Nitrate is a naturally occurring compound in plants. Nitrate accumulation in the plant can be compounded by conditions of plant stress, such as drought, heavy fertilization or young plants.

Acute nitrate toxicity occurs when animals consume high-nitrate forages for a short period of time. Nitrate is converted to nitrite by rumen microbes as an intermediate step in converting the nitrate to microbial protein. Ruminant animals are specifically at risk, as they bring up the feed bolus for chewing and inhale the nitrite.