Johnson Grass contains cyanide??

Pooh BearMay 7, 2007

Last week I was looking up info about black cherry trees

being poisonous to cattle. I found what I was looking for.

But I also found this. According to the page below,

Johnson Grass is poisonous to cattle until it is well cured.

I asked my friend/neighbor that raises cows about this

and he told me cows love Johnson Grass and it was wrong.

Can someone explain the descreptancy between

what I read and what I was told?

Leaves and stems possess cyanide. The young shoots are the most toxic, and when wilted or frost-damaged, cyanide becomes readily available in the leaves. Nitrates can also accumulate in johnsongrass. Well-cured hay is relatively safe for animal consumption as mature plants have much lower toxicity.

University of Missouri Extension - Plants Poisonous to Livestock.

And what about the Polk Salad it mentions.

Fence rows here are overgrown with the stuff.

Common pokeweed (Phytolacca americana)

Poisonous part

All parts, especially roots and seeds.


Irritant effects due to phytolaccigenin are salivation, abdominal pain and diarrhea. In rare cases where large doses are consumed, animals may show anemia and alterations in heart rate and respiration.


Pooh Bear

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Dibbit(z7b SC)

What was written about Jonson grass is true. I think I might be inclined to keep cattle off a pasture if that is the principle grass growing in it, after a frost gets the young grass, for at least a week, maybe longer. As written, I don't think hay, if well cured, would be a problem. I think it is more toxic for horses than for cattle, but can also affect cattle, if eaten at the wrong times. It is one of the grasses that, in general, is not a problem, but which can become one. I think, because it's only sometimes a problem, people get complacent and start to disbelieve. And, once it gets into a field, it's hard to get out, due to its growth habits, and can crowd out other grasses. It is also a fast growing grass, so offers a lot of feed value quickly - if you discount the toxicity.

Red maple leaves, when wilted, are toxic to horses because of the cyanide they develop. I think a couple of the other maples can be toxic as well. I don't knw about their affect on cattle, but imagine it affects them as well. Fresh are fine, it's only as they wilt...

Wilted wild cherries are also known to be toxic to horses. I believe that the "abortion storm" that hit the Tb breeding farms in KY a few years ago was caused by broodmares ingesting tent caterpillars that had been eating wild cherry, but may be misremembering - it was a couple of years ago, and I don't have brodmares, so only noted it in passing, so to speak.

Most grazing animals won't eat pokeweed, as far as I know, although birds love the berries. If there was little else to eat in a field, then it might become a problem. I think I would do what I could to limit its presence in any fields I had access to.

    Bookmark   May 7, 2007 at 3:09PM
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As I recall Poke becomes much more toxic after frost. There is wide variation between opinions on poke. Some folk say that one should never eat it (human consumption). Others counter with statements like "Grandma had to have her poke salad every spring and she lived to 102!" Our neighbors have it growing all over their fields and I've seen them graze horses over there for months at a time, with almost no attention. They've never lost a horse. But we do try to eliminate it in our fields.


    Bookmark   May 7, 2007 at 3:59PM
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Pooh Bear

I wouldn't know young Johnson Grass if I saw it.
I know when it gets tall the tops get seedy.

Never seen a cow eat poke weed. They ignore the stuff.
The only reason it gets cut is to keep the fence rows cleared.
I remember when I was a little kid picking the stuff
for my Grandmother to cook. I couldn't stand the stuff.

Pooh Bear

    Bookmark   May 7, 2007 at 10:24PM
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kydaylilylady(z6 KY)

Johnson grass is a warm season grass and usually doesn't start to make an appearance until after frost in the spring. It's just now starting to show itself on bare ground in Central KY. There is no problem in letting your stock graze this grass until frost, early to middle October here. Johnson grass makes excellent summer pasture and hay. It should be good for something since it's rather noxious in row crops and gardens....

Just before frost my husband goes out and anywhere there's a stand of Johnson Grass he cuts with the disc mower or haybine. That way you cut before the frost and there's no chance of the prussic acid forming.

Sorghums also develop this acid upon frosts so if you are raising any for hay or grazing you want to take the same precautions.

Just a reminder too, Taxus shrubs are deadly to cattle. Be extra careful where you dispose of this shrubs trimmings.


    Bookmark   May 8, 2007 at 8:52AM
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marquisella(z4 NY)

Dibbit is right about the eastern tent catepillar..

We had a day long seminar just a month ago about it, and the reason the horses died from the catepillars is because of the spines on the catepillar. Something about they got stuck in the intestines, I should have paid more attention, but they were the cause of death & abortion. Somehow they could either pass to the fetus or affected it in some way.

Last year we had an epidemic with these catepillars, and in some areas were so numerous they covered roads, & cars slid off the roads due to the slime, yuck. I heard that some farms were covered with them.
They are cyclic, but we expect more this year again.

I didn't have a problem, but now have Guineas so I am hoping they will eat everything that moves...


    Bookmark   May 8, 2007 at 9:45AM
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