Oleander (Nerium oleander) is an attractive, hardy, ornamental, evergreen shrub that is a major cause of animal poisonings worldwide. N. oleander is found in tropical and subtropical regions. It has dark gray-green, leathery leaves. It's showy clusters of flowers bloom from early summer until mid-autumn.

N. oleander is a highly toxic plant. It contains several cardiac glycosides--the most toxic chemicals being oleandrin and neriine. Cardiac glycoside poisoning acts by inhibiting Na+/K+ ATPase. Cattle don't need to ingest very much to have fatal consequences. As little as 0.005% of it's body weight in dry oleander leaves can be fatal. The most frequent source for oleander exposure in livestock is yard/garden clippings. There have also been incidences where cattle consumed hay that was contaminated with oleander leaves. Bored cattle may also chew on plants that grow near their pastures. Oftentimes, cattle are found suddenly dead, or present with rapidly developing nonspecific signs that may resemble colic.

Incubation Period
If signs do appear, there is usually a 2-5 hour delay from ingestion of the plant to apparent symptoms. Signs of poisoning may begin with diarrhea, excessive salivation, depression and loss of appetite and progresses to the development of cardiac signs such as bradycardiaor tachycardia, weak and irregular pulse, heart blocks, and arrhythmias.