With the evolution of life on earth millions of years ago, certain plants began to develop toxic or repugnant substances that protected them and made them distasteful to many mammals including man. As a result of this evolutionary process, poisonous plants were able to survive because they induced discomfort to anyone that disturbed them. About 18-20 thousand flowering plants present in our country, many plant species are utilized as food, fodder, medicine and fibre. Quite a few flowering plant species are poisonous. Knowledge on poisonous plants is important as some of them are used in medicine. The poisonous properties are due to toxic substances such as alkaloids, glucosides, saponins, amines, tannins, resins, etc. Poisonous plants are plants that produce toxins that deter herbivores from consuming them. Plants cannot move to escape their predators, so they must have other means of protecting themselves from herbivorous animals. Some plants have physical defenses such as thorns, spines and prickles, but by far the most common type of protection is chemical.
Many plants commonly used as food possess toxic parts, are toxic unless processed, or are toxic at certain stages of their lives. Some only pose a serious threat to livestock. Most of these food plants are safe for the average adult to eat in modest quantities. Poisonous plants are plants that contain harmful toxins in high enough concentration that can cause serious injuries if they are ingested or touched. They can be found everywhere from flower and vegetable gardens, in crop fields, in areas where there are ornamental trees, in homes where there are household plants and in pastures where animals graze. The severity of the poisoning depends on the quantity of the plant eaten, the part of the plant eaten, the season in which the plant eaten, the age of the plant, the ground moisture, the health of the animal prior to consuming the plant and the size and age of the animal. Young animals are generally more susceptible to plant poisoning than older animals. Older animals, can consume enough poisonous plants to build-up resistance to these toxins after being exposed to small quantities overtime.
Why Do Animals Consume Toxic Plant Materials?
In most instances, ruminants will resort to eating toxic vegetation and chemicals when there is a shortage of food and if their ration is unbalanced. Goats in this situation may crave for nutrients that they are missing. To compensate for these deficiencies, goats may consume vegetation and chemicals they would normally not eat. The stocking rate for pastures should be 7-10 goats/sheep per two acres for a year-round basis. The number of goats can be increased in these areas, but this will depend on the quantity and quality of the vegetation that is available. Also, provide supplements for the herd during the drought. This may include hay, feed or grain and make sure you have plenty of fresh water for the goat herd. Animals may also ingest chemicals and toxic plant materials out of curiosity or if they have access to yard wastage. Animals that are fed discarded plants or other toxic substance are at risk for poisoning. Therefore, it is best to keep the herd away from areas where there is yard waste to prevent accidental exposure to toxic roots, leaves or seedlings. Pastures that have been recently plowed must be checked for exposed poisonous roots which could make a good meal for the goat herd.
Symptoms of poisoning
Symptoms of poisoning may range from showing no signs of illness to showing symptoms of bloat (swollen abdomen), lameness, cries of pain, colic, frothing of the mouth, severed digestive disturbance, sunburn, listless, weight loss or death. Toxic plants and different chemicals can also cause irreparable damage to the liver and kidneys as well as lower the glucose level in the body, interfere with blood clotting, prevent cell division, affect the immune system or affect the skin and eyes of the animal if they come in contact to certain toxic plants. Therefore, early diagnosis can mean the differences between life or death.
|Common Name||Botanical Name||Toxic principle||Predominant Clinical Signs|
|Plants containing cyanogenic glycosides|
|Johnson grass Sudan grass||Sorghum spp.||HCN||Dyspnea, Sudden death|
|Arrow grass||Triglochin spp.|
|Choke cherry||Prunus spp.|
|Christmas berry||Heteromeles arbutifolia|
|Nitrate poisoning Plants|
|Annual weeds||Nitrate||Dyspnea, Sudden death|
|Avocado||Persea americana||Persin||Mastitis, cardiac failure|
|Oleander||Nerium oleander||Nerin||Cardiac arrhythmias, death|
|Milk weeds||Asclepias spp||Cardenolides||Arrhythmias, nervous signs, death|
|Yew||Taxus spp.||Taxine||Sudden death|
|Dogbane, Indian hemp||Apocynum spp.||Cymarin||Arrhythmias|
|Halogeton||Halogeton glomeratus||Oxalates||Renal failure|
|Oak||Quercus spp.||Gallotanins||Gastro enteritis, Renal failure|
|Greasewood||Sarcobatus vermiculatus||Oxalates||Renal failure|
|Lupine||Lupinus spp.||Anagyrine||Nervous signs, teratogenic|
|Locoweeds||Astragalus/Oxytropi s spp.||Swainsonine||Neurologic signs, congenital defects|
|Poison hemlock||Conium maculatum||Coniene||Death|
|Water hemlock||Cicuta spp.||Cicutoxin||Respiratory depression, death|
|Burrow weed||Isocoma spp.||Tremetol||Muscle tremors, weakness, death|
|Lupine||Lupinus spp.||Anagyrine||Congenital deformities|
