By now, the story of the GMO grass that gassed a herd of cows in Texas has gone round the world at least twice, perhaps more.
Truth is still trying to catch up, and Deborah Blum has a good dose of truth available at Wired.
First, and pointed out by Blum, Tifton-85 is not genetically modified. It is a hybrid grass. Two different grasses were bred to produce this tasty green grass that is easy to digest. And even if it was GM, drought stressed grasses tend to produce cyanide. Non hybrid, hybrid, GMO, all of them are capable of doing this, and by so doing, can become toxic to grazers. The fact that many people are afraid of GMOs led people to immediately assume that the cows were killed by careless mad scientists at the behest of multinational corporations. Meh.
Second, I am highly skeptical that the plants were producing much cyanide gas. The cattle that were grazing in the field were most likely poisoned by eating the grass, not from breathing in cyanide, which would have caused a much higher dose to the cattle. The farmer, not eating the grass, but breathing the same air, would not have been affected.