by: Stephen B. Blezinger
Ph.D., PAS

Part 1

At the cow/calf and stocker cattle level, production systems are generally built on forage production, pastures, hay, etc. For these operations forages provide the bulk of the nutrients needed for the animals. In many cases because of inadequate management or simply uncooperative weather patterns, forage quality is not suitable for the pasture and hays to maintain the type of digestibility needed for the animal to extract the needed nutrients. In other cases, the plant species is not the best and as-is, may not possess the nutrient digestibility required.

Whatever the case, it is often necessary for the producer to take steps to improve digestion of the forages on the farm or in cases where forages are purchased for feeding. This article will discuss a number of these factors and the tools the cattleman may use to improve the digestion of forages.

Simple Estimates of Forage Digestibility

Digestibility is often measure by the level of certain fibers in grasses and legumes. The main components of fiber include cellulose, hemicellulose and lignin. Cellulose makes up a great deal of fiber and is largely broken in the rumen fairly effectively. As the plant matures the hemi cellulose (less digestible) and lignin (poorly digestible) contents increase and the overall digestibility of the plant declines. Since the other nutrients in the plant material are intertwined in these fiber matrices, as the fiber digestibility decreases so does the digestibility of protein, simpler sugars, fat, minerals and vitamins.

By sampling and analyses we can determine the content of these fiber components and get and estimate of how digestible a given sample of plant material really is. At the most basic level a forage lab can analyze for acid detergent fiber (ADF) and neutral detergent fiber (NDF), both of which provide an indicator of the levels of cellulose, hemicellulose and lignin. As the ADF and NDF values increase, the digestibility decreases. More recent lab techniques not only provide values of actual digestibility but also rate of digestion. These numbers are used increasingly in dairy ration formulation to improve rumen performance in dairy cows for improved milk production. No doubt we will see applications for these values in beef production as well.

At a practical level, one way to get an idea of the digestibility of the forages that a producer is using is by observing manure. If the manure in a given area with a given group of cows “stacks up” more than a couple of inches, one can assume the digestibility of the fiber and concurrently the nutrients. Most producers have seen manure that will stack up six or eight inches and is made up of individual lumps or balls that are very firm. Upon closer examinations or when broken apart it is generally noted that the fiber particles are obvious and in many cases are fairly large. This indicates that the fiber is not broken down well in the animal's digestive tract and that much of the nutrients are unavailable to the animal. In many case this may also indicate the overall nutrient content is not very high (a.e. protein content). More about this later. This manure appears very dry and hard. When the manure in a given group of cows is observed to be of this type you can assume they are not receiving the nutrients needed for normal performance. You would also expect to see body condition to decline concurrently.

On the other end of the spectrum, manure from cows that are on highly digestible forages (such as winter annuals or small grain pastures) will be seen to be very “liquid.” In many cases manure piles are more like pools and may only stack up slightly. While this indicates very digestible fiber components it may also indicate that the material flowing through the digestive tract is moving so fast that nutrient absorption may not be the best. In these cases, it is useful for producers to provide forages that can slow down this process such as dry hay. It also may indicate that the protein content of the forage is very high, much higher than the animal can utilize. In some instances, these high protein levels are also a problem, particularly for heifers attempting to be bred. The excessive protein can often reduce reproductive performance in these classes of cattle. This falls into the category of too much of a good thing.

The more optimum situation is manure that somewhere between the two types described. It should not stack up more than a couple of inches and appears to have a fibrous, semisolid form that will actually create “rings” when deposited. The fiber particles can be seen but are not terribly large (less than 3/4 inch in length). When scraped over with your boot or a shovel or other implement, the consistency is very good throughout the pile and has a smooth, even texture.

