Test for nitrate levels before cutting summer annuals for hay

Tuesday, July 11, 2017

Hot summer weather means Oklahoma forage producers should be testing their summer annuals before cutting them for hay, especially for those areas of the state suffering from drought conditions.

“Stressed plants such as forage sorghums can accumulate dangerous concentrations of nitrates,” said Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist and managing editor of the university’s popular Cow-Calf Corner newsletter.

The major sources of nitrate toxicity in Oklahoma will be summer annual sorghum type plants such as sudan hybrids, sorgo-sudans, sorghum-sudans, millets and Johnsongrass. These high-nitrate plants, either standing in the field or fed as hay, can cause abortion in pregnant cattle and even death if consumed in great enough quantities.

“Nitrates do not dissipate from sun-cured hay, in contrast to prussic acid, therefore once the hay is cut the nitrate levels remain constant,” Selk said. “Producers who are unsure how to test properly should contact their OSU Cooperative Extension county office for assistance.”

Although the risk of possible animal poisoning cannot be totally eliminated, management techniques scientifically proven to reduce the risk of nitrate toxicity include:
● Test the crop before harvesting it. If the crop has an elevated concentration of nitrates, the producer still has the option of waiting for normal plant metabolism to bring the concentration back to a safe level. A producer – no matter his or her level of experience – can accurately estimate nitrate content simply by looking at a field.
● Raise the cutter bar when harvesting hay. Nitrates are in greatest concentration in the lower stem. Raising the cutter bar may reduce the tonnage, but Selk reminds producers that cutting more tons of a toxic material has no particular value.
● Know the extent of nitrate accumulation in the hay and review materials about levels that are dangerous to different classes of cattle such as pregnant cows, open cows or stocker steers.
● A producer who still has doubts about the quality of his or her hay should send a forage sample to a reputable laboratory for analysis and get an estimate of nitrate concentration. This will provide guidelines as to the extent of dilution that may be necessary to more safely feed the hay.

Selk reminds forage producers it is important to allow cattle to become adapted to nitrate in the hay. By feeding small amounts of the forage sorghum along with other feeds such as grass hay or grains, cattle begin to adapt to the nitrates in the feed and develop a capability to digest the nitrate with less danger.

“It is imperative producers avoid the temptation of feeding high-nitrate forage for the first time after a snow or ice storm,” he said. “The stressed, hungry cattle will not be adapted to the nitrates present. They are likely to consume unusually large amounts of the forage and be at high risk for nitrate toxicity.

Selk added adaptation as the only management strategy may not be sufficient to provide complete safety from high-nitrate forages, which is why OSU recommends producers be prepared for winter feeding by testing the forage before it is cut and turned into hay.

Anyone seeking additional information about nitrate toxicity in livestock should read OSU Extension Fact Sheet PSS-2903, available online at http://osufacts.okstate,edu and through all OSU Cooperative Extension county offices, typically located under “County Government” in local directories.

The Oklahoma Cooperative Extension Service is a state agency administered by OSU’s Division of Agricultural Sciences and Natural Resources, and one of three equal parts comprising the university’s state and federally mandated teaching, research and Extension land-grant mission.