This year’s drought is having a negative impact on the corn crop in most of the U.S., including Michigan. The intensity of the drought varies widely across the state. However, there will be thousands of acres of Michigan’s corn crop that will be unfit for harvesting for grain, but may be suitable for harvest as corn silage.
Chopping drought-damaged corn for corn silage can be a good strategy if producers keep several factors in mind and properly educate themselves on the major issues influencing this decision. Harvesting drought-damaged corn for silage presents a wide range of issues. Very importantly, some of these issues pose potentially lethal situations to both humans and livestock. This article is designed to educate producers concerning these issues so they can make an informed and logical decision which takes these factors into account and reduces the associated risks and dangers.
Quality and Yield Issues: Drought-damaged corn almost always yields less dry matter per acre than normal corn. Therefore, economic considerations play a key role in making the decision whether or not to harvest drought-damaged corn as silage. Economic considerations will be addressed in a follow-up article. Be aware that yield is very difficult to estimate. A “thumb rule” is that yields of drought-damaged corn for silage are one ton of dry matter per foot of corn plant height. Drought-damaged corn silage may contain 60-100 percent of the nutrient value of normal corn silage. Research at Michigan State University during the 1988 drought indicated drought-damaged corn silage had increased NDF digestibility. Drought-stressed corn silage generally has more fiber and less energy than normal silage, but may have up to 1-2 percent more crude protein. Even though drought-stressed corn silage requires increased grain supplementation, overall milk yield is not necessarily reduced.
Potential Problems: The major potential problem with drought-damaged corn silage is the excess accumulation of nitrate-nitrogen in the harvested plant material. When the nitrate ion (NO3) is ingested by ruminants it is converted to the nitrite ion (NO2), which is rapidly absorbed into the bloodstream. Here it binds with hemoglobin in red blood cells which dramatically reduces the oxygen-carrying capacity of the blood and may result in asphyxiation and death of the animal consuming the excess nitrates.
Drought-stressed corn silage high in nitrate levels also has the potential to produce deadly nitrogen-based silo gases that are extremely dangerous to humans and livestock. These deadly gases are produced in all types of storage structures. Therefore, extreme caution must be exercised for at least three weeks following harvest and silo filling. Even though most corn silage is now stored in bunkers, don’t assume these toxic gases do not present a danger. They may still accumulate in low lying areas near bunkers and pose a deadly hazard to humans and livestock that venture into these areas.