Grazing Corn Stalks with Beef Cattle
By : Jessica A Williamson, Ph.D., Extension Forage Specialist and Tara L. Felix, Beef Extension Specialist,
In 2017, Pennsylvania harvested 920,000 acres of corn, which produced approximately 150 million bushels (161 bu/acre) of corn grain (USDA’s National Agricultural Statistics Service – NASS, 2018). For every bushel of corn, there are approximately 18 lb of stem, 16 lb of husk and leaves, and 5.8 to 6.0 lb of cobs left as residue (all on a dry matter [DM] basis) in the field (University of Nebraska – Lincoln, Beef Extension Program). Using these estimates, the state of PA produced enough husk and leaves in 2017 to feed more than 6 million Animal Unit Months (AUM1) – how many months 1, 1,000 lb grazing animal could graze. Six million AUMs would equate to more than enough residue to feed the entire PA beef herd during fall and winter.
While gaining winter feed is one benefit, there are several other potential benefits of incorporating corn residue into a beef cattle operation. For example, during corn harvest, there are always kernels that are dropped or lost from the combine. Cows grazing in the harvested corn field will consume most of this corn left behind on the ground, thereby reducing volunteer corn in the subsequent years. This reduction in volunteer corn is beneficial because volunteer corn is one of the most important yield robbers in the subsequent years’ soybean crop. Also, cattle grazing corn crop residue break down corn stalks more efficiently than simply weathering might. The cattle convert these corn stalks to manure, leaving carbon and nutrients on the soil, where crops can benefit from them. This is more efficient than baling corn stalks and feeding them at an offsite location. Baled corn stalks, while an excellent winter feed option in some cases, do require additional input costs (e.g. baling, storing, labor, etc.) when compared to simply grazing that corn crop residue in the field.
While there are several potential benefits of incorporating corn residue in to a beef cattle operation, some worry about compaction of the soil and subsequent yield losses. However, not only has research has shown no difference between grazed and ungrazed fields in subsequent yields (Nebraska Beef Report, 2001), but it has also demonstrated that on high-yielding fields, removing some of the residue by grazing may increase subsequent crop yield (Nebraska Beef Report, 2003).
Table 1. Nutritional content of corn crop residue
|Corn||Dry Matter (%)||Crude Protein Range (%)||Average Crude Protein (%)||IVDMD1 Range (%)||Average IVDMD1(%)|
|Grain||73||9.5 – 11.2||10.2||88 – 95||90|
|Leaf||76||6.2 – 7.5||7||41 – 65||58|
|Husk||55||3.0 – 4.0||3.5||63 – 72||68|
|Cob||58||2.1 – 3.8||2.8||59 – 65||60|
|Stalk||31||3.0 – 5.1||3.7||45 – 60||51|
1 In Vitro Dry Matter Digestibility (IVDMD) is approximately equal to total digestible nutrients (TDN). Adapted from: University of Nebraska – Lincoln, Extension (document EC278)
Strategies for Optimizing Residue Grazing
While corn crop residue can provide some additional grazing days to a beef system, there are some factors that must be considered to optimize the use of the residue. The nutrient of corn crop residue varies depending on the part of the plant that animals selectively graze (Table 1). Using managed grazing strategies can help force cattle to consume more uniform diets and improve their utilization of the residue.
For example, given access to an entire corn field, cattle will select and eat any grain still in the field first, followed by the husk and leaf (which are more palatable than stalks), and finally eat the cob and stalk. Thus, producers interested in grazing corn residue should consider implementing grazing management techniques , like strip grazing, which is a managed grazing system that involves giving livestock a fresh allocation of forage, usually controlled by the use of an electric fence, to maximize the use of the available residue. Results may improve if cattle are not forced to eat cobs and stalks.
While managed grazing of corn residue can help optimize the number of grazing days possible, it is always important to keep in mind how probable it may be. Weather can often be the major factor determining the actual number of grazing days in a given operation. Corn crop residue grazing works great after corn harvest until winter weather conditions start kicking in. In fact, most beef cows can successfully graze corn residue fields that have up to 4 to 6 inches of snow cover. However, cattle will not be able to graze fields that are covered with ice. Therefore, as many as 120 days could be possible, it could be just as likely that you may only get 45 days before a weather event halts grazing. Because of this reliance on the weather, always keep in mind the importance of having an emergency feed supply, such as hay or silage, for use in case severe weather does limit grazing.
