It is hard to pick up a livestock magazine today without reading about the impact of drought in much of the US. Grain markets have been responding daily with large increases and cattle markets have soften considerably given the current conditions. As producers evaluate the amount of forage they have in their pastures and that which will help them make it through the winter, the desire to put up hay or ensile any fiber source they can find, can lead to forages with hidden dangers. Nitrate poisoning is one that can affect annual crops that may be cut for hay or put into silage given the harsh growing conditions that many are facing. Below are some general guidelines when dealing with the potential for Nitrate poisoning:
- Common forages susceptible to Nitrate accumulation include but are not limited to: corn, barley, oats, millet, rye, sudan grass, sweet clover, soybean, wheat
- Plant growth closest to the ground have the highest levels of Nitrates
- Raise the cutter bar above 6 inches to avoid highest accumulations of Nitrates
- Younger plants have highest levels of Nitrates compared to more mature plants
- Nitrates accumulate in plants when normal growing conditions are interrupted such as during a drought, frost or periods of cool weather
- Nitrates are converted to Nitrites and finally to Ammonia which is the normal pathway in Nitrogen metabolism in plants. Excessive levels of Nitrates can lead to an accumulation of Nitrites in the rumen which is the most toxic form and can lead to toxicity
- Nitrite is absorbed into red blood cells and interferes with the Oxygen carrying capacity of Hemoglobin which leads to suffocation in livestock
- Dilute forages known to contain high levels of Nitrate with forages that are low in Nitrates
- If high Nitrate forages must be fed, gradually increase the amount fed in the diet so that cattle will adapt to the increased Nitrate levels.
- Try to avoid over grazing of forages that are high in Nitrates so livestock will not be forced to graze lower plant parts that contain increased Nitrate levels
- Fill cattle up on low Nitrate forages prior to introduction onto high Nitrate pastures to limit their exposure to large amounts of high Nitrate forages
- Limit the time that cattle are grazing or are exposed to high Nitrate pastures when first introduced to these pastures
- Ensiling forages can help reduce the Nitrate levels of forages through the fermentation process
- Cattle that are in thin condition or that are in poor health are more susceptible to Nitrate toxicity
- Don’t graze cattle after a killing frost for at least one week if possible with forages high in Nitrates
- Observe cattle frequently when introducing them to forages high in Nitrates
There are numerous Extension bulletins available on guidelines for grazing forages with high Nitrates for the various regions of the country. I have listed a few common guidelines that you should consider to help avoid or significantly reduce cattle losses from Nitrate poisoning. Drought conditions followed by some light rains can interrupt the normal Nitrogen metabolism of plants and result in forages that contain high Nitrate levels leading to toxicity.
Ruminant animals can deal with many feedstuffs resulting from the drought such as corn or small grains that fall short in crop production. These do not come without potential health hazards. Make sure you have your forages tested prior to feeding or pasture turn-out if you have any indications that Nitrate toxicity may be an issue. The value of cattle is too great to turn a blind eye.