Drought-stricken forages that accumulate nitrates can kill grazing livestock, quickly. The problem is showing up already in some Midwestern states and could be a concern in Ohio too.

"We're getting reports of cattle dying," says Rob Kallenbach, a University of Missouri forage specialist. "As hot weather without rain continues, we expect to hear of more death losses. It happens at the start of every drought."

Large grasses, such as corn, sorghum and sudangrass hybrids, are most often the cause of problems, Kallenbach says. Many plants, even ryegrass and fescue, can accumulate nitrates when soil moisture becomes short.
http://farmprogress.com/ohio-farmer/story.aspx/nl0_27nl/drought-raises-concerns-nitrate-poisoning-0-61185