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

Summary

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.