Feeding Drought Stressed Corn to Livestock

The rainfall this summer has been highly variable throughout the region, and some areas have been exceedingly dry, particularly during July. During times of extended drought when corn grain yield potential is severely limited or nonexistent, the plants may still offer a valuable source of nutrients for livestock provided careful attention is given to how it is harvested and fed. Due to the danger of nitrate levels being elevated during periods of drought, the safest option to use the crop as feed is to ensile it.  One-fifth to two-thirds of the nitrate in the plant may be dissipated during the fermentation process, but remember that this process takes up to 21 days to occur.  Nitrate concentration is highest in the lower one-third of the corn stalk.  If the crop is to be cut for use as feed, leave the bottom third of the plants in the field.

If moisture conditions improve and the corn begins to green up and resume growth, nitrate conversion to proteins accelerates rapidly and ultimately will return to normal. DO NOT harvest or graze corn plants for 5 to 7 days after a heavy rain has stimulated renewed growth! When the plant begins to grow again, nitrate levels will increase for a few days, creating very high concentrations in the plant.

If you want to test the crop for the potential of high nitrate, obtain a representative sample of the field by cutting 15 to 20 plants at the height they will be harvested and cut those plants up to resemble a silage sample.  Ship the sample in a paper bag In order to reduce the risk of the sample rotting on the way to the laboratory.  The following interpretive guidelines can be used to assess the test results. More information about nitrate testing for feed can be found in our FactSheet, Nitrate Toxicity in Feed, available on our website.


Nitrate (NO3) in dry matter

Feeding Instructions

(summary from several sources)

0.0 - 0.44 % or 0 - 4,400 ppm

Safe to feed.

0.44 - 0.88 % or 4,400 - 8,800 ppm

Limit to 50% of total dry ration for pregnant animals by either mixing, diluting, or limiting use of forages.

0.88 - 1.50 % or 8,800 - 15,000 ppm

Limit to 25% of total dry ration by mixing, diluting or limiting use of forages. Avoid feeding to pregnant animals.

Over 1.50 % or over 15,000 ppm

TOXIC. Do not feed.

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