|
Arrowgrass is a perennial that has fleshy, dark-green, half-rounded, grasslike leaves that grow from the base of the plant. Although clumps of leaves are only 15 to 45 cm tall, slender flower stalks may reach a height of 1.5 m. Small, green flowers appear close together along the upper part of the stalk early in the season. Later, the flowers develop into golden-brown fruits.
Where it Grows
Species of arrowgrass that poison livestock are widely distributed in marshy pastures and native grass hay areas throughout the United States. Arrowgrass grows on wet, alkaline soils and may be found growing over large areas or in small patches near springs. Arrowgrass starts growing in the early spring. It is often found growing in native meadows that are cut for hay and, if sufficiently dense, such hay may be toxic.
Signs and Lesions of Poisoning
Distress
Dyspnea; rapid breathing and gasping
Increased salivation
Muscular twitching, staggering, and convulsions
Bloat may occur; rumen contents may smell like almonds
Convulsions
Coma
Death (animals consuming large amounts of the plant may die in 1 to 60 minutes and
show only convulsions and death as signs of poisoning)
Blood and tissues are a bright cherry red (hyper oxygenation)
Tracheal and pulmonary congestion
How it Affects Livestock
All species of livestock are susceptible, but cattle and sheep are most often poisoned when they eat large amounts of arrowgrass leaves in a short time. The leaves may contain the toxic substance hydrocyanic acid. Toxin concentrations in the plant vary and are greatly influenced by environment. Arrowgrass that has adequate moisture does not cause poisoning. When growth is stunted from lack of moisture or frost, plants quickly produce and accumulate hydrocyanic acid. Arrowgrass and chokecherry both contain hydrocyanic acid. About three grams of hydrocyanic acid (0.4 to 1.5 kg of stunted arrowgrass) may kill a 300-pound animal. The toxic dose must be eaten over a short time as the toxin is not cumulative. Death results from respiratory failure.
How to Reduce Losses
Keep animals off areas where the growth of arrowgrass has been retarded by drought or frost, and regrowth following harvest of hay. Harvested forage may be toxic if not properly cured. The action of hydrocyanic acid is so rapid that it is usually too late to treat affected animals after the signs of poisoning are recognized. However, poisoned animals may be treated with immediate intraperitoneal or intravenous injections of 20% sodium thiosulfate and 20% sodium nitrite at 4 ml/45 kg BW. Commercial solutions for treatment of prussic acid poisoning are available. Always consult your veterinarian regarding both drugs and treatment.
As dried arrowgrass remains toxic, avoid including retarded or stressed arrowgrass in hay or stored forages.
Arrowgrass can be controlled by metsulfuron when applied during seed stalk elongation. Consult with both extension services and the herbicide manufacture’s recommendations for proper dosages and precautions. | 
Printable Version
E-mail this page
