Sickness and death are becoming increasingly common in livestock this summer — a result of the current drought, which has covered almost two-thirds of the continental U.S. and caused nitrate levels in corn to rise drastically.
The chemical, usually found around the base of crops at concentrations less than 0.2 percent, has spread higher up the stalk in the dry crops and reached levels of toxicity in plants such as corn, sorghum and weeds eaten by grazing animals.
“When the feed being used is high in nitrate, the oxygen in the blood doesn’t bind, and a cow’s ability to get pregnant is significantly lessened,” said Robert Kallenbach, a professor in the Division of Plant Sciences. “The nitrate can get high enough to where it can kill an animal, but this will only happen in less than 1 percent of cattle.”
Since many crops are planted in fertilizer containing nitrogen, nitrate is almost always present and remains in the bottom 12 to 18 inches of the stalk.
When the concentration reaches its current rate, the nitrate reaches such levels in the blood of livestock that the animals’ blood turns a “chocolate brown” color. Once this occurs, miscarriages and infertility become much more common.
In order to prevent harm to animals, farmers are urged to take several steps to reduce nitrate levels in feed. Kallenbach said farmers should mix crops with either low levels of nitrate or alternatives such as soybeans with the feed. They are also strongly encouraged to get their feed tested.
Tim Evans, an associate professor of veterinary pathobiology, heads a toxicology section at MU’s Veterinary Medical Diagnostic Laboratory. The laboratory, as well as at many extension sites across Missouri, tests samples of feed.
“Missouri farmers should definitely contact their local MU Extension offices for help in the preliminary stages of testing the nitrate concentrations in their crops,” Evans said in an MU news release.
Other members of the VMDL staff share similar sentiments.
“I mean, just look at the weather,” said George Rottinghaus from the VMDL’s toxicology department. “I would just say it’s a Midwestern problem.”
Though many crops are affected, the nitrate levels in the crops do not pose a danger to humans, Kallenbach said. Livestock is affected because farm animals eat plants and vegetation in huge quantities. The true effect on humans might be seen in the impact this drought has on the population of livestock.
“Since the population may only be cut by such a small amount this year, it is doubtful that it will impact our immediate food supply,” he said. “The problem is we are expecting the calf crop to be reduced by up to 10 percent.”
This drop, as a result of the miscarriages and infertility due to this season’s drought, means effects could be seen in the next 18 months, Kallenbach said.
The VMDL staff has developed several different tests to determine which foods are safe for consumption. Crops are put through “spot” testing at $16.25 per sample and then can go through further tests, which give a more accurate view of the nitrate levels.
The issue requires attention and the testing of samples, Kallenbach said.
“This is not the first time we’ve seen this problem, but it is certainly more widespread than it has been in years,” he said.
