Grazed crop residues are among the lowest cost feed resources. This advantage is a result of the agronomic cost of production being borne by the crop enterprise. For livestock producers, the major expenses associated with grazing corn residue include rent (for residue grazing only), fencing, water development, freight, and labor. These costs must be included in the beef production enterprise. Even with these added costs it may be possible to significantly
Corn residue is one of the most commonly harvested and highest quality residue forages. Under most conditions, one acre of residue, from a corn field that has been combined, can provide 30 to 45 days of grazing for a 1200-lb pregnant cow; however, this can be quite variable.
Utilizing strip-grazing can extend grazing time and make the quality of the diet more uniform over the grazing period. By limiting access to only a small portion of the field, the cattle are forced to consume residual corn and both the high- and low-quality forage components of the residue. Generally, a single strand of electric fence is sufficient to control grazing.
When determining the appropriate stocking rate and grazing time, it is important to consider the amount of residue that will be trampled and wasted in the grazing process. Research indicates that cattle grazing a whole field will utilize only 20% of the residue. This percentage can be substantially higher when fields are strip-grazed. The nutritional quality of grazed corn residue is quite high early in the grazing period; approximately 70% TDN and 8% crude protein, then will gradually decrease over time to approximately 40% TDN and 5% crude protein. This reduction is a result of the cattle selecting the highest quality feeds first and a weathering, or leaching of nutrients from the residue over time. Cattle will first consume any grain that remains in the field. Then they will shift their preference to leaves and husks and finally cobs and stalks.
As the nutritional quality of the corn residue decreases, producers will need to provide supplemental protein. The microbial population requires rumen degradable protein sources, commonly found in plant proteins, to effectively digest fiber. Non-protein nitrogen sources, such as urea and biuret, should be avoided. These nitrogen sources require the presence of readily fermentable carbohydrates to be utilized effectively. Unfortunately, once the grain has been consumed, the residue is essentially devoid of readily fermentable carbohydrates.
To determine when supplementation is necessary, producers should watch the manure from the cows. As the corn in the manure begins to disappear, it is time to begin protein supplementation. Generally mature, pregnant beef cows should receive 0.5 to 1 lb of supplemental protein from a natural source. Common protein sources include alfalfa, oilseed meals, and various alternative feeds. Commercial protein supplements are also acceptable.
Corn residue is also quite low in most minerals, especially calcium, phosphorus and vitamin A. As a result, a well balanced vitamin and mineral mix should be provided free-choice. Keep in mind that many of the feeds used as protein supplements will provide significant amounts of calcium and(or) phosphorus and may reduce the need for additional supplementation. However, vitamin A and white salt should be provided at all times.
Producers that elect to graze corn residue will likely be faced with two significant challenges, fencing and water. Many crop fields in the Upper Midwest do not have perimeter fencing; however, it is relatively easy and inexpensive to purchase and erect temporary fencing. As long as there is some grain, leaves and husks remaining in the field, a single strand of electric fence attached to temporary posts will be sufficient. Once the cattle are forced to consume stalks and cobs, they will likely begin to challenge the fences.
For most producers, hauling water is the only option for getting water to cattle grazing corn residue. However, if grazing residue is to become a normal part of the production system, it may be cost effective to develop water supplies nearer to the corn fields. This is a decision that will have to be weighed out on an individual basis.
Grazing corn residue also brings a slight risk for digestive disturbances in the cattle. Nutritional disorders such as bloat, acidosis, and founder can occur in cattle grazing corn residue. However, the risk for these conditions will vary greatly with the amount of grain in the field. Producers can help alleviate concerns by providing the cattle with increasing amounts of grain for 10 to 14 days prior to turning them out on the residue. This practice will help the rumen microbial population adapt to a higher grain diet.
Another potential health concern is nitrate toxicity, a potentially deadly disorder in beef cattle. It is generally accepted that the highest nitrate concentrations in a corn plant are in the lowest 18 to 24 inches of the stalk. As discussed previously, the stalk is near the bottom of the list of preferred feeds for cattle grazing corn residue. Thus, unless the fields are grazed extremely heavily, nitrate toxicity under grazing conditions is unlikely. The risk for nitrate toxicity is greater in drought conditions.
Grazing corn stalks offers beef cattle producers a tremendous opportunity to extend the grazing season and reduce winter feed costs. With a small amount of management and labor, one acre of corn stalks can provide a mature, gestating beef cow with 30 to 45 days of feed and forage. Furthermore, all of the expenses related to corn production are borne by the corn enterprise, so the cost of grazing residue is minimal. Beef cattle producers that do not raise crops should investigate rental arrangements with neighboring crop producers. Considering the many advantages grazing corn residue has for beef producers and the removal of corn and residue for crop producers, it appears that grazing corn residue can be a win-win situation.