The truthful answer to this question is that nobody knows for certain how many horses die of ragwort poisoning. However there is sufficient research available to show that the figure is probably not very high. A significant quantity needs to be ingested by an animal before poisoning occurs. See Ragwort Toxicity
Ragwort poisoning does not have distinctive symptoms. Ragwort causes destruction of the liver and any other ailment which affects the liver in the same way will cause the same symptoms. This is further complicated by the fact that the the alkaloids that cause the problems are found in many other plants. In fact they occur in 3 percent of all flowering plants. (European Food Safety Authority. 2007) It is actually the breakdown products of these alkaloids produced in the liver that cause the problem and there are other sources of these too. The symptoms can only be confirmed by a post mortem and these are often not carried out.
The picture in the UK has been distorted by media publicity and the actions of prominent lobbyists. In particular there is a well publicised, but unreliable figure of 6,500 deaths that appears in many sources without its origins being examined.
This figure was widely publicised by the British Horse Society and led to action by the Advertising Standards Authority against people who were repeating it. See British Horse Society and Advertising Standards Authority
This figure resulted from a survey sent to all members of the British Equestrian Veterinary Association( Equiworld 2003)). Replies were received from only 4% . In addition the figures were calculated on only suspected cases. This yielded 283 reports of SUSPECTED poisoning. A serious statistical error was then committed by extrapolating the results to all members of the association. Whilst some may feel this is a valid conclusion, It is very bad science as it is very dangerous to extrapolate from such a small sample. This is especially the case as a vet is more likely to respond to a survey if they treated cases of Ragwort poisoning themselves . This is corroborated by the fact of the high percentage of vets (89%) that said that they had treated suspected cases. There was a further flaw in that the possibility cannot be excluded that several vets reported the same cases, and that therefore cases would have been included more than once. This survey is therefore useless in determining the truth. Indeed the design and the statistical treatment seems to indicate that it was actually deliberately designed to give a false high figure.
Properly derived statistics show a much lower figure. UK government figures for 2005 show a total number of 13 deaths and further figures from the same laboratories in the same source list only 10 deaths between 2005 and 2010 (EFRA/AHT/BEVA Equine Quarterly Disease Surveillance Reports). A survey well-publicised survey in the Netherlands, where the panic had spread from the UK, and where Post Mortem examinations are performed for certainty, has had no cases at all since 2007. Similarly an animal hospital which is well known for publicising ragwort cases, reports in a Freedom of Information request that they recorded no cases at all of ragwort poisoning over a 5 year period 2006-2010. ( Freedom of Information Request University of Liverpool.) One set of figures from a UK Government study for a period in the 1980s and 1990s in cattle shows figures in the 10-20 or to deaths a year range. See Ragwort Reference 5 A French study shows 18 suspected cases in cattle over the period of a decade of which only 6 were actually confirmed to be ragwort (4).
Certainly if it were the case that thousands of horses were dying annually there would have to be an epidemic of bad horse care. Horses generally avoid the weed except where it is dried in hay.
An interesting letter was published in the Sunday Telegraph on 3rd August 2003 It was written by Frances Wolferstan BA, Vet MB, MRCVS. It heavily criticised the claims of 6,500 deaths of horses.
The following are some quotes.
"In the agricultural depression of the 1930s and during the Second World War, there was far more ragwort around than there is today. .... There were also many more horses in the country, working on farms or pulling delivery vans. Ragwort poisoning was a recognised disease, but not a major problem."
"I find it hard to believe that so many of today's horsemen and women leave their horses on bare ragwort-infested pasture that 6,500 of animals succumb to ragwort poisoning annually."
I suggest that if 6,500 horses are dying of "ragwort-like" liver damage each year, it is time to look for other possible toxins. Pesticides added to grain to control weevils and mites are certainly one possibility."
The website of Buglife has An interesting page on ragwort which also covers this issue.
Another statement that supports the point that in the absence of publicity ragwort is not considered a serious problem, was made on June 5th 2005 by the Irish Minister for Agriculture and Food who stated that ," "There are no official figures available in Ireland for deaths of horses due to ragwort poisoning. Unofficial estimates indicate that the level is very low and does not warrant any special attention or investigation."
Return to Ragwort Facts index
(1) European Food Safety Authority. 2007. Opinion of the Scientific Panel on contaminants in the food chain on a request from the European Commission related to Pyrrolizidine alkaloids as undesirable substances in animal feed. The EFSA Journal 447: 1-51.
(2) Equiworld Horsemagazine British Horse Society Ragwort survey reveals disturbing new figures on horse fatalities. http://www.equiworld.net/uk/ezine/0803/bhs01.htm
(3) DEFRA/AHT/BEVA Equine Quarterly Disease Surveillance Reports. http://www.aht.org.uk/equine_disease.html
(4) Damien, Thomas ACHARD (2005) EXPLORATION DES AFFECTIONS HEPATIQUES CHEZ LA VACHE LAITIERE These pour le diplome d' Etat de DOCTEUR VETERINAIRE aculte de Medecine de Nantes
(5) Freedom of information Request University of Liverpool 2011.