Forage Nitrate Testing and Making Feeding Recommendations Based on the Results

Kern S. Hendrix
Professor Emeritus
Department of Animal Sciences
Purdue University

Several areas of Indiana have experienced lack of adequate rainfall and high temperatures in the mid-late summer growing season this year.

The normal process for conversion of nitrate (NO3) into plant proteins can be slowed when plants are subjected to stress such as lack of moisture. As a result, excess nitrate can accumulate. Forages such as corn, sorghum, and sudangrass are most likely to accumulate nitrate followed by oats and other small grain crops, followed by grasses. Legumes are less likely to accumulate nitrate. In all cases, the lower stem of plants is where the greatest nitrate levels are found. Forage feeding method influences the degree of risk from nitrate toxicity. Feeding greenchop forage is the highest risk followed by grazing, followed by hay. Silage feeding is the least risk, as significant amounts of nitrates are lost or converted to other compounds during the ensiling process.

If there is concern about the possibility of elevated nitrate levels in forage crops, cattle producers may wish to have a nitrate analysis done.

Fresh, dry or ensiled samples may be submitted for assay. Submit one to two quarts of chopped forage in unsealed paper or plastic bag(s). Listed below are names and addresses of laboratories that perform nitrate assays on forages. Cost will be in the range of $10.00 to $15.00 per sample. Turnaround time is within a few days in most cases. For shipping, it is recommended to use a carrier that provides next-day delivery service.

Laboratories may report results differently. It is important that results be evaluated on a dry matter rather than as-fed basis. Methods in which nitrate levels are commonly expressed and recommendations for feeding are shown in the table "Cattle Feeding Guidelines for Forages Containing Varying Levels of Nitrate".

Animal Disease Diagnostic Laboratory
1175 ADDL
Purdue University
West Lafayette, IN 47907-1175
Phone: 765-494-7440
FAX: 765-494-9181

A&L Great Lakes Laboratories
3505 Conestoga Drive
Ft. Wayne, IN 46808-4413
Phone: 260-483-4759

Sure-Tech Laboratories
2435 Kentucky Avenue, Bldg. 9
Indianapolis, IN 46221
Phone: 317-243-1502
FAX: 317-243-1527

Cattle Feeding Guidelines for Forages Containing Varying Levels of Nitrate1

Method of Reporting Nitrate Level





For Feeding

Percent of Forage Dry Matter


0.0 - 0.44

0.0 - .10

0.0 - 0.73

Safe to feed in all situations.

0.44 - 0.66

0.10 - 0.15

0.73 - 1.10

Safe for non-pregnant animals. Limit to 50% of diet dry matter for pregnant animals.

0.66 - 0.88

0.15 - 0.20

1.10 - 1.47

Limit to 50% of diet dry matter.

0.88 - 1.54

0.20 - 0.35

1.47 - 2.57

Limit to 35-40% of diet dry matter. Avoid feeding to pregnant animals.

1.54 - 1.76

0.35 - 0.40

2.57 - 2.93

Limit to 25% of diet dry matter. Avoid feeding to pregnant animals.

over 1.76

over 0.40

over 2.93


To convert from parts per million (ppm) to percent, move the decimal point four places to the left (i.e. 8800 ppm = 0.88%).
1 Source: Sniffen, C.J. and L.E. Chase. 1981. Nitrates in Dairy Rations, Department of Animal Science, Cornell University.

August 2007

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