Mineral Spotlight: Understanding Ruminal Protein

black and white cows on green grass

Just what is ruminal protein?

Basically, it’s the protein produced by the microorganisms in the rumen.  They take the nitrogen and amino acids that are available to them in the rumen and use it to reproduce themselves.  As some of these microorganisms wash out of the rumen and into the abomasum, the DNA and RNA within the cells of these microorganisms becomes protein available for absorption into the bloodstream.

Why is this ruminal protein so good?  Because these microorganisms evolved along with  the particular species of ruminant, and it is assumed that the amino acid proportions (called an amino acid profile) are ideal for the requirements of the tissues of the body of that species.  I say assumed because the study of amino acids in ruminants is not as far along as the study of proteins.  But all indications show that the amino acid profile of ruminal protein is the most desirable.

The number one principle in the nutritional management of ruminant animals is to maximize this ruminal protein.  Supplemental protein is usually one your costliest ingredients, so it only stands to reason that the more the livestock can make for themselves, the more economical and efficient they should be.

So how do you maximize the production of ruminal protein?  There are two main limiting factors in ruminal protein production, the energy and nitrogen available to the microorganisms in the rumen.

Energy can be a limiting factor in that the microorganisms in the rumen must have sufficient energy available to reproduce.   Without available energy, the microorganisms can’t convert the ammonia to amino acids and protein chains.   When there is an ample amount of  ruminally degradable protein or nitrogen in the rumen, the more energy that can be put into the rumen, without causing other metabolic problem such as acidosis, the more ruminal protein can be produced by the microorganisms.

The most common, and economical source of this needed energy is from the forage.  As long as animals have an ample source of digestible forages that fit their digestive system (grasses for cattle, browse and forbs for deer, etc.), the livestock should have an ample amount of energy entering the rumen to produce the levels of ruminal protein needed for maintenance and a low level of productivity, as long as the nitrogen source is available as well.

If ruminants don’t have their preferred forages available, or if the available forages are limited, then energy may be limiting in the production of ruminal protein.  In this case, some energy, from grains, oilseeds, or other forages must be fed in order for the microorganisms to produce all the ruminal protein possible.

Care must be taken in supplementing energy, especially when using starch containing ingredients like grains (corn, milo, oats, barley, and rye).   High levels of starch can make the rumen environment more acidic which can hinder the growth of many of the fiber digesting microbes.  Also, energy from fats is generally not available to the microorganisms, so trying to provide energy from a high fat source like whole cottonseed may not solve an energy deficiency in the rumen.

If energy is not limiting, then protein, or nitrogen, available in the rumen can be the limiting factor in ruminal protein production.  The degradable protein faction in the forages the animals eat is normally the primary source of the protein and nitrogen needed by the microbes.  However, if the protein in the forage is insufficient to provide enough nitrogen to the rumen, some form of supplement will be needed to make sure the microorganisms can produce amino acids.

If we review the normal pattern of degradable protein levels in forages, you can get a general idea of when degradable protein may be limiting in a ruminant’s diet.   When forages are young and vegetative, they generally have high protein levels which are also high in rumen degradability.  However, as the plants mature, or as animals are forced to change their diets in the hot summer weather, the degradability of the protein decreases.

In the case of deer and goats, the annual forbs that are occasionally available are high in both total and degradable protein, providing the microorganisms with an extremely high level of degradable protein with which to make ruminal protein.  When the annual forbs flower and die later in the spring or early summer, however, the deer’s diet shifts to perennial forbs and browse which have moderate total protein and lower degradable protein levels.  Especially for lactating does and bucks growing antlers, the summer can be a time when degradable protein supplementation may be needed to keep ruminal protein production high.

For cattle and sheep, young tender grasses also have a high level of total and degradable protein for the microorganisms.  As the grasses mature and the summer sun begins to cure the forages, the degradability of the protein decreases, creating a nitrogen deficiency in the rumen which can hinder production of ruminal protein.

Winter can provide a double whammy for degradable protein as both total protein and degradability decline with frost on our native forages.  However, livestock producers know that in winter they normally need some type of protein supplementation.  The management key here is to provide the types of protein (degradable or undegradable) that the animals need.

So how do you know when and what to supplement to keep ruminal protein production high?  Taking a forage sample and having it analyzed by a lab that can do degradable protein analysis is one way.  I know of only one lab that is doing a degradable protein analysis for the public and that is the Dairy One DHIA Forage Testing Lab in Ithaca, NY (phone – 800-496-3344).  Using forage samples, you can begin to build a database, and personal experience, of the availability of protein in your forages at different times of the year.

