Abstract
This proposal will assist in the development and implementation of policy relating to the Water Framework Directive, the most substantial piece of EU water legislation to date. The primary purpose of the work will be to investigate and monitor strategies that reduce nutrient leaching (nitrogen and phosphorus) from grassland dairy farms to water catchments; a secondary purpose is to monitor the potential reduction in pathogen contamination to water courses. The programme will investigate the effects on nutrient leaching and pathogen shedding when alternative forages are incorporated into the diets of cows in grassland-based dairy systems. The research relates to work being conducted at IGER to investigate the effects of alternative forage crops on nitrogen partitioning, milk composition and organoleptic qualities and the risk of enteric pathogens entering the food chain as part of an EU project (QLIF; FOOD-CT-2003-506358). In pursuit of sustainable and economically-viable livestock systems, conventional and particularly organic grassland farmers are under increasing pressure to maximise their use of home-grown forage-based diets for their livestock. Dairy cows are typically fed ensiled ryegrass as the main forage component of their diet over the winter period when pasture productivity is low. However, this feeding strategy requires the addition of concentrates to meet the animals’ energy and protein requirements and achieve commercially-viable productivity. In addition, restrictions in the use of fish, meat and bone meal, organic farming regulations, and fluctuations in the price of imported Soya have resulted in a demand for alternative, traceable and low-cost sources of protein and energy feed for livestock. Advances in silage technology (including Defra funded advances) make it possible for alternative forages to be ensiled as high protein, winter forage for livestock (Wilkinson, 2005). For example, legume forages such as red clover, popular with oirganic livestock producers and previously regarded as unsuitable for ensiling due to it's low water-soluble carbohydrate content and high buffering capacity, can now be ensiled quite effectively (Frame et al., 1998). Previous studies have focussed on enhancing the efficiency of use of nutrient by livestock (Dewhurst et al., 2003a; Marley et al., submitted). However, despite the fact that agricultural manures contribute about 30% of phosphorous (P) inputs to surface waters in the UK, previous studies have tended to focus on the efficiency of use of nitrogen (N) at the whole animal level and take little or no account of nutrients such as P and the whole farm system. Recent data from Defra LS3642 indicate that lambs fed ensiled red clover retain 5 times more P, resulting in a lower P excretion, than lambs fed ensiled lucerne. These findings highlight a need for further research into P cycling at a farm systems level. Alongside the concerns regarding the efficient use of nutrients, livestock contribute to the pool of human enteric pathogens in the food chain and wider environment. Current feeding regimes, using high inputs of cereal based concentrate supplements, may be adding to the problem (Dargatz et al., 1997; Harmon et al., 1999). Whilst the risk of transfer of pathogens through the food chain can be minimized by Hazard Analysis Critical Control Points (HACCP), control of pathogens in the wider environment is more complex and the ruminant animal represents a critical point at which control should be exerted. Legumes and high oil crops contain compounds, such as polyphenolics (Garber et al., 1995) and fatty acids (Dierick et al., 2002), that have the potential to reduce pathogen load and therefore shedding from ruminants. In order to fully determine the impact of incorporating ensiled, home-grown forages on UK dairy farms, research is needed to determine their economic and environmental impact on farm nutrient budgets. Nutrient budgeting is a widely used tool for maximising the efficiency of use of nutrients on farms and as an indicator of the sustainability of farming practices. However, there is currently little information available on the effects of incorporating ensiled home-grown forages into livestock production systems on farm-gate nutrient efficiency. Research is needed, for example, to determine the effect of using slurries from livestock fed on ensiled alternative forage as plant fertiliser when compared with slurries from animals fed on ensiled ryegrass. Only by considering all these factors can the full benefits of using alternative home-grown forages within dairy production be determined. Overall, the research will test the hypothesis that using ensiled home-grown alternative forages (compared with ensiled ryegrass) in UK dairy systems, while not affecting productivity, will significantly improve farm-gate nutrient use efficiency and pathogen control. This will provide strategies for sustainable, low input, grassland-based, conventional and organic dairy farmers which enable them to contribute to implementation of the Water Framework Directive.
United Kingdom