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Click for more information on using drought-stressed forages
Don't graze or feed drought-injured crops with cattle or other ruminant livestock unless they have been tested for nitrates. All forage-testing laboratories contacted in the High Plains Region have reported that a record number of the samples analyzed have toxic nitrate levels. Some labs have reported that more than 60% of samples have tested higher than the 5,000 parts per million considered the upper limit safe for nitrate nitrogen in livestock forage. Furthermore, they are reporting extremely high levels in some samples, much higher than they have ever found in previous years.
It should be noted that the nitrates will not affect the corn on the ear for either sweet corn, or corn used for human consumption (corn meal, corn flakes, etc.), or livestock feeds and other corn grain products. Nitrates accumulate in plant stems and to a lesser degree in leaves because normal growth of corn and other forages is been stunted and grain production severely reduced or stopped. The roots, on the other hand, continue to pick up soil nitrogen at nearly normal rates. Therefore, the plants concentrate the same amount of nitrogen into smaller stalks and leaves. Finally, nitrate poisoning from forages primarily affects cattle, sheep, goats and other ruminant animals. Non-ruminants such as horses, swine and rabbits can tolerate a much higher level of nitrate.
Crop and livestock producers should take these warnings very seriously because nitrate poisoning can kill cattle and other livestock very quickly. Nitrate concentrations can vary across small areas of a field or pasture so that forages that may be good in one area may be toxic just a few feet away. Weeds, such as pigweed, are especially prone to pick up and concentrate nitrates. For these reasons sampling for nitrate toxicity in a field or pasture is nearly impossible. Taking samples in baled or ensiled forages using approved probes and sampling techniques are the only reliable methods for minimizing sampling errors. However, one bale or even a portion of a bale may contain forages and or weeds that can have high enough nitrate levels to poison livestock.
As a result of these conditions, Colorado State University Extension provides the following guidelines regarding harvesting and feeding drought damaged crops:
- Don't graze crops such as corn, sunflowers, sorghum, or millet that have been abandoned due to drought stress. The risks are just too great this year.
- Test any of this years forages to be fed to livestock for nitrate levels (always recommended).
- Test livestock water sources for nitrates because nitrate toxicity results from total daily consumption from feed and water. Feeds that may be safe under normal conditions may cause nitrate poisoning when water also is moderate to high in nitrate.
- Use approved sampling methods for testing baled or ensiled forages. Taking at least the number of probe samples recommended and perhaps even more. Err on the side of caution.
Forages that test at moderate risk levels for nitrates can still be used. These forages can be mixed with lower testing lots to produce a blend with a safe nitrate level. Increasing the energy content of total feed consumption with grain supplements also can reduce the nitrate risks for a forage. To be on the safe side it is advisable to consult with a nutritional consultant in making these feed adjustments.
A final piece of advice is to carefully compare the costs of labor, fuel, and equipment depreciation in harvesting forages from these drought-damaged crops against their potential economic returns to the farm operation. Forages that are risky to sell or feed or have low market value may have more value left in place for helping to capture and retain moisture for the next crop and to help build soil quality.
Contact your local county or area office of the Colorado State Extension network for more information on nitrate toxicities, interpreting nitrate test levels, the proper method for taking a forage sample and general information of using high-nitrated feeds. Go here for a list of certified forage-testing laboratories.
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