Kochia weed, Mexican fire weed, summer cypress, morenita
It is a common weed of disturbed soils along roadsides, edges of cultivated fields and wastes areas.
A variety of toxicity problems in cattle, sheep, and horses have been associated with Kochia weed. Toxicity varies with the growing conditions of the plant, with more problems associated with the mature, droughted plant. Kochia weed has been associated with the following:
Photosensitization secondary to liver disease
Thiaminase activity leading to polioencephalomalacia (This is possibly a sulfate related toxicity)
Sulfate toxicity - Kochia weed may accumulate high levels of sulfate which can result in sulfide production in the rumen and subsequent blindness and death. This syndrome may be precipitated by hot weather that increases water consumption, especially if the water is high in sulfates.
Other potential toxins present in the plant include saponins, and alkaloids.
A rapidly growing, drought tolerant annual weed growing to a height of 6 feet under ideal growing conditions. It is a bushy plant with a many branched stem, and soft hairy lanceolate, alternate leaves. The inconspicuous flowers formed in the axils of the upper leaves, are green in color, sessile, and often in dense bracted spikes. Leaf veins and mature stems are often red in color. In the fall the stems turn bright red. Many wedge-shaped seeds are produced in late summer which are readily dispersed in the fall when the dried plant is blown about by the wind
If nitrate poisoning is suspected, methylene blue should be administered intravenously. The recommended dose range for methylene blue is from 4-15 mg/kg body weight administered as a 2-4% solution. A dose of 8 mg/kg body weight intravenously has been reported to be effective in cattle. The half-life of methylene blue is about 2 hours in sheep, indicating that small doses of the drug can be repeated as needed every few minutes to reduce methemaglobinemia to the point that the animal is not in severe respiratory distress. Excessive administration of methylene blue to animals other than ruminants will result in a hemolytic anemia due to Heinz body formation. Horses, and especially dogs and cats are particularly susceptable to methylene blue toxicity.
Sudden death may result if Kochia is high in nitrates(>1% nitrates is poisonous to ruminants). Brown colored mucous membranes and blood are typical of nitrate poisoning.
Severe difficulty in breathing due to nitrate poisoning inducing methemoglobinemia.
Severe depression, blindness, incoordination due to sulfate induced polioencephalomalacia.
Kidney failure due to high levels of soluble oxalates in the plant causing precipitation of calcium oxalate in the kidney tubules..
Photosensitization, especially of the white skinned areas is secondary to liver failure.
Blindness is due to polioencepalomalacia that is secondary to the high sulfate levels in some kochia weed.
Liver disease has been associated with Kochia weed that induces a secondary photosensitization.
Kochia weed containing in excess of 1% nitrate dry matter should be considered toxic. Water levels of 1,500 ppm or greater are potentially toxic especially if consumed with forages high in nitrate.
In some areas of the arid southwestern States Kochia weed is grown as a forage crop for cattle because it has a higher yield per acre than alfalfa and various grasses. The nutritive value of Kochia is also comparable to alfalfa although it may be less palatable and digestible. The toxicity of Kochia weed is poorly understood and appears to be influenced by the conditions in which it is grown.
MANAGING HIGH NITRATES IN FORAGES FOR CATTLE
Do not feed pregnant cattle forages containing nitrates. Levels of nitrate approaching 1% nitrate have the potential to cause abortions.
Ensure cattle receive adequate energy (grain)in their ration to ensure the conversion of nitrate to protein occurs rapidly, and thereby prevents the build up of toxic nitrite in the rumen. Feeding some grain concentrate enables rumen bacteria to effectively utilize nitrite and reduce the chance for toxicity.
Dilute nitrate rich hay with hay contain no nitrates, so that the total nitrate level is <1%.
Nitrate levels are often highest in the plants in the early morning or on cloudy, overcast days. Delay putting cattle on to forages high in nitrates until late in the day. Allow cattle time to adapt to nitrates in forages by introducing them to the forage a littel at a time over several days.
Drought conditions will increase nitrate levels in plants. Under such conditions, it is always wise to test forages for nitrate levels before feeding them to ruminants.
Green-chopped forages high in nitrate should not be allowed to sit over night as they may increase in toxicity. Cut only sufficient green-chop to feed immediately.
Suplementing high nitrate diets with chlorteracycline (30mg/kg of feed) helps reduce nitrate toxicity. Consideration must be given to the presence of antiobiotic levels in the meat of animals intended for human consumption
Boiling water does not remove nitrate from the water.