You’ll need to have a way to estimate the degradable protein requirements of your animals, and that is a more complicated subject.  However, some ruminant nutritionists can help you with determining the degradable protein recommendations for your livestock at different periods of productivity.

An easier method of a ballpark estimation for cattle is to study the manure droppings.  As long as the manure is loose and high in moisture, you can be assured your animals are receiving plenty of degradable protein for the microorganisms.  If the degradable protein level in the forages begins to decline to a level below what the microorganisms require, the manure droppings will become more coarse, stack up higher, and have less moisture in the piles.  If you see this situation, your animals need a form of supplemental protein that is high in degradable protein.

Unfortunately, it is more difficult to use manure droppings of sheep, goats, and deer to determine potential ruminal protein deficiencies.  I do think there should be a correlation of moisture in the droppings to the amount of degradable protein intake.  However, you would need to experiment to develop your own criteria as to when protein supplement is needed.

When you determine your animals need a protein supplement, you need to determine what supplement is needed to provide the types of protein required by your ruminants.  If you will remember from the last issue of “The Forage Sampler”, the different protein supplements that are available to you have different factions of degradable and undegradable protein.

The equivalent proteins, urea and the ammonium compounds (ammonium sulfate, ammonium chloride, etc.) can provide only degradable protein and are very inexpensive sources of protein for cattle and sheep.  Goats and deer don’t seem to be able to utilize equivalent proteins as well as cattle and sheep, so I suggest you do not try to use them to correct degradable proteins in these species.

Unfortunately, the equivalent proteins provide no energy, so if your animals need energy as well as degradable protein, you will have to feed a mixture of energy and protein sources such as grains with urea.  As mentioned earlier, you have to be careful if you have to feed high levels of grains due to starch interactions with the microorganism population in the rumen.

For the natural protein (organic) sources, soybean meal has the highest level of degradable protein compared to total protein.  Cottonseed meal has a slightly lower level of degradable protein than soybean.  These two protein sources also have an energy value to them, since they are from an organic source, and can be much better sources of protein supplementation if energy is also deficient for the rumen microorganisms.   Because the energy from these natural protein sources is not from starch, there is very little negative effect on the microorganism population.

How much protein to supplement is another difficult question to answer.  If  you have forage analysis data and animal requirements to compare them to, you can make a pretty accurate estimation of the amount of actual protein that may be needed.  From this you can calculate the volume of your chosen supplement to feed.

However, if you are using manure droppings to estimate the amount of feed needed for cattle.  I suggest that if you see the change in the manure droppings, that you begin to supplement with approximately 0.20 pounds of protein per day.  It would take 1.0 pound of a 20% protein supplement, or 0.50 pound of a 41% supplement to provide 0.20 pounds of protein.  If the first 0.20 pound doesn’t correct the manure problem by the third feeding, continue to increase the supplement in 0.20 pound increments until you see the manure begin to change in consistency.

The minimal consistency should be what is called a “pancake” form for manure.   This is where the manure may pile up a bit, but the top is relatively flat.  There is no economic or nutritional reason to feed more protein to make the manure more loose than the pancake consistency.

For sheep, goats, and deer, you should add protein in increments of 0.05 pounds per day.  If using a 20% protein supplement, it would take 0.25 pounds per day of the supplement to provide 0.05 pounds of protein.

One final point, while ruminal protein is the best form of protein for a ruminant animal, under conditions of high productivity, such as lactation, high levels of gain, or antler growth in deer, the microorganisms cannot provide enough ruminal proteins for the total protein requirement of the animal.  In these cases, some undegradable protein will be needed to meet all of the animal’s needs.

This does not necessarily mean that some must be supplemented, though, because much undegradable protein can be provided by the forages that the ruminants eat.  Whether they need undegradable protein supplementation will depend on determining the total protein requirement and how much of it can be met by ruminal protein.

Ruminal protein will always be the most economical and the most nutritionally effective protein that an ruminant animal can digest in the abomasum.  As a livestock manger, you can maintain a high level of productivity with the least supplemental feed costs, if you can maximize the production of ruminal protein by the microorganisms n the rumen.

It will take some effort on your part to monitor and insure your animals have the degradable protein intake they need.  However, it is the key to keeping your livestock operation as profitable as possible.

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