Farmers urged to familiarise themselves with poisonous plants

A significant number of livestock mortalities in many farming areas can be attributed to plant poisoning - especially during spring months, at the onset of rainfall activities or during periods of drought - and specifically in degraded rangelands.

Agribank’s technical advisor for livestock and rangeland management Erastus Ngaruka said many rangeland plant species contain chemicals that are poisonous to livestock when consumed. Generally, the level of toxicity can be classified into two: Plants that are extremely toxic and those with low toxicity levels, he said.

According to Ngaruka, the extremely toxic plants such as poison leaf only have to be ingested in small amounts to cause harm or to show signs of poisoning, and may result in sudden death.

Plants with lower toxicity such as vermeerbos show their effects after being consumed in larger amounts and over a longer period. Ngaruka noted that the toxicity of poisonous plants is influenced by several factors such as soil type, climatic factors, seasons, plant growth stage, the plant segment eaten and plant moisture content, among other things.

“Different poisonous plants cause varying effects and clinical signs in animals.” He said these can range from heart problems, nervousness, diarrhoea, liver damage, obstruction in the gut, skeletal and skin problems and reproduction problems, as well as a taint in meat and milk.

Furthermore, some valuable forage plants exhibit toxic effects when overconsumed, eaten at a certain growth stage, or when certain plant components such as flowers are eaten.

Even lucerne can be dangerous

Ngaruka said devil’s thorn is a common weed in many areas. While it is a valuable forage plant that is well-utilised when green, it becomes poisonous at the wilting stage. Others include quick grass and guinea grass, among others, he noted.

“Moreover, fodder plants such as lucerne, maize and others can also cause poisoning, for example when hay is spoiled and mouldy,” he said.

Ngaruka said in many rangelands, poisonous plants mostly emerge during the spring months from July to October and when pastures are in poor condition or overgrazed. In some rangelands, they form part of the plant composition throughout the year.

“Animals are vulnerable to poisonous plants due to a combination of factors.” According to him, one of the contributing factors is hunger, especially during periods of forage scarcity or drought when animals can be tempted to consume these plants as they could be the most available green forage.

The second factor is inexperienced animals such as the young or animals introduced in a new grazing area that are not familiar or cannot distinguish between the local valuable plants and potentially harmful plants.

He said a third factor is accidental poisoning, when these plants can grow in a mix and blend well with grazeable plants, resulting in animals consuming them all together.

Prevention and treatment

Ngaruka said that the basic means of preventing and treating plant poisoning are to avoid overgrazing and not allow animals to graze in areas where poisonous plants dominate.

Such areas can be camped-off and grazed only when the poisonous plants disappear, and valuable plants dominate especially during the rainy months.

In the event of suspected poisoning, the animal should not be allowed to drink water for at least two days, especially when poisoning is suspected to be from an extremely toxic plant. “Moreover, the animal should be handled with care and not stressed.”

Ngaruka said there are remedies used to neutralise the poison in the animal’s body. Some of them include Hypo, which resembles crystal-like content that should be mixed with water. It can be added to the water in the drinking trough and all animals can drink as they arrive from the veld.

Another remedy is charcoal. This can either be activated charcoal sold commercially or the normal charcoal from the fire. He noted that normal charcoal is the easiest home remedy to use.

“Make sure to finely grind it and mix it with water before giving it to the affected animal orally.” These remedies and others are readily available in agriculture shops and their use should be according to the instructions on the labels, Ngaruka added.

Meanwhile, farmers should familiarise themselves with their rangeland and develop an inventory of local valuable plants and poisonous plants, he urged.