What is Nitrate Toxicity?
Nitrate is not always toxic to animals. Almost all forages contain some nitrates. When feeds containing nitrates are consumed by ruminants, nitrates are changed in the rumen to ammonia that then may be converted by bacteria in the rumen into microbial protein. Nitrite is one of the intermediate products in the breakdown of nitrate and is the cause of nitrate poisoning. Nitrite can be absorbed into the bloodstream. Nitrite in the bloodstream changes hemoglobin to methemoglobin. Hemoglobin carries oxygen from the lungs to other tissues but methemoglobin is incapable of carrying oxygen. Thus, nitrates become a problem when enough methemoglobin is produced that the oxygen carrying capacity of blood is reduced to a critical level. If enough methemoglobin is produced (more than 80 percent of the total hemoglobin) the animal will die. The level of toxicity depends upon the amount of nitrate in the feed and how fast the feed that contains nitrate is consumed. For example, it takes about twice
