Keeping an Eye on Nitrates in Plants Back »

Current weather patterns are bringing drought concerns throughout South Dakota. As such, it is more than appropriate for producers to think about the risk of nitrates in feed supplies and how it will affect their livestock operations.

Plants to Watch

It is well known that certain plants are nitrate accumulators and can contain toxic levels of nitrate when consumed by cattle and sheep. Some examples are:

  • Small grains
  • Corn
  • Sudangrass
  • Sorghum
  • Millet
  • Bromegrass
  • Orchardgrass
  • Tall Fescue
  • Sweet-clover
  • Alfalfa

Testing for Nitrates

Nitrates reduce animal performance, and if concentrated enough will lead to the death of some animals. Performing a Nitrate Quick Test will help producers to determine whether or not they might have problems with nitrates. If a test indicates they are at risk it may be prudent to further proceed with a laboratory analysis. The Quick Test results show if nitrates are present, or not present, in the plant.

Sampling Considerations

Proper sampling is critical for the best results. It is important to know that where livestock are allowed access to forage for a limited amount of time, testing the upper portions of the plant is recommended. If livestock are in a rotational system, sampling should focus more on the lower third of the forage where higher concentrations would be expected.

When dealing with nitrates never forget to:

  • Consider field variation before cutting.
  • Take multiple samples within your field (at least 15 samples).
  • ALWAYS cut at ground level.
  • When collected, samples should be placed in a paper bag. Deliver your samples to a lab the same day, or if you need to ship them use ice packs to prevent mold build-up (Be sure to ask your shipping company about their preferences in shipping material).
  • Consider nitrates in water as well since high levels can turn deadly for livestock.

Sample Analysis

Most of the preliminary testing can be done at any SDSU Extension Regional Center using a “Nitrate Quick Test Kit”. However, this test will only recognize the presence or absence of nitrates in plants. To see and understand the actual levels of nitrates, samples should be sent to a private laboratory.

Table 1. Guide for Nitrate Levels in Forage for Mature Cattle.

% Nitrate
(Dry matter basis)
Content of Nitrogen
(NO3-N) Dry matter basis
Percentage Percentage ppm  
Less than 0.44 0.0-0.10 0-1,000 Safe to feed if adequate feed and water are available.
0.44-0.66 0.1-0.15 1,000-1,500 Safe for non-pregnant animals. Limit 50% of total ration dry matter for pregnant animals. Animals may go off feed, have a slow drop in production, some abortions are possible.
0.66-0.88 0.15-0.20 1,500-2,000 Limit to 50% of total ration dry matter for all animals; may experience some symptoms and possible death.
0.88-1.54 0.20-0.35 2,000-3,500 Limit to 35-40% total ration dry matter. Do not feed to pregnant animals.
1.54-1.76 0.35-0.40 3,500-4,000 Limit to 28% total ration dry matter. DO NOT feed to PREGNANT ANIMALS.
>1.76 >0.40 >4,000 Toxic. DO NOT FEED.
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