Using cornstalks, Crop can maintain mature cows through winter
Producers who need some extra feed for their mature cows this winter could check into leasing some corn residue fields, according to a University of Nebraska Extension Specialist. Aaron Stalker recently presented a webinar about grazing mature cows on cornfields.
“Mature cows can perform as well on corn residue at less cost than cows on winter range receiving two pounds of supplements,” he said.
In addition, corn residue is a feed source that is dramatically under-utilized, not only in Nebraska but in its surrounding states.
According to Stalker, the key to grazing mature cows on a cornfield is determining the correct stocking rate.
Corn grain is 90 percent of the total digestible nutrients (TDN) required, while the husk is 58 percent, leaves are 52 percent and the cob and stems are low quality feed, at 48 percent and 49 percent, respectively.
“The husks and leaves make up about 40 percent of the residue,” Stalker said. “It is the most nutritious part of the corn plant. Producers should set their stocking rate according to how many husks and leaves are in the field.”
Cattle are selective grazers, and when they are first turned into the cornfield, they will eat all the ears and downed corn they can find, followed by the husks and leaves. They will eat the cob and stem last because of the low quality.
“When producers first turn a group of cows out into the cornfield, they will start with a high quality diet, but that will decline over time as they utilize all the higher quality feed in the field,” he explained.
To calculate a stocking rate, Stalker said producers need to realize the amount of residue available to be grazed is a function of grain yield.
“Basically, 16 pounds of dry leaves and husks is equal to a bushel of corn produced,” he explained. “So, if the corn made 175 bushels per acre, that amount multiplied by 16 pounds gives 2,800 pounds of dry matter per acre.”
Of the 2,800 pounds of dry matter, it is typical to assume only 50 percent will be grazed due to trampling, blowing away and other losses, so 1,400 pounds of residue per acre is available for grazing.
Stalker said generally one animal unit month (AUM) is equivalent to 780 pounds of dry matter, and a 1,200-pound cow is equivalent to 1.2 animal units (AU).
To determine how much dry matter that cow will eat in one month, Stalker said to multiply 1.2 AU by 780 pounds, which is equivalent to 936 pounds of forage dry matter per month. Next, take 1,400 pounds of leaves and husks available per acre divided by 936 pounds of dry matter for a 1,200-pound cow, and that is equivalent to 1.5 months. Stalker said based on those figures, one acre will supply a 1,200-pound cow with enough forage for 45 days.
Ranchers can also access an excel spreadsheet on beef.unl.edu to determine how many acres they need to graze their cows.
The corn stalk grazing calculator can calculate costs of grazing a cornfield, trucking and other costs, in addition to calculating how many acres it will take to graze a group of cows on a corn residue field. Ranchers will need to determine what the corn yielded, the number of cows they want to graze and their weight and the number of acres in the field.
If ranchers stock the cornfield correctly, they shouldn’t need to provide a daily supplement for the cows.
“If ranchers supplement mature cows on the cornfield, they will increase body condition, but they won’t get any return for that investment in the supplement,” he said. “There is really no economic advantage to supplementing.”
However, when the weather turns bad and the snow gets deep, ranchers should have a plan in place for feeding the cows.
“Cows can usually move powder up to six inches and be fine,” Stalker said.
But, if there is crusting or ice, the cows may not be able to break through to graze the residue, he noted.
Producers should also examine a cornfield before turning their cows into it for combine spills and ear droppage, which can cause founder or acidosis.
“If the eardrop is greater than eight bushels per acre or if the combine spills or overshoots the transport wagon, the cows may need to be monitored more carefully,” Stalker said.
Producers can overcome this problem by adding sodium bicarbonate to the drinking water at 2.5 pounds per 100 gallons of water, he said.