Proper management needed while feeding drought-stricken grains to cattle
By Jennifer Carrico
While most of the corn is harvested and many farmers and ranchers want to put the drought of 2012 behind us, the livestock producers have to continue to be concerned about the grains and crop residue they are feeding their cattle.
University of Nebraska-Lincoln Beef Range System Specialist Aaron Stalker said economically, corn residue is a great source of feed for cows.
"There is a lot of corn residue available, even during a drought year, and only about one-fourth of the residue in Nebraska is actually utilized. However, only 14 percent of corn residue is utilized nationwide," he said.
Stalker warns of some problems that might occur in a drought year. Those problems include high nitrates and aflatoxin.
"After cows eat the grain, they will then mainly graze on the leaves and husks, which tend to be lower in nitrates. But since drought-stressed corn is sometimes smaller and stunted, it's more likely the cattle will eat lower into the stalk where the nitrate levels may be high," he said.
Stalker recommends producers test corn stalks for nitrate levels before turning cows out to prevent the problems.
According to UNL information, high nitrates may not only be an issue in dryland acres, but also on irrigated corn edges and in the corners where water hasn't reached and plants are stunted.
Due to the shortage of feed this year, producers are more likely to leave cows grazing cornstalks longer than they normally would to try to stretch feed resources. Forcing cows to eat more of the stalks increases the risk they will be consuming parts of the corn plant that could have high nitrate toxicity.
Nitrate toxicity isn't always fatal to livestock, according to Steve Ensley, senior clinician at the Iowa State University Veterinary Diagnostic Laboratory.
"In the rumen, nitrates are changed to ammonia and then converted into the microbial protein which reduces the oxygen-carrying capacity of blood," he said. "In cows and first-calf heifers, this may cause abortions. Symptoms of nitrate toxicity include rapid and difficult breathing, brownish discoloration of the blood, muscle tremors, incoordination and diarrhea."
Ensley suggests testing a sample of corn to determine nitrate levels. Nitrate levels in the total ration can be diluted by mixing with an appropriate amount of grass or alfalfa hay. He also suggests testing cornstalk bales if they are from an unknown origin.
Properly ensiled corn cut for silage should not have a problem with nitrate levels.
Iowa State University Extension information said corn plants suffering from inadequate nitrogen availability remove nitrogen from the lower cornstalks and leaves during the grain-filling period. Corn plants that have more nitrogen than needed to attain maximum yields, however, accumulate nitrate in their lower stalks at the end of the season.
When cornstalk nitrate levels are excessive--more than 2,000 parts per million--it indicates the concentration of nitrate in the stalk at the end of the season reflects all factors that influenced nitrate availability and nitrate needs during the growing season. In years of drought, this is likely to happen.
Another common problem in years of drought is the growth of Aspergillous on corn because of higher nighttime temperatures during silking. This fungus may or may not result in aflatoxin production. Ensley said just because the mold is there does not mean that aflatoxin will be produced.
"Aflatoxin can be fatal to livestock, and if it's being fed to a dairy animals, can be passed through the milk," he said.
He recommends testing grain to determine the presence of aflatoxin and then make management decisions based on the results of the test.
Corn containing aflatoxin can still be fed to livestock, but it is important to know at what level the problem might be. Finishing beef cattle can consume corn with a level of 300 ppm. Finishing swine over 100 pounds can consume corn with the level of 200 ppm. Breeding cattle and breeding swine should consumer corn with no higher a level than 100 ppm. Immature animals and dairy cows can only consume at a level of 20 ppm.
Ensley said with proper testing for nitrates and aflatoxins, producers should be able to continue to manage through this droughty year.
Jennifer Carrico can be reached by phone at 515-833-2120, or by email at firstname.lastname@example.org.