by: Stephen B. Blezinger

Part 2

In the previous part of this series we began a discussion of the potential problems that can be encountered if cattle graze forages that are high or moderately high in nitrate. Coupled with potentially high nitrates in water sources this situation can create real problems for the animal and the producer. The observation was made that this year, in many parts of the country, conditions are particularly good for the accumulation of nitrates in certain forages especially remaining corn stalks and sorghums. Additionally, with forages in short supply and producers struggling to meet their herd forage needs, attempting to graze or even purchasing affected forages or hays tends to become more common.

At the end of Part 1 we were discussing taking samples for analysis of both forages and water. We'll pick up here where that discussion left off and examine more of the particulars about dealing with samples and interpreting the assays that the producer may get from the lab.

The Lab Results

Results of analysis on the same sample of feed can vary considerably due to limitations of chemical test used. Variations of 100 parts per million (.01%) in a feed are well within a range of expected errors. Results of tests on feeds containing small amounts of nitrate might appear large but could be within the normal tolerance of test used. For example, if a report on one sample of silage shows 200 ppm of NO3-N and another report shows 300 ppm of NO3-N, they are for all practical purposes the same. If reported as percent, the variation does not appear as large. As indicated, in the above example, the percent NO3-N is .02 and .03.

Interpreting and Using Nitrate Reports

Results of nitrate analysis can be confusing because of the variation in methods of reporting. In the chemical analysis for nitrate, the actual element determined is the oxidized nitrogen. However, values may be reported as percent nitrate (NO3), or nitrate-nitrogen (NO3-N). Efforts have been made to have nitrate analysis and tolerances for safety uniformly reported as nitrate-nitrogen on 100 percent dry matter basis. However, depending on the lab, reports may still be given as nitrate or nitrate-nitrogen and may be reported as either percent or as ppm. Table 1 below can help convert the different reported forms.

For example:

0.1% NO3-N is equal to 0.44% NO3 (.1 x 4.4)

0.44% NO3 is equal to 0.1% NO3-N (.44 x .23)

Toxic Effects of Nitrate

With all the biological variation that can exist in both plants and animals, it can be challenging to develop specific guidelines that fit all conditions. Safe levels of nitrate are not specifically known for all the various livestock feeding conditions. However, some general guidelines are needed. As such the following guidelines have been developed.

There are two kinds of possible toxicity that are of concern: (1) Acute or lethal and (2) Chronic or non-lethal.

Again, remember that these are only guidelines and that many conditions can affect the situation to make these levels more or less problematic.

Reports on Nitrates in Water

Nitrate content of water is usually reported as ppm but both NO3 and NO3-N are used. Conversion factors are the same as those in table 1.

Example: 10 ppm of NO3-N is the same as 44 ppm of NO3 (nitrate).

If reported as milligrams per liter (mg/1), this is the same as ppm. Guidelines for the use of drinking water with known nitrate content are presented in table 3.


High nitrate levels can create problems for animal health and performance. Recognizing the potential problems in advance is important to avoiding any losses in performance or animal life. The previous guidelines can help the producer recognize some of these issues. Remember it is always best to be cautious if you have any reason to suspect a problem.

Finally, as we approach the Christmas season, from our family to yours, I'd like to wish you all the most blessed of Holidays as we celebrate the birth of our Savior, Jesus Christ. Have an enjoyable and safe holiday and the happiest of New Years!

Dr. Steve Blezinger is a management and nutritional consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711, Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at sblez@verizon.net. For more information you can visit follow us on Facebook at www.facebook/reveillelivestockconcepts.

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