By Rory Lewandowski
A lot of acres of corn have been harvested in our area. The residue that remains after corn grain harvest includes husks, leaves, stalks, and some corn grain. That residue represents a potential feed source for ruminant livestock that can be utilized to decrease stored feed costs and /or to stretch stockpiled forage. Livestock in mid-gestation can do well on corn residue without additional supplementation provided they are not forced to begin eating the actual corn stalks as a significant portion of the diet. Beef cattle are particularly well suited to graze corn residue. A 2012 Nebraska Beef Cattle Report included the topic of “Supplementing Gestating Beef Cows Grazing Cornstalk Residue” (http://beef.unl.edu/nebeefreport2012). This was a 5- year study that evaluated the effects of protein supplementation to beef cows grazing corn residue in late gestation. The study concluded that “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).”
The nutritional value of corn residue varies depending upon how the residue is grazed, the lag time between harvest and grazing and environmental conditions. 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 when there are ears of corn or corn grain to select. Over time the nutritional content will decrease to 5% CP and 40% TDN. This is a typical pattern where livestock are provided with an entire field or a large section of a field and allowed to graze over an extended time period of 30 to 60 days. The nutrient content decreases because livestock are selecting the highest quality, most palatable portions of the residue first and because nutrient content decreases as the residue weathers and soluble nutrients are leached out.
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. According to the Extension beef specialists who authored this publication, there will be between 13 and 16 pounds of corn leaf and husk on a dry matter (DM) basis available for every bushel of corn produced. Utilization rate of this residue is generally around 50 percent. If we use 14.5 lbs. / bushel and a yield of 160 bushels/acre along with a 50% utilization rate, there are 1160 lbs. DM of leaves and husks per acre available for consumption. A 1300 lb. cow consuming 2.3% of her body weigh needs about 30 lbs. of DM per day. So this 1160 lbs. /acre will provide about 38 days of grazing for this cow. 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 some helpful tools to calculate the stocking rate. The “Corn Stalk Grazing Calculator” (http://go.unl.edu/7ejj) is an Excel® spreadsheet that is available for download or as a Mobile App (http://beef.unl.edu/mobile-apps).
There have been reports this year of weak stalks and corn ear shanks that may result in higher harvest losses and more corn grain in the residue. This can be a cause for concern when grazing corn residue because animals can consume too much grain which can lead to digestive problems, acidosis and even founder. In these situations, there should be a plan or strategy on how to utilize these fields without causing livestock performance issues. Fara Brummer, area livestock systems specialist at the Central Grasslands Research Extension Center with North Dakota State University, has the following suggestions to reduce the risk in these situations:
- Carefully consider the class of cattle allowed to graze cornstalks. Cattle new to eating corn (calves or yearlings) will take some time before they actively seek corn. This delayed consumption can serve as a good acclimation period. Cows with experience grazing corn aftermath will look for grain and downed ears immediately when turned out. Consider grazing calves, yearlings or cull cows on fields to clean up some of the corn before turning out pregnant cows.
- Provide some type of ionophore-containing supplement.
- Adapt cattle to corn before turning out to graze corn stalks. Start with 3 pounds daily and move up to 7 or 8 pounds during a 10-day period before turnout.
- Cross-fence fields to minimize the amount of the field that cows have access to at any one time. Early in the grazing period, this may mean moving the fence daily.
- Do not turn hungry cattle out to graze. Provide good-quality hay so cattle don’t over eat corn immediately. Also, set out bales of good-quality hay in corn fields so cattle have access to hay while grazing corn.
Corn residue represents another opportunity to extend the grazing season. Those livestock managers willing to find a way to use corn residues by utilizing temporary fencing and water systems can reduce the amount of stored forage needed for winter feeding and reduce production costs.
Source: osu.edu