Farm Talk

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July 31, 2012

MU Extension teaches nitrate awareness

Parsons, Kansas — Recently the University of Missouri Extension held a Nitrate workshop in Halfway, Mo., to give producers an opportunity to learn more about Nitrate and prussic acid levels in crops and forage.

Interactive clickers were handed out upon arrival and used throughout the workshop so the crowd could participate in quizzes to test their previous knowledge along with information picked up during the evening.

Those who attended were also encouraged to bring samples of their own pasture forages that could be high in nitrate such as johnsongrass, or crops that could be fed to livestock such as cornstalks so Extension agents could perform a “quick nitrate test” and give  producers an idea whether what they are growing was safe to feed.

Brie Menjoulet, an agronomy specialist from the University of Missouri Extension was the first speaker. She began by explaining how nitrate builds up in forages and stressed the importance of knowing if your grasses were positive for nitrate before letting your cattle graze them in drought years.

Menjoulet said the difference between legumes and grasses is that legumes can make their own nitrogen, while grasses can’t.

“Slow growing conditions increase nitrate,” she said.

Grasses depend on nitrogen for growth, during a drought year when the forage isn’t receiving all the nutrients it needs to process nitrogen, it remains in the plant instead of being converted to protein, which is vital for grazing livestock.

“Cows are eating nitrate, not protein in drought years,” Menjoulet said.

She continued to say,  weeds can accumulate nitrogen as well, but johnsongrass and sudangrass are a couple of the biggest nitrate accumulators in a drought year. Even during a regular year producers need to watch nitrate levels in johnsongrass, she warned.

Another issue in nitrate build up is herbicide usage, she continued.

She emphasized the importance of reading the labels of the product and knowing what chemicals can potentially stress the plant before appling it.

“Herbicides can stunt your grass growth,” Menjoulet said. “Stunting stresses the plant and stops nitrate conversion.”

The second speaker of the evening, Andy McCorkill, a livestock specialist with the University of Missouri Extension explained that, in cattle, nitrate is converted to nitrite in their digestive system. This chemical reaction begins in the rumen and is then absorbed into the blood stream, combining with the hemoglobin and reducing oxygen in the their body.

“Essentially this process suffocates cattle,” McCorkill said.

Early signs of nitrate poisoning include panting, frothing at the mouth, labored breathing and staggering. He said cattle may not show all the signs or symptoms, but if a producer knows what to watch for they may potentially be able to save their livestock from death.

“Within six to eight hours of cattle being turned out on really hot (high in nitrate) grasses, cattle will collapse, have convulsions and die,” McCorkill said. “Look for dark chocolate blood, this is brought on from lack of oxygen in the blood.”

Prevention is the best treatment, he said. Methylene Blue, which is often used in dye works to counteract the nitrate poisoning. However McCorkill said it can only be given intravenously, so it is important to know beforehand that your vet has this drug readily available.

“You only have 30 minutes to counteract nitrate poisoning once cattle start showing symptoms,” he said.  

Feeding high nitrate forages will result in bred cows aborting calves, reduction in rate of gain in growing animals, lower conception rates, and reduced milk production, McCorkill said.

Both Menjoulet and McCorkill stressed that prevention is the best way to handle “hot” forages.

The University of Missouri Extension can provide a quick nitrate test on forage samples. Menjoulet said since there are 16 counties in the MU Extension region it is important to call ahead before a producer brings in a sample, that way they are insured someone will be in the office capable of performing the test before they make the drive.

While she said the quick test will show if the forage tests positive in nitrate or not, she recommends taking testing one step further.

“The quick test is a simple yes or no to the presence of nitrate, the quantitative analysis, or lab test, shows levels,” Menjoulet said. “They are fast, pay for the postage, and the test is only $10.”

Nitrate levels do not hay out. Hay can be fed with nitrate in it, but it has to be rationed out, she added.

“Grazing is better than feeding out,” McCorkill said. “It gives cattle time to pick and choose. Given the choice they will eat the leaves first which are lower in nitrate.”

Grazing also helps to build up an adaption to nitrate, but while grazing is better for livestock, it is important not to overgraze an area. The lower stem is where the higher accumulation of nitrates are, he added.

Both Menjoulet and McCorkill agree the only safe way to feed forage or corn stalks positive in nitrate is to ensile it.

“Silage is a magic process,” McCorkill said. “It can reduce nitrate levels as much as 30-50 percent.”

However Menjoulet adds for some producers the costs of silage equipment or not having access to custom harvesters may make the silage solution out of the question, therefore she recommends talking to an Extension agent about nitrate and having testing done.

“Test, Test, Test, I can’t emphasize it enough,” McCorkill concluded.£

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