Across the Corn Belt, crop-residue grazing has become increasingly popular as a low-cost option for wintering cattle and an income opportunity for crop farmers. The system also builds efficiency into beef production by converting a low-value
byproduct—crop residue—into high-value protein.
Whether you move your cows to cornstalks immediately after corn harvest or later in the winter, you can expect some decline in the quality of available forage over the course of the grazing season. Understanding that decline, cattle owners can adjust their supplemental feeding, use a rotational-grazing system or change grazing schedules accordingly. In any case, whether you graze your own corn ground or leased fields, producers can turn their cattle out with confidence their grazing practices will not negatively affect future crop yields.
A series of studies, featured in the University of Nebraska’s 2017 Beef Cattle Report, could help beef producers and farmers plan their stalk-grazing programs for optimum benefits to beef and crop production.
Plan on Declining Quality
By late-winter, the quality of forage available in harvested corn fields has begun to decline. If cattle have grazed a field since harvest, they’ve likely selectively consumed the most nutritious plant components. When producers turn cattle out on stalks in late winter or early spring, weathering probably has reduced the nutritional value of the forage somewhat, and wildlife might have consumed much of the grain.
To quantify that decline in forage quality, University of Nebraska researchers conducted a study to measure the quality of corn residue from the fall through spring grazing periods and to evaluate the effects of crop rotation on subsequent corn-residue quality.
For this trial, the team used an irrigated field in eastern Nebraska. One section of the field had been managed in a corn-soybean rotation, while the other produced continuous corn. On each section, they used four replications of three treatments: fall grazing (November to February) spring grazing (March) and no grazing.
Prior to harvest, the researchers collected whole-plant samples and measured the dry-matter contribution of plant components including stalks, leaves and husks. They also analyzed the material for digestibility and nutrient contents. Through the grazing period, they used ruminally fistulated steers, so they could collect and analyze “in-vivo” samples of the forage each steer consumed.
The researchers found no significant difference in digestible organic matter (DOM) between crops following the corn-corn and corn-soybean rotations, or crops following fall or spring grazing. Not surprisingly, DOM of the residue was highest at the beginning of the fall grazing period. In the spring-grazed plots, DOM was higher at the beginning of the spring grazing period than at the end of fall grazing, while DOM was lowest at the end of spring grazing. Overall, DOM declined by 32% from the beginning to end of fall grazing, and declined 52% during spring grazing. Starch in the diet ranged from 0.04% to 6.44% at the beginning of grazing in fall or spring, and averaged 1.6%, suggesting wide variability in the amount of grain cattle consumed.
The researchers concluded that as the availability of nutrients in corn residue declines, producers should adjust feeding management or institute rotational grazing to ensure they meet the energy requirements of cattle through the grazing season.