Feeding in Corn Crop Residue in Various Cattle Systems
In addition to grazing strategies, managing corn crop residue for specific classes of cattle can also be beneficial. For instance, spring-calving cows grazing corn crop residue will have sufficient energy and protein to meet their requirements in mid-gestation. In addition, dry cows should easily maintain body weight, and may gain weight, in corn crop residue grazing programs because grazing corn crop residue supplies sufficient nutrients for this production stage. Unlike the cows, first-calf heifers in the 90 days prior to calving will need protein and energy supplementation to meet nutrient requirements if they are grazed on corn crop residue. Feeding, on a dry matter basis, 3.5 lb of whole soybeans, 4.5 lb of dry brewers grains, or 3.5 lb of dried distillers grains (DDGS) per head per day would meet this need. Salt, mineral, and Vitamin A supplements are recommended for all cattle grazing crop residue.
Fall-calving cows will also need additional protein and energy to meet their nutrient requirements when grazing corn crop residue. Because fall calving cows will generally be grazing corn crop residue less than 3 months after calving. Within the first 3 months after calving, cows have the greatest nutrient requirements and will need 4.5 lb per head per day of a supplement that is at least 30% protein and 90% total digestible nutrients (TDN) on a dry matter basis (whole soybeans are an option) in addition to the corn crop residue they are grazing. Alternatively, feeding, on a dry matter basis, 6 lb of dry brewers grains or 5 lb of DDGS per head per day would meet this need.
Spring-born calves weaned in the fall can also be wintered, or grown, on corn crop residue. Research has demonstrated that DDGS fed at 2 lb per head per day when calves are grazing corn crop residue will usually meet protein requirements to allow calves to achieve 1 lb of daily gain. Also, feeding whole soybeans at 2.5 lb per head per day or dry brewers grains at 3 lb per head per day will meet the same requirements.
Important Considerations to Keep in Mind
Regardless of the class of cattle grazed on corn crop residue, cattle turned into a harvested corn field will selectively consume all the corn grain left behind first. Thus, it is important to scout fields prior to grazing in order to determine the amount of corn present and to look for piles that could cause grain overload which can result in bloat or death in cattle. If there is more than 8 to 10 bushels of corn per acre on the ground, a grazing strategy such as strip grazing to control corn intake will be imperative to limit the corn grain intake.
It is also essential to recognize the variations in quality of the residue grazed throughout the season. While the quality of a grazed corn crop residue diet may start at approximately 70% TDN, it then decreases to as low as 45% TDN at the end of the grazing period. The rate of quality decline is dependent on stocking rate and environmental factors such as moisture, precipitation, and field conditions. Thus, because of these environmental factors, there is an advantage of letting cows graze during the first months after harvest (October, November, December), instead of using the field later in winter (January and February).
Calculating Stocking Density
Calculating an adequate stocking density, so you neither underfeed nor overfeed expensive supplements to certain classes of cattle, is imperative. The amount of grain, husk, and leaf available per animal will define stocking density and directly affect diet quality as these plant structures are highly digestible.
Grazing days and stocking density can be determined using the estimate of 50% utilization of the leaf and husk, to maintain some residue on the field to assist with erosion control and organic matter management and taking into consideration that some residue disappears by trampling and other factors. Therefore, 160 bu corn produces 2,560 lb (160 bu/acre x 16 lb per bu, as mentioned before) of leaf and husk per acre on a dry matter basis. Half of that (1,280 lb) of husk and leaf is available for the animal to consume. This would be equivalent to 1.88 AUM, or 1,280 lb of husk and leaf per acre at 50% use divided by 680 lb of feed per AUM. One AUM is the amount of forage required to sustain a 1,000 lb cow or equivalent for a month, and it has been determined that a 1,000 lb cow will consume 680 lb of dry mater monthly. This same acre would be able to provide feed for a 1,000 lb cow for 56 days (1.88 x 30 days). It’s important to mention that cob and stalk won’t meet nutrient requirements of the late gestation cow, and it would lose weight if kept in the field for a few more weeks.
Corn crop residue grazing is a viable and economical option for late fall and winter in Pennsylvania. Coupling corn crop residue grazing with byproduct supplementation can help keep winter feed costs low. Strategies to maximize the number of grazing days possible should be considered. With these strategies, beef farmers can extend the grazing season and keep productivity, even improve it with supplemental energy and protein according to various cattle systems.