In the last issue we discussed silage and some of the basics for this method of forage preservation. While ensiling of crops has been used extensively for many years, many parts of the country are just now beginning to recognize the value of this practice. Interestingly, a number of methods have evolved to make implementing this process simpler and start-up costs lower. In this issue we'll discuss some of the basics of storage as well as getting a silage program developed and implemented.
To review what we discussed in the last issue just a bit, remember that a well-preserved silage of high nutritional value is achieved by harvesting the crop at the proper stage of maturity; minimizing the activities of plant enzymes and undesirable epiphytic microorganisms (i.e., those naturally present on the plant) and encouraging the dominance of lactic acid bacteria (LAB). Two singularly important features must be considered for every silage: 1) the crop and its stage of maturity, and 2) the management and know-how of the silage-maker.
The key ‘ensileability' criteria for a crop are: 1) dry matter content, 2) sugar content, and 3) buffering capacity (resistance to acidification or reduction of pH). In these respects, corn is the ‘nearly perfect' crop, whereas alfalfa is at the other extreme and is the most difficult crop to preserve as silage. On of the primary reasons for this is a high mineral content, particularly Calcium which acts as a buffering agent and creates a situation where the forage mass is resistant to decreasing pH. Grasses usually contain more water-soluble carbohydrates (WSC) and have less resistance to acidification than legumes. When making decisions about silage management techniques, it is important to have a good understanding of the events that occur during silage preservation. The major processes involved can be divided into four phases: 1) aerobic, 2) fermentation, 3) stable, and 4) feedout. Each phase has distinctive characteristics that must be controlled in order to maintain forage (silage) quality throughout the periods of harvesting, silo filling, silage storing and feeding.
Methods of Storage
A. Upright Silos
Typically, when we think of silage a picture comes to mind of the multitude of tall, slender silos we see throughout the Midwest. While we do see these structures occasionally in other area, seldom do we see them with the frequency that we do in the center of the United States. As mentioned above, production of silage has been common in the Midwest and upper Midwest for years and the presence of silos is a statement of that fact. These structures are built of wood (older models), concrete or steel (often glass lined) with the intent of providing an “airtight” environment where the silage can be produced and stored. Different models of upright silos are more effective than others at keeping air out. You also see them in a variety diameters and heights according to the storage volume needed.
Use of upright silos requires that the chopped forage be brought to the silo and blown up to the to of the silo via a silage blower, typically powered by a tractor PTO. Once at the top the forage falls down into the interior of the silo and gradually accumulates. As ton after ton is piled it forces out much (or most) of the air and packs itself tightly into the structure until it is filled. After sufficient time has passed the silage can be removed from the structure. Depending on the model, the forage is removed either from the top or the bottom. An advantage to this type of silage storage method is that it generally does a very good job of reducing air exposure and creating an environment very conducive to the ensiling process. Disadvantages include cost of construction, permanent nature of the structure, slow filling and unloading. We tend to see a lot of unused upright silos.
B. Bunker or Horizontal Silos
A big advantage to the use of bunker silos is the volume of material that can be placed in the structure. A bunker silo is a structure built in a number of ways, normally having two or three walls in which the silage is piled horizontally into the structure and packed with a tractor or other heavy, wheeled vehicle. Bunkers can be built with concrete walls of varying heights or can, in fact be dug out of a hillside. As mentioned a large advantage to this system is the ability to build a very large structure which can hold a huge volume of material. If the bunker is dug out of a hill, should the producer elect to discontinue the practice he can simply back fill the trench. Obviously, concrete bunkers are more permanent.
A rather significant problem with bunker silos is the large amount of air exposure by the forage mass. Since the bunker is generally fairly wide and long, a lot of the forage at the top of the pile is exposed to air. This creates a need to cover the silage with something. This is commonly accomplished with polyethylene plastic and old discarded tires. Many recommendations state to cover the pile as soon as possible with the plastic and then place the tires in a layer on top of the plastic, touching one another. While the plastic is not terribly expensive, placement of the tires is labor intensive and cumbersome. They also create a haven for mosquitoes in the warmer months. This type of silage storage is coming under fire by environmental concerns due to contamination of the land with the plastic and rubber tires. Research is currently under way to find a replacement for this method of covering and sealing the “pile.” Finally, there is generally considerably more waste to this storage method than with an upright.
