Locoweed

Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some solid in amounts sufficient to produce serious effects on animals feeding on plants, such as locoweed, grown in such soils. Exposure to selenium compounds (as Se) in air should not exceed 0.2 mg/m3 (8-hour time-weighted average - 40-hour week). 

Figure 2.13 The indolizidine alkaloid toxin swainsonine (a potent inhibitor of a-mannosidase), responsible for locoweed toxicosis.

Like simple sugars, swainsonine is water-soluble and therefore distributed to many parts of the body. It is rapidly excreted, primarily in the urine, but in lactating animals a portion of it is transferred to the milk (James and Hartley, 1977). This fast excretion rate suggests that occasional consumption of locoweeds for short periods is unlikely to have serious effects, but continuous consumption, even at low levels, results in poisoning. Short intensive grazing episodes have been used as a management tool for grazing pastures heavily infested with locoweed (Ralphs et ah, 1984). 

Locoweed poisoning mimics exactly the genetic mannosidosis. Thus, the availability of specific inhibitors (plant toxins) of these enzymes provides a mechanism for induction of phenocopies of these genetic diseases in animal... 

Molyneux, R.J. and James, L.F. (1982). Loco Intoxication indolizidine alkaloids of spotted locoweed Astragalus lentiginosus), Science, 216, 190-191. 

Ralphs, M.H., James, L.F., Nielsen, D.B. and Banter, K.E. (1984). Management practices reduce cattle loss to locoweed on high mountain range. Rangelands, 6, 175-177. 

Aberrant behavior -very excitable, muscle weakness, death Locoweed -Australian and Western US plant Swainsonine toxin - liver enzyme inhibitor - well known to affect cattle... 

Molyneux, R. J. and James, L. F. 1982. Loco intoxification Indolizidine alkaloids of spotted locoweed (Astragalus lentiginous). Science, 216 190-191. 

Some plants classified as mineral accumulators become toxic because of the inorganic materials that they absorb from soil and water and retain in the plant biomass. An important example of such a plant is Astragalus, sometimes called locoweed. This plant causes serious problems in some western U.S. grazing areas because it accumulates selenium. Animals that eat too much of it get selenium poisoning, characterized by anemia and a condition known descriptively as blind staggers. ... 

Certain poisonous plants often cause serious livestock losses. The Australian legume, Swainsona, is known as poison peas, and sheep eating them develop a syndrome called pea struck [46,47]. Livestock is also poisoned by the closely related Astragalus and Oxytropis species, which are found throughout the world, and intoxication of livestock by some species known as locoweeds in the western... 

Ralphs, M.H., Creamer, R., Baucom, D., Gardner, D.R., Welsh, S.L., Graham, J.D., Hart, C., Cook, D. and Stegelmeier, B.L. (2008) Relationship between the endophyte Em-bellisia spp. and the toxic alkalod swainsonine in major locoweed species (Astragalus and Oxytropis). ]. Chem. EcoL, 34, 32-8. 

Polyhydroxyindolizidines are a class of alkaloids, occurring primarily in the family Leguminosae [86]. Within the group the most important members are swainsonine (1,7,8-trihydroxyindolizidine), the toxin of locoweeds Astragalus and Oxytropis species) of North America and the poison peas (Swainsona species) of Austraha, and castanospermine (1,6,7,8-tetrahydroxyindolizidine), the major alkaloid of the Moreton Bay chestnut or Black Bean Castanospermum australe). In contrast to the herbaceous locoweeds and poison peas, the latter is a large tree native of Northeastern Australia, which has been introduced as an ornamental in... 

Swainsonine is water soluble and is rapidly absorbed from the gastrointestinal (GI) tract. It circulates through the body system, and is excreted in the urine, milk and fece after 5-6 days pratically no toxin remains in the serxun. Swainsonine is eliminated partially in milk and it can be fed to nursing calves and lambs, developing lesion, such as cats that feed milk from cows that consumed locoweed. Reversal of the effects of intoxications are slower, thus week or months may be required for recovery of cell function. Some CNS neurons are lost and cannot replaced [158]. 

Locoweed is devasting to liverstok reproduction. Principal effects on the developing fetus include delayed placentation, decreased vascularization, fetal edema and hemorrhage then reduces fetal heart rate and causes cardiac irregularity, which may contribute to fluid accumulation in the placenta. These factors contribute to fetal death and trigger abortion [158]... 

No effective medical treatment is known for nitro, selenium or locoweed poisoning. 

What connection might there be between the name of the locoweed plant and the plant s effect on an animal s behavior ... 

Selenium Some people supplement their diet with tablets that contain essential vitamins and minerals. These supplements may include a small amount of sodium selenate. Selenium also can be found in such foods as fish, eggs, and grains. Selenium works with vitamin E to prevent cell damage. It may help to inhibit the growth of cancer cells. However, in the case of nutrients, more is not always better. The locoweed plant shown in Figure 7-18 provides an example of this principle related to selenium. When a locoweed plant absorbs selenium from the soil, the concentration of selenium increases to a toxic level. Grazing animals that feed on locoweed can become quite ill. 

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