Nitrate Toxicity In Summer Hay

During a drought, there's a potential for buildup in some summer grasses.

Published on: Aug 8, 2012

By Gary Bates

Most of the hay produced for beef cows in Tennessee comes from tall fescue field.

There are, however, a significant number of producers who use summer grasses like Bermudagrss, soghum x sudangrass hybrids and pearl millet. These plants can be used successfully in hay production.

But there is the potential for a buildup of nitrates in these plants, especially during a drought.

What is nitrate poisoning?

Nitrate Toxicity In Summer Hay
Nitrate Toxicity In Summer Hay

Nitrate poisoning occurs when animals consume hay containing high levels of free nitrates. Under drought conditions, both sorghum X sudangrass hybrids and pearl millet have the potential to accumulate high levels of nitrates, especially if they have been fertilized with nitrogen.

Feeding hay that was cut during or just after a drought should be avoided. Nitrate accumulation occurs because the plant continues to take up nitrogen through the roots, but drought conditions cause an inadequate water supply for rapid plant growth. Nitrates accumulate in the plant for use in protein formation when adequate water becomes available.

Animals suffering from nitrate poisoning exhibit labored breathing, muscle tremors and staggering. Membranes of the eyes and mouth are bluish because of the lack of oxygen. Death can occur relatively quickly.

Detecting high nitrate hays

Prevention is the best way to deal with nitrate toxicity. The nitrate level in hay will not decrease during storage. The UT Extension Soil, Plant and Pest Center can test nitrate levels in hay.

Prevention of the problem next summer

Nitrate toxicity is most common during a drought. The chances for high nitrates are increased if the crop has been fertilized with nitrogen. Do not fertilize summer grasses with nitrogen if adequate moisture for growth is not available.

If a period of drought occurs, do not cut or graze the crop until it starts to grow after a rain. If you have any suspicions that nitrate levels may be high, contact your local Extension office for more information.

Nitrate levels of 0-2,500 ppm, DM basis are generally considered safe to feed.

Nitrate levels of 2,500-5,000  are generally safe to feed with a balanced ration. For pregnant or young animals, limit to one-half of the total ration.

Nitrate levels 5,000-15,000  should be limited to one-fourth of the ration and should be fortified with energy, minerals and Vitamin A.

Nitrate levels over 15,000 are toxic and shouldn't be used in a free-choice feeding program.

Bates is director of the University of Tennessee Beef and Forage Center.