Annual grasses and other forages could hold dangerous levels of nitrates that can kill cattle and cause abortions, warns Bruce Anderson, University of Nebraska Extension forage specialist.

Lab-test forage sorghum, millet and oat hay, as well as corn stalks, before using them for feed this year, Anderson suggests.

Weeds like pigweed, lambsquarter and kochia, which amass nitrates, can also be problematic this time of year.

High-nitrate feeds can be fed safely; they should be lab-tested to determine nitrate levels. Those with concentrations of more than 4,400 ppm of nitrate, as a conservative estimate, should be mixed with grain or low-nitrate forages in rations. Any feed with more than 9,000 ppm of nitrate is potentially lethal.

Nitrate poisoning symptoms in cattle include rapid or noisy breathing, salivation, muscle tremors, diarrhea and frequent urination.

Cattle fed small, frequent meals with a slowly increasing amount of nitrate can eventually adapt to high-nitrate hay. Make sure cattle have enough low-nitrate water at all times, Anderson says.