Nitrate Poisoning in Cattle: How Much Is Too Much?

All plants can contain some nitrate, but buildup of nitrates to toxic levels in forage plants can occur. Nitrate is not particularly toxic to cattle, at normal levels, but how much is 'too much?' Forage testing laboratories report nitrate results in different ways. Guidelines for forage nitrate tests depend on the unit being presented. Results can be based on nitrate (NO3), nitrate-nitrogen (NO3-N), or potassium nitrate (KNO3). The toxicity levels are broken down in the table below.
All plants can contain some nitrate, but buildup of nitrates to toxic levels in forage plants can occur. Nitrate is not particularly toxic to cattle, at normal levels, but how much is 'too much?' Forage testing laboratories report nitrate results in different ways. Guidelines for forage nitrate tests depend on the unit being presented. Results can be based on nitrate (NO3), nitrate-nitrogen (NO3-N), or potassium nitrate (KNO3). The toxicity levels are broken down in the table below.
(Texas A&M University)

All plants can contain some nitrate, but buildup of nitrates to toxic levels in forage plants occur when they are under excessive stress. Certain plant species are more likely to accumulate nitrates. Certain weeds (such as pigweed), Johnsongrass, corn, sorghums, and Sudan grasses are the most common causes of nitrate poisoning, but any grass or weed with a high leaf-to-stem ratio can be a problem. Nitrates are usually highest in young plants and nitrates decrease as plant mature, unless growth stress is encountered. Stressors that cause abrupt decrease in plant growth such as lack of sunlight, drought and high temperatures, disease, or herbicide application can contribute to increased nitrates. Nitrate concentrations are usually greatest in the lower third of the plant stem, but can be found in leaves. Very little nitrate is found in flowers or stems. Nitrate is not particularly toxic to cattle, at normal levels. When nitrate containing forages are consumed the nitrate is converted in the rumen into ammonia and used by ruminal microbes as a protein source. An intermediate product in this process is nitrite, when too much nitrite is produced it is absorbed into the blood. The nitrite binds to hemoglobin in the blood, forming methemoglobin – a substance that cannot take up oxygen in the lungs for delivery to body tissues. Lack of oxygen in the tissues can cause abortions of calves and death. Nitrates may cause death within 30 minutes to 4 hours after symptoms appear.

Forage testing laboratories report nitrate results in different ways. Guidelines for forage nitrate tests depend on the unit being presented. Results can be based on nitrate (NO3), nitrate-nitrogen (NO3-N), or potassium nitrate (KNO3). The toxicity levels are broken down in the following table.

Nitrate Levels in Forage, Animal Response

Producers need to be aware of the feedstuffs they are using. It is important to use caution in your feeding programs when known nitrate accumulators are undergoing stress before harvest or grazing. If you are unsure, you need to send in a random sampling of your forage or hay to a testing center. Many county Extension offices have quick tests available for testing the presence of nitrates or prussic acid, it is good to test multiple forages and any samples showing presence of nitrates can be sent off to the lab for analysis of the concentration. Preventative measures should be taken to help prevent loss in your herd.

Refer to the Oklahoma State University Extension Fact Sheet, PSS-2903 Nitrate Toxicity in Livestock available.

On a recent SunUp TV episode from July 25, 2022, Dr. David Lalman and Rick Clovis, Pawnee and Osage County Extension Educator, offer management and forage testing advise for forage nitrates. 

 

Latest News

Biden Administration Restores Wildlife Protections
Biden Administration Restores Wildlife Protections

The U.S. Fish and Wildlife Service plans to reinstate rules protecting endangered plants and animals, action that would reverse changes made during the Trump Administration that weakened the Endangered Species Act.

Across Breed EPD Adjustment Factors
Across Breed EPD Adjustment Factors

EPDs from multiple breeds can be compared by adding/subtracting the appropriate adjustment factors to the EPDs resulting from the most recent genetic evaluations for each of 18 breeds.

APHIS Now Thinks Wild Birds Are to Blame for Highly Pathogenic Avian Influenza's Arrival on Four U.S. Dairies
APHIS Now Thinks Wild Birds Are to Blame for Highly Pathogenic Avian Influenza's Arrival on Four U.S. Dairies

The livestock industry continues to grapple with the first confirmed cases of HPAI in cattle, while federal and state agencies continue to assure consumers there's no concern about the safety of the U.S. milk supply.

Skills Survey Reveals U.S. Agriculture & Food Industry Workforce Needs and Gaps
Skills Survey Reveals U.S. Agriculture & Food Industry Workforce Needs and Gaps

U.S. employers report challenges in finding suitable job candidates with work-ready skills to fill open roles in ag. The AgCareers.com U.S. Skills Survey offers insights, data and trends to address skill development.

USDA Authorizes CRP Graze and Hay Donations to Wildfire Victims
USDA Authorizes CRP Graze and Hay Donations to Wildfire Victims

Conservation Reserve Program (CRP) participants can donate emergency grazing authority to ranchers in Nebraska, Oklahoma and Texas impacted by recent wildfires.

New Guide Helps Producers Maximize Values of Cull Cows
New Guide Helps Producers Maximize Values of Cull Cows

A new resource developed by the National Cattlemen’s Beef Association and CattleFax helps cattle producers maximize profitability from their culling decisions.