US - Corn (maize) residue left over from harvest can be a great option for livestock producers wanting to extend the grazing season, but producers should watch out that cattle do not eat too much grain, US universities have said.
Reports from Ohio State University (OSU) and North Dakota State University (NDSU) both said that corn residue can be a great option to supplement feed.
In Ohio, excessive rain has resulted in a lower hay crop this year, making alternative feed sources necessary, whilst in North Dakota, recent wind storms have left significant amounts of downed ears left in corn fields.
"In some cases, producers have reported up to 70 bushels of corn per acre remaining on the ground. In this extreme case, for each acre of field that cows can access, 3,920 pounds of corn remain. That is just less than 40 pounds of corn per acre for every 100 cows," said John Dhuyvetter, area livestock systems specialist at the North Central Research Extension Center near Minot.
Grazing corn residue typically is the most cost-effective method to take advantage of nutrients remaining in the field after combining.
"Grazing cows on harvested corn acres within the first 30 to 60 days after harvesting can be a great way for producers to stretch their feed supplies," said Rory Lewandowski, agriculture and natural resources educator for OSU Extension.
“Using temporary fencing allows this as an inexpensive option for many producers,” he added.
Based on calculations by Rick Rasby, a beef specialist at the University of Nebraska, for every bushel of corn there are about 45 pounds of residue on a dry matter (DM) basis, Mr Lewandowski said.
And for every bushel of corn there are about 16 pounds of husks and leaves on a dry matter basis, he said.
“Using those figures, a 170 bushels per acre corn crop will leave 7,650 pounds of dry matter of total residue, with the husks and leaves accounting for about 2,720 pounds of that total,” he said. “And typical harvest leaves about one bushel per acre of corn grain that the animals can graze.”
Cows in mid-gestation and ewes in the middle trimester or earlier of gestation typically do well with grazing corn residue, Mr Lewandowski said.
Use caution to prevent cattle health issues
Although corn residue is a useful feed supplement for producers, too much grain can cause digestive upsets and other health issues, NDSU said.
"Producers must evaluate individual fields and grazing scenarios, and make appropriate management plans to ensure cattle health,” beef cattle specialist Carl Dahlen said.
“Cattle preferentially will consume grain and leaves before consuming lower-quality stalk material. This is an important consideration when developing strategies to graze crop residues.”
Consuming too much grain can cause acidosis, lameness and abortions, and death in extreme cases. But not all issues will be observed right away. For example, founder will be seen during the course of several months as cattle’s hooves continue to grow and abscesses develop.
“Any time in which corn ear drop is greater than 8 to 10 bushels per acre, producers must develop a strategy to mitigate potential grain overload in cows,” said Karl Hoppe, area livestock systems specialist at the Carrington Research Extension Center. “Each 8-inch ear of corn contains roughly 1/2 pound of grain.”
To determine the amount of corn remaining in fields planted in 30-inch rows, NDSU suggested producers count the number of 8-inch ears (or equivalent) on the ground along 100 feet between two rows, then divide the total by 2. Do this for at least three 100-foot-long strips in the field to get a good estimate of corn remaining in the field.
Fara Brummer, area livestock systems specialist at the Central Grasslands Research Extension Center, suggested getting animals to adapt to eating corn before letting them loose in the fields, for example by starting with 3 pounds daily, then moving up to 7 or 8 pounds during a 10-day period before turnout.
Other suggestions include limiting the field space cattle have access to, and preventing overeating by not turning out cattle when they are hungry.
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