http://www.cnn.com/2004/US/Central/03/04/dying.elks.ap/index.html

$bob$

I've seen cattle die from Prussic acid forming in the forage. It's naturally occurring under the right conditions.

The mild winter may have set up those conditions.

Once all the bugs in a rumninant's stomach die, the critter will die soon after, almost without fail.

Hope it's nothing "new"!