Agriculture Information

Drought Conditions Create Concern of Nitrate Accumulation in Cereal Grains and Weeds
by Al Kowitz

This year's hot dry conditions have stressed cereal grains and weeds creating the possibility of increased levels of nitrates in stalk and stems. When this accumulation reaches a threshold of 5000 ppm NO3 the feed is considered potentially toxic and levels over 10,000 ppm NO3 are considered dangerous.

Causes of Nitrate Accumulation in Forages

Nitrates accumulate in plants when there is a large amount of nitrogen in the soil due to manure or application of nitrogen fertilizer. This presence of nitrogen in the soil and an adverse growing condition such as drought or shade that interferes with the normal growth of the plant can result in a nitrate buildup in the plan tissue. The process for converting nitrate to amino acids, proteins and other compounds is actively growing green leaves and sunlight.

Nitrate Toxicity in Livestock

Ruminant animals use the nitrogen in nitrates to make protein. The nitrates are changed in the rumen to ammonia that is converted by bacterial into microbial protein. Nitrite, one of the intermediate products in this conversion process, is the cause of nitrate poisoning. High levels of nitrates in feed overwhelm the animal's digestive system where the conversion of nitrates to nitrites is faster than the conversion of nitrites to ammonia. Nitrites are then absorbed into the bloodstream. This presence of nitrites interferes with the transport of oxygen to the lungs and body tissues and the animal literally suffocates.

Symptoms of Nitrate Toxicity

Symptoms include difficulty in breathing including mouth breathing, muscular weakness and staggering gait, and dilation of pupils. Death may occur within an hour after the onset of difficult breathing, but more typically in 3 or 4 hours. Lack of oxygen to the fetus may cause abortions following subacute levels of nitrate poisoning. Accurate diagnosis is sometimes missed since these abortions will occur several days after the animal has consumed the toxic forage.

Treatment

When nitrate poisoning is suspected remove the animal from the feed and handle the animal as quietly as possible to minimize their oxygen needs. Providing high energy feed such as corn may be useful. A veterinarian should be called immediately. Administration of a methylene blue solution intravenously helps to restore the oxygen carrying capacity of the blood and reverses the poisoning process.

Reducing the Threat of Nitrate Toxicity

Plants vary in their accumulation of nitrate. Certain weeds, such as pigweed, kochia and lambsquarter are often high in nitrate. Oats cut for hay at an immature stage can have high nitrate concentrations. Brome and orchard grass store very little nitrate under normal growing conditions and legumes generally do not contain high nitrate concentrations. For crops such as oats it may be wise to harvest the crop at a more mature state (heavy dough) than is desirable for optimal nutritional components and to cut the crop later in the day. Some moisture is required for the uptake of nitrates. When the supply of nitrates is in the dry soil surface, the plant roots are unable to absorb nitrate.

Drought-stressed small grain forages and any forage suspected of being high in nitrates should be tested before feeding. Dilute high nitrate forages with other feed which is low in nitrates. Allow cattle time to adapt to the increased nitrate in the diet by frequent and slow introduction of small amount of high nitrate feed.

The Extension office has several publications on the cause and prevention of nitrate poisoning of livestock. If you are concerned please call our office at 684-2588 for additional information.

Additional Information

Nitrates in Livestock Feeding

Nitrate Poisoning

Causes and Prevention - Nitrate Poisoning of Livestock