Page 879 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

VetBooks.ir Chapter 61

Poisonous Plants of the United States

Kip E. Panter, Kevin D. Welch, Dale R. Gardner, Steven T. Lee, Ben T. Green, James A. Pfister, Daniel Cook,
Thomas Z. Davis and Bryan L. Stegelmeier

INTRODUCTION when animals are fed contaminated hay, they may be
poisoned. Poisonous plant problems are often exacerbated
Poisonous plants and the secondary compounds they pro-
during periods of below normal rainfall when the abun-
duce cause major economic losses to the livestock indus-
dance of grasses is reduced. Frequently, the animal’s diet
tries throughout the world. Based on 1989 data, it was
shifts during the season as grasses and palatable forbs
determined that poisonous plants cause losses of more than
mature and senesce; for example, the consumption of some
$340 million annually to the livestock industry in the 17
poisonous plants such as lupines, locoweeds, or larkspurs,
western states of the United States (Nielsen et al., 1988;
which stay green longer into the season, may increase as
Nielsen and James, 1992). This cost only considered death
the season progresses. In other instances, poisoning occurs
losses and specific reproductive losses in cattle and sheep,
early in the season before grasses begin to grow but poi-
and only the 17 western states were included. Less obvious
sonous plants have emerged and are usually very toxic.
costs such as lost grazing opportunities, additional feed
Poisoning by plants only occurs when animals eat too
costs, increased health care costs, management changes,
much too fast or graze it over a prolonged period of time.
increased culling costs, lost weight gains, delayed or failed
Therefore, management strategies to control these factors
reproduction, and the emotional stress accompanying many
can minimize losses from poisonous plants.
poisonous plant cases were not included in the Nielsen and
At the Poisonous Plant Research Laboratory in Logan,
James analysis. When one considers these other costs,
Utah, poisonous plant problems are dealt with using a mul-
inflation, and current animal values, and when all pastures
tidisciplinary approach. Veterinary medicine, chemistry,
and ranges in the United States are factored in, the eco-
toxicology, pathology, animal and plant physiology, and
nomic cost of poisonous plants to the livestock industry is
range management are all key in the approach to reduce
very high. In addition, an often ignored cost is the lost bio-
losses to the livestock industry. The plants discussed in this
diversity frequently resulting from invasive species, many
chapter are some of the most important poisonous plants in
of which are poisonous. These invasive and poisonous spe-
the United States, and considerable research has been con-
cies are often aggressive invaders and reduce optimum uti-
ducted to reduce their incidence of poisoning.
lization of private, federal, and state managed forest, range,
This chapter is not intended to be all-inclusive but
and pasture lands. This aspect alone has far-reaching impli-
focuses on some of the most economically important and
cations, not only for livestock producers but also for many
geographically widespread poisonous plants to livestock
other segments of society.
producers in the United States. There are excellent compre-
A frequently asked question is why do animals con-
hensive texts available with a more general and broad cov-
sume plants that may harm them or their offspring? In
erage of specific poisonous plants (Burrows and Tyrl,
some cases, it is a matter of survival. For example, in the
2001; Knight and Walter, 2001; Keeler et al., 1978
arid livestock-producing regions of the world, such as the
(ISOPP1); Seawright et al., 1985 (ISOPP2); James et al.,
western United States, regions of South Africa, Australia,
1992 (ISOPP3); Colegate and Dorling, 1994 (ISOPP4);
China, and others, browsing or grazing animals may have
Garland and Barr, 1998 (ISOPP5); Acamovic et al., 2004
limited access to high-quality forage at certain times of the
(ISOPP6); Panter et al., 2007 (ISOPP7); Riet-Correa et al.,
year and are forced to survive by grazing some poisonous
2011 (ISOPP8)). The ISOPP series, 1 8, 1978 2011
species. In other instances, hay or forages harvested in
(Proceedings of the International Symposium on Poisonous
areas where poisonous plants are abundant may be contam-
Plants), provides a worldwide view of poisonous plant
inated with a high percentage of poisonous plants, and
research. In 2013, the ninth international symposium
Veterinary Toxicology. DOI: http://dx.doi.org/10.1016/B978-0-12-811410-0.00061-1
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