Page 905 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

860 SECTION | XIV Poisonous Plants

VetBooks.ir true, a recent case of poisoning and death in cattle near natural water sources. If few plants are present, hand
pulling may be accomplished using caution to discard
after ingesting flower and green seed heads implicates this
tubers away from possible exposure to animals or humans.
phenological stage as dangerous also (Panter et al., 2011).
Chemical comparison of green seed and tubers and mouse Successful treatment with barbiturates or perhaps tran-
bioassay studies showed that green seed was equally as quilizers prevents death and the lesions and serum chem-
toxic as tubers. Like tubers, the more mature vegetation, istry changes; however, treatment must be prompt (Panter
including leaves, flowers, and green seed heads, was very et al., 1996a). This treatment has been successful in
palatable. Free choice exposure of hamsters to the white humans, but in animals it has never been demonstrated in
parsnip-like roots suggests that they are quite palatable and the field and would require a veterinarian to be on sight
are less toxic than the tuber. Observations of cattle grazing soon after the ingestion of this plant.
early in spring suggest that the young shoots of water hem-
lock are very palatable because young plants growing in PONDEROSA PINE NEEDLES (PINUS SPP.)
streambeds were frequently and extensively grazed (Panter,
personal observation). The needles of ponderosa pine have been known for years
Clinical signs of poisoning appear within 10 15 min to induce abortion in pregnant cows when grazed, particu-
after ingestion and progress from nervousness, frothing, larly during the last trimester of pregnancy (Gardner
ataxia, dyspnea, muscular tremors, and weakness to invol- et al., 1999). Occasional toxicosis in pregnant cows
untary, spastic head and neck movements accompanied by occurs; however, cases of toxicosis in nonpregnant cows,
rapid eye blinking and partial occlusion of the eyes from steers, or bulls are not reported.
the nictitating membranes. This is quickly followed by col-
lapse and intermittent grand mal seizures lasting 1 or 2 min Description
each followed by relaxation periods of 8 10 min.
Depending on the dosage, recovery may occur or seizures Ponderosa pine (Pinus ponderosa) is one of the most
continue until death from exhaustion or respiratory failure. prevalent species of Pinus in the western United States.
There appears to be a threshold response in which very Under ideal conditions, it grows to heights of more than
small increases in dosage will induce an apparently normal 60 m and 1.5 2.5 m in diameter. It is extensively har-
animal into grand mal seizures (Panter et al., 1996a). vested for lumber. During early growth, the bark is dark
Upon necropsy, gross lesions are confined to pale areas in brown to black, hence the name “black jack” pine. Older
heart muscle and skeletal muscles, particularly the long digi- trees have a bark of cinnamon brown to yellow, hence the
tal extensor muscle groups (Panter et al., 1996a). Microscopic name “yellow” pine. Ponderosa pine is a three-needled
lesions include multifocal, sub-acute to chronic myocardial pine, although groups of two and three can be found on
degeneration characterized by granular degeneration of myo- the same tree. The needles are approximately 8 20 cm
fiber cytoplasm necrosis and replacement fibrosis in the heart. long growing in clusters. They are soft and quite palat-
These areas correspond to the pale areas observed grossly. able, especially in the winter, when green feed is limited.
There is bilateral symmetrical, subacute to chronic myofiber The cones are brown, 7 15 cm long, and frequently grow
degeneration and necrosis of the long digital extensor muscle in clusters. Two varieties of ponderosa pine have been
groups. Clinical serum chemistry changes of elevated lactic identified, var. ponderosa and var. scopulorum, along
dehydrogenase, aspartate aminotransferase, and creatine with a separate five-needled species Pinus arizonica.
kinase occur in relation to severity of seizures. The extent of
gross and microscopic lesions and clinical chemistries are a Distribution
result of the severity of the seizures. Experimentally, barbitu-
rates prevented seizures, death, and lesions in sheep, and a Ponderosa pine grows in every state west of the Great
33 lethal dose of water hemlock could be reversed with Plains and in western Canada. It has a total stand greater
pentobarbital and no death occurred (Panter et al., 1996a). In than any native tree in the western United States except
animals in which seizures were prevented by barbiturates, Douglas fir. It grows at elevations between 1500 and
there were no lesions observed even though doses of two and 2500 m, although populations in California do extend
threetimesthelethaldosewereadministered. almost to sea level. Ponderosa pine is drought resistant
and is extensively harvested for lumber. Gardner and
James (1999) surveyed numerous other Pinus, Juniperus,
Prevention and Treatment
Abies species, etc. for isocupressic acid content, and
Prevention of poisoning is accomplished by recognizing Table 61.6 lists common name, location, and isocupressic
the plant and avoiding exposing animals to it early in the acid concentration of many species of trees or shrubs. The
spring or when in flower/seed stage. Water hemlock is eas- bark from both Utah juniper and western juniper trees has
ily controlled with herbicides (2,4-D per manufacturer’s also been found to be abortifacient to cattle (Gardner
specification); however, herbicide use is often restricted et al., 2010; Welch et al., 2011a).