FARGO — As farmers look for livestock forage due to drought, harvesting stressed crops brings its own challenges. NDSU Extension livestock specialists said there is an increased risk of nitrate poisoning in drought-stressed feed. ADVERTISEMENTNitrates can build up in cattle over time, causing nitrate poisoning. Tim Erbele, vice president of the North Dakota Stockmen's Association, said its important that farmers test low-yield crops for nitrates before the crops are used for feed. Experts said cattle can show signs of poisoning a half hour to four hours after eating toxic levels of nitrates.