Everglades Station Mimeo Report EES65-20 March 1965
WHAT PLANTS POISON FARM ANIMALS?
R. W. Kidder
Cattle depend upon plants or vegetative products as a source of nourishment
and generally, any plant which an animal. consumes .can be digested by the animal
as feed. Some plants or some growth conditions in plants render them undesira.
ble as animal feed. These are referred to as "toxic plants".
I. Conditions IThich Promote Consumption of .Toxic Plants
Many plants in the toxic category normally are unpalatable and animals
usually refuse to consume such plants unless an abnormal situation exists.
Shortage of good feed is the most comion factor influencing an animal to eat
toxic plant growth. An animal may be forced to consume plants which are nor-
mally refused when starvation is produced by overgrazing, drouth, excess rain-
fall, or low temperature. Such conditions occur more frequently during the
winter and early spring than at other seasons.
II. Cold Resistant Plants
In south Florida, a group of plants which are cold resistant may become
fodder for animals following a period of cold weather. These plants contain
toxic chemical material, such as an alkaloid or a glucocide. The kind and a-
mount of toxic substance varies in different plants or parts of plants.' How
the.affected animal acts may indicate which plant has been consumed since these
toxic chemicals affect the .animals in various ways. Cold resistant toxic plants
include the .following:
1. Butterweed, Senecio
2. Graceful nightshade, Solanum
3. Horsenettle, Solanum
4. Elderberry, Sambucus
5. Castor Bean, Ricinus
6. pokeweed, Phytolacca
III. Cyanogenic Plants
A group of forages, under particular conditions of growth, may produce and
contain cyanide prussicc acid). These are members of the Sorghum family and
the group includes the following:
1. Sorgums, such as hegari
Cyanide is the highest in these plants when the seedlings are 4 to 8 inches
tall or when sucker or ratoon growth is near this length. A simple test for the
presence of cyanide in forage can be made with picric acid and chloroform.
IV. Plants with High Nitrates
Forage under specific conditions of growth may contain toxic levels of
nitrate nitrogen. Nitrogen is necessary for the formation of protein in the
plant but is taken up from the soil as a nitrate, in which condition it may
be toxic to animals. When plants contain 1.5 or more parts per million (ppm)
of nitrate nitrogen (NOg), cattle consuming them may develop methemoglobin in
their blood and unless treated, die from a shortage of oxygen in the blood.
Pregnant cows consuming forage containing as little as 0.5 ppm of NO3 may abort.
When diagnosed promptly, cattle suffering from nitrate toxicity can be cured
quickly with intravenous injections of methylene blue in dextrose. The feeding
of high energy feeds such as molasses may alleviate the toxicity from forage
containing 1/2 to 1 ppm of N03.
High nitrate nitrogen has produced toxicity from the following forages
which normally are excellent feeds.
1. Italian ryegrass
Simple tests for the presence of an excess of nitrates in forage can be
made by using special tablets available for that purpose.
V. Forage may Produce Bloat
Sometimes cattle suffer from bloat (abnormal gas formation in the rumen).
In most cases, bloat occurs in only one or a few individuals of a group of cat-
tle. Plant species or forage condition of growth may cause bloat. Three common
causes of bloat are:
1. An abrupt change of rations
2. Frozen forage--(change from green to dry forage)
3. Certain legumes
VI. Toxic Trees
At least two trees grow in the Everglades which are objectionable as pas-
ture shade because of their toxic properties. These are:
1. Tung Oil
2. China Berry
VII. Some Door-Yard Plants are Toxic
Many of the common shrubs and house plants, which grow well in south Florida,
are toxic if consumed by children or in sufficient quantities by farm animals or
pets such as horses and ponies. The following list is incomplete;
1. Lantana 5. Angel trumpet
2. Common Oleander white 6. Mountain laurel
or pink flowers 7. Hydrangea
3. Allamanda yellow flower 8. Diffenbachia
4. Poinsettia Christmas
VIII. Mineral Content of Plants May Make Them Toxic
Some plants become toxic from abnormal levels of mineral elements taken in-
to the plant from the soil. For example, in some rocky mountain areas the ele-
ment selenium is absorbed by plants in quantities which make them toxic to animals.
In some areas of south Florida, the element molybdenum is absorbed from the
soil in quantities which produce a type of toxicity. Copper has been demonstrated
as the corrective treatment or alleviator for this condition. Copper deficiency
and molybdenum toxicity have similar effects on cattle. In the absence of ade-
quate copper, a low level of molybdenum in forage will produce symptoms of copper
deficiency in the cattle. When copper levels in forage are high or normal, the
molybdenum content of forage has to be greater to affect the animal. Some plants,
such as ramie and pangolagrass, have greater power to concentrate molybdenum than
IX. Dead Moldy Grass May Be Toxic
Molds on dead grass either from freezing or mowing may have a toxic effect
on cattle consuming such forage. The problem of sunburn or photosensitization
is brought about by an abnormal sequence of assimilation in the animal triggered
or set off by mold on the dead grass. The forage usually is frozen Bermudagrass
and the mold is Fericonia minutissima. The material causing the sensitivity to
sunlight is phylloerythrin a by-product from the digestion of chlorophyll, the
green coloring matter in growing plants. Normally this phylloerythrin is ex-
creted through the bile and intestinal tract. The mold affects the liver in some
way to prevent normal excretion, and to make it accumulate in the blood. Then
the sunburn effect begins to appear on the animal.
Although some of the problems involving toxic weeds and forage in south
Florida are presented, this should not be considered a complete list of toxic
plants for south Florida.