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September 27, 2018
Corn harvest is just getting started in our neck of the woods, and soon we’ll pull the herd off summer pastures and move them onto these fields to graze the crop residue. It’s an affordable way to extend the grazing season that allows us to save our hay supplies for when winter weather hits.
Meteorologists are predicting the first round of snow to fall by Nov. 15. Hopefully, it’s just a dusting of powder and we’ll be able to make it until late December or early January before we need to move cows home and start feeding hay. That would be an ideal scenario that would cost us pennies on the dollar compared to the scenario we would face if winter hits hard and early.
While this period of time isn’t as critical in a spring-calving cow herd’s gestation as when she enters the third trimester, having those cows on a level plane of nutrition this fall helps to prepare the mama cows for the rigors of winter weather.
As a result, there are some important nutritional considerations to keep in mind when turning cows on corn stalks.
Victor Shelton, an agronomist grazing specialist, offers some tips best utilizing corn stalks and extending the grazing season in a recent article he wrote for the Ohio Beef Cattle Letter.
Shelton writes, “Corn residues normally are best utilized within 60 days of harvest and also allocated out in portions to reduce waste. In general, corn stalks have a crude protein value of about 8% and a total digestible nutrient value of about 70%. The nutritional value falls over time to about 5% crude protein and to about 40% digestibility.
“This reduction can be two-fold. First, if livestock are not managed in such a way to allocate the residue out over time, they will eat their dessert first, which is the most palatable, and leave the broccoli for later. Second, nutrient content decreases over time as the residue weathers and soluble nutrients leach out.
“Stalks are best utilized for spring calving cows due to lack of sufficient energy for lactating or growing animals, especially over time, unless winter annuals or brassicas have been added.”
When considering the stocking rate for the field, Shelton says to calculate at the rate of 1,000 pounds per acre per 30 days.
He says, “Though it can vary a lot, most corn produces about 56 pounds of residue per bushel. So, a 200-bushel corn crop should yield about 11,000 pounds of residue.
“Of that residue, about 40% is leaf and husk, the part that is most readily consumed. So in this example, there is about 4,400 pounds of desirable grazable fodder available or about 75 animal unit days at 50% harvest efficiency; and yes, they are going to waste some.
“One animal unit, which is 1,000 pounds live weight, will consume about 3% of their weight in dry matter per day or roughly 30 pounds of fodder. You can do your own math from there, using your livestock numbers and acres that can be grazed. Certainly, if annuals are also part of the picture, then there is even more available.”
Shelton stressed the importance of checking for nitrates if there was crop failure or the chance that applied nitrogen was not normally utilized.
Water is another consideration, and ideally, he says water should be moved with the livestock to new allocations of stalks.
And if your cattle are on sudangrass, as some of ours are currently, watch the temperature as frost causes these forages to produce toxic prussic acid.
Shelton says, “Livestock should be removed from these forages for at least two weeks to allow for the forages to ‘dry down’ and the prussic acid to dissipate before grazing again. Frosted areas could start with only ‘pockets’ in a field. Any regrowth from the base of the plant after a frost can also be very high in prussic acid. If in doubt about nitrates or prussic acid, test before grazing!”
If possible, pull the herd off those summer grazing pastures to allow them to rest before the dormant season and take advantage of cheap crop residues to extend the grazing season and save that valuable hay supply!
The opinions of Amanda Radke are not necessarily those of beefmagazine.com or Farm Progress.
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