide some optimism for effective vaccination against gastrointestinal nematodes in the future. 28. Commercial vaccines are not yet available, but considerable progress has been made in isolating various parasite enzymes and proteins which may be used as antigens. As knowledge of the immune response increases, so too does the ability to select appropriate antigens to stimulate an immune response in the host. Improvements in adjuvants will ensure the right type of response is induced. 29. Much of the work has been undertaken with H. contortus - it’s blood sucking feeding habit providing a good means of delivering antibody to the digestive system of the parasite. However, this species is of limited importance in the UK. For practical use, control of Ostertagia in particular, will need to be incorporated in any commercial vaccine. 30. While a vaccine for the control of parasitic gastro-enteritis may be available in the future, its adoption within organic systems will depend on how its acceptance by the Organic Sector Bodies. Draft EU Standards would allow vaccination in circumstances where disease had been identified and treatment recommended. Role of homeopathy 31. There is little evidence to confirm any direct effect of homeopathy in the treatment of parasitic gastro-enteritis. However, homeopathic preparations may have a useful role in aiding the recovery of tissues damaged by parasitic attack. An effective nosode is available to provide protection against lungworm infection. Herbal treatments 32. Many plants and their extracts have been shown to act as mild verimfuges. However, little comparative information is available on their potential for worm control in farm animals. A herbal approach may have better longterm prospects for nematode control than homeopathy, but further screening and evaluation is necessary. 33. With both homeopathy and herbal treatment, a practical method of delivery under field conditions can be difficult. One option could be to establish monocultures of certain plants (vermifuges, or CT’s) to be grazed strategically by organic stock, for example immediately after weaning. Biological control 34. Fungi are only one type of organism with potential for controlling the free living stages of gastrointestinal worms, but these have been the most studied. Other biological control agents are theoretically possible, particularly bacteria. 35. Initial screening work carried out in Australia identified approximately 100 species of fungi with nematophagous activity. Progress has been made under laboratory conditions in selecting fungal species which meet this criteria, and which can survive passage through the ruminant gastrointestinal tract. Some field testing has been carried out under Australian conditions with selected fungal species. Significant reductions in the number of infective larvae present on the pasture were reported, and a level of control comparable to the use of anthelmintic was claimed. 36. Research is ongoing to determine threshold dose levels and to investigate systems of sustained delivery of the fungi. Genetic typing and manipulation, while less acceptable for organic systems, could be another option to increase efficacy. The ultimate aim might be to develop a biological control system through a feed supplement, feed block or an intraruminal controlled release device. 37. New Zealand research has concentrated on understanding the role, and factors which affect the activity, of fungi already present on the pasture, rather than artificially deploy fungi onto faeces. There is little or no information on either aspect available from the UK. With a better understanding of fungal distribution on pasture, it may be possible to encourage sward conditions to maximise the impact of nematophagous fungi which are already present on the sward Controlling internal parasites without anthelmintics - Conclusions 38. Effective systems of clean grazing have been developed in the UK. With current knowledge, these must be rigidly applied to be fully effective, often reducing their chances of being taken up on farms whose infrastructure and enterprise mix are not ideal. Furthermore, current systems of clean grazing generally depend on strategically timed anthelmintic treatment. To retain effective parasite control, while simultaneously reducing anthelmintic input and relaxing some of the more rigid features of conventional clean grazing systems, poses a considerable challenge. 39. An increasing number of factors are recognised as affecting parasitic burden. The need is to understand how collectively to harness some, or all of these, to bring practical benefits to parasite control. The best prospect is to combine several approaches in an integrated control programme, which could vary depending on individual farm circumstances. Some research has been carried out in New Zealand, but this work has been curtailed because of lack of funding. More information is required on parasite epidemiology, the effect of pasture species, grazing management and factors affecting larval movement and survival, which can be incorporated into a predictive model. Some of this basic modelling work is already taking place. However, practical evaluation under commercial conditions is still some time away. 40. Breeding for host resistance to parasites is a relatively new subject in the UK. Carried out on a flock basis, there is the advantage that selection is specific to farm conditions. However, if selection is based solely on the incidence of scouring the accuracy of selection and rate of progress will be low. Accuracy of selection may be improved by the use of faecal egg counts, replicated over time. The use of genetic markers, although promising, requires further investigation and validation in the field. Ultimately selection should be based on a multi-component selection index. The weighting of this index for disease resistance may need to be greater for organic systems, simply because the costs (economic or ideological) are higher, and the response to improvement in disease control greater in a parasitised environment, where the aim is to avoid anthelmintic treatment. Serious consideration should be given to developing a protocol for selecting more resistant animals on a within-flock basis, perhaps using existing Sire Reference Schemes as a model framework. 41. Experience of biological control outside of controlled glasshouse situations is often unconvincing. In terms of biological control of roundworms, there are reasonable prospects of developing a delivery system through the grazing animal to target the parasite in the faecal environment. Alternatively, a better understanding of how to optimise pasture conditions in favour of the control agent, probably a fungus, could significantly reduce the viability of free living stages. Further research needs to be undertaken in the UK. 42. The approach which might give the best return, could be the strategic use of specific forages. These are likely to be those containing condensed tannins, or perhaps plants with specific vermifuge qualities. Typically, these could be used for freshly lambed ewes before being moved on to clean pasture, so that periparturient worm burdens are reduced, or for lambs after weaning. Alternatively, weaned lambs from organic hill farms could be put onto such forages, before being released onto finishing pastures. There is a need to evaluate the role of these forages on organic farms, their effectiveness, agronomy, and short/longterm effects on the grazing animal

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