Dealing with High Nitrates in Forage

With dry weather in western KY, be cautious of the potential for nitrate poisoning before grazing or harvesting drought stressed summer annual forages like sorghum-sudan, pearl millet or silage corn. Several management strategies are available to reduce the risk of nitrate poisoning.

  • The majority of cases in KY come from cattle eating fertilizer, so store properly and clean spills.
  • Avoid grazing warm season grasses fertilized with excess manure or high N rates when growth slows from drought, frost, hail, or herbicide exposure.
  • Corn silage should be properly ensiled at least 3 weeks and tested for nitrates before feeding.
  • Mix high nitrate forage with forage known to be low.
  • Feeding low nitrate forage or hay before turning cattle on to high nitrate forages.
  • Splitting grazing times will also allow nitrates to be utilized properly by the rumen microflora.
  • Cattle can increase their tolerance to nitrates in their diet with time. Provide time for adaptation.
  • To aid in increasing this tolerance, the diet should be sufficient in vitamin A and trace minerals.
  • Delay harvest of high nitrate forages until nitrate levels are safe or raise the cutter bar to 18 inches.
  • When in doubt, take the time to send samples for nitrate testing before introducing cattle to the pasture.
  • Consult your county Extension agent for information on sampling for nitrates, conducting a quick field test, and/or to send samples for testing.

For more information see UK publication “Nitrate Poisoning”.