Maple Leaf Poisoning Horses

http://cal.vet.upenn.edu/projects/poison/plants/ppredma.htm

acording to this:
“as little as 0.3 % of the body weight as leaves”

That is tragic. I am surprised that the website can only speculate that the toxicity is due to tannins. There has been a lot of work done with animals consuming tannins since they are a type of chemical defense used by some plants. Tannins usually bind with protein and have a negative impact on protein digestion. Certain species, like deer, that mostly browse leaf material as a primary part of their diet, have evolved a counter-mechanism in which specific proteins in their saliva bind the tannins and render them ineffective in the gut.

Interestingly, that dry after taste in a red or burgundy wine is the result of the tannins interacting with proteins in our mouths.

Again, it’s a sad, sad thing to lose animals to something like this. We just need more information regarding plant toxicities in livestock.

Here’s a good review of tannins for those so inclined – it should be noted that oaks are noted for their tannin content – certainly more than maples.

http://www.ansci.cornell.edu/plants/toxicagents/tannin.html

This story hits close to home for me, my farm is just down the road from him and I have a lot of maples, too. And though my horses and I are not there yet, you can bet I’ve added maple tree culling at pasture edges to my to-do list for when I get there.

Shocked by the news, I spent some time researching this online last night. Many experts point out that fresh leaves do not have the toxic effect, but others note that the chemical is present even in fresh leaves, just in subdued amounts; also that silver and sugar maples have it too.

The responsible chemical is thought to be gallic acid, which breaks down red blood cells and essentially disrupts the transport of oxygen in the blood. In black cherry leaves, it is prussic acid that does the same thing. I knew about black cherry, but not red maple.

Interestingly, one article mentioned that the leaves of storm-downed trees may look fresh and green for quite some time, but they are stressed all the same, and the toxin is there.

The Ontario Ministry of Agriculture – Food and Rural Affairs has a good fact sheet here, with excellent photos of the different species of maple leaves, a great help to me as I’m still learning my hardwoods.

It’s amazing the plants that “can” be toxic to horses. About 10 yrs back a guy lost some horses to what the vets considered to be clover poisoning – not sure which one alsike or sweet (different plant all together)….

we were always told wilted grass would sicken a horse also. let them pull as much grass as they wished, but not to cut it and bring it to them. and to keep them out after cutting the pasture back for a couple days. always did what i was told so i have no knowledge on this subject. any truth to it? mitch

Hey guys,

I’m the one that lost the horses that Jason is referring to. I’ll give you a brief summary of what transpired. Sometime Saturday night or early Sunday morning a red maple tree blew down in their pasture and we noticed one of the horses didn’t feel good. At first we thought he had caught a cold, so we took them both to the barn. A little later, the second one starting sweating and looked uncomfortable. We called a vet and he said that it was probably just a bad belly ache from eating too many of the leaves, but that it couldn’t hurt them since the leaves were still green. He said to just give them all the water they wanted and some hay if they wanted to eat. By 10:15 Sunday night one horse looked completely better, and the other was much improved. Dad checked on them at midnight, and said they both looked good then.

Monday morning brought bad news. The second horse was weak as water and was pissing blood. He was up and down in the stall. We had to help him load in the trailer and took him to the vet as quick as we could get there. The first horse was still looking 100% when we left, but right after we got to the vet’s, mom called saying he was doing the same thing. So we rushed back to get him. They put them both on IV’s to flush out the toxins, and because they had lost so much blood they were preparing to give them a transfusion once the toxins were out.

To make a long story short, by 5:00 p.m. both horses were gone. They died within 5 minutes of each other. The vet is baffled as well as the specialist in Lexington that he had conferred with. As some of you have already said, green leaves were not supposed to do this. The blood work results did not satisfy them, so they’re doing an autopsy to confirm. The vet said that the symptoms were exactly like red maple poisoning, and since nothing else had changed in their pasture I can’t think that it’s anything else.

I bought these horses in Utah. My wife thought that maybe since they hadn’t grown up around any maple trees, they didn’t have any resistance to it. I don’t know…but the whole ordeal has been a crushing blow on all of us. I’ll keep you posted on the final word, but hopefully this won’t happen to any one else.

Ben

Hey everyone,

Just wanted to let you guys know that I received word today from the vet that the autopsy results were conclusive. It was 100% definite that red maple poisoning killed my horses.

This might be a good time to check your pastures and cut out any trees that look suspect. Also, please pass this information along to others that may not know. There’s no need for this to happen to anyone else.

Ben