By Kim Ricardo
The combine leaves the field, the grain is in the bin, and for most people, the corn crop is finished. However, for livestock producers, the harvest may only be entering its second phase. A field still produces something of value after the grain has been harvested. Husks, leaves, cobs, stalks, and some amount of grain and ears are scattered across the field. For the cow, it simply isn’t residue, it’s another source of feed.
Traditionally, we might discuss grazing corn residue in simple terms: 200 acres, 100 cows, 40 days of additional grazing. While those numbers help shape the big picture, they don’t necessarily tell us what the grazing accomplished.
How much feed did the cattle harvest? How much stored feed did those additional grazing days replace? How much value did the cattle capture from a crop that had been previously harvested? And how much residue remained in the field to continue doing its job for the soil? Instead, maybe we should look at the entire flow of value:
Corn produced → residue left behind → feed harvested by livestock → nutrients returned to the soil and stored feed replaced.
Measuring More Than Grazing Days
Grazing days are easy to understand, but they only serve as representative of what we truly want to know. Factors such as livestock size and class, stocking density, weather, residue availability, amount of grain, and grazing management can all influence how much feed cattle actually consume. Perhaps a better question is: How much of the available residue did the livestock harvest?
Cattle are selective grazers, meaning they tend to naturally select more palatable and easier digestible portions first. In the case of corn residue, this is the husks and leaves, leaving stalk and cob material for last. As grazing continues, the quality and quantity of the residue that remains decreases over time, meaning that residue is not simply how long cattle remain in the field, but how much usable feed they harvested during that time.
Another way to evaluate the value of grazing crop residue is to factor in the value of grazing compared to conventional feeding. The time spent grazing residue likely means those cattle were not consuming feed that otherwise might have been supplied form hay, silage, or other stored sources. Therefore, the value of grazing corn residue should include the feed that was harvested, stored, transported, and delivered.
Source : sdstate.edu