Putting cattle on cornstalks can help keep perennial and annual forages growing through the fall.
“Every day the livestock are ingesting corn residue, they are not grazing forages,” says Victor Shelton, a grazing specialist with the Natural Resource Conservation Service in Ohio. “This allows for additional forage that can be utilized later this fall and early winter.”
In last week’s Ohio Beef Cattle Letter, Shelton points out that corn residues are best utilized within 60 days of harvest and when allocated in portions to reduce waste.
“In general, cornstalks have a crude protein value of about 8 percent and a total digestible nutrient (TDN) value of about 70 percent, Shelton notes. “The nutritional value falls over time to about 5 percent crude protein and to about 40 percent TDN.”
The grazing specialist explains that there are two reasons for the quality decline over time. If the stalks are not allocated in field portions, the most digestible plant parts will be eaten first across the entire field, leaving the poorer quality components for last.
Second, nutrient content declines over time as plant residue weathers and soluble nutrients leach out. Shelton suggests that cornstalks are best utilized for spring-calving cows, which have lower energy and protein demands in the fall compared to lactating or growing animals.
Using rough estimates, Shelton suggests stocking cornstalks at the rate of 1,000 pounds of live weight per acre per 30 days. Though residue mass can vary, most corn yields are about 56 pounds of residue per bushel harvested. This translates to a 200-bushel corn crop yielding about 11,000 pounds of residue.
Of that residue, about 40 percent is leaf and husk, which are the plant parts most readily consumed. Hence, there is about 4,400 pounds of desirable grazeable fodder available.
One animal unit, which is 1,000 pounds of live weight, will consume about 3 percent of its weight in dry matter per day or roughly 30 pounds of fodder. If a 50 percent harvest efficiency is realized, one acre of cornstalks should feed one animal unit for about 75 days. Keep in mind that heavier cows will consume more than 30 pounds of fodder per day.
Cornstalks provide a valuable grazing resource in the fall. But also keep in mind that they provide the double benefit of allowing other forages to grow and accumulate yield for late fall and winter grazing, conserving stored hay and labor resources.