Corn residue is an abundant, affordable feedstuff in the Corn Belt. Yet each year, acres upon acres go ungrazed, even on diversified farms. Grazing cornstalks is a significant source of feed for a cow-calf operation, but there are challenges: fencing, water, supplementation, compaction and the impact of grazing on the following grain crop, to name a few.
Over three years, University of Illinois researchers measured cow performance, residue quality and utilization as well as subsequent crop yield. Two grazing methods—strip grazing and continuous grazing— and an ungrazed control were used. Following corn harvest, cows were allowed to graze for six weeks.
In the continuous-grazed treatment, cows were allowed access to the full paddock the entire time. The stocking rate was 1.2 cows per acre.
In the strip-grazed treatment, the field was divided into three sections. Cows were allowed access to a new strip every two weeks. No back fencing was used. Thus, after 14 days, cows had access to the first strip and the new second strip. During the last two weeks, the cows had access to the entire paddock.
Residue grazing started in late September the first year, in early November the second year and in early October the third year. The acres were maintained in continuous corn during the trial period. Spring tillage occurred each year.
The research resulted in four main points:
- Grazing residue for a six-week period following corn harvest did not impact subsequent crop yield. This was true for both continuous grazing and strip grazing.
- Grazing helped remove and incorporate residue. Roughly 4 tons of dry matter per acre were available for grazing. Residue available after grazing in either treatment was close to half of what was initially in the field. In the ungrazed control paddock, 78% of residue remained, with losses likely due to wind and plant degradation.
- Cattle consumed mainly husks and leaves. Cobs also declined.
- Stalk percentage increased due to reduction of other components. After grazing, the actual weight of the stalk component was similar across all treatments, which illustrates the selectivity of cattle grazing cornstalks. Cattle look for more palatable feedstuffs. Cattle first eat the remaining corn grain, then husks, then leaves and finally the stalk.
Cows that strip grazed corn residue had increased bodyweight gains and weighed more than cows in the continuous-grazed trial. It’s likely that the strip-grazed treatment potentially partitioned nutrients more evenly over the period.
Measures of residue showed strip grazing had more nutritive quality toward the end of the grazing period. The strip-grazed cows were allowed less area to travel for the first two two-week periods. Continuous-grazed cows spent more time searching for palatable residue. This extra time spent traveling the area not only resulted in increased maintenance requirement, but also could have increased trampling of husks and leaves, thus reducing available residue for consumption.
Operations on heavy, deep, poorly drained soils can still benefit from cornstalk grazing, but management is needed to reduce traffic and avoid higher stocking rates during wet periods. But if the operation is not limited in corn acres, then stocking density is easily addressed by allowing more acres per paddock or by using a continuous-grazing system.
Because cattle eat the more-digestible and higher-protein portions first, a good mineral may be the only supplementation needed for the first month. The exception is a herd that includes fall-calving cows or stocker calves. For them, a supplement will be necessary to meet nutrient demands of lactation and growth, respectively
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