Glyceria maxima
Reed meadow grass
An aquatic, reed-like perennial, growing up to 2.5 metres in height. It has broad, bright green leaves up to 20mm across and ranging from 20 to 60mm in length. A noticeable brown mark is present where the leaf meets the sheath, and it has a blunt, or abruptly pointed ligule. Habitat:
Other reeds. There are other spp. of Glyceria in NZ, but although they are aquatic, they are not very large.
Restricted mostly to Otago and Southland in NZ. The plant is located mostly in fresh or brackish water especially at the edge of marshes, and can survive in water up to 80cm in depth.
Has been recommended as a nutritional fodder plant for livestock grazing wet areas, and consequently its introduction to NZ was not discouraged. However there are several sporadic accounts of poisoning of cattle by this plant. The toxic agent within Glyceria maxima is cyanide, which acts by blocking cytochrome oxidases, preventing cellular respiration. Poisoning: The majority of cases of G. maxima poisoning have occurred between September and November, coinciding with the period of maximal growth by the plant. Rapidly growing vegetative tillers contain the highest concentrations of cyanide within the plant, while flowering culms have mild levels, and seed heads have not been shown to contain any of the poison. However, overall cyanide levels within the plant peak largely in the spring, with a smaller, second rise in the autumn.
Hungry cattle.
Typical of cyanide poisoning. These include restlessness, convulsions, dyspnoea, as well as depression. However, these are only noted early in a case of toxicity, and usually the first sign of poisoning that is noted is sudden death of affected animals.
Presence of the plant in the ruminal contents. Also a reddening and inflammation of the rumen and abomasal wall has been recorded.
Clinical signs, post mortem findings, as well as the animal having grazed with access to the plant.
Ingestion of other sources of cyanide. This includes plants such as sorghum grasses, or artificial sources, for example misplaced possum bait. Another possible differential is "grain overload syndrome" or rumen acidosis. This could be ruled out as a differential by examination of the rumen contents, as well as investigating the recent grazing history of the cattle (supplemental feeding? Grazed near a source of G. maxima?).
Sodium nitrate can be given at 10-20 mg/kg iv or sodium thiosulphate at 500 mg/kg iv.
Very poor. Usually found dead.
Conner H.E. The Poisonous Plants In New Zealand. 1992. GP Publications Ltd, Wellington
Parton K, Bruere A.N. and Chambers J.P. Veterinary Clinical Toxicology, 2nd ed. 2001. Veterinary Continuing Education Publication No. 208
4 October, 2007