Plants poisonous to livestock

Livestock managers should be aware of how poisonous plants can affect livestock. Following flood events, periods of high rainfall, and during drought, pastures grazed by cattle, sheep, goats, and horses are more likely to contain potentially toxic plants.

When grazed in small amounts, many of these potentially toxic plants may be tolerated well by livestock. However, under certain conditions, or if grazed to excess, poisonings can occur. Cattle, sheep, and horses are vulnerable to plant poisonings that can result in death or permanent damage to organs such as liver or kidneys.

Plants may be toxic in small amounts, or have a cumulative effect on animal health over time as plant toxins cause damage to internal organs.

Good farm management includes learning to recognise plants in your area that are toxic to livestock, as well as how to remove poisonous plants from pastures or control the conditions under which poisonings are more common.

Plants toxic to livestock

Examples of potentially toxic plants grazed by livestock in Australia include:

Pimelea
Flatweed
St John's Wort
Common heliotrope
Paterson's curse
Cathead
Panicum grasses
Green cestrum
Mother-of-millions
Hairy panic

Flatweed

Flatweed (Hypochaeris radicata) is also known as catsear and false dandelion. Flatweed is a perennial plant originally from Europe, and because it has yellow daisy-like flowers, it is often confused with Dandelion (Taraxacum officinale) and Hawkbit (Leontodon taraxacoides).

Flatweed is a problem in horse pastures because it can cause stringhalt when it is grazed by horses. Australian Stringhalt is a condition of horses resulting in the hindlegs jerking upwards as the horse walks, with the legs reaching up and sometimes making contact with the belly. The abnormal gait is a result of involuntary control of the hindlimbs, which is suspected to be caused from a neurotoxin that affects the long nerves in a horse’s body.

Veterinary attention should be sought if you suspect stringhalt in a horse.

On smaller areas, flatweed can be controlled by removing the entire plant and taproot, while in larger areas, a broadleaf weed herbicide maybe appropriate. Best practice should also include establishing a competitive pasture, so that pasture grasses and legumes can out compete the weeds.

Identification note: Flatweed, Dandelion and Hawkbit are very similar. The main distinguishing feature is to look at the plant stems and the cut the steam in half. Flatweed has a branched solid stem, dandelion has unbranched hollow stems and Hawkbit has unbranched solid stems.