Page 959 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

VetBooks.ir Chapter 63

Poisonous Plants of Australia and

New Zealand

Rhian Cope and Selina Ossedryver

INTRODUCTION provided as Table 63.1. Common and important plants that
are hazardous to live stock are described in Table 63.2.
Due to space constraints, this chapter largely focuses on
The long biogeographic isolation of the Zealandia con-
the indigenous flora of Australia and New Zealand that has
tinent and the islands of New Zealand has also resulted in
been noted to produce substantial livestock losses and
a unique variety of native flora and associated unique tox-
some of the major problematic introduced plants. It is not
icological concerns (Table 63.3).
possible to cover all of the poisonous plants in Australia
and New Zealand that are known to have caused livestock
losses in a single chapter, and the reader is referred to
REDUCING LIVESTOCK LOSSES
more authoritative references for this. To allow for reason-
able coverage of the most important species, the informa- ASSOCIATED WITH POISONOUS PLANTS
tion is presented in tabular form. IN AUSTRALIA AND NEW ZEALAND
The climate of Australia is unique compared with those
The key factors in reducing losses due to plant toxicoses
of the other continents, and this has a substantial impact
are an awareness of the types of potentially toxic plants
upon plant poisonings in grazing livestock. Australia is
relevant to the geographical area of production, an under-
easily the driest of all continents: most of Australia is des-
standing of both the plant and the animal factors that
ert or semiarid, and 40% of the landmass is covered by
influence the risk of poisoning, and an understanding of
sand dunes. Eighty percent of Australia’s landmass has an
what indigenous plants can and cannot be used as feed for
average annual rainfall of less than 600 mm, with 50% of
livestock under drought conditions.
the landmass having less than 300 mm. Rainfall for much
A common, important plant-related factor in Australia
of the continent is highly variable, and droughts, which
is the ability of indigenous plants in the semiarid and arid
may last several years, are a regular feature over much of
areas of the country to outgrow and outcompete intro-
the agriculturally productive areas of Australia.
duced fodder plants, particularly following the breaking
Accordingly, many of the toxicologically problematic
of a drought or under poor environmental conditions. In
indigenous plants are well adapted to this climate: they are
such circumstances, the new plant growth may contain
extremely drought resistant (or their seeds are resilient),
relatively high amounts of relevant toxins. This situation,
and they are able to grow very rapidly during the short per-
combined with cold, stressed, hungry and/or inexperi-
iods of relatively suitable conditions. In these circum-
enced stock is a recipe for significant stock losses. This
stances, poisonous indigenous flora often outcompete
type of scenario has been classically associated with the
introduced fodder plants or they emerge earlier after the
rangeland northern cattle industry and the arid zone and
onset of ideal conditions or they persist longer than intro-
semiarid zone sheep industries in Australia. The following
duced fodder plants when less than ideal conditions set it.
are approaches known to reduce the risks associated with
Poisonings often occur under such conditions. Another
these circumstances:
common circumstance of poisoning is when indigenous
plants are the last remaining plants and they are cut and Mechanical methods of plant removal: Because of the
fed to livestock during drought as survival feed (drought sheer physical size of livestock properties in the semi-
lotting). A summary of the characteristics of important arid and arid regions of Australia, such methods are
plant species used in drought lotting in Australia is often impractical. However, on a small scale, such
Veterinary Toxicology. DOI: http://dx.doi.org/10.1016/B978-0-12-811410-0.00063-5
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