Understanding the Metabolism of Nitrogen Means Profit for Your Clients

Robert G. Scott, D.V.M. Supplied by Pro Ag Consulting PTY LTD. +64 212956469                                                                 

1120 Lois Court

Shoreview, MN 55126

What is over Nitrification? How does it affect animals? Where is it most             

likely to occur? What can be done to prevent problems connected with nitrates?



The nitrate problem has been with us a long time. The first reference I have found in the literature is in Second Kings Chapter 2, verse 19. This was about 840 B.C. “The men of the town said to Elisha, the town is pleasant to live in as you can see, but the water is foul, and the people suffer from miscarriages.”

Dr William. Albrecht of the Dept. of Agronomy at the University of Mo. gave me the best advice of anyone about 1965 when he told me to study nature as well as books.

The first illustration I’ll ask you to use is to have you go with me in your mind’s eye to a cow pasture. I want you to remember the beautiful lush green ring of grass, which grows up around a cow platter. Almost every one of us has seen this highly fertilized growth of grass, which results from the natural process of too much fertilizer. The grass is taller, greener and more luxurious than the surrounding grass. It also has higher NPN or non-protein nitrogen and an imbalanced cation ratio and under normal grazing conditions the cows won’t eat it.

Now compare what we are doing with our corn crops. We fertilize with every imaginable type of Nitrogen until we have the tallest lushest growth possible and we harvest prior to natural maturity. Then we force the cow to eat this feed with the most sophisticated of automatic machinery. Then we stand in amazement and watch them get sick even after we increase their protein and supply them with more of the same poison through a lick tank filled with urea.

When we are in the business of making meat or milk we have only 5 basic materials to compose the diet. They are: Water, Energy Feeds, Protein, Vitamins and Minerals.

The most important ingredient in any diet is water. If you don’t remember anything else that you hear from me today the emphasis on pure, wholesome and plenty of water is by far the most important thing about balancing any ration. It is also the best treatment that can be applied to correcting a nutritional problem.

The real difference in the chemical composition of the energy and protein portions of the diet is the inclusion of the element nitrogen and maybe phosphorus and sulfur in the molecule. Nitrogen is the key element in the structure of all protein. The cow with her wonderful rumen is able to make meat or milk from the most amazing array of junk foods. The cow is able to make use of the production of millions of acres of this planet which are of no use to man’s diet because she can take NPN and cellulose both of which we cannot digest and make some of the best food we can eat.

The cow performs best in this synthesis if the diet contains the proper ratio of energy to protein and if the minerals are in the proper relationship. If the NPN or NO3 is in excess in the diet we see the following 4 major problems. Remember that the symptoms are going to vary with the degree of insult and will all be superimposed one on the other so that all your God given talent must be utilized to the highest degree to interpret what you are seeing. You may see a variation in symptoms ranging from sudden death to only a mild lowering of production but the problem will be exhibited with some or all of the following conditions.

1. Lowered Production

2. Anoxia

3. Vitamin Interference

4. Antibody Impairment

Lowered Production.

I’m sure most of you have seen the dramatic drop in milk production which can occur from changing feeds. One day you will read the dipstick on the tank and read it again in dismay when you realize that overnight your production has plummeted.


If a feed is introduced with a higher NPN or too much nitrate some of the energy has simply been used to make the conversion of NPN to protein and the energy spent on this process is not then available for production. It does not matter whether the conversion of nitrate to protein happens in the plant growing in the field or in the rumen of the cow, the chemistry is the same.

The simplest way to illustrate the chemical equation is:

NO3 + Energy + H + proper catalysts and enzymes Amino groups > NH2

The energy used in the field to produce protein comes from the sun. There is no sunlight in the rumen and any energy consumed to make the change from NPN to protein must come from energy in the diet.

You cannot spend your paycheck on two things at once. The cow cannot use the energy in her diet for both nitrate reduction and production. It must be one or the other. If she spent it for nitrate reduction the production suffers.

The second insult of N03 to the system is anoxia. Anoxia results from the formation of methaemoglobin. We need to go back to the formula of NO3 reduction to illustrate:

Nitrate > Nitrite > Nitroxyl > Hydroxylamine > Ammonia

Cu Cu Mn

N03 > NO2 — > (HNO)2 — > NH2 OH —-

> NH3

Fe Fe Mg

(There are probably more additional catalysts in addition to Cu, Fe, Mn., Mg )

The change also needs an input of energy and a Hydrogen donor.

