As corn harvest progresses, don't overlook corn stalks as a feed resource. Corn residue can meet the nutrient needs of ruminant livestock that are in early to mid-gestation. The University of Nebraska has done a lot of research on the topic of grazing corn residue. A University of Nebraska study conducted over a 5 year period from 2004 to 2009 measured corn grain left in the field after harvest. An average of 1.0 bu/acre was available for livestock grazing. A 2004 Nebraska beef report on corn stalk grazing included more information about the make-up of corn residue. Generally, stalks account for 49% of the residue dry matter, leaves 27%, husks 12% and cobs another 12% of the residue dry matter. Livestock typically consume any corn grain first. After the grain, plant leaves and husks are eaten and the last portions of residue eaten are cobs and stalks.
Strip grazing across a corn field can even out the nutritional quality because livestock will be forced to consume both the higher and lower quality components of the residue within a given grazing period before the fence is moved to provide a new strip. According to a South Dakota State University Extension publication entitled "Grazing Corn Stalks" a crude protein (CP) content of 8% and a total digestible nutrient (TDN) content of 70% can be expected early in the grazing period. Over time the nutritional content will decrease to 5% CP and 40% TDN. A 2004 Nebraska beef report on corn stalk grazing listed the average TDN value at 54-55%.
The University of Nebraska has a corn stalk grazing calculator spreadsheet available at: http://beef.unl.edu/learning/cornStalkGrazingCalc.shtml. I entered a 165 bushel/acre corn crop and an animal weight of 1400 lbs. According to the calculator, using a 50% harvest efficiency, one acre of this corn stalk residue could provide up to 60 grazing days for that 1400 lb. beef cow.