Reed canarygrass (Phalaris arundinacea
) is a stout, erect, perennial grass that is a major weed in winter crops and pastures worldwide. Flat, green leaf blades occur from spring to early summer, but tend to turn brown as the summer progresses. P. arundinacea
is a highly variable species, varying in height, size and shape of inflorescence, and coloration.
All parts of P. arundinacea
contains tryptamine alkaloids. It has also been known to accumulate high levels of selenium, causing selenium toxicity
in horses. The toxicity increases when the plant is stressed, such as during certain environmental conditions such as drought, nitrogen fertilization, cloudy days, new growth or regrowth, top growth consumption, and leaf versus stem consumption. Cases of poisoning in livestock have been documented since 1942, primarily in Australia and New Zealand, with recent poisonings reported in Argentina, South Africa, Norway, and the United States. Sheep are considered to be the most susceptible species, but cattle and horses can also be affected.
Consumption of P. arundinacea
can manifest in two different forms in horses---as "sudden death", presenting as a neurologic or a cardiac syndrome or as "staggers", affecting the horse's locomotor abilities in an acute or chronic form. The acute form is reversible, but the chronic form is not and is usually lethal.