Nitrates

What is a nitrate (NO₃)?

Chemically, NO₃ are a combination of two elements, nitrogen and oxygen, in the proportion of one nitrogen atom combined with three oxygen atoms.

Where does NO₃ come from?

1. NO₃ in Water & Feed.
NO₃ in the water and feed supply can come from several sources. A primary source is fertilizer containing a nitrogen source. For example, potassium nitrate (KNO₃), ammonium nitrate (NH₄NO₃), urea (CO[NH₂]₂), and anhydrous ammonia (NH₃), common in a variety of frequently used fertilizers, are all sources of NO₃, since the NH₄⁺ and NH₂ groups can both be oxidized (i.e., broken down) by air and bacteria in the soil to become NO_3. Furthermore, manure and urine are also excellent sources of NO₃. The form of nitrogen in manure and urine is mostly NH₂, but also includes NH₄⁺ and proteins (proteins are carbohydrates with NH₂ groups attached).

2. Natural Sources.
In some parts of the world, there are natural deposits of NO₃.

3. NO₃ in Plants.



PHOTOSYNTHESIS

Plants (e.g., grass, hay, corn silage, etc.) and several types of bacteria can make their own NO₃. Some types of bacteria in the soil are solely associated with plants, such as legumes (symbiotic bacteria), while other types live everywhere (asymbiotic bacteria) taking the nitrogen from the air (air is 78% nitrogen!) and fixing it into NO₃, which then can be utilized by plants. Most plants take up nitrogen from the soil in the form of NO₃. NO₃ are absorbed by the roots and transported up the stalk with water. Carbon dioxide (CO₂) is absorbed from the air and into the plant through the leaves (via stomata).

PHOTOSYNTHETIC REACTIONS

During photosynthesis, a water molecule (H₂O) is split and oxygen (O₂) is released into the air for us to breathe. The leftover hydrogen atoms are then combined with CO₂ to become sugar, starches, fats, cellulose (e.g., fiber, wood, etc.), and will also combine with NO₃ to become amino acids, the building blocks of proteins. Here is where a problem with NO₃ in the plant can occur.

First, there must be plenty of water. If the plant is stressed from dehydration, after the photosynthetic reaction there will not be enough hydrogen to convert NO₃ into an amino acid. Thus, the unused NO₃ just sits around waiting for more hydrogen. Second, if there is a lack of sunshine because of cloudy/rainy days, night-time, or frost (i.e., frozen water) NO₃ can accrue because without the sun, there is no photosynthesis.

Helpful Hint #1: Never cut hay in the early morning.

Helpful Hint #2: Do not overgraze, NO₃ are higher in the lower parts of the plant.

What are the effects on cows, bison, sheep, people, & pigs?

There are two ways NO₃ become a health risk. One way is that the ingested NO₃ will be converted to ammonium (NH₄⁺), which is absorbed into the bloodstream. Once the NH₄⁺ is absorbed into the bloodstream, it combines with hemoglobin, inhibiting hemoglobin from binding oxygen and preventing the transport of oxygen from the lungs to the cell. The hemoglobin attached to NH₄⁺ is called methemoglobin. Young animals are affected the most by this. When enough hemoglobin is converted to methemoglobin, the animal begins to suffer oxygen starvation. In humans, this is called "Blue Baby Syndrome." In cows, it is often described as "hard breathing."

Helpful Hint #3: Some summertime hard breathing is not a result of the heat; it is from an imbalanced feed ration!

Second, bloating can also occur when NO₃ is converted to NH₄⁺. NH₄⁺ is an alkaline substance, which will increase the pH in the rumen. Increasing rumen pH will depress growth and multiplication of rumen microflora (bacteria). Excess NH₄⁺ in the rumen is also associated with a considerable number of additional health problems, including foot rot, mastitis, retained placenta, pink-eye, breeding issues, respiratory infections, etc. Excess NH₄⁺ from high protein rations will compound the problem.