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Nitrates In Crops

September 20th 2011

By Dave Cubbon, P Ag

Every year frost impacts some of our forage feeds.  When this happens, nitrtates can become an issue.  Understanding nitrates and what happens to the feed and the animals is essential to adequate manage this issue in a feeding operation.
 
Nitrates are a problem in a cattle feeding operation.  If present in high enough percentages in the feed, they can tie up enough of the oxygen carrying sites in the blood that the animals will asphyxiate.  Every time there is a stress on a plant, nitrate levels increase and the potential for nitrate poisoning develops.
 
Nitrates can be present in all crops but the crop that presents the highest risk in our area is oats.  This crop will take the nitrates  from the roots of a plant and accumulate them in the stalks of the plant after a frost.  This is because the head and the leaves of the affected plants cannot receive any significant amounts of nitrates because of the damaged tissue present.  The nitrates that are moving from the roots which have not been damaged are tied up in the stacks.
 
If the nitrates are present in the stalks of the plants, they can be toxic to ruminant animals (beef and sheep).  In the fall when there is other plant material to forage on, the risk is less for nitrate poisoning because the levels of nitrates are reduced through dilution.  If the animals have no other source of feed to graze on, the feed that is high in nitrates becomes a very high risk one.  It can be managed by limit grazing the feed (restricting the time that the animals have access to the feed), by introducing the feed slowly to stock with increasing levels as time goes on or by diluting the amount of nitrates by adding other feeds to the ration.
 
If the oats are to be baled, the thing to do is wait until the nitrate levels are reduced in the stalks.  As time goes on, the nitrate levels in affected plants are reduced because the nitrates return to the roots.  With good growing conditions, this happens in between 4 and 7 days.  If the frosts or stress on the plant continues, the nitrate levels can stay high indefinitely.  Being aware of the weather conditions if a producer is waiting for the nitrate levels to go down is essential.  Better growing conditions means that the nitrates are reduced more quickly.
 
Nitrates in a crop can be managed.  Every year there are generally issues with some oat fields in the area.  Understanding the nitrates move up from the roots and become lodged in the stems because of damage to the leaves and heads helps a producer determine the risk that is present in his crop.  Be aware of this and manage accordingly and the risk of nitrate poisoning in your herd will be reduced.