plants when excessive rates of nitrogen fertilizers or effluents have been applied, or when plants have been under environmental stress, such as drought. Nitrate levels tend to be higher in the lower one-third of plants, and to increase or accumulate levels at night and on cloudy overcast days. Cattle, sheep and horses are most susceptible. Bacteria in the rumen of cattle and sheep, and the cecum of the horse, convert consumed nitrate into nitrite, which is very toxic in animals. For this reason nitrate poisoning rarely bothers pigs and poultry.
Some species of plants are known nitrate accumulators. Johnsongrass, sorghum, sudangrass, russian thistle, puncture vine pigweed, sweetclover, bromegrass, orchardgrass, lambsquarter, oat hay, turnips, rape, barley, triticale, wheat and corn are some of the more common nitrate accumulators. The ensiling of forages suspected to have elevated nitrate levels reduces the chance for problems. It must be remembered, however, that stored high nitrate hay continues to be dangerous, as the nitrates do not reduce over time.
Low levels of elevated nitrates may cause abortions without any other symptoms. Severely affected animals develop muscle tremors, lose coordination and become weak. Moving these animals will initiate difficulty breathing commonly followed by collapse and death.
Nitrate poisoning can be confused with prussic acid poisoning, but is distinguished by a marked difference in blood color of affected animals. Animals with nitrate poisoning will have a chocolate brown blood color. In Prussic acid poisoning, the blood color is bright red. Treatment by your