Livestock keepers need to be able to identify poisonous plants for livestock. It is important to know what is dangerous for sheep, goats and cattle to eat.
Poisonous plants, both indigenous and alien, often do well in drought conditions or they might be the first to come up after fires and early in spring.
Animals usually avoid poisonous plants, but they might eat them when they first go into an area or when there is little else to eat. Animals that are moved from familiar areas to new pastures tend to graze less selectively and will get poisoned more easily.
A number of poisonous plants for livestock are also at their most poisonous in the young stage when they are most attractive to stock.
Drying some plants does not affect the toxicity (degree of poisonousness), so the animal might unwittingly eat it in hay and then suffer the same consequences as if it had been eaten in the field.
The different toxins affect different organs in the body.
If the nervous system is affected, symptoms include restlessness, sensitivity to sounds and touch, high-stepping, difficulty in walking, muscle tremors, aimless wandering, staggering, stumbling, pushing against objects, star-gazing, blindness, convulsions or paralysis. Cotyledon orbiculata can be the cause of this poisoning.
If there is damage to the digestive system, the animal stops eating, salivation, dehydration, fluid from the mouth and nose. There might be vomiting, stomach pains, stomach stops working, constipation, diarrhoea, swollen belly. In dead animals large quantities of fluid or gas in the gut may be visible. There may be changes in colour and smell of the gut contents, reddening of areas of the gut, bleeding.
Kidneys and Urinary Tract
When plants affect the urinary tract, the signs include little or no urine production or swelling of the belly with fluid. There is a change in colour of the urine and the urine may contain crystals (small stones) and the animal drinks a lot. In dead animals crystals in the kidney, swollen, wet kidneys filled with fluid. The kidneys may be large and pale, changed in shape and bleeding.
Plants that affect the functioning of the heart account for 33 % of all mortalities from plant poisonings of cattle and 10 % of those in small stock. (Prof C J Botha). When there is heart damage, an animal may drop dead suddenly, for example, when it runs or when drinking water.
The animal tends to stand with its head in a low position and the stomach tucked in. It sometimes grinds its teeth or groans, and the heart rate increases. Bloat, diarrhoea and weakness of the hind legs can also occur. In the dead animal you may notice pinpoint or larger areas of bleeding. The lungs are swollen with fluid, fluid in the chest cavity, around the stomach and in the sac around the heart. There might be froth in the windpipe and a heart that is enlarged, flabby or pale.
Other poisonous plants for livestock include Moraea pallida (yellow “tulp”, Drimia sanguinea (“Transvaal slangkop”), Nerium oleander (oleander/“selonsroos”) and Gomphocarpus fruticosus (milkweed/“melkbos”). These all contain cardiac glycoside.
Respiratory System and Liver
If the plant has affected the respiratory system signs include increased breathing rate, difficult breathing. The animal grunts when breathing, frothing at the mouth.
If the plant has affected the liver, there might be vomiting, weight loss, yellow discoloration of membranes. The belly could swell with fluid, sunburn, swelling of the face or sore feet.
In dead animals you may notice yellow colour of the carcass, bleeding in the body, fluid in the chest and abdomen. The liver is hard and small , intense reddening of the liver, soft and swollen liver, swollen gall bladder.
Lantana camara poisoning damages the livers of cattle.
Other plants that affect livestock include Fadogia homblei which causes gousiekte, Seneciosi spp and Dichapetalum cymosum (Gifblaar). Diplodiosis kills cattle. This is poisoning caused by a toxic fungus which grows on corn grain.
Tribulus terrestris (duwweltjie, devil’s thorn) poisons sheep and goats, causing “geeldikkop”.
Unfortunately, in many cases there is no treatment for plant poisoning. In specific cases there may be treatment available (such as activated charcoal), but you first need to know which type of poisoning has occurred.
Although many animals recover, a number of plant toxins affect the animals for the rest of their lives. The poison reduces growth and productivity, as well as their resistance to diseases. Poisoned animals have a better chance of surviving if they are not forced to walk long distances.
Prevention is therefore better than treatment. Try to keep your livestock away from the localities where the plants grow. Prevent overgrazing and veld fires.
Keep animals in good condition with supplementary food and licks during the dry season. Always provide water for livestock.
Take care when introducing animals from other areas (especially exotic breeds).
It may be necessary to eradicate some of the poisonous plants.
Do not feed mouldy hay or hay cut from areas with poisonous plants to your animals.
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