The British Horse Society gets set to combat the spread of Ragwort
22/03/2006

The British Horse Society will provide leaflets and advice during its first Ragwort Awareness Week of 2006, from 3-7 April.

Ragwort is an injurious weed that causes liver failure and often death to animals that consume it. The BHS has campaigned for a number of years to raise awareness of this deadly weed, resulting in success in 2003 with the introduction of the Ragwort Act and in 2004 with the introduction of a ‘Code of Practice on how to control Ragwort’.

This year the Society is planning two Ragwort Awareness Weeks in April and September. The aim is to alert horse owners of the dangers, and to encourage them to remove the weed from their pastures before it gets the chance to spread. April and September are the common growth periods for immature plants.

Helen Owens, Senior Executive of the BHS Welfare Department, said: “Prevention through education symbolises the essence of BHS Welfare. We encourage horse owners to clear their paddocks of the small ‘rosette-stage’ ragwort growths instead of waiting until the weed is in its full yellow bloom”.

“This is the key to reducing the number of horse deaths from Ragwort poisoning, and reducing its spread across the countryside.”

If you are interested in finding out more about ragwort - from how to identify it to how best to clear it - you can find more information on the BHS website or you can contact the BHS Welfare Department on 01926 707807 or welfare@bhs.org.uk

Ragwort: The facts.

What is Ragwort?

Ragwort is a common weed that grows throughout the British Isles. It has always been a problem, however recently it has become apparent that ragwort may be getting out of control and potentially posing a threat to the horse population.

Ragwort contains the toxic compounds pyrrolizidine alkaloids. These principally damage the liver, resulting in severe disease and in many cases death.

The life of ragwort

Ragwort is normally biennial – taking two years to grow and flower. Seedlings have a spade shaped leaf that is notched at the top. In the first year of growth ragwort has a dense rosette of leaves low to the ground.

Plants in their second year grow to between 30 and 100cm high and have woody stems and dark green leaves with ragged irregular edges. They produce bright yellow densely packed flowers from May to October.

Ragwort can behave like a perennial (flowering every year) if the long stems are cut or mown. Each plant produces thousands of seeds that are dispersed widely by the wind resulting in rapid spread of the weed. Seeds are able to lie dormant for years before germinating.

Ragwort and horses

Ragwort thrives on wasteland, road verges and railway land. From these locations it can spread to pasture. Poor quality and poorly managed horse pastures are particularly susceptible to ragwort infestations. Closely growing grass sward prevents ragwort growth but when the grass becomes thinned out, due to poaching or over grazing, the seeds are able to germinate in the exposed soil.

Most animals will avoid eating ragwort as long as they have an alternative source of good food. Ragwort can therefore be a problem on sparse and over grazed pastures which ragwort can thrive on.

There are reports that some horses develop an acquired taste for the plant, especially if there is little else to eat.

When cut or wilted (during hay of haylage making) ragwort loses its bitter taste, becoming more palatable. However, drying does not destroy the toxins. Dried grass, hay and haylage are common sources of ragwort poisoning.

Liver damage by ragwort

The effect of ragwort toxins are cumulative, thus it is common for ragwort poisoning to occur following consumption of small quantities of the plant over a long period of time. Development of disease can be delayed from four weeks to six months after eating the weed. Different horses have different susceptibilities to the toxin.

When a horse eats ragwort, the pyrrolizidine alkaloids are absorbed into the body from the intestines. These then pass straight to the liver where they are further metabolised to produce toxic agents that damage liver cells. These damaged liver cells can no longer manufacture protein and can no longer manufacture protein and cannot multiply in order to replace themselves.

When these cells die, they are replaced by fibrous tissue. Slowly, as more and more cells are damaged, the liver shrinks and becomes more fibrous in structure. Eventually there are not enough functional liver cells left to conduct the essential functions of the liver and liver failure is inevitable.

Ragwort poisoning – clinical signs

The clinical signs tend only to become apparent when liver failure has occurred. There is often no warning of impending failure. The signs of liver failure are a direct reflection of the loss of liver function.

The principal sign is bizarre or depressed behaviour due to altered mental status. This is thought to occur because the liver is no longer able to remove chemicals or toxins from the blood that have harmful effects on the brain.

Another common clinical sign is inflammation of white, unpigmented areas of the skin when they have been exposed to sunlight. The degradation of grass in the intestines produces a photodynamic agent that reacts to sunlight. This agent is normally removed and eliminated by the liver.

Other signs may also occur, these include jaundice, weight loss and diarrhoea.

Diagnosis

Liver failure diagnosis can be aided by a laboratory analysis of blood samples that often show evidence of liver damage and reduced liver function. Performing a liver biopsy can make a definitive diagnosis but is potentially dangerous. It is hoped that a simple blood test will soon be available to detect early signs of ragwort poisoning before significant and untreatable damage is done to the liver.

Treatment

Once liver failure has occurred treatment is very difficult. It relies on supportive therapies in the hope that the liver can regenerate. Unfortunately in many cases the liver is too damaged, although some horses do survive.

Field companions

Attention should also be turned to companion horses that are showing no clinical signs of liver failure. It is essential that the possible source of ragwort is eliminated from their diet.

Prevention

Prevention of ragwort poisoning is the best and most effective option. Control methods for ragwort such as pulling, spraying and cutting should all be viewed as short-term methods. Maintaining or improving the quality of pasture should be the long-term priority to ensure the prevention of ragwort growth. If ragwort begins to grow in paddocks it must be removed immediately before it spreads new seeds.

Pulling ragwort plants up

This is the most basic control method and is particularly appropriate when the ragwort is not an extensive problem. Rubber gloves should be worn, as the plants are potentially harmful to people. Fragments of root will remain in the ground so new growth will have to be monitored and removed every year.

All pulled plant material should be removed and burnt to prevent animals all animals from eating it.

Moving / cutting

Cutting will not kill the ragwort and it may even encourage growth. However in an emergency situation mowing may prevent seed production.

Chemical spraying

This is effective against the less mature rosette form of ragwort, but older stemmed plants are more resistant. Spring is the ideal time for spraying grazing pasture, but is too late if hay production is intended. Spraying for hay production should be carried out the previous autumn.

All affected paddocks should be sprayed at the same time to avoid ragwort spreading to the bare areas left by dead weeds. As the ragwort dies it should be removed and burnt before pasture can be grazed.

Improving pasture quality

Ploughing is very effective at removing ragwort as long as it is ensured that the grass reseeding produces a healthy thick sward. Fertiliser encourages thick sward growth. Good grazing management is essential to prevent overstocking, overuse and poaching.

What to do if you are concerned about ragwort spreading to your land

The control of ragwort comes under two government acts: the Weeds act 1959 (for the whole of the UK) and the ragwort act 2003 (England and Wales only). Under these laws governmental authorities can serve clearance notices to prevent the weed from spreading. If appropriate, in the first instance, approach the owner/occupier of the land and request they take steps to clear the weed.

http://www.bhs.org.uk/

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