Nitrate poisoning has hit herds in Southwest Missouri, livestock specialist cautions producers to test forages

The impact of the 2018 drought continues to linger in the Ozarks as some cattle producers are dealing the loss of livestock due to elevated nitrate levels in forages.

University of Missouri Extension officials report that as many as 300 head of cattle have succumbed to nitrate poisoning.

Most cases are coming from Southwest and South Central Missouri, according to Tim Evans, head toxicologist at the University of Missouri Veterinary Medical Diagnostic lab in Columbia, Mo.

University of Missouri Livestock Field Specialist Andy McCorkill told Ozarks Farm & Neighbor that he has not dealt with any cases of nitrate poisoning, but there have been several reports in Lawrence County.

“Most of those cases are from corn silage,” McCorkill said. “It was hot when it went into the pit and it hadn’t dissipated yet.”

Nitrate poisoning is a result of high nitrates levels in forages consumed by livestock.

Issues with nitrate poisoning actually began to develop last year when the Ozarks suffered from prolonged hot and dry conditions.

“The plant takes nitrogen up in the form of nitrate, but instead of using it to grow, they can’t burn it up when it’s hot and dry so it sits there in the plant, mostly in the stem,” McCorkill explained. “When it goes through the rumen, normally cattle can break it up and digest it, and it goes right on through their system. But, when there’s too much, it’s converted to nitrite and gets into the blood system, and as it circulates through the blood, it messes with the ability to carry oxygen and (animals) pretty much suffocate.”

He went on to say corn silage, Johnsongrass and sorghum varieties – such as Green Graze, milo and sudangrass – tend to be the biggest offenders when it comes to nitrate poisoning.

“Johnsongrass is the one we see the most problem with by far, but we don’t see it in normal Johnsongrass,” McCorkill said. “There were a few people who put down some fertilizer a little late hoping to get some growth. Then we had a lot of rain in a short amount of time that have had some Johnsongrass that tested hot.”

Nitrate levels of less than 3,000 parts per million are generally safe, according to the University of Missouri Extension Service. Between 3,000 and 5,000 ppm could be dangerous to pregnant cows and unborn calves. Levels of 10,000 ppm are extremely dangerous, according to the Extension.

High levels of nitrates can reduce milk production, cause abortions in short-bred females or premature calves.

“A dairy producer will notice if he’s on questionable ground the next day after the levels are elevated,” McCorkill said. “In beef cows, cows might abort or calves will come early. If those early calves make it, if their mommas have been eating a lot of that high nitrate stuff, they will have the same problem with the blood’s ability to carry oxygen. They also may be slow to thrive and it could potentially affect how they perform in their lives.”

Cattle are not the only species susceptible to nitrate poisoning. Sheep, goats and horses can also be afflicted.

Many producers were forced to buy hay to feed their livestock this winter, which can also contribute to the issue.

“Anytime you buy hay that you don’t know the story on, the chance of problems arise,” McCorkill said. “There is always a chance for failure when you bring in hay sight unseen.”

McCorkill advised producers to test any questionable forages before feeding it to livestock.

“That’s the key,” he said. “It’s kind of hard to do the quick test on dry hay, but we can still send it off to the lab and have results of the nitrate concentrate on it within a week to 10 days. Even if the levels are a little high, we can mix it with something else to dilute it down so you can still feed it; you just have to be cautious so that they don’t eat too much of it at one time. If it is marginally high, try to feed that to young, growing cattle.”

As the Ozarks transitions into spring and the need to feed hay diminishes and McCorkill said the nitrate issue will diminish, but there’s still cooler weather ahead.

“The mature cows we are seeing die right now are a combination of factors,” he said. “It could be that some of those cows were compromised by anaplasmosis in the past and they aren’t doing the best nutritionally. There’s an old saying that January shakes them, February breaks them and March takes them. There’s a lot of things that are going to come together in the next few weeks that can potentially take a lot of cows if we get a cold snap. I think the nitrates is just the tip of the iceberg for some of the older cows for some of these older cows that are stressed.”


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