Identifying Nitrate Toxicity Symptoms in Livestock

Jun 29, 2023

Now is the time to avoid potential nitrate toxicity when feeding livestock.

Nitrate concentration in oats, barley, sudangrass, sorghum, sorghum-sudan hybrids, brassicas, and some common weeds such as kochia, lambsquarters and pigweeds can be high enough to cause livestock nitrate poisoning.

Guojie Wang, Penn State Extension forage specialist, notes that nitrate is easily converted to nitrite in blood, and the nitrite will react with hemoglobin, stopping blood cells from carrying oxygen.

In low-nitrate forages, the nitrite can be converted to ammonium and then amino acids and proteins. With high nitrate levels, the nitrite will accumulate and cause toxicity.

Under poor growing conditions, such as drought, those listed plants tend to store lots of nitrate in their lower stems. When we apply nitrogen fertilizer in one big application, plants also tend to build up lots of nitrates.

If the nitrate level in the forages is over 1,000 ppm, pregnant and milking livestock are sensitive. If the nitrate level is over 4,400 ppm, it is toxic for all livestock metabolic stages.

Nitrate testing is a must for an accurate and safe management plan, especially for oats in drought areas this year.

You can add a nitrate test to the standard forage quality test when you send forages to the lab.

If the test results are unsuitable for any livestock species and stage, mixing oat forage with other low-nitrate forages is your only option for feeding.

Mix forages thoroughly and feed them in small quantities often to reduce animal preference for oat forage.

Making green chop for direct feeding is worse than making dry hay. Drought-stressed oats right after rain will promote tillering and new growth. The nitrate accumulation for the first several days right after significant rainfall following drought will be worse than normal.

Cutting oat hay with higher than normal stubble will help this problem.

Making silage will lower the forage nitrate levels because the ensiling bacteria will change some nitrates into proteins. When feeding oat hay with high nitrate levels, providing energy supplements like corn will help.

Nitrate toxicity symptoms include rapid breathing, muscle tremors, poor coordination, diarrhea and frequent urination.

Your veterinarian may recommend an intravenous injection of a methylene blue solution as the last solution.

With nitrate testing and good feed management we hope to never get to that point.

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Heidi Reed is a Penn State Extension educator in York County.

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