Improving Digestibility of Forages

The best means of improving forage digestibility under normal circumstances is through good management. Proper grazing management including keeping forages, particularly summer perennials is a key. Keeping these plants grazed to a level where they are continuously growing and somewhat immature, helps insure the more poorly digested fiber components, hemicellulose and lignin levels are kept down. This is more difficult as the season progresses and the plant just naturally ages but keeping the plant material harvested either by the animal or mechanically is an important factor. This is the same situation when harvesting the plants for hay or silage. Harvesting the plant before excessive amounts of seed heads begin to emerge will help this process. This will also depend on moisture conditions and plant variety. Working with a knowledgeable agronomist can be very helpful in understanding these dynamics. Remember the forages you are producing during the growing season are what you have to work with the rest of the year. If the operation depends on stored forages for fall and winter feeding (or when summer supplies run short), producing a high quality, digestible hay or silage supply will go a long way to improving animal performance and keeping costs down.

Managing Dietary Protein

One of the best known ways of improving plant digestibility is by properly managing protein levels in the animal's diet. More correctly, what the producer is attempting to do here is to provide the necessary nitrogen from protein for the rumen microbes to maximize their activity. A proper nitrogen supplies helps optimize microbial activity so that their digestion of plant materials, particularly fiber, is maximized. As referenced above, when protein levels are adequate, the result is a more extensive breakdown of fiber particles that results in manure that stacks less and where fewer, smaller fiber particles will be observed. The actual protein level necessary will vary depending on the class of animal (mature milking cows will have a lower protein requirement than a recently weaned growing calf), level of protein in the plant material and supplement type. Supplementing protein can take a multitude of forms and may include feeding a second, higher protein forage (i.e. alfalfa hay), a protein meal (cottonseed meal, soybean meal, others), dry protein supplements such as range cubes or liquid feed and tub supplements (some of the protein here may be from protein equivalent from urea – non-protein nitrogen). Whichever source is used it should be evaluated against the forage base as well as the cost of the supplement.

Other Digestibility Enhancing Technologies

Over recent years, the technology to increase forage digestibility for ruminants has increased and improved significantly. A great deal of this has been through the use of additives that enhance rumen bacteria activity. Other products such as fungal and bacterial cultures known to be rich in fibrolytic (fiber digesting) enzymes (particularly cellulose and hemicellulose) have become increasingly popular in various feed delivery systems. Other products such as essential oils/plant extracts have been shown to also modify the rumen bacteria population in such a way that fiber (and other nutrient) digestion is increased as well. A challenge here is that there is some variability to how these products perform. So careful research is needed to be certain that the right product is selected. For instance, there are a very wide variety of “enzyme” products that are available for use in cattle. Again, these are generally based on fungal or bacterial fermentation products that claim an enzyme content. Often the cost of these products is fairly high so some companies may use only very low amounts of these products and essentially use them as “tag dressing.” In order to receive the benefits of a product of this nature they need to be fed at or close to the recommended level. Generally, these feeding rates are established by company or university research. Also it is important to use products that have a decent body of research. Products such as AmafermTM (Biozyme Company, St. Joseph, MO) or Bovazyme TM (York Ag Products, York, PA) have research indicating the effectiveness of their products. Others will claim to be “just like Amaferm or Bovazyme.” Products that enter the market in the “me too” category seldom have actual research that support their claims.

In general products of this nature can be included in a variety of supplements that are fed along with forages needing added nutrient levels. Mineral supplements are commonly fed year-round and thus an enzyme product, essential oil or other “rumen fermentation enhancer” can be delivered using the mineral supplement. Given the increased cost of the supplement when the additive is included, it is important that proper feeding management is used and that the feeder provides protection for the supplement from the elements. Other delivery methods include mixed feeds, tub supplements and liquid feeds. Some of these are better than others. Supplement forms that require significant levels of heat and or moisture in the manufacturing process (pellets, cubes, “cooked” tub supplements) may require heat levels that can denature or break down the additives.


The use of technologies to increase forage digestibility is becoming increasingly common. IN the next part of this series we will review some of the research that has been performed with some of the products in order to help the producer better understand these products and what can be expected from their use and the concurrent investment.

NOTE: Reference to specific products or companies should not be considered an endorsement.

Copyright 2016 – Dr. Stephen B. Blezinger. Dr. Stephen Blezinger is a nutritional and management consultant with an office in Sulphur Springs, Texas. He can be reached at or at (903) 352-3475. For more information please visit Facebook/Reveille Livestock Concepts.

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