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Virginia Cooperative Extension - Knowledge for the CommonWealth

Here we go again with drought stressed feeds

Dairy Pipeline: August 2002

Charles C. Stallings
Extension Dairy Scientist, Nutrition
(540) 231-4758

Nitrates accumulate in plants when growth in slowed. This can be from a lack of water as has been the case this year. Nitrates tend to accumulate in the stem with little in the grain. When the plant is actively growing the nitrates will be converted to plant protein. This stops when plant growth stops. Certain species of plants such as sorghum tends to accumulate nitrates more than other species. Even in normal years these plants may have elevated nitrate levels. I'm hearing reports of corn being chopped for silage in mid July because growth has stopped. Do not feed freshly chopped, green silage if the plant has been drought stressed. Ensiling will reduce nitrates by about 50%. Usually it is best to wait at least 3 weeks before feeding. Also it is possible to check plants for nitrates before feeding. The Virginia Tech Forage Testing Lab can do this but remember to chop plants before submitting to the lab. The following are some precautions if feeding drought stressed feeds.

  1. Ensile forage if possible to reduce nitrate level. It is best to ensile for three weeks before feeding, however, any is better than none.
  2. Raising the cutter bar during chopping will leave more of the stalk in the field and reduce nitrate levels.
  3. After a rain wait at least three days before chopping drought stressed corn plant to allow nitrates to be converted in the plant.
  4. Introduce feeds containing nitrates slowly and do not allow access when cows are extremely hungry.
  5. Dilute forages containing nitrates with clean feeds by using another forage and/or high fiber by-products such as whole cottonseeds, brewers grains, etc.
  6. Feed a balanced ration with adequate nutrients, especially vitamin A.
  7. Young, growing, and pregnant animals are the most susceptible to nitrates and should be observed for signs of toxicity if fed feeds containing nitrates.
  8. There are no magic feed additives to counteract the effect of nitrates.
  9. Avoid water with high levels of nitrates.
  10. Test feeds after ensiling if there is reason to expect problems with nitrates. Your local Extension agent can assist in doing this.

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