These feeds are potentially toxic. Do not feed. First, ease the transition of animals onto the high nitrate feeds. Animals that are adapted to high nitrate diets generally are not as prone to exhibit problems as non adapted animals. Make sure rations are balanced to meet performance expectations.
Nutritional deficiencies increase the likelihood of animals to exhibit nitrate toxicity.
Also, take special precautions to not stress livestock on high nitrate feeds. Stress often increases the occurrence of nitrate problems. Finally, dilute the high nitrate feeds as recommended above and you will likely be able to utilize the feedstuff with minimal risks associated with the nitrate hazard.