" Ingestion of 0.005% of bodyweight of
green oleander can be lethal to horses.22 Azaleas are reportedly
toxic to stock that ingest 0.2% to 0.6% of bodyweight of plant
material."

http://www.ava.com.au/content/avj/0207/0207.pdf

"There are in the order of 45 species of plants that contain
cardiac glycosides and are potentially poisonous to animals1,3
and humans.13,14,18 Many of the cardiac glycoside containing
plants, including oleander, yellow oleander, azaleas, and
Japanese pieris are evergreen shrubs or small trees that are
commonly used as ornamental garden plants.3,16 Most cardiac
glycoside poisonings occur when these plants are grown in or
around animal enclosures,2,11,16,19 when they are accidentally
incorporated in feedstuffs,1,20 or when clippings are fed to
animals.1,3-5,16 Only two species, Nerium oleander (oleander)
and Cryptostegia grandiflora (rubber vine) have been reported to
cause poisoning of horses.2-5 In this horse, ingestion of oleander
clippings inadvertently deposited into the horse’s yard was the
suspected cause.
Cardiac glycosides are found in most parts of the plants,"

On 29 Apr 2003 00:02:53 GMT, pamfree (Zemedelec)
wrote:

Poisonous enough to kill a horse. One of the first things I was told when out
riding in partially suburban areas was not to let my hirse chew on oleander.

And read the book, "White Oleander." Much better than the movie, but aren't
they all?
zemedelec



"Nature, left alone, is in perfect balance.
Harmful insects and plant diseases are always present,
but do not occur in nature to an extent which requires the use of poisonous chemicals.
The sensible approach to disease and insect control is to grow sturdy crops in a healthy environment."

Masanobu Fukuoka, One Straw Revolution--1978