Caution, poisonous plants!

There are many poisonous plants that if ingested can cause toxic reactions. Our horses generally know to avoid most poisonous plants that turn up in their pastures. However, a shortage of feed can lead to these plants being consumed. Young, inexperienced horses also run the risk of not being able to discern poisonous plants from harmless ones, and eating them together.

The spread of the ragwort has increased in particular over the last two years.

Common ragwort (Senecio jacobaea)

Common ragwort, also known as St. James-wort, is found not only on moderately maintained grasslands, but also on fallow land, farmland, and along roads and railway embankments. Lack of maintenance to green spaces, under-use, over-use or a weakened turf encourages the spread of ragwort.

This poisonous plant belongs to the group of Asteraceae or composite family, with a racemose corymb consisting of 15-20 yellow flower heads. The stem has a reddish violet colour at the base, but the rest is green. Stem lengths are between 20 and 130 cm, depending on growth height. Ragwort blooms between June and October, with its peak season being around 25 July. The seeds spread mainly by wind and can remain viable in the soil for up to 25 years. There are other ragworts in addition to common ragwort, such as marsh ragwort, alpine ragwort and wood ragwort, all of which are poisonous.

They contain pyrrolizidine alkaloids (PA), which protect the plants from herbivores, and when ingested lead to acute or chronic signs of toxicity. Damage typically is to the liver. Chronic poisoning often involves loss of appetite, emaciation and fatigue. Because the absorbed PA accumulate in the liver, even repeated ingestion of smaller quantities can lead to fatal poisoning. Horses have especially sensitive reactions to the toxins in common ragwort. For a full-sized horse with a body weight of 500 kg, ingestion of 20-40 kg of fresh plants or 3.4 kg dried in hay can be fatal. PA can also be found in other plants, however, so a higher increased PA content does not necessarily mean there is common ragwort in the feed.

In the case of acute symptoms from PA poisoning, the prognosis is usually poor and treatment often ineffective. Depending on the extent of damage to the organs, symptomatic liver treatment and avoidance of further intake of common ragwort or other PA offer little chance of a cure for chronic poisoning. It is therefore highly recommended that preventive measures be taken to control the spread of this plant and keep it out of the feed. Pastures should be regularly and consistently maintained to promote a dense, healthy sward. Such preventive and mechanical measures include regular alternation between mown areas and pastures, regular mowing and clearing of green areas and early reseeding of bald patches with an appropriate seed (for example Pre Alpin® Saatgut, AGROBS Pferdeweide Sensitiv or AGROBS Kräutermix).

This consistent maintenance to pastures and meadows should be supplemented with planting of grassland and farmland, for instance with lucerne. Here, too, inadequate maintenance of the cultivated areas can lead to the spread of poisonous plants, particularly if these are cultivated on heavily used grasslands and not on arable land intended for this purpose, which is subject to consistent maintenance.

Increased PA levels are being found not just in animal feed but also in products such as herbal teas and honey.

AGROBS quality control for poisonous plants

The control of poisonous plants is a special and important issue for us with regard to the production of animal feed.

Our quality control is structured as follows for poisonous plants such as common ragwort:

1. Information  
a. For 10 years we have been providing our contracted farmers, agricultural workers, employees and all persons involved in the production process with training and informational materials with visual aids for the recognition and determination of poisonous plants (with a clear focus on common ragwort). 
b. Supply agreements with provisions for the reporting, containment of area and control of poisonous plants.

c. Information provided to riding stables and farmers on sighting poisonous plants. i. Also information to authorities and the media, e.g. Ministry of Agriculture, Farmers’ Association, the highway authority, the newspaper Münchner Merkur, road maintenance depots, municipalities, veterinary inspection office, local machine cooperatives, etc.

2. Inspection  
a. The fields we harvest are inspected several times each year by us or by our employees.       We take samples to determine the following:         
i. Plant stock         
ii. Soil properties         
iii. General field maintenance

3. Control  
a. When an occurrence is identified, we provide the farmer with information and advice on its optimal disposal and subsequent steps for the next several years.  

B. Information to non-supplying farmers and authorities who identify poisonous plants growing on their land.

As a roughage producer and agricultural business, we will continue to contribution as best we can to the production of healthy and high-quality roughage.

We hope, however, that the public will become fully aware of this information about common ragwort and its control, and that common ragwort will soon be subject to statutory declaration.

  • The Chamber of Agriculture of North Rhine-Westphalia: Jakobskreuzkraut (Senecio jacobaea) - Eine Giftpflanze auf dem Vormarsch. 4th Edition, Version from November 2012    
  • Gottschalk C., Ostertag J., Meyer K., Gareis M.: Pyrrolizidinalkaloide in Futtermitteln. Presentation given at the 16th   BfR Consumer Protection Forum 2015 Berlin
  • German Federal Institute for Risk Assessment: Pyrrolizidinalkaloide in Kräutertees und Tees. Opinion           018/2013 of the BfR from 05 July 2013    
  • Meyer H., Coenen M.: Pferdefütterung. Enke Verlag, Stuttgart 2014

Dr. med. vet. Katharina Boes
April 2016  ©AGROBS GmbH

(* The references refer to the technical content of the text and not to the product recommendations.)