However, despite all of this, there is still the risk of the weather turning against you. Weather events in the weeks, days, and even hours leading up to the harvest can ruin your best efforts. It can transform a carefully raised feed source into a nutritional time bomb. If you are not careful, it can not only reduce your production. Still, it can also endanger the lives of your animals.
Times of extreme stress, like currently with the drought, can cause a build-up of nitrates. While consuming some of them is not bad for your animals, if they eat too much of them, then it can become deadly. Here are some things to look for to prevent this from happening.
What causes nitrate toxicity?
All plants contain some nitrates, but things like drought can raise the number. Nitrogen is an integral part of the proteins required for growth but needs balanced measures of sunlight, water, and nutrients. Plants have developed the ability to stockpile nitrogen during times of plenty to use during that time. When things are not good, they accumulate it until the growing conditions have improved.
Typically nitrogen will be stored in the bottom one-third of plant stems, waiting to be needed for new leaf and stem formation. Research from Oklahoma has shown that the lower 6 inches of the stem in pearl millet contain three times as much nitrate as the top part of the plant. So as you can imagine allowing animals to graze on short grass is terrible in more ways than one. One is that it could be better for the overall condition of the range. The second is that it makes your animals more susceptible to nitrate toxicity.
All in the rumen
Nitrate itself is not particularly toxic to ruminants when consumed at normal levels. When nitrate-containing forages are consumed, it is converted in the rumen into ammonia and used by the microbes there as a protein source. A by-product of this is the creation of nitrite, which is where you get the problems if it accumulates too much.
When too much of it is built up, nitrite will enter the bloodstream, binding to red blood cells. What this does is clog the sites needed for oxygen transport. Plugging the sites means that nitrate toxicity leads to suffocation because the animal is starved of oxygen.
Testing is an excellent way to know how much is present in your forages. Forage testing labs report nitrate results in different ways. The jest is that the tests depend on the unit being presented. The results you can get can be based on nitrate (NO3), nitrate-nitrogen (NO3-N), or potassium nitrate (KNO3). I have included a table to give you an idea of what the breakdown can look like.
Some forages are more susceptible.
While all of your forages will have some build-up of this, some types are more prone to have this toxicity problem. Sorghum varieties, such as Sudan and sorghum-sudan hybrids, are part of this list. Corn, millet, and perennial grasses can also cause you some problems. Some weeds like jimsonweed, Johnson grass, and pigweed can also accumulate nitrates.
Photo courtesy of Drovers Magazine
Nitrates are usually highest in young plants and then decrease as the plant matures unless growth stress occurs. These stressors can cause growth to decline while continuing to stockpile nitrates. While more immature plants have this problem, mature plants can have excessive concentrations if both environmental and soil conditions are favorable.
Too much fertilizer can also cause this problem to pop up. Plants that have been fertilized typically have higher levels than nonfertilized ones. To keep this from happening, it is essential that you have your forages tested regularly and follow the recommendations on your soil test.
Symptoms of nitrate toxicity
As I mentioned earlier, nitrite binds to red blood cells stopping oxygen from getting to the lungs. As you may remember from Biology class, oxygen is essential for living organisms. Without it, the animal will die pretty quickly.
Because of the lack of oxygen, labored breathing is another symptom this is occurring. Muscle tremors, weakness, lack of coordination, diarrhea, frequent urination, and dark red blood are other typical symptoms.
Some other symptoms can include:
- bluish/chocolate brown mucous membranes
- rapid/difficult breathing
- noisy breathing
- rapid pulse (150+ per minute)
- salivation, bloat
- weakness, coma, death
- pregnant females that survive this may abort due to a lack of oxygen in the fetus
One problem people face with this is that the symptoms are similar to prussic acid poisoning. Add to the fact that drought conditions cause both of these, and you can easily misdiagnose your animals. A blood test can quickly tell you if it is prussic acid or nitrate. With prussic acid, the blood will be cherry red, whereas it will be a darker, almost chocolate brown color with the other.
How quickly this kills your animals is another problem when dealing with this. Once toxic levels are consumed, death can occur between 30 minutes to 4 hours. With how quickly it kills, treatment is doubtful, and it serves more as a warning than as a possible diagnosis.
Prevention and Treatment
As I just mentioned, death can happen pretty quickly, so treating it is highly unlikely. Another issue is that there are not really any good options out there either. So with those two, prevention is the key here.
Testing your forages is one way to keep nitrate toxicity from happening. Many county extension offices will have quick tests available to test the presence of any nitrates. Use caution in your feeding programs when known plants are dealing with stress before and after harvest.
Some more steps you can take to reduce nitrate levels in forages:
- Raise the cutter bar 6 inches or more above the ground
- Wait 3-5 days or more after a “good” rain for plants to regrow before grazing
- Increase residual grazing and/or harvest height
- Make silage, which will cause forages to lose 25%-50% of nitrates
- Slowly increase levels in feed
- Mix with non-nitrate toxic forages to “water down” the amount
Properly handling new growth is vital in keeping this at bay. I went into detail on how you can help your pasture bounce back from drought in a previous article, “How to bring a pasture back from drought.”