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Nitrate Levels in Selected Cocktails in 2016: The Risk of Nitrate Toxicity

By Akim Omokanye, PCBFA

From: Peace Country Beef & Forage Association 2016 Annual Report

Cocktail cover crops are often used to further increase the benefits of a one-species cover crop. Cocktail cover crops offer more diversity and allow more goals to be achieved than with one crop. For example, tillage radishes could be added to a mix to reduce compaction, a legume seeded to fix nitrogen and barley added to the mix because it has an extensive root system and will increase the organic matter. In the end, the soil condition is improved and there would be forage available for grazing. There are many options based on a farm’s needs, and to implement a cover-crop program many things must be considered, including the economics, as many of the benefits will be seen over the

long-term, not immediately.

While nitrates (N03) are not very toxic, nitrites (N02) are toxic. Nitrate poisoning occurs when the nitrite level in the rumen exceeds the capacity of the microbes to convert it to ammonia. When this happens, nitrate and nitrite are absorbed through the rumen wall into the bloodstream. It is the nitrite that causes toxicity. Nitrite combines with hemoglobin to form methemoglobin. Hemoglobin carries oxygen to body tissues while methemoglobin is unable to do so. When enough hemoglobin is converted to methemoglobin the animal begins to suffer