All of us know that NO2 or nitrite is not a stable molecule and will combine with something very quickly. When nitrite combines with haemoglobin the result is a stable compound. The red blood cell, which has combined with nitrite, is no longer capable of transferring oxygen to the tissues.

This gives us the pneumonia symptoms in the weaner calf. We may diagnose the symptoms as shipping fever. It will starve a foetus for oxygen and the cow will abort, and we will vaccinate for all manner of abortion-related disease and watch in dismay and frustration when our treatments are applied with no benefit and cows continue to abort.

Anoxia can be exhibited in many different sets of symptoms but the underlying cause of these symptoms will go undetected and may be hidden because we do not study nature.

Sometimes when we get a negative culture back from the laboratory on an abortion for example, that points a red flag at the cause and suggests anoxia due to nitrates and yet the ingrained urge in most of our thinking immediately wants to find the offending “bug” and give a shot to fix it.

Often there is no infection, the aborted foetus simply ran out of oxygen and said, “let me out of here” remember it is the foetus and not the mother who decides the time of birth. In this case the decision to leave the uterus on the part of the foetus was a mistake, but it was a case of being destroyed if it stayed or destroyed if it left.

I know there are literally thousands of abortions that are due to anoxia that cause entire herds to be vaccinated against something and the vaccination was a waste of time and effort and added stress to the cow herd.


The wise owner needs to always consider that there may be an error in diet formulation that is responsible for nitrate poisoning.

Abortion may not be the only disturbing symptom. As a foetus nears full term the oxygen demands are increased as the size of the foetus increases. A calf or lamb that comes a few days early may never be recognized as a birth that was not really normal. This sort of “accident” or early birth has some accompanying symptoms that may be connected but more often than not are overlooked.

It is possible that the early birth came before the mother had time to manufacture wholesome Colostrum. As a consequence of this we see different forms of scours in the newborn. If the Colostrum, which in itself is a miraculous combination of protein, based antibodies is “hurried” it simply cannot protect like it could have if the birth had been delayed a few days. Making good Colostrum is similar to baking a good cake, it takes the right ingredients, the proper mixing and the proper timing in the oven

The instinctive mothering characteristic of the new mother may not have been allowed to fully develop, ewes may lamb and then not be interested in taking care of the babies. If her complex system of hormones, again many of the hormones contain protein fractions may be inadequate. If she doesn’t get the right blend of chemical messages to her brain the mothering instinct is simply not programmed into her action.

I’m sure there have been millions of ewes sent to slaughter with a curse in the mind of the owner because they were poor mothers. The fault was the owner’s because he allowed the ewe to graze on grass that had more nitrates in the grass than the grass had been able to process into wholesome protein.

All growing plants are expected to take up nitrates from the soil. That is the normal pathway toward manufacture of protein. If the plant is taking up lots of nitrates and there isn’t adequate time or sunshine to allow the grass to manufacture wholesome protein, we have a situation that requires additional dietary supplementation to the grass.

Our method of reporting protein on a laboratory analysis compounds the problem. When we send a sample of grass to the lab for protein content the lab measures the amount of the nitrogen in the grass. Nitrogen is present in all protein and the analysis of the total nitrogen multiplied by a factor of 6.25% is reported as the protein content of the sample. Very often this factor of a high protein is not accurate at all.

Some of the protein is there but much of the rest of the nitrogenous compounds are either, nitrates, nitrates, nitroso compounds, hydroxylamine’s and the intermediate steps in the process where the plant was in the process of making protein but they aren’t good protein, they are toxic or junk protein.

Grasses or hay or silage can all have a label of level of protein that isn’t protein at all but part of he content of the feed is actually a poison to the animal that eats it. There isn’t enough nitrate to be causing severe sickness or death but certainly is capable of disrupting the metabolism of the animal to 1. Diminish production, 2. Cause anoxia, 3. Cause vitamin interference, 4. Cause antibody impairment. These four factors are all exhibited in combinations so it makes diagnosis more easily confused. We need to learn to see what we are looking at. . Mastitis is certainly a possible result of too much nitrogen somewhere in the system. When we make a cornfield green by using nitrogen we do it by stimulating bacterial activity in the field. Nitrogen stimulates bacterial action. If we starve an udder for oxygen by having nitrates in the blood stream and in the red blood corpuscles, then limit the proper vitamin availability and add insult to injury by depriving the animal of good antibody level we should not be surprised to have mastitis prevalent in a herd that is suffering from an overload of nitrogen.


