Anything that disrupts the normal growth of a plant can set the stage for excessive levels of nitrates (e.g. drought, hail, frost damage). While the plant is growing, it is in the process of transporting nitrogen from the soil (in the form of nitrates) and synthesizing it into plant protein. When that growth process is slowed or interrupted, the metabolic machinery that converts nitrates to protein does not work efficiently and consequently nitrates accumulate, especially in the lower portion of the stalk. For the first few days after a rain, nitrate levels can be excessive since the plant takes up additional nutrients, yet there has not been adequate time to convert nitrates to plant protein. Extended cloudy weather or dense plant populations that create shading of the leaves can also cause toxic levels of nitrates in plants.

1. Forage test to know the levels in the forages that you are going to feed.
2. Put the forage crop up as silage rather than green chop or hay. During the fermentation process, the bacterial action will convert much of the nitrate to protein. Nitrate content can be reduced by about 50% after the fermentation process is complete.

Note: Some of the nitrates are lost in the conversion to nitrogen oxide gasses. These are often visible as yellow-red fumes. These gasses are toxic to man and animals and are heavier than air. If upright silos are used, extreme caution must be used to aerate the silo before one enters the silo and to prevent build-up in closed barns to which silos are attached.

3. Cut the silage or forage extra high. The highest concentration of nitrates is in the lower part of the stalk. By raising the cutter bar an extra 6" to 12", the nitrate content can be reduced in the total crop harvested.
4. Blend the high nitrate forage with other feeds so that it is only a portion of the ration. Using a good mixer wagon is helpful to get a good blend with other feedstuffs. This dilutes the overall nitrate concentration of the diet and insures that one animal doesn’t get a disproportionate amount of the toxic forage.
5. Gradually introduce livestock to the feed that has high nitrates over a period of time rather than abruptly feeding it to animals. Also split the feeding up over several meals during the day. Small amounts spread out over time prevents overloading the system. Also, the rumen microbial population can adapt such that microbial species more efficient at metabolizing nitrates begin to flourish. There is still, however, a limit to the amount of nitrates that can be tolerated in the diet.

Forage crops and the form in which they are fed differ in their risk level pertaining to nitrate toxicity.

Sorghums, sudan hybrids, and corn put up as forages can have high nitrate levels.

Oat hay and straw tends to have high nitrates more so than wheat, barley, or rye hays and straws. Also, certain weeds (wild sunflowers, pigeon grass, pig weed, kochia, and thistle) are known to accumulate nitrates.

The grain of oats, other cereals, corn and sorghums does not contain nitrates in toxic amounts. Native grasses, timothy and bromegrass hays, and alfalfa do not appear to be a concern.