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Corn+Soybean Digest

SDSU Publication Tells How to Determine The Value of Drought-stressed Corn

A South Dakota State University (SDSU) publication helps producers find the feeding value and dollar value of corn grown under drought conditions. SDSU Extension Dairy Specialist Alvaro Garcia said the Extension Extra 4018, "Determining the Value of Drought-stressed Corn" can be found on the SDSU drought Web site,

or from any county Extension office. Drought-stressed corn or corn that is unpollinated will produce little or no grain crop for the crop farmer to sell, but producers can use the unpollinated corn for silage. On a dry matter basis, the drought-stressed corn may be nearly equal in feeding value to normal corn silage. The best way to determine the feeding value of drought-stressed silage is to test the forage. Forage analysis is useful for buying, selling, or using the silage for ration balancing. Buyers of drought-stressed silage high in crude protein and slightly lower total digestible nutrients values may be willing to pay almost the same price as they do for well-eared silage of equal dry matter content. One common pricing formula for silage of approximately 30 percent dry matter is to multiply the market price of corn by six, then add $10-12/ton to cover the costs of harvesting and storing the silage. The market price of corn is the price the livestock producer must pay for the grain. To determine the price of silage based on feeding value, approximately one ton of 30 percent dry matter silage is equal to one-third ton of hay or 8-10 bu of corn. Petersen's constants for corn and soybean meal provide a convenient way to determine feeding values for many feeds. In the Petersen method, the value of any feed depends on the price of a base carbohydrate-rich feed (corn) and the price of a base protein-rich feed (soybean meal). The constant for corn shows the extent to which the price of corn affects the value of the given feed in question (drought-stressed corn silage in this case). The constant for soybean meal shows the extent to which the price of soybean meal affects the value of the given feed in question. The Feed Valuation Template developed by Pennsylvania State University Cooperative Extension uses Petersen's constants along with adjustments for fiber requirements to determine the value of feeds relative to shelled corn (energy), 44 percent soybean meal (protein), and average analysis legume hay (forage). Since corn silage is an energy feed, the value of corn silage will increase as the price of shelled corn increases and soybean meal and hay prices remain constant. The value will decrease as the price of soybean meal increases and the prices of corn and hay remain constant. One objective of least-cost ration balancing is to provide a specific level of nutrients for the least amount of dollars while maintaining animal performance. To best determine the value of silage in a dairy operation, a customized least-cost ration program is suggested for individual situations. The output from least-cost rations can be a valuable tool for pricing feeds relative to each other for a given level of animal performance. The economic value of feeds used and not used in the ration are calculated based on the price and nutrient content of all feeds and how they best meet the nutrient requirements of the animal. Producers with adequate hay supplies should use the lower hay price to value the silage. If hay supplies are limited, the higher hay price should be used. The increasing value of the silage as corn prices increase is an expected result, since the silage and corn are competing sources of energy. Regardless of the pricing method, both the seller and buyer must value the silage according to how they will use it in their operations. Producers can use silage for forage, and crop farmers can use the drought-stressed silage to recover some of the cost of producing the crop. Drought-stressed corn can be valuable, but there can be problems related to its use:

  • Because drought-stressed corn has the potential to accumulate nitrates, nitrate toxicity of animals is possible.
  • Nitrogen oxide gas may build up during fermentation of drought-stressed silage. Precautions must be taken when ensiling and when removing the silage from the silo for feeding.
  • The use of non-protein nitrogen (NPN) on drought-stressed silage is not recommended.
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