MMM 373 August 7, 1998

Common Poisoning Problems Under Drought Conditions
B. W. Pinkerton, Agronomy
H.D. Hupp, Animal and Veterinary Sciences
P.J. Rathwell, Extension Ag. Economist

During a drought, preferred forage becomes limited in pastures and hay fields. Animals become hungry and start to eat those plants, which are available. Not all of these plants are good and nutritious. Some plants are toxic and, if eaten, can cause death.

Minimize Risk

Crops grown and harvested under drought conditions can cause problems. But, using good judgement should keep these problems to a minimum. Introduce suspect forage and feeds gradually over several weeks. Animals can then adapt to higher levels. Do not feed suspect materials to hungry animals. TEST, WHEN IN DOUBT, FOR NITRATE AND MYCOTOXINS. Severely restrict or stop intake of suspect materials if problems are encountered.

Poisoning by Weeds

In dry years, most poisoning most often occurs in overgrazed pastures. Check your pastures for toxic plants. Pastures are subject to many potentially harmful toxic plants. Exposure can come through weedy pastures, hay, along ditches, in wooded areas, in corrals and holding lots. Signs of poisoning may include chronic wasting disease, abortions, congenital defects, and death.

Ferns, night shade, crotalaria, oleander, sicklepod, horsenettle and many other plants, which stay green in a drought have toxic components. The following is a listing by class of poisoning.

Cyanide Potential:

Black Cherry

Johnson grass

Cherry Laurel

Sorghum

Chokecherry

Sudan grass

Nitrate Potential:

Amaranthus

Oats / Wheat

Sorghum

Grasses

Ryegrass

Sudan grass

Millet

Turnips

Others

Toxic Ornamentals:

Azaleas

Lantana

Oleander

Castorbean

Japanese Yew

Rhododendrons

Cherry Laurel

Ligustrum

Mountain Laurel

Vegetable crops:

Tomato

Onion

Mustard

Potato

Sweet Potato

Eggplant

Turnips

Toxins in Hay:

Nitrate-Nitrites

Hemp Dogbane

Mold Toxins

Ergot

Milkweed

Horsenettle

Nightshade

Bermuda grass Tremors

Other weeds


Fungi known as ergot are common in the seed heads of warm season grasses such as Dallisgrass and Bahia grass. Prevention of poisonings requires you to know that you have a problem, and to move cattle away from the hazard when grass is short. Supplementing cattle with feed and hay may suffice without having to move them. But watch the grazing patterns of the cattle for signs of substantial amounts of toxic plant material consumption. For more information, consult "Poisonous Plants," Section 6009 of the Southern Region Beef Management Handbook.

Nitrate Poisoning

The recent droughts, their damage to corn and grain sorghum crops and the use of these crops for livestock feed have brought up many questions concerning nitrate poisoning. There is a web site dealing with nitrate poisoning:

http://virtual.clemson.edu/groups/psapublishing/DISASTER/drought/Drout12.htm.

Here are some major considerations: Don't feed drought-stricken forages for one to two weeks after a recovery rain. Don't cut drought-stricken forages with known high levels of nitrates for hay, since nitrate levels do not leach out of the forage when cut for hay. The best method is to harvest forage as wet silage and let it go through a 21-day heat and fermentation process before feeding. As much as 50-60% reduction of nitrates is reduced by this process. TEST ALL SUSPECT SILAGE AND HAY FOR NITRATES PRIOR TO FEEDING. Dilute suspected high level nitrate feeds with known low nitrate level feeds. Don't allow hungry animals free access to suspect forages. When cutting suspect forages, mow at a higher level than normal to avoid the higher nitrate-containing portions in the lower stalk. The following is a recommended feeding rate for known problem forages. Remember to convert the analysis to nitrate-nitrogen on a dry matter basis because not all analyses report nitrate-nitrogen.

Recommendations of Nitrate-Nitrogen on a dry matter basis
up to 1000 ppm Safe to feed under all conditions
1000 to 1500 ppm Safe for non pregnant cows. Only 50% of feed for pregnant cows
1500 to 2000 ppm Limit to 50% of ration on total dry matter
2000 to 3500 ppm Limit to 30-40% of ration on total dry matter - NOT for pregnant cows
3500 to 4000 ppm Limit to 25% of ration on total dry matter - NOT for pregnant cows

Mycotoxin or Mold Poisoning

Some feeds and forages may contain highly toxic substances produced by molds. Material with relatively small amounts of mold may contain these poisons. They are more likely to be present in corn and small grains than in forages, hay and silage. Mycotoxin can be produced on some feeds before they are harvested and others develop during storage. These molds can have a detrimental effect when fed to most livestock including swine, poultry and cattle. There are two web sites discussing Aflatoxin and mycotoxins:

http://www.ces.ncsu.edu/drought/dro-29.html and

http://virtual.clemson.edu/groups/psapublishing/DISASTER/drought/Drout13.htm


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