Thursday, 26 May 2011

What utter tripe!

I picked this up from a posting on facebook page put out by a Cumbrian horse group. It is a prime example of how hysteria about ragwort spreads.
The site starts with:-

Ragwort poisoning is one of the most common causes of plant poisoning in equines.

Anyone who can use proper critical thinking skills should stop and ask a few questions at this point. The first is how common is poisoning in general in animals?
Well actually it is extremely difficult to know. The reason being is it is rare.

This is one of the things that started me looking at this in the first place all those years ago when told that lots of animals were dying I immediately thought of the science and immediately thought there is something wrong with that claim.

You see we have known for the last hundred and fifty odd years that animals that do silly things like eat poison do not have as many offspring as those that don't. Since offspring resemble their parents any animal will have been shaped by nature in such a way that it becomes part of their nature to avoid eating poison.

Even to us human animals ragwort tastes nasty. Our taste systems have developed in such away that we detect the poisons as nasty. This is hardly surprising since the poisons in ragwort actually present in 3% of all plants. You may well ask why we never hear about all the others?

It sounds a simple idea, but it is one of the fundamental principles of modern science. So much so that the man who came up with the idea is so idolised that if you are British you are probably carrying his picture in your wallet!
The idea was developed by Charles Darwin whose picture is on the Bank of England Ten Pound Note.

What we do know is that ragwort is only a problem in hay and that ragwort poisoning is rare. When you look at proper studies and not hysterical claims of thousands of deaths you see that this is true. As an example, ragwort hysteria spread to the Netherlands, there has been a survey running there that has not had one single confirmed case of ragwort poisoning in a horse since 2007. This is in agreement with what we might expect from other studies.

The real piece of hogwash on this website however, is this:-

A horse or pony can be poisoned by ragwort without even having any plants in their grazing area. Seeds from ragwort plants in neighbouring paddocks and fields can be blown across and contaminate an area apparently free from ragwort. A horse or pony can inhale or eat these seeds and become affected by cumulative poisoning.

I try to write this blog with a dispassionate style as reflects the proper nature of the science behind it, but on this occasion this piece of prose deserves to be described properly.


When you have been studying the subject for a long time these things become really obvious. The person writing this appears to have no understanding of the biochemistry involved at all.

Firstly, whilst it is true that ragwort poisoning can be cumulative. The lethal dose is so high that it is often measured in percentages of body weight. The dose is minuscule!

Secondly, if you look at the biochemistry you can see the impossibility of this kind of poisoning. The toxins in ragwort are not actually poisonous in themselves. They have to undergo a conversion process. Some are destroyed in the digestive process. Some will be excreted unchanged. If they get through this then, and only then, they are converted into the breakdown products are they toxic and then those breakdown products are so reactive that they will react with anything ion the cell. It is only those that reach the DNA in the cell nucleus that have a toxic effect and then if the damage is minor which it certainly would be, there are DNA repair mechanisms which would likely nullify any damage.

Oh and of course there is the third point, unlike the claim on the website that they are dispersed widely by the wind. Ragwort seeds don't blow very far. Most sit at the base of the plant and the rest are almost without exception deposited within a few yards.

There is then the obvious fourth point. Horses inhaling seeds? How often do you as a human animal inhale any old seed that is wafting around? Well If you did you would soon cough it up. This is just hysterical hyperbole.

Of course now it has been posted on this horsey facebook page more people will be frightened and more hysteria will be generated. To be fair this is rather a common claim on websites and it seems that critical thinking on this issue is very much in short supply.
Ragwort Hysteria latest entries


  1. ooh now that was a good one - snorting ragwort for a hit!!! Just keep the hayfield clear of the stuff.

  2. Excellent stuff, this blog. Thanks for comment on Martin's Moths and I've updated the post with a link to you
    Long live ragwort and the millions of Cinnabar moths it sustains!
    All v best M