If you will be feeding cane, millet, or oat hay to your cows this winter, University of Nebraska’s Bruce Anderson says to be cautions so high nitrate levels won’t kill your cows or cause abortions.

Anderson explains that nitrates occur naturally in all forages. At low levels, nitrates either are converted into microbial protein by bacteria in the rumen or they are excreted. But when nitrate concentrations get too high, they can kill cows and maybe abort calves.

Some plants are much more likely to be high in nitrates than others. Annual grasses like cane, millet, and oats often have elevated nitrate levels. So do certain weeds like pigweed, kochia, and lambsquarter. If your hay has lots of these weeds or is an annual grass, be alert to the potential for high nitrates.

That doesn’t mean these feeds always are toxic, nor does it mean that high-nitrate hay can’t be fed safely. But always test these feeds for nitrates in a lab to determine how to feed them safely.

Remember, there are many ways to feed high nitrate hay safely. Diluting with grain or low nitrate forages is most common. Frequent, small meals that slowly increase the amount of nitrate fed helps cattle adapt to high nitrate hay. And make sure cattle have plenty of clean, low nitrate water at all times.

Anderson says, “I’ve seen nitrates cause deaths most often after a snow storm has prevented animals from eating naturally for a day or more. Avoid feeding high or even marginally high nitrate hay at this time because cattle will eat an extra large meal when very hungry. This could create an overload of nitrates to their system, leading to death.”