Page 909 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

864 SECTION | XIV Poisonous Plants

VetBooks.ir early spring. Abortions have been induced as early as 3 bed with accompanying necrosis and hemorrhage are the
Extensive vasoconstriction of the caruncular vascular
months of gestation and have been reported by ranchers
only reported pathological changes in maternal tissues.
to occur any time; however, the closer to the time of nor-
mal parturition that ingestion of pine needles occurs, the These findings are supported by Ford et al. (1992), who
higher the risk of abortion. Abortions may occur follow- reported that serum from pregnant cows fed pine needles
ing a single exposure to the needles, but results from con- showed vaso (vasoconstriction) activity in vitro.
trolled experiments indicate the highest incidence of
abortion is in cows eating the needles over a period Prevention and Treatment
of days. Abortions have been associated with grazing of
green needles from trees, slash from the lumber industry, The only recommendation to prevent pine needle abortion
and dead, dry needles from the ground. is to avoid grazing pregnant cows around pine trees, espe-
Abortions are generally characterized by weak uterine cially in the third trimester. There is no known treatment
contractions, uterine bleeding, incomplete cervical dila- for cattle once ingestion of pine needles has occurred.
tion, dystocia, birth of weak but viable calves, agalactia, Open cows, steers, or bulls are apparently unaffected by
and retained fetal membranes (Gardner et al., 1999). Two pine needles; likewise, sheep, goats (pregnant or not), and
syndromes seem to occur depending on the amount of horses can graze pine needles with impunity and experi-
pine needles eaten. In the first syndrome, abortion occurs ence no adverse effects. Supportive therapy (antibiotic
relatively quickly (3 6 days) with no signs of pending treatment or uterine infusion for retained fetal mem-
abortion, such as udder filling, vulvar swelling, or pelvic branes) is recommended for cows that have aborted, and
relaxation, but a small weak calf is quickly delivered. In intensive care of the calf may save its life. Grazing of
the second syndrome, abortion occurs after 6 14 days, pine needles intensifies during cold inclement weather
and all the previously mentioned signs occur before the and if other forage is in short supply. In spring, before
calf is born. Unless complications occur, most calves are green grass is available, cows will leave feeding grounds
born alive, and the closer to normal parturition, the higher in search of new green grass and frequently graze old, dry
the survival rate. Calves born Isocupressic acid after 255 needles from surrounding trees where the snow has
days of gestation will often survive with extra care but melted. These cows are at risk and should be kept away
need to be supplemented with colostrum and milk from from the pines. Research has also determined that low
other sources until the dam begins to lactate. Cows with body conditioned cows are more likely to eat pine needles
retained fetal membranes may need antibiotic therapy to than cattle in adequate body condition (Pfister et al.,
avoid uterine infections. 2008b). Consequently, it is recommended that pregnant
Pine needles will induce abortion in buffalo, but cattle grazing in ponderosa pine areas be maintained in
sheep, elk, and goats do not abort. Pine needles, pine good body condition (Pfister et al., 2008b). Anecdotal
bark, and new growth tips of branches are all abortifacient information suggests that pregnant llamas may be at risk
and new growth tips are also toxic (Panter et al., 1990b). from pine needles, but no experimental support has been
A separate toxic syndrome has been described in addi- presented (Panter, personal communications).
tion to abortion in which the abietane-type diterpene resin
acids cause depression, feed refusal, weakness, neurologi- BROOM SNAKEWEED (GUTIERREZIA SPP.)
cal problems, and, eventually, death. Specific compounds
include abietic acid, dehydroabietic acid, and other related Broom snakeweed causes significant loss to cattle, sheep,
compounds (Stegelmeier et al., 1996). At 15 30% of the and goat producers in Texas and New Mexico from abor-
diet, pine needles have been shown to alter rumen micro- tions and toxicoses. There are some similarities with pon-
flora and affect the rumen fermentation (Pfister et al., derosa pine needles, except pine needles apparently affect
1992). Rumen stasis is part of the toxic syndrome only cattle.
(Stegelmeier et al., 1996).
Pine needle-induced abortion appears to mimic normal Description and Distribution
parturition except it is premature. The mechanism of
action appears to be a reduction in blood flow to the car- There are two major species of broom snakeweed,
uncular vascular bed stimulating the fetal parturition Gutierrezia sarothrae (perennial snakeweed or turpentine
mechanism (Ford et al., 1992). ICA has not been found to weed) and G. microcephala (threadleaf broomweed).
be directly vasoactive, and it is unclear if ICA metabolites Snakeweeds are short-lived perennial half shrubs ranging
are vasoactive or if the vasoconstriction is a secondary from 15 to 60 cm tall (Ralphs and McDaniel, 2011).
response to ICA or ICA metabolites. Further research is Many unbranched erect stems originate from a woody
needed to determine the cellular or biochemical mecha- base and die back when the plant enters dormancy. They
nism and whether metabolic alteration of the ICA occurs. have a suffrutescent growth form, with new stems