Corn harvest is underway in our area and the residue that remains on those harvested fields has value as a low-cost feedstuff for beef cattle, especially those in early to mid-gestation. Based on the 2000 National Research Council’s (NRC) Nutrient Requirement of beef cattle, mature cattle in mid-gestation require a ration with about 7% crude protein (CP) and 50% energy as measured by total digestible nutrients (TDN). While corn stalks, husks and cobs are a low CP, low energy feedstuff, the corn leaves and any corn grain remaining can more than meet the nutritional requirements of a mid-gestation cow. Cows will graze selectively, eating dropped ears, partial ears and grain kernels first along with corn leaves followed by husks and finally cobs and stalks if necessary.
According to a publication from the University of Iowa entitled “Grazing Corn Residue” by Leu, Sellers and Loy, (www.iowabeefcenter.org/Forages/grazingcornresidue.pdf) early in a 30 to 60 day corn residue grazing period cattle could select a ration in the 6-7% crude protein range with a TDN content of 65-70%. By the end of the grazing period the expected nutrient content is lower, a CP of 5% and a TDN level of 40-45%. As cattle are forced to consume a higher percentage of the low nutrient value corn stalks and husks, protein and energy supplementation may be necessary. A 2012 Nebraska Beef Cattle Report (http://beef.unl.edu/nebeefreport2012) includes a five-year study that evaluated the effects of protein supplementation to beef cows grazing corn residue in late gestation. The study concluded, “supplementing cows grazing corn stalks in mid to late gestation did not improve cow reproduction or calf performance. Protein supplementation is not necessary for cows grazing cornstalks, given they begin the grazing period in adequate body condition (BCS greater than or equal to 5).
An October 24, 2017 article on the University of Nebraska web site (https://cropwatch.unl.edu/2017/impacts-cattle-grazing-corn-residue) cites a 16-year study that looked at the impact on soil health from cattle grazing corn residues. Grazing corn residues did not cause any negative effects on soil properties, including soil bulk density and penetration resistance measurements. There were no differences in corn yields on continuous cornfields comparing grazed to non-grazed management. The 16-year study also found that “grazing cattle on corn residues in the field could have a slightly positive impact on soil quality, such as soil microbial community structure. That's because grazing leaves more residues on the ground than clearing the field with machinery and adds nutrient- and microbe-rich manure to the fields.” The study authors also said that if producers do not over-stock and don’t graze when soils are wet then negative impacts are unlikely to occur.
Stocking rate should be determined based on corn bushel yield per acre and the average weight of cattle that will be grazing. The University of Nebraska has an excel spreadsheet, the “Corn Stalk Grazing Calculator” (http://go.unl.edu/7ejj) available on-line to help calculate a stocking rate on corn residue. A simple calculation is that each bushel of corn yield will leave about 16 pounds of corn leaves and husks. A common recommendation is to use a 50% utilization rate of that residue amount, so 8 pounds for each bushel of grain yield. Therefore, a 150 bushel per acre crop will leave 1200 lbs. of utilizable residue and a 175-bushel yield will leave 1400 lbs. of utilizable residue. For a 1400 lb. beef cow consuming 2.5% of her body weight in dry matter per day, this will result in 34 days of grazing per acre for the 150-bushel yield and 40 grazing days for the 175-bushel yield.
For more information, the University of Nebraska Extension has a very good publication entitled “Grazing Crop Residues with Beef Cattle” available on-line as a pdf download at http://go.unl.edu/4m7m, or contact the Wayne County Extension office at 330-264-8722.