Plant extracts as antimicrobials in ruminants

Growth-promoting antibiotics in animal feeds were banned by the EC from the end of 2005. This decision was based on public and political concerns that the heavy use of antibiotics in general can give rise to transmissible resistance factors that compromise the potency of therapeutic antibiotics in man. Growth promotion was a clearly avoidable use. Other international legislators may soon follow suit. Thus, livestock producers in many countries must face a future without antibiotic growth promoters. Problems may be more acute in pig and poultry production, but ruminants will also be affected in the sense that existing and potential new strategies for manipulating rumen fermentation must avoid selective antimicrobials. Organically produced meat and milk are increasing in demand by consumers, and organic farmers therefore face the same problems. Thus, there is increasing interest in exploiting natural products, which have no similar public health hazard, as feed additives to solve problems in animal nutrition and livestock production. The 'natural' products include probiotics, prebiotics, enzymes, organic acids, and secondary plant compounds or their nature-identical chemicals. This chapter describes plants and their constituent phytochemicals in relation to manipulating ruminal fermentation, and reports progress in EC research projects that investigate the broader potential of plants and their extracts: 'Rumen-up' and its successor, 'REPLACE'.