The proper treatment is often neglected because we are too busy “bug hunting” and medicating instead of looking for factors that allow the “bugs” to be active in the first place. Insulting the udder with an improperly functioning milking machine and then exposing the cow to stray voltage or some electrical insult like exposure to electric current flow, and then having an infection like Chlamydia to lower her resistance is the formula for disaster. When you see the total picture, it makes the expenditure of thousands of dollars for antibiotics to treat mastitis look rather foolish doesn’t it?

The primary objective when mastitis or abortion is present should be to investigate what insults are we giving the cow.

Where are the factors that may lower her resistance?

When is the beginning of the insult?

How can we change the exposure to unwanted factors in our management ?

Mastitis is certainly a possible result of too much nitrogen somewhere in the system. When we make a cornfield green by using nitrogen we do it by stimulating bacterial activity in the soil. If we stimulate bacteria in the udder, which is starved for oxygen, has inadequate vitamin A and a lowered antibody response we can expect the result to be exhibited as mastitis. The proper treatment that is often neglected because we are too busy “bug hunting” cultures and attempts to kill the bacteria. We need instead to find out why the natural defence mechanisms in the cow are not functioning at the optimum level.

3. Vitamin interference is the third aspect of the over nitrification. Vitamin A is that foreman in the factory of the body whose job is the manufacture of new cells in the lining structures of the body. The surface of the cornea in the eyeball is kept healthy due to the influence of Vitamin A. When Vitamin A is in short supply we see “pinkeye”. The mechanism of vitamin interference is more complicated than can be covered in the time we have here today. This simple illustration will give you the idea.

Carotene, the precursor of Vitamin A is a long skinny molecule. It might resemble a shoelace. In order for it to be absorbed into the system it must be attached to a protein complex which grasps the end of the molecule. The plastic end on your shoelace serves a similar function. When the plastic end is missing your cannot thread the shoelace into the eyelet on your shoe.

When the protein complex, which works with carotene, is missing or not proper the system cannot effectively absorb carotene. The symptoms we see are a dull hair coat, sore eyes, lameness, diarrhoea, and in appetence. These are nature’s red flags to tell us that something is wrong with our vitamin delivery system.


4. Impairment of the antibody system. All antibodies are delicate proteins. All of the antibodies contain nitrogen. No manufacturing process is efficient with an imbalance of supply of raw materials. When nitrogen is in such abundance as can happen in our animals diets it is little wonder that occasionally we don’t have the natural immunity we could enjoy.

The times when we may see evidence of a diet imbalance and especially too much nitrogen are times of natural stress to the animal.

I would start with the dry cow late in gestation. Her oxygen demands are greater than ever. Birth puts a stress on both the mother and infant. Weaning and changing the diet, especially removing the natural balanced minerals in the milk and subjecting the calf to stress of all sorts surely accentuates the imbalance in the diet.

Entry into a feed lot of the man who does not understand that urea is only a raw material of protein manufacture can be disaster. In a word STRESS is a time in the life of the plant or animal when too much nitrogen can be the straw which literally breaks the animal and ruins its life.

We need to consider then what we do to help remedy the situation.

Prevention begins with understanding.

Water containing nitrate is beneficial to a degree in crop fertilization. It has no benefit to a living animal. Water supplies to animals should be regularly tested for nitrate content. Stagnant water whether in a pond, water cup or troughs which is liberally contaminated with feed can be the incubation area for bacteria. The waste products of this contamination can change the nitrate content. When you test the water, test it the way the animals get it and not just sample it at the end of the faucet. Dip it out of the watering device.

Plants accumulate nitrates due to stress. If the Cations in the soil are imbalanced the plant grows under stress and cannot effectively utilize the nitrogen it absorbs through the root system. This increases the NPN because the plant simply bites off more than it can chew. One illustration is an imbalance of magnesium and calcium in the soil. The soil should have about 4 times as much calcium as magnesium. Both of these elements contribute to the pH reading on the soil. If you are not aware of this relationship it will go undetected in routine soil analysis. If Magnesium is too high in relation to Calcium for some strange reason the plant will grow under stress and will accumulate a greater amount of nitrogen that will be present either as nitrate or NPN.

The other complication is that this same plant will often be deficient in Magnesium. This combination can produce symptoms of grass tetany, scours, foot problems and other things which rob profits.

All good balanced nutrition must come from a well balanced soil. We have been fertilizing with NPK for 50 years or more. The fertilizer companies label their products with three numbers which stand for nitrogen, phosphorous and potassium. No one disputes the necessity for NPK but too few of us are concerned about calcium, magnesium and sodium, which also have a great influence on the plant growth.

