Anyone have knowledge of Johnson Grass and prussic acid poisoning?

We are so dry, I am having to open pastures we don't normally graze! In the pasture I am opening today, there are a few smallish stands of Johnson grass, about 2 feet tall. The ONLY green grass in the pasture, and it comprises less than 2% of the total pasture area (maybe three spots of around 10 x 10 feet patches). We baled this field back in May when we had grass  :-\  How much grass is too much for cattle? Anyone have experience with it? I looked on the Internet, but most of the information I found was on symptoms and when it is most dangerous. Of course, we are in a drought situation, that is why I am having to graze where I normally bale!

Thanks for any feedback!!!

When Johnson grass is stressed (times of drought) it can be very poisenous.  I have seen cows only eat a small amount and die.  If it was me I would try and pull up any that was in the field.  Once we were in your situation and thier was too much to pull up so we turned in a few less valuable older cows for a couple days.  Our thought process was if we lost some we wanted to controll what ones we lost.

frost is worse than drought but there is a shot(in the vein i think) you can get from vet for any affected if you are fast enough on the few you turn in

I talked about this with my vet, just Monday morning as a matter of fact.  He said that the prussic acid (unlike nitrates) go away 2 to 3 days after the plant is dead, so his recommendation was to shred those small patches of Johnson grass (I have a similiar situation) and wait 3 days then turn the cows in.  He said that Johnson grass will have some nitrates, but at a much smaller (thus safer) level of concentration than Sudan... Again, I'm just repeating what he said, but he's a pretty sharp guy and has been at this for alot of years, so I'm inclined to trust him on it.

Prusic acid will decline after the plant is dead...the most concern with it is within that 3 day time period after a frost because the ice crystals will burst the cells of the plant thus making prussic acid poisoning more of a concern

DLD said:

I talked about this with my vet, just Monday morning as a matter of fact.  He said that the prussic acid (unlike nitrates) go away 2 to 3 days after the plant is dead, so his recommendation was to shred those small patches of Johnson grass (I have a similiar situation) and wait 3 days then turn the cows in.  He said that Johnson grass will have some nitrates, but at a much smaller (thus safer) level of concentration than Sudan... Again, I'm just repeating what he said, but he's a pretty sharp guy and has been at this for alot of years, so I'm inclined to trust him on it.

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I have heard the same thing, and I believe that some of our neighbors with grass problems do this..

So it is OK for pastures with Johnson grass to be cut for hay?

savaged said:

So it is OK for pastures with Johnson grass to be cut for hay?

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From what I understand it should be fine.  There's been plenty of it baled up around here this summer.