Page 913 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

868 SECTION | XIV Poisonous Plants

VetBooks.ir providing dry bedding, good shelter, and fresh feed and Description and Ecology
Treatment is generally symptomatic and supportive,
Halogeton is an annual plant germinating from seed each
water. Activated charcoal and saline cathartic may be
beneficial. Treatment may include fluids, B vitamins, year. Its stems are branched from the base and tinged
with red and purple. Its leaves are fleshy and “hot dog”
ketosis therapy, and tube feeding. Hay and water should
shaped, with the distinguishing feature of a single spine
be placed within reach if the animal is recumbent. In lac-
on its tip. It can be distinguished from Russian thistle and
tating cows, frequent milking may facilitate a more rapid
pigweed (with which it grows) by the tubular, spine-
elimination of the toxins. In horses, monitoring of cardiac
tipped leaf. It does not have flowers but, rather, bracteoles
arrhythmias and electrocardiogram will provide informa-
formed in the axils of leaves from which seed clusters
tion concerning heart damage and associated circulatory
develop. These seed clusters occur throughout the length
dysfunction. Treatment is the same for rayless goldenrod
of its stems. A robust plant may have 1500 linear inches
and white snakeroot because the toxins are the same.
of stem, with 75 seeds/in., producing 200 400 lb seed/
acre. The seeds are winged and are spread by wind and
rodents.
HALOGETON (HALOĢETON Its seeds are dimorphic, which is key to its successful
¸ GLOMERATUS) survival strategy. The majority of its seeds are black and
readily germinate anytime when temperature and soil
Halogeton is an alien, invasive, noxious, and poisonous
moisture are favorable. However, the black seeds are via-
weed introduced from central Asia in the early 20th cen-
ble for less than 1 year. A small percentage of the seeds
tury. It was first collected along a railroad spur near
are hard and brown with low germination rates, but they
Wells, Nevada, in 1934 and rapidly invaded 11.2 million
survive for long periods in the soil and germinate when
acres of the cold deserts of the western United States
favorable conditions return. The dimorphic seed provided
(Young, 1999). There has been no appreciable spread
abundant seed for germination each year but also a reserve
since the 1980s because halogeton has filled all the
if drought killed its populations over successive years.
suitable niches within its tolerance limits. It currently
Although halogeton will germinate whenever condi-
infests disturbed areas within the salt-desert shrub and
tions are favorable, it remains as a seedling until May, at
sage-brush plant communities in the Great Basin,
which time lateral branches develop and ascend. It
Colorado Plateau, and Wyoming’s Red Desert physio-
reaches its reproductive stage by mid-summer, or when
graphic provinces, which have 3 15 in. of annual
soil moisture becomes limiting. When mature, the winged
precipitation.
fruits are blown by wind or carried and deposited by
Halogeton’s infamy began in the 1940s and 1950s by
rodents.
causing large, catastrophic sheep losses. There were many
Halogeton is not competitive with perennial shrubs
instances of large dramatic losses; sometimes entire bands
and grasses. It will not invade healthy desert plant com-
of sheep died overnight from halogeton poisoning. Life
munities. When a site is disturbed, halogeton will invade
magazine ran a cover story titled “Stock Killing Weed”
and establish, and its allelopathic properties provide an
that focused national attention on halogeton. Congress
added advantage to its invasive nature. It takes up sodium
passed the Halogeton Act in 1952 with the intent to
and potassium from saline soils, forming the respective
detect the presence of halogeton; oxalates. These oxalates provide an important metabolic
determine its effects on livestock; and function to maintain high cell sap osmotic potential to
control, suppress, and eradicate this stock-killing allow the plant to take up saline water. Oxalates accumu-
weed. late during the growing season, reaching peak concentra-
tion in the fall (20 36% of plant dry weight). Soluble
Federal research was reallocated from the Forest
oxalates leach out of the senescent foliage during the win-
Service Experiment Stations to the Bureau of Plant
ter and accumulate on the soil surface, increasing its
Industries, creating the Range Research unit devoted spe-
salinity. Thus, halogeton modifies its environment, mak-
cifically to “solving” the halogeton problem. It was real-
ing it more saline to meet its requirements, while exceed-
ized that halogeton was not the problem but a symptom
ing the tolerance limits of associated species.
of a larger problem that of degradation of desert range-
lands (Young, 1999). It invaded disturbed sites where
sheep congregated around railroad loading sites, trail Toxicology
heads, stock drive ways, and water holes. When hungry
sheep were turned loose to graze, halogeton was the only The toxins are sodium and potassium oxalates, and plants
feed available, and they consumed too much, too rapidly, are high in these oxalates in the fall and early winter
and were poisoned. when sheep enter the desert winter ranges. Poisoning