Many pastures grazed by cattle, sheep and goats contain potentially toxic plants. In small amounts, some of these plants are tolerated well by livestock. If grazed to excess or under particular conditions, poisonings can occur.
However, some plants are toxic even in small amounts. Other plant toxins can be cumulative, with damage to internal organs developing over time.
It is important that producers are able to recognise the plants in their area that are toxic to livestock.
Examples of potentially toxic plants grazed by livestock in Australia include:
Some poisonings by toxic plants have highly visible consequences, while others remain silent for weeks or months. Where, in the absence of a drought or seasonal feed shortage, there has been a dramatic change in the condition of animals, producers should suspect that disease, including poisoning by toxic plants, may be present. If this is the case a veterinary investigation should be carried out.
With all diseases, nutritional deficiencies and poisonings by toxic plants, assess the risk based on previous local district history.
Managing poisoning risk from toxic plants
- Toxic plants may include pastures species at certain growth stages, native species and garden plants.
- The relative toxicity of plants may vary according to season and the stage of plant growth:
- Wilting in dry conditions and rapid growth after rain can increase the toxicity of some plants.
- Applying fertiliser to promote lush growth may increase toxicity.
- Some plants may only be toxic when growing in particular soil types.
- Stressful growth conditions, such as drought or insect attack, may cause toxins to concentrate in a plant.
- Plant parts can vary in their relative toxicity.
- Herbicide treatments can increase the palatability of plants.
- When livestock are hungry they may gorge themselves on things that they would not normally eat. Do not introduce hungry livestock to areas when toxic plants are known to be growing.
- Livestock grazing in a particular area for extended periods may become accustomed to eating small amounts of toxic plant material. New mobs introduced to the same area will not have the same tolerance.