Answer / Justification:
Due to a high concentration of pyrrolizidine alkaloids, it is poisonous to grazing livestock, especially those with simple digestive systems, like horses. The toxins are cumulative in the liver, and death results from too much Paterson's curse in the diet. Where introduced it has established and spread successfully in pastures where it can outcompete native species. In Uruguay, it was a browse species eaten mainly by sheep and was regarded as a weedy invader of pastures. Its importance might be on the increase, however, with more recent records of poisoning of cattle in Brazil following ingestion of the weed. In South Africa, it was introduced as a stock feed and spread along roadsides. In the annual pasture-cropping zone in southern Australia, E. plantagineum is a major component of an introduced pasture agro-ecosystem. E. plantagineum competes strongly with more valuable pasture species, especially under light grazing which favours the development of large rosettes, but the high productivity of E. plantagineum can make it a useful forage species. Depending on the rainfall it either dries off in spring leaving little feed for the critical summer/early autumn period or continues to grow vigorously and provide some green feed over summer, especially when heavily grazed, at a time when other species have dried off. Young growth is readily eaten and provides considerable sustenance to stock, whilst older growth is rough and hairy and generally avoided by stock. The plant appears to be eaten readily by sheep, less-readily by cattle and reluctantly by horses, but little data support this so it is possible that differences observed are due, at least partly, to differences in grazing pressure and pasture height. Rosettes contain 6-14% dry matter, 2.0 to 4.8% d.m. nitrogen and are 50 -75% d.m. digestible. Flowering plants contain 20-70% dry matter, 0.5-4.7% d.m. nitrogen and are 37-69% d.m. digestible. Comparisons suggest that E. plantagineum is as nutritious as most recognized pasture species with low dry matter content (20-30%) and relatively high nitrogen content (4.1-4.3%) and digestibility (61-64%) and so should provide useful fodder. The hairiness can cause slavering, dermatitis, inflammation and itching to animals and man. The key problem associated with E. plantagineum, however is that it contains eight hepatotoxic pyrrolizidine alkaloids, particularly echiumine and echimidine, which are at higher levels in rosettes and also vary with soil type, soil fertility and climate. These alkaloids can cause cumulative chronic liver damage and animal mortality, especially if substantial amounts of herbage are eaten over prolonged periods. Monogastric grazing animals such as horses are more susceptible than ruminants because the alkaloids are largely broken down in the rumen. E. plantagineum was considered the primary cause of pyrrolizidine alkaloid poisoning in horses in Australia and toxicity in cattle in Brazil. E. plantagineum is also the major cause of sheep deaths from primary pyrrolizidine alkaloid and associated hepatogenous chronic copper poisoning in New South Wales, particularly in crossbred ewes. Cross-breeds grazing pasture that was up to 61% E. plantagineum had reduced weight and wool growth, but no mortality after 19 months, while the same animals fed solely on fresh E. plantagineum showed some 40% mortality after 16 weeks due to progressive liver damage. The plant has also been implicated in several reported cases of mortality in horses and occasionally young pigs and even caged canaries. Such effects can be minimized if good pasture and livestock management maintains the E. plantagineum percent pasture consumption below 50%. E. plantagineum has been associated with human allergy problems. Use or contamination in foodstuffs can lead to human health risks from the pyrrolizidine alkaloids and threatens bans on contaminated cereal exports from affected areas (CABI). Echium plantagineum contains pyrrolizidine alkaloids and is poisonous. When eaten in large quantities, it causes reduced livestock weight and death, in severe cases. Paterson's curse can kill horses and irritate the udders of dairy cows and the skin of humans. After the 2003 Canberra bushfires a large bloom of the plant occurred on the burned land, and many horses became ill and died from grazing on it. Because the alkaloids can also be found in the nectar of Paterson's curse, the honey made from it should be blended with other honeys to dilute the toxins (EOL). Paterson’s curse (Echium plantagineum ) quickly replaces other more palatable plants in heavily grazed pastures, reducing the value of the pasture and replaces the natural vegetation of the area. Though it is occasionally considered useful in some semi-arid rangeland pastures, it costs Australian graziers approximately $30 million every year in lost production and control costs (Weeds of Australia Biosecurity Queensland Edition).