Feeding issues persist for ranchers as temps cool
KANSAS CITY, Mo. (AP)--Ranchers are being urged to watch what they feed their cattle this fall and winter because some drought-stressed plants that were harvested for animal feed or whose stalks remain in fields contain dangerous levels of nitrates.
University Extension officials in Kansas and Missouri said high nitrate levels can cause pregnant cows to miscarry or kill adults. Animals that eat the nitrate-laden plants stumble and appear to be suffocating because nitrate poisoning inhibits the ability of blood to transport oxygen.
"We need to have everyone watch their cattle,'' said Eldon Cole, a livestock specialist for the University of Missouri Extension. "Have your eyes wide open.''
Nitrates are a naturally occurring form of nitrogen found in the soil. Normally, little nitrate accumulates in plants because they rapidly convert nitrate to amino acids and proteins. But when conditions are dry, as they were this past summer, the roots will take up nitrate faster than the plant can convert it.
That leads to large amount of nitrates being stored in the leaves and stem, particularly in plants such as corn, Johnsongrass, sudan grass and millet. The application of large amounts of nitrogen-rich fertilizers only exasperates the situation.
The issue first cropped up this summer among cattle grazing on hard-hit grasses. And farmers are being urged to be cautious as they begin feeding hay and even silage to their animals because it may contain high levels of nitrates. Problems also can occur when cattle get loose in corn fields and nibble on the remnants of crops that weren't worth harvesting because it was so dry.
Extension agents in Kansas and Missouri have been receiving reports of cattle succumbing to what appears to be nitrate poisoning this summer and even this fall. There are no good overall numbers.
"They get out and they're hungry and they get out on corn stalks,'' said Doug Shoup, the southeast area crops and soils specialist for Kansas State University Research and Extension. "Or they get fed bales that are high in nitrates.
"This is not typical. It's been bad.''
Dr. Mike Bloss, a veterinarian in Aurora, recalled getting a frantic call from a farmer who grazed 30 cows and their calves in a barn lot filled with Johnsongrass. In less than an hour, the animals were staggering. Two cows died; three other sickened cows and a 400-pound calf survived.
"It can tie up the red blood cells really quickly,'' Bloss said.
While rains eventually fell and reduced the grazing risk, there is concern that high nitrate levels have been preserved in plants cut at the peak of the drought. Corn poses a particular concern this year because it is heavily fertilized and was widely planted because the crop was fetching top dollar, said Tim Schnakenberg, an agronomy specialist for the University of Missouri Extension headquartered in Stone County.
Now that winter is coming, those plants are being fed to cattle.
Extension agents are urging ranchers to test their animal feed if there are any doubts about the nitrate levels. Many samples have tested high.
"Most of the time, even though the nitrate is risky, we try to help manage around it so they don't totally lose the crop,'' said Dr. Harold Haskins, a veterinarian who is from Diamond, Mo.
One of the most common ways to make nitrate-laden plants safe is to turn them into silage by chopping the leaves and stems into pieces and allowing them to ferment, Schnakenberg said.
Microbes that grow in the silage process consume nitrates, resulting in levels of the compound dropping by 30 to 50 percent. But given how dry the crop was this year, nitrate levels may still remain high if the plants were particularly dry when they were harvested.
Cole said a few farmers in his area have been feeding silage for two or three weeks now. The good news is no problems have been reported, he said.
"I'm going to keep my fingers crossed,'' Cole said. "It's still early. There is a lot of that kind of high-nitrate feed that is still sitting in the barn and in fence rows and bale yards that we will be seeing feed on into the winter.''
Unlike with silage, high nitrate levels don't dissipate over time in drought-stressed plants baled for hay. But the risk can be reduced if the high nitrate hay is mixed with other forage.
"Dilution is the solution,'' said Shoup of Kansas State University.