Manage N Applications to Cereal Hays to Avoid Livestock Nitrate Poisoning

By Chad Cheyney, Extension Educator

As we are facing a water-short year, I suspect that some ranchers are planning to plant some kind of cereal hay crop that might make pretty good tonnage with a limited amount of water.  Livestock operators that are planning a pea and oat or other cereal hay crop should be cognizant of the potential for livestock nitrate poisoning.  The Extension Offices in Butte and Custer Counties can help you minimize this risk with soil analysis and field nitrate testing of suspect forages.

Certain plants, including cereals and some weeds, including kochia, lambsquarter and pigweed, have a propensity to accumulate nitrogen under stress conditions.  This tendency in cereal hay crops can be increased to a dangerous level if operators attempt to increase production by heavy nitrogen fertilizer applications, especially if drought or lack of irrigation water does not permit the crop to mature fully.

In reality, animals are not poisoned by nitrate per se, but one of the intermediate products in the rumen is nitrite.  If the feed is high in nitrate, not all of the nitrite is converted to ammonia in the rumen and passes into the intestine and finally the blood stream.  In the blood, the nitrite combines with hemoglobin to form meth-hemoglobin which cannot transport oxygen.  The animals die of asphyxia.  Chocolate colored blood is an indicated of the condition.

Prevention of nitrate poisoning has five components:

·         Soil testing and split applications of N in challenging environments to prevent over fertilization

·         Control of weeds, especially kockia, lambsquarter and pigweed which are nitrate accumulators

·         Use cereals with higher water use efficiencies such as winter wheat or spring grains

·         Plant cool season forages that are likely to mature before stress sets in.

·         Qualitatively test forages in the field using the “quick test” method from the Extension Office and lab test all forages that show moderate or high nitrate levels by the “quick test”.

For more information on nitrate toxicity see MontGuide MT200205AG, which can be found by “googling” MontGuide MT200205AG, or stop by or call your local University of Idaho Extension Office.