| Posted: Sat Jan 15th, 2011 03:51 am||
|We have a 5yo connemara gelding, Lalla, who has become photosensitive 2 winters in a row, this continued on into the late summer last year, and is still occurring now in mid summer of this year. This happened in two different areas of the same property in south Canberra, Australia.
The first paddock was pasture improved and treated with minerals by the previous user, the current paddock is native pasture, not improved and not overgrazed.
This also happened to Lalla as a 2yo when he lived in northern victoria on totally different country with different weeds. It happened in the winter then too, when we had rain on severely drought affected land that did have lots of weeds. The vet at that time thought Lalla had been poisoned by a plant so we moved him properties and the problem went away.
I have read Dr Deb's comments, in another topic, about this being caused by plants and I'm sure this is the answer. I will order the poisonous plants book tonight but we have already discovered we have plenty of St John's Wort which is in the stage of the flowers dying off.
Will a blood test show up if Lalla has liver damage?
In which case I think we can rule out the St John's Wort?
How long after ingesting St Johns' Wort would it be before the effects wore off?
I imagine the length of time it took for the symptoms to disappear would vary from plant to plant?
Because we have a large paddock (approx 10 acres) I would like to try and nail down the cause so we can eliminate it quickly.
I am also concerned about Lalla's liver, now and in the future. If this keeps happening is he likely to sustain irrepairable damage?
Last summer we did lock him in a bare area for 3 weeks without any noticeable improvement.Having read some other posts here I think that was not long enough to see a result.
He was also treated extensively with herbal/homeopathic to no avail, I imagine because he was still ingesting the poison.
On an interesting note, the winter/spring/summer has been very wet and green around Canberra, the drought has broken in spectacular fashion. Everywhere you go people are talking about the same problem, they have a horse with mud fever or clover burn. Many are horses that have never had it before. So, despite there being lots of grass for them to eat for the first time, they are choosing to eat poisonous weeds!
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|| Posted: Sat Jan 15th, 2011 04:57 am||
|Robyn, no horse has any mechanism by which he can know that one weed or another is poisonous. The only thing the horse knows is whether the weed tastes bitter, salty, or sweet. If it's sweet, you may be guaranteed that he will eat it. You may conclude from this that poisonous plants are at their most dangerous when they are in a green and growing condition, when their sap is rising, which is one of the two times when they will have the highest chance of tasting sweet. The other time is in the several days after they have been sprayed with herbicide: in a last-ditch effort to survive, the plant will then also pump up its sap.
Your post is otherwise full of "apparently" good reasoning -- thoughts that just about anyone would have -- that don't, unfortunately, turn out to be true or safe. For example -- your horse is in as much danger, or almost as much, if he's on drought-stricken pasture as he would be on lush, wet pasture in a green and growing state. The problem that occurs on dry, droughty pasture is precisely that the horses will have "et" everything that's at all tasty, leaving some of the more bitter weeds that contain oxalates -- stuff like dock. Then, with the bad owner who does not give them enough hay, they will eat the dock because they must have something in their gut at all times. With the good owner who puts out plenty of hay -- but who is not playing with their horse 10 hours a day (and who does?), the horse may eat the dock just because he's bored. You may conclude from this that if you are going to dry-lot your horse, then there must be absolutely nothing in the enclosure whatsoever other than the feedstuffs that you provide him with.
As to St. John's wort -- even if blood tests indicate no liver damage, you will still need to get rid of the stuff. The logic works this way: if you have no liver damage, but you know (as you do) that you have abundant St. John's wort -- and your horse has mud fever -- then the only reasonable conclusion is that it is the St. John's wort that is causing it.
So long as the animal eats ANY St. John's wort, he will be symptomatic. Ingestion of St. John's wort from one year to the next has a tendency to sensitize the horse, so that smaller and smaller amounts of it are sufficient to cause symptoms. St. John's wort does not damage the liver but it is very dangerous nonetheless.
If blood tests do show abnormal liver function, you will then have to go looking for some plant that is not a primary photosensitizer like St. John's wort, but instead one (like Paterson's Curse) that is a plant that contains pyrrolizidine alkaloids (PA's). PA plants damage the liver. And yes, like the alcoholic who has cirrhosis, the damage that PA does to the liver is similar to cirrhosis. It is "cumulative" in the sense that PA is difficult for the liver to break down and thus difficult to excrete from the body. However, if the horse totally stops eating the plant, the liver will probably largely be able to regenerate itself. If a horse has more than 50% of its liver still functional, it will not be symptomatic.
You will of course need to consult with your veterinarian concerning the specific results of any blood work that you do. Your vet will be able to interpret those for you and will be able to tell you whether your horse has sustained damage to his liver.
So long as the animal is symptomatic, i.e. has mud fever lesions, then he needs to be in a drylot and only get carefully-inspected feed -- inspected so that you know whatever hay he gets is free of toxic plants, and in a drylot so that he can't eat weeds that may be in the paddock.
To get rid of the St. John's wort, you have several options: burning, plowing under, and broadcast herbicide/wholesale re-seeding. You will want to consult with other landowners who are your neighbors and/or with whatever University or government agencies you can to discuss what the best option might be. DO NOT let anybody bamboozle you into planting ryegrass (Lolium) or fescue (Festuca), or any type of clover, i.e. red, white, subterranean, etc. If you overseed or re-seed as part of your pasture-development strategy, educate yourself as to grasses that might once have been native to your part of the continent, and consider redtop, brome (called 'prairie grass' in Australia), and windmill grass (Chloris). The Poison Plants book will give you many other ideas about this, but you should also look in specifically Australian books on pasture management and grasses. You'll find references to several of these in the bibliography to the Poison Plants volume. -- Dr. Deb
| Posted: Sat Jan 15th, 2011 03:37 pm||
|Thankyou Dr Deb, you have told me what I wanted to know.
I certainly do want to eliminate this problem whether it is damaging Lalla's liver, or not! The trauma he goes through with the burning is horrible.
As we have a large paddock, and do not own it, I want to prioritise the actions we take.
The flowers on the St John's Wort are browning off so I don't imagine it is palatable any longer.
There appears to be too much for us to chip out by hand so I have spoken to a local landowner who has very well managed pasture and she has advised me when it is best to spray it.
We don't have any patterson's curse.
I don't intend to seed down at all, there is loads of native pasture in this paddock for our 2 ponies, and after this season when it has gone to seed there should be more next year.
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