He says nitrate levels can accumulate in drought-stressed corn and pose a risk to animal health. Many farmers across the Midwest are abandoning ruined corn crops and salvaging what they can to feed to their animals, especially cattle. Evans says high nitrate levels also can build up in naturally growing plants and weeds that livestock might be forced to eat because of limited pasture or hay availability. He suggests farmers test the nitrate levels of their crops and pastures before allowing their animals to eat any of the plants.