Right now, harvest is in full swing. Following harvest, many cows will be turned out to harvested corn fields to graze the residue remaining for the winter. Corn residue can be a great winter feed resource for both cows and growing calves. Cows grazing preference is a diet of dropped corn, husks, and leaves. The total digestible nutrients (abbreviated as TDN) of the selected diet ranges from 50 to 60% and crude protein about 5 to 5.5%. It is important to remember that the highest forage quality is available at the start of grazing and declines as the amount of residue remaining decreases. This affects how we manage certain stages of cattle in different production stages to meet their nutritional demands.
Growing Calf (Weaned)
Weaned calves have a high nutritional demand as they are growing. When grazing corn residue, these calves will need supplementation, otherwise without, they will lose weight. For example, if we want a 600-pound calf to gain 1 pound per-day, the calves will need 8.3 pounds of TDN and 1.31 pounds of crude protein (abbreviated as CP). Grazing alone, calves likely consume 6.8 pounds of TDN and 0.66 pounds of CP, which falls short of their nutrients needs to reach our performance goal. Research has shown that supplementing dried distillers grains plus solubes (abbreviated as DDGS) at 2.0 pounds (as-fed) per-day, calves will gain 1 pound per-day. Increasing levels of distillers grain supplementation increased average daily gain. Calves grazing corn residue with DDGS supplementation can reach 2.0 pounds per-day of gain. The gain of these calves depends on your desired target in mind.
Dry Pregnant Cows
When spring calving herds are grazing corn residue, cows are only in their second trimester of pregnancy and have their lowest nutrient requirements if they are in a good body condition (BCS of 5 to 6). A mature cow can maintain her weight consuming 26 pounds of residue (dry matter basis). If the cows need to gain body condition, a supplement will need to be provided. Dry pregnant cows require little to no protein or energy supplementation until late in gestation. While supplementation is not needed, it is still important to provide cows with a free-choice mineral targeting intake of 4 ounces per day. This amount changes based on your mineral. Check your mineral feed tag for recommended intake level. Consult with your nutritionist or extension specialists to determine the best mineral for your area.
Weather plays a big factor in how long our cows can graze corn residue. Most cows can graze fields that have up to 4 to 6 inches of snow cover. However, cattle are not able to graze fields that are covered in ice. Therefore, the length of grazing time is variable and dependent on weather conditions.
Subsequent Crop Concerns
It is not uncommon to hear concerns about grazing corn residue affecting the soil and subsequent crop productivity. Soil compaction is commonly talked about, as compaction can subsequently reduce crop yield. However, several studies conducted by the University of Nebraska-Lincoln found that grazing in the late fall or winter did not result in significant compaction on cropland or negative impacts on crop yields. The specific fields in the studies were managed under a no-till land management strategy and in a corn-soybean rotation. Fall grazing of corn residue improved soybean yields by 3.4 bushels per-acre. Grazing fields managed under continuous corn had no impact on subsequent crop yield, 239 bushels per-acre grazed versus 223 bushels per-acre ungrazed. It is also important to remember that most of the nutrients (including Nitrogen, Phosphorus, Potassium, and Calcium) consumed by the cattle are excreted back on the land.
Compaction is a main concern for crop producers, and minor surface compaction can result from grazing during wet weather. This compaction disappears through natural wetting, drying, freezing, and thawing processes. Compaction levels for restricting root growth do not carry over into following growing seasons.
Corn residue grazing can benefit both cattle and crop producers. Corn residue is an economical feed source for cattle over the winter months and can provide an extra source of income for crop producers without detrimental effects to the land.