The southern half of Alabama is experiencing severe drought conditions, which can lead to nitrate problems for beef cattle. Many producers begin to look for alternative sources of feed for the cow herd and one possibility that comes up is to turn the cows into the corn fields which have been deemed a loss from the standpoint of grain production. Nitrate levels in the corn plants should be considered before turning the cows in. Cattle will generally graze the upper stalk, leaves and ears first. Fortunately, nitrates are usually highest in the lower stalks and lesser concentrations exist in the leaves and upper stalk. The best way to proceed is to actually take some representative samples of the corn and send them to the Forage Testing Laboratory at Auburn. Take several random samples from the field of both lower and upper stalks, then pool the samples such that you have one representative sample of the upper portion and one representative sample of the lower portion. Send these two samples to the Forage Testing Lab, Funchess Hall, Auburn University, AL 36849. Indicate that you want a nitrate analysis and the fee is $6.00 per sample.
Pay particular attention to the way in which the nitrate concentrations are reported. Some labs report it as nitrates (NO3) and some report it as nitrate nitrogen (NO3-N). Nitrate nitrogen is how the AU Forage Lab will report it. To convert nitrate to nitrate nitrogen multiply the nitrate level by .23.
The following guidelines can be used once the level of nitrate nitrogen has been determined. 0 to 575 ppm NO3-N: Generally considered safe.
575 to 1150 ppm NO3-N: Use caution. Allow cattle to graze this forage for less than 2 hours after having access to hay for 3 to 4 hours. Do not feed with liquid feed or other non-protein nitrogen sources. Be careful with pregnant and young cattle.
1150 to 3450 ppm NO3-N: Dangerous level. Limit to one-fourth of the total intake. Adequate levels of Vitamin A should be provided.
greater than 3450 ppm NO3-N: Potentially fatal. Can be used in very limited amounts but will need to be mixed with other feeds or hand-fed.
In summary, the best policy is to have the corn tested for nitrate prior to use by cattle. Other potential problems will be from hay that will be produced when (if) it rains. That hay will be potentially high in nitrate levels so it would be a good idea to have this year's hay tested, if any is ever produced.
Animals experiencing nitrate toxicosis may show signs of labored breathing, muscle tremors and a staggering gait, after which the cow falls down, gasps for breath and dies quickly. The cause of death is lack of oxygen and the membranes of the eyes and mouth are usually bluish while the blood will be reddish brown and turns brighter red once exposed to the air. If prompt action is taken some animals can be saved so it is advisable to call a veterinarian as soon as possible.