Mark, the nitrate poisoning case that sticks in my mind was definitely not a "slow build" thing. It came on in a couple days after putting cows on corn stalks that were still way too green. Fortunately I noticed something wrong, took them off the stalks and put them on hay. It definitely does affect some cows more than others. The nitrates must have caused one to abort also. The worst affected cow came up open at preg check a few weeks later. This was a couple years ago with a small group.

Jim at Dawn