Page 67 - The Mini Horse Magazine 2023 No 1

Bracken fern Oleander
(Pteridum (Nerium oleander)
aquilinum)

Also known as: brake fern, eagle fern Also known as: Rose laurel, adelfa, rosenlorbeer
ID: A perennial fern with triangular leaves ID: An evergreen shrub that can reach the size
that can reach two to three feet high. Grows in of a small tree, oleander has elongated, thick
clumps in woodlands and moist open areas. leathery leaves that can grow to three to 10

The danger: Bracken fern contains thiaminase, inches long. The flowers, which grow in large
which inhibits absorption of thiamin, which clusters at the end of branches, are one to
is vitamin B1. Thiamin is necessary to nerve three inches in diameter and can be white, pink
function, and deficiencies can lead to neurological or red.
impairment. The relative toxicity of individual The danger: All parts of the plant contain the
leaves is low—horses must consume hundreds toxins oleandrin and neriin, which disrupt the
of pounds to experience ill effects. However, beating of the heart. The leaves remain toxic
bracken fern is unique among the toxic plants when dried. About 30 to 40 leaves can be
in that some horses seem to develop a taste for deadly to a horse.
it and will seek it out even when other forages Signs: Effects are usually seen several hours
are available.
after ingestion and last over 24 hours. Signs
Signs: Signs are related to neural dysfunctions include colic, difficulty breathing, tremors,
resulting from vitamin B1 deficiency and recumbency and an irregular heart rate. The
can include depression, incoordination and pulse may be either slowed or accelerated.
blindness.
What to do: Horses can survive if treated early
What to do: Large doses of thiamin over the with supportive care, such as the administration
course of a week or two can aid in the recovery of of activated charcoal to inhibit further toxin
horses whose bracken consumption is discovered absorption and the use of anti-arrhythmic drugs
before the neurological signs are severe. to stabilize the hear.

The danger: All parts of the yew plant, except
for the fleshy portion of the berries, contain

Yew taxine, an alkaloid that causes respiratory and
cardiac collapse. The leaves remain toxic even
(Taxus spp.) after dried. A single mouthful can be deadly to a
horse within minutes.

Signs: Sudden death is the most typical sign
of yew ingestion. Animals found alive may be
trembling and colicky, with difficulty breathing

ID: A woody evergreen shrub with closely and a slowed heart rate.
spaced, flat, needlelike leaves a half-inch to one What to do: There is no treatment for yew
inch long. Berries are bright red or yellow, soft poisoning. Avoidance is critical; most yew
and juicy with a hole in the end, where the dark poisonings occur when trimmings are thrown
seed is visible. into a pasture after a pruning.

Miniature Horse Magazine • Issue 1/2023 | 67