Much of what I know about soils began with what I learned from the University of Mo. and the Brookside Laboratory in New Knoxville, Ohio. Then the next segment of learning comes from doing the testing, observing the results and comparing animal performance with what you know about their diet. If the farmer has a consistent high accumulation of nitrate or too much NPN in his crop then a systematic soils study can often reveal the source of the problem.

Not all problems in the soil are a matter of imbalance. Tillage practices on our farms need to be examined. When the mouldboard plow turns up a slab of soil which is shiny and slick the part we never see down under the ground is also shiny and slick. One hundred years of plowing has produced an almost impervious layer, which is easy to discover if you ever have to dig a post hole. That plow sole layer in the farm can be an effective barrier to the movement of soil moisture. When the root hairs penetrate to the depth of the plow sole they are often bathed in the excess fertilizer we have applied through ignorance of what the ability of that soil can safely hold. All too often the excess nitrogen applied winds up in our surface water. I had occasion to effectively treat calf scours with a D8 caterpillar and a subsoil ripper. The hay after this procedure was much more wholesome and the calf crop appreciated it. We can do little about the weather but we can realize that stricken forage usually has a high NPN content. Feeds harvested early due to drought can be loaded with problems. Troubles have a way of compounding themselves. The oat hay crop harvested because of not enough water is stressed. Our earliest studies on oat hay poisoning or nitrate poisoning told us that oat hay could be toxic. Virtually any forage crop can be a nitrate accumulator under the proper conditions. The worst case I have ever seen was with Bermuda grass hay in S. Carolina. This hay would kill a cow if she filled her rumen with nothing but this hay.

In general the forage sections of the plant are the areas where the nitrates and NPN are accumulated. The plant simply has not gotten around to finishing the job of conversion to protein of all the nitrogen it has absorbed. The lower portions of the cornstalk may be dangerously high in nitrate content while the stalk and leaf portions above the ear contains N which is already processed into wholesome protein.

The seed portions of plants contain little NPN or NO3 because nature tends to make the finished product perfect. The simple answer then if you have questionable forage is to blend out the nitrate with grain. Adding shelled corn to haylage is an excellent way to blend out nitrates and balance the diet.

No discussion of NPN can omit the concept of Urea Fermentation Potential.

Urea is a simple chemical compound. It is formed by combining two ammonia and one carbon dioxide molecules. It can supply the amino group in the synthesis of amino acids for the manufacture of protein. Urea is one of the cheapest sources of protein available. Urea has some very definite limitations, which are best understood using the concept of Urea Fermentation Potential. In order for urea to be processed into protein, energy is necessary. Different plant and portions of plants contain different ratios of energy to protein in their structure. A kernel of corn has much more starch than a kernel of wheat. Urea is a safe, reliable and economical protein supplement to shelled corn or ground ear corn but it simply will not do good things for a ration composed of wheat.

There are tables available which will tell you the UFP of feedstuff. Any feed or combination of feeds, which have a positive UFP, can benefit from the use of urea as a protein supplement. If the feed is alfalfa, for example, the UFP is negative. This tells us that you cannot effectively or safely add urea and expect benefits from that combination. Only about 20% of our feeds listed in the NRC tables have a positive UFP; 80% have a negative UFP.

Any plant grown or harvested under stress may contain NPN or nitrate. These levels may exceed what is listed in the tables in the NRC for the analysis of that plant. When Nitrate and NPN are high this lowers the UFP of that ration. The balance of the major minerals available in the rumen can influence UFP. No energy exchange can be efficient with a deficiency of phosphorus. The Phosphorus fraction is the most expensive ingredient used in the manufacture of minerals, which are made for sale to livestock owners. The price is the determining factor in the purchase of many feed supplements.

Learn to read mineral labels. Remember that the more Phosphorus you need it the mineral the more it will cost.

If you have a diet that has a negative UFP (Urea Fermentation Potential) do not use urea. That includes the lick tank with molasses and urea.

The hazards of too much nitrogen are easily encountered in our modern way of farming. Too many farms have used too much salt-based NPK fertilizers. The nitrates travel to the well. Polluted water is not delivered to the water tank with any warning labels on it. Water with nitrates can demand that you have low nitrates in your feedstuffs.

There are answers. Study and learn to balance rations.

One company and I am sure there are others, has isolated a bacterium that can be introduced into the feed. This product inoculates the rumen with bacteria that have the unique ability to metabolize Nitrates and make protein in their own bodies from the nitrate. The bodies of these bacteria make good cow feed as they travel into the abomasum.

Robert Scott USA. Photos by Colin Trengove senior lecturer Roseworthy Agricultural College South Australia

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