One of the greatest risks to farmers is the loss of livestock as a result of plant poisoning. So it’s important to know what promotes their growth and how to avoid them.

Hundreds of indigenous poisonous plant species are found in East Africa, and different parts of these plants – the leaves, pods or seeds – may be toxic. Losses due to plant poisoning can be direct, causing instant death, for example, or indirect, leading to loss of condition, poor production, such as loss of milk yield, or reproductive failure, such as abortions, birth defects or failure to become pregnant.

Except in the case of individual, newly introduced animals, isolated cases of plant poisoning are rare. Plant poisoning usually occurs as an outbreak and as a result when it does occur, losses may be heavy.
Further economic losses include the cost of control and treatment measures, such as fencing, strategic grazing practices, supplementary feeding, veterinary expenses, or diminished land value. Eating meat from animals that have died from plant poisoning can also lead to severe sickness or even prove fatal. Animals usually know to avoid poisonous plants. But if there’s a shortage of food – due to drought, veld fires or overstocking – starving livestock will have no choice but to eat what’s available.

Factors contributing to the likelihood of plant poisoning include:

  • After the dry season or a veld fire, poisonous plants are usually among the first green plants to appear. A number are also at their most toxic in the young stage when they’re most attractive to stock.
  • Some poisonous plants are highly resistant to drought and may be the only green plants available for animals to eat.
  • Poisonous plants are often found as weeds in harvested lands and along roads – areas used for grazing in times of scarcity.
  • Wind or hail can knock acorns or pods from poisonous plants to the ground, making them available to animals.
  • Fertilisers may increase the toxicity of some plants.
  • Animals are sometimes poisoned when feeding on fodder such as hay, silage, stover or concentrates containing poisonous plants, fungi or chemicals.
  • Young and older animals are more susceptible. Their livers do not have the capacity to eliminate the toxins.
  • Hungry animals graze more greedily and are less selective and therefore more likely to be poisoned. As noted, this can occur in conditions of drought, veld fires or overgrazing. Pregnant animals also tend to be less selective and have a higher intake than normal and may therefore be poisoned.
  • Thirsty animals look for plants with a high moisture content which they would normally avoid. Some of these plants may be poisonous.

Symptoms

The various poisonous plants contain many types of toxins that affect the body in different ways. For example, some might affect organs such as the heart, while others might affect the liver. In some cases, a single toxin will target more than one organ. Some signs of poisoning are listed in the table below . Unfortunately, many of these resemble those of other diseases, so it’s a good idea to know which poisonous plants are found in your area.

Signs of poisoning

URINARY SIGNS: Little or no urine production, swelling of the belly, change in colour of the urine, which may also contain crystals (small stones), a great thirst. In dead animals: crystals in the kidney, swollen, wet kidneys filled with fluid. DIGESTIVE SIGNS: Animal stops eating, salivation, dehydration, fluid from the mouth and nose, vomiting, constipation, diarrhoea, swollen belly. In dead animals: large quantities of fluid may be seen in the gut, as well as changes in colour and smell of the gut contents.
NERVOUS SIGNS: Restlessness, sensitivity to sounds and touch, high-stepping, difficulty in walking, muscle tremors, aimless wandering, staggering, blindness, convulsions, paralysis. REPRODUCTIVE SIGNS: Difficulty giving birth, poorly developed udder, enlarged belly, enlarged vulva, suppressed milk production, abortions, deformed young, males not interested in mating.
HEART SIGNS: When the heart is affected, an animal may drop dead suddenly when it is being chased, for example. Also, the animal tends to stand with its head low 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. BLOOD/BLOOD-COMPONENT SIGNS: Pale, yellow, bluish or brownish membranes, green-tinged faeces, listlessness, animal stops eating, will bleed easily, red-wine to coffee-coloured urine. In dead animals: ulcers in the stomach, bleeding, and a pale yellow, blue or brown colouring of the carcass.
RESPIRATORY SIGNS: Increased breathing rate, animal grunts when breathing, frothing at the mouth. In dead animals: fluid and gas in the lungs, signs of infection in the lungs (pneumonia), froth in the windpipe. SKIN SIGNS: Itchiness and reddening of skin, scale or crust formation, rough coat, thick fluid on the skin, hair or wool loss, animals seek shade, feet are warm and painful to the touch, difficulty in walking.
SIGNS OF BONES & TEETH: Uneven, mottled or black teeth, animal shifts weight from one leg to the other, stiffness, bones fracture easily. LIVER SIGNS: Vomiting, yellow discoloration of membranes, swelling of the belly and face. In dead animals: fluid in the chest and abdomen.

If an animal gets sick or dies, inform your animal health technician or local vet. They will examine dead animals and send samples to a laboratory for testing, as well as searching for poisonous plants where the animal grazed. Once you know what type of poisoning has occurred, you can decide on the best treatment and prevention. In many cases, there is no treatment.

But if you know which type of plant is involved, you will know whether treatment, such as feeding the animal activated charcoal to ‘soak up’ the poison, will help. Although many animals recover with or without treatment, a number of plant toxins affect them for the rest of their lives, reducing growth and productivity of stock as well as their resistance to other diseases.

Prevention

  • Know which poisonous plants occur in your area, and keep your livestock away from them.
  • Keep animals in good condition with supplementary food and licks during the dry season – and always make sure they have enough water.
  • Take care when introducing animals from other areas (especially exotic breeds); they may be unaccustomed to the plants on your land.
  • It may be necessary to eradicate some of the poisonous plants.
  • Don’t feed your animals mouldy hay or hay cut from areas where poisonous plants occur.
  • Avoid pastures that have just been fertilised with nitrogen in any form or sprayed with herbicides or pesticides
  • Do not let animals graze near rubbish where people have thrown things that may be poisonous like old paint.

Treatment

in many cases, in the absence of a specific diagnosis, treatment has to be symptomatic, but if poisoning is suspected any of the following can be tried.

  • Giving a purgative, such as Epsom’s salts, may help to remove the toxin from the gut. Give 100g Epsom salt in half litre of water to small animals and up to 500 g Epsom salt in 1 litre of water for large animals given by mouth. Only use about 50 g Epsom salt for horses. Epsom salt (magnesium sulphate) is useful for treating poisoning. It makes more water go into the intestines from the body and gives the animal diarrhea so most of the poison in the intestines mixes with water and comes out as diarrhea.
  • Mix kaolin (fine white clay powder) in water until it is a milky liquid. Give by mouth. For a large animal use about 200g Kaolin for a small animal about 10 g. Give every day for a few days if needed.
  • Mixing a handful of charcoal powder in a bottle of clean water and give the solution by mouth may help in some cases. Charcoal can inactivate poisons in the stomach.
  • Give milk or coconut milk by mouth
  • Mix ground cereals or rice with water and give by mouth
  • Mix 6 eggs and half kilo of sugar with about 1 litre of water and give by mouth.
  • Animals which are depressed may benefit from the administration of stimulants.
  • Animals which are excited may benefit from sedatives.
  • In some cases, eg Prussic Acid Poisoning, or Nitrate/Nitrite Poisoning, there is a specific antidote, but in the majority of plant poisoning there is not and so one has to treat the symptoms as they appear.

 

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