Page 912 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Poisonous Plants of the United States Chapter | 61 867

VetBooks.ir grasses such as crested, pubescent, and bluebunch wheat- are numerous, small, and clustered at the top of the stem,
with 7 15 yellow flowers on each head.
grass will compete with snakeweed seedlings. Following
drought, wildfires, or herbicide control, it was recom-
mended that cool-season grasses should be seeded in an
attempt to establish a solid stand that will prevent snake- Distribution
weed establishment and subsequent domination in the
Rayless goldenrod grows in the desert rangelands of the
plant community. If this approach is not successful,
southwestern United States from southern Colorado into
downy brome will likely fill in, which will also often sup-
Texas, New Mexico, Arizona, and California into
press the establishment of broom snakeweed.
Mexico. The plant grows abundantly on alkaline and gyp-
Insects may play a role in snakeweed population die-
sic soils in western Texas and the Pecos River Valley.
off. Many insects are associated with snakeweed: defolia-
tors (leaf tyers, grasshoppers, and weevils), sap suckers
(scale insects and mealybugs), and root-boring weevils Toxicology
and gall formers. Individually and collectively, they con-
The toxic constituents of rayless goldenrod are similar to
tribute to the demise of mature snakeweed populations.
those found in white snakeroot, and the original term, tre-
However, it is unlikely that they will contribute to pre-
metol, is a mixture of ketones and alcohols. Tremetone
venting a population buildup because of the time lag of
(5-acetyl-2,3-dihydro-2-isopropenyl-benzofuran) was
their populations in relation to that of snakeweed.
thought to be the principle toxic factor; however, 11 dif-
Treatment of sick animals is only symptomatic, pro-
ferent compounds have now been isolated and identified
viding supplementation to weak calves and antibiotic ther-
(Lee et al., 2010). This elucidation of different chemo-
apy to cows with retained fetal membranes to avoid
types of white snakeroot partially explains the sporadic
infection.
and unpredictable toxicoses reported in livestock through-
out the midwestern United States.
RAYLESS GOLDENROD (HAPLOPAPPUS The toxicity of rayless goldenrod mimics that of white
HETEROPHYLLUS) snakeroot. Clinical signs of poisoning may occur after
ingestion of 1 15% BW during a 1- to 3-week period.
Rayless goldenrod (Haplopappus heterophyllus) is a toxic Signs begin with depression or inactivity, followed by
range plant of the southwestern United States. The disease noticeable trembling of the fine muscles of the nose and
associated with toxicity has been referred to as “alkali dis- legs. Most cases of poisoning reported constipation, nau-
ease” because originally it was associated with drinking sea, vomition, rapid labored respiration, progressive mus-
of alkali water. Currently, it is referred to as “milk sick- cular weakness, stiff gait, standing in a humped-up
ness” or “trembles” (the same as white snake-root in the position, dribbling urine, inability to stand, coma, and
Midwest) because the toxin tremetone (10) is excreted in death. Signs are similar in cattle, sheep, and goats. The
the milk and subsequently results in poisoning of humans disease is often more acute and severe in horses than in
and nursing offspring. Haplopappus acradenius was cattle, and horses may die of heart failure after subacute
implicated in poisoning in cattle in southern California ingestion of white snakeroot and presumably rayless gold-
(Galey et al., 1991). enrod. Cattle have also been poisoned on a related plant
(Haplopappus acradenius) in southern California (Galey
CH 3 et al., 1991). In this case, 21 of 60 cattle died and 15 of
60 were affected but recovered. Creatine phosphokinase
C CH 3 and ketones were elevated, and severe myonecrosis was
described in the dead animals.
O
C
Prevention and Treatment
CH 2
(10) Rayless goldenrod is not readily palatable, and toxicity
Tremetone
results from animals being forced to graze the plant due
to lack of good quality forage. Avoiding overgrazing will
usually minimize poisoning in livestock.
Description
Control of rayless goldenrod can be accomplished
Rayless goldenrod is an erect, bushy, unbranched with herbicide applications. Late summer and early fall
Peromial shrub that grows 0.5 1.5 m tall. The base is application of picloram or 2,4-D ester is successful in
woody, and leaves alternate linearly up the stem. Heads reducing plant populations.