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Don't get stalked
Manage threats from acidosis and nitrates to get the most benefit from cornstalks as a feed source.
When grazing cattle on cornstalks after grain harvest, a couple of health risks to livestock may require specialized management strategies. “The main health problem to watch out for is the potential for grain overload, which causes acidosis,” says Russ Daly, South Dakota State University Extension veterinarian.
“When cattle not formerly getting grain are suddenly eating a lot of corn or other kinds of grain, they end up consuming more carbohydrates than the bacteria in the rumen can process,” he says. “This produces acid, which lowers the pH in the rumen. The bacterial populations change, which results in more acid. Eventually, with too much acid formation in the rumen, the acid gets absorbed into the bloodstream, causing clinical acidosis.”
Symptoms include foul, watery diarrhea and a loss of coordination, possible bloat, and founder in animals that recover. As acidosis progresses, cattle can go down and are not able to get back on their feet.
“If animals are not too badly affected, there are some anti-acid medications you can use for treatment,” says Daly. “But once an animal gets really weak, the chance for successful treatment is pretty slim.”
Appraising corn yield loss in a field before turning cattle out can give you an idea of the potential risk for grain overload. As a rule of thumb, if you find one ear of corn per 140 feet of 30-inch row, you might figure cows have the potential to consume at least 1 bushel of corn per acre. If a lot of corn has been left in the field, acclimating cattle to grain consumption before turnout can help ward off the potential for acidosis.
“Acidosis is not so much a problem resulting from an animal eating too much grain; it’s a problem of them eating too much grain when they’re not used to it,” says Daly. “One preventive strategy might be to adapt them to a diet of corn before they get out to the field.”
Feeding cattle a small amount of corn before turnout is one option, as is limit-grazing a small area of the harvested cornfield. Using temporary fencing to strip-graze an entire field gives more efficient overall use of the forage resource by limiting feed loss due to trampling.
Besides grain overload, nitrate poisoning presents another potential health risk from grazing cornstalks, particularly when corn was drought-stressed during the growing season.
“Nitrates tend to accumulate in the lower 2 feet of the stalk,” says Daly.
“So if cattle are grazing cornstalks with a lot of leaf material and corncobs, the cattle won’t eat much of the lower parts of the plant.”
If you anticipate grazing harvested cornfields to the point where cattle may begin consuming the lower stalks of plants, testing for nitrate levels will show potential health risks.
After cattle consume the most nutritious parts of cornstalks, supplementing with protein may be needed. The nutritional quality of grazed corn decreases throughout fall and winter, dropping to about 40% total digestible nutrients and 5% crude protein.
Supplementing with natural-source proteins at a rate of .5 to 1 pound per cow per day will increase the digestibility of the lower-quality forage.