If moisture conditions improve, the conversion process accelerates and within a few days nitrate levels in the plant return to normal. Not all drought conditions cause high nitrate levels in plants. If the supply of soil nitrates is in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates. Nitrate Toxicity in the Animal Like plants, ruminant animals also use the nitrogen in nitrates to make protein.
Conversion is made by bacteria in the rumen.
Nitrite, one of the intermediate products in this conversion, is the cause of nitrate poisoning. When this happens, nitrite accumulates and is absorbed into the bloodstream. Cattle are much more likely to be affected than are sheep or horses. The toxic level depends both on how much and how fast nitrate was consumed. In the case of forage, toxicity generally occurs when cattle consume large amounts of forage containing 1.76 percent or more nitrate ion on a dry matter basis.