Phalaris Toxicoses in Australian Livestock Production Systems: Prevalence, Aetiology and Toxicology

The perennial grass Phalaris is a valuable pasture species which features predominantly in Australian and North American grazing systems. Its usefulness, however, has been tempered by the presentation of sporadic outbreaks of severe toxicoses associated with its ingestion by grazing livestock. Phalaris toxicoses present as one of two clinical entities: phalaris ‘staggers' or ‘sudden death'. Although alkaloid toxins have been implicated in both syndromes their identification and mechanism of action are yet to be fully defined, and the specific nature of phalaris toxicity is currently poorly understood. Mitigation strategies currently centre on changed management practices, such as sowing low alkaloid cultivars and supplementation with cobalt. This review examines the prevalence, aetiology and pathogenesis of phalaris ‘staggers' and ‘sudden death' syndromes as well as current knowledge of environmental and agronomic interactions associated with the production of nitrogenous compounds and bioactive secondary metabolites in the plant.