|False hellebore||Veratrum spp.||Cyclopamine||Cyclopia, fetal tracheal agenisis|
|Tree tobacco||Nicotiana glauca||Anabasine||Cleft palate|
|Fiddleneck||Amsinckia spp.||Pyrrolizidine alkaloids Hypericin||Liver failure, photosensitization Photosensitization|
|Rattle pod||Crotolaria spp.|
|Hound’s Tongue||Cynoglossum officinale|
|St John’s wort||Hypericum perforatum|
|Spring parsley||Cymopterus watsonii||Furanocoumarins||Photosensitization Liver failure, death|
List of common poisonous plants and their potential toxic effects
|S. No.||Plant Name||Common name||Adverse effects|
|1||Abrus precatorius||Chirmi||Seed powder is given to cattle in case of constipation but if given in higher doses or seeds are consumed accidentally by cattle, it causes gastrointestinal irritation, nausea, vomiting, severe diarrhoea, weakness, trembling of legs|
|2||Argemone mexicana||Satyanashi||Seeds are emetic and narcotic; poisonous if taken in large quantities. The plant when eaten by animals causes diarrhoea and sleepiness|
|3||Datura metal Linn||Dhatura||Whole plant is toxic and narcotic; seeds are poisonous and used for committing crimes. Intake of the leaves, fruits and seeds causes fatal poisoning, dryness of throat, giddiness, hallucination and staggering; voice is unrecognizable and vision is affected and leads to coma|
|4||Agave spp||Century plant||The juice of several species causes acute contact dermatitis, with blistering lasting several weeks and recurring itching for several years thereafter|
|5||Euphorbia hirta||Dudhi||Plant extract has sedative effect on the mucous membrane of the respiratory and genitourinary tract. The latex is injurious to eyes|
|6||Areca catechu||Betel nut palm||The nut contains an alkaloid related to nicotine which is addictive. It produces a mild high, some stimulation, and much red saliva, which cannot be swallowed as it causes nausea. Withdrawal causes headache and sweats. Use is correlated with mouth cancer, and to a lesser extent asthma and heart disease|
|7||Melia azedarach||Bakain||Poisoning most often results from ingestion of toxic fruits containing uncharacterized resinous fraction. It causes severe irritation, nausea and degeneration of the liver and kidney|
|8||Moringa oleifera||Sainjna||Root bark extract causes severe skin inflammation and skin dermatitis. Root and stem bark are used as abortifacient|
|9||Nerium indicum||Lal kaner||Root is poisonous; used for criminal and suicidal purposes; seeds are used to poison and kill enemy’s livestock|
|10||Parthenium hysterophorus||Gajar ghas||Seeds and plants cause eczema and allergic dermatitis on contact. If consumed by livestock, causes severe diarrhoea followed by death with severe ulceration in the liver, gastrointestinal tracts and kidney. It poses danger to the livestock particularly in drought condition|
|11||Ricinus communis||Arandi||Intake of higher doses of seed oil is fatal with symptoms of vomiting, colic, gastroenteritis and circulatory collapse; in small quantity cure constipation|
|12||Cascabela thevetia||Yellow oleander||All parts of the plant are toxic to most vertebrates as they contain cardiac glycosides. Many cases of intentional and accidental poisoning of humans are known.|
|13||Digitalis purpurea||Foxglove||The leaves, seeds, and flowers are poisonous, containing cardiac or other steroid glycosides. These cause irregular heartbeat, general digestive upset, and confusion; can be fatal.|
Identification of some common poisonous plants
What We Can Do?
When you are placing the herd in a new grazing area, always check the pastures or woods for poisonous plants and backyard and industrial wastes. It is important to note that most woodland or swampy ground pastures contain poisonous plants that can be accidentally consumed by the animals. The toxins may be found in the seedlings, leaves, roots, young shoots fruit or the entire plant. In some cases, only certain parts of the plant may be toxic and the concentration of the toxins may vary from season to season and from year to year.
So, learn which plants are toxic on your farm and when they can become a threat to your livestock. Other ways the herd can be poisoned on the farm may include exposure to the following: (1.) creosote-treated wood, (2.) anti-freeze, (3.) rodent poisoning, (4.) herbicides, (5.) insecticides, (6.) lead paint, or from (7.) overdosing them with their medications, (8.) consuming excessive grain and (9.) nitrate poisoning from releasing the herd on freshly fertilized pastures.
Primary and effective management of an acutely poisoned animal
On arrival of a patient with poisoning, the initial priorities are the maintenance of airway, breathing and circulation. Keep all of the other potential poisonings out of the reach of all farm animals. If you suspect your animal has been poisoned do the following: (1.) Prevent further exposure to the poisoning, (2.) Isolate the animal and provide fresh water, (3.) Avoid stressing the animal, (4.) If possible, keep samples of the toxic substance for further diagnosis and (5.) call a veterinarian for immediate diagnosis and treatment.
Dr. Atul Prakash and Dr. Yashwant Singh*Associate Professor, Department of Veterinary Pharmacology and Toxicology
*Professor, Department of Livestock Farm Complex
College of Veterinary Science, Rampura Phul-151103 (GADVASU)