C. Bagged Silos
A relatively new silage storage method is the use of “bags” into which the silage is blown and packed. The filled silage bags resemble a large sausage laying out on the farm. This method is generally considered fairly cost effective. It also does a pretty good job of storing the silage if the operator knows how to use the equipment and does not over fill the bag which can burst. Once again, however, this situation creates a need to dispose of large volumes of plastic material. One big advantage is that the bags can be conveniently placed near the feeding area and location can be changed if one particular area turns out to be less than suitable. A disadvantage is that this method requires the specific bag-filling machinery to do the job which creates an additional capital expenditure. In general, however, this system appears to work quite well for preserving the forage crop.
D. Drive-Over Piles
Another method, which has become quite popular in certain areas, is that of drive-over piled silage. In this situation no permanent structure is needed. A clean level area is selected where the chopped forage is piled, pushed up and packed. Over the course of unloading numerous loads of material a large “bread-load” pile is created. Tractors repeatedly drive over the material to compact the forage as much as possible taking care to keep from making the sides too steep and causing a roll over of the tractor. Once the pile is completed, it is covered with polyethylene and weighted down with tires. At the ground level, loose dirt is typically piled to keep the plastic in place and prevent air flow into the pile. Obvious advantage is that this is the least expensive program, requiring only the basic equipment and the plastic and tires as noted above with the bunker silos. It also allows for the pile to be located in different areas as necessary or as the program changes. Disadvantages include the exposed surface area, which is considerable. The ability to pack the pile as consistently as needed since you cannot pack the sides as well as necessary. Also, since in many cases, the silage is piled directly on the ground and not on concrete, more material is wasted and a certain amount of dirt will inevitably contaminate the silage when feeding.
E. Baled Silage
Another method, which has gained popularity in recent years, has been that of baled silage. Typically, hay is cut and rolled into round bales with a specially outfitted round baler. The special outfitting is primarily to allow the baler to handle the heavier bales due to the high moisture content. The bales are then wrapped individually or placed end-to-end and wrapped in a long roll. Occasionally you will see hay of this nature stacked up in a pyramid of sorts and then covered with plastic ads with the drive over piles. This tends not to work too well since it allows for a lot of air exposure. This method has gained a lot of popularity since it is more or less in a form that many cattlemen are well associated with. The big advantage here is the creation of a form of silage that is easily handled and fed. In other words, they can handle the silage with equipment they currently own. Once again, the downside is the disposal of the plastic wrapping material.
Forage Type Selection
Many types of forage, most in fact, preserved as silage. Obviously, corn silage is of the most common and typically, makes some of the best silage, having high levels of soluble carbohydrates, which act as a substrate for the bacteria to function. Corn is a good silage crop since it produces a lot of volume as well as a good nutrient source for cattle. Corn can also be stored in a high moisture form where the grain is placed in the silo much wetter than under normal circumstances but the preservation process is much the same. Other grains which can effectively be utilized in a silage program include grain sorghum or milo. In some circumstances soybeans have even been ensiled. Small grain crops such as wheat, oats, and barley have also been effectively preserved through ensiling. In many, cases, however, these are used more as a forage source than as a grain.
Grass silage is becoming more common all the time. Winter pasture forage such as ryegrass, wheat, oats, and triticale have shown to be excellent forage sources and make superb quality silage. A client I have made 5 cutting of his winter annual forage for silage and averaged 26.5% protein in his silage in 1999. Other grasses such as sorghum sudangrass and even bermudagrass have been effectively preserved in this manner. Legumes such as alfalfa and clovers can also be used but the silage making process is quite a bit more difficult as mentioned above. As stated, legumes typically have a high buffering capacity and are resistant to the reduction of pH which is essential to the preservation process.
Selection of a forage to use depends a lot on what can be grown or access in your area and/or what you are set up to do. Obviously, production of corn or other grain silages takes significant farming capability. Grass silage is normally a lot simpler and can often be accomplished with the forages you normally produce.
Silage Programs May not be for Everyone
With the exception of the baled silage, implementing a comprehensive silage program may take a sizable investment. The obvious advantage is the ability to produce a superior quality forage that is typically very palatable and digestible. The downside is the up-front cost. If one of the less-expensive storage methods is used (i.e., drive-over pile, bunker) the producer still must have a tractor with a front-end loader to remove the material from the pile and some type of a mixer or feeder wagon which can deliver the material out to the animals. Once all the economics are considered, however, and we consider that hay that often has a 20 to 30% waste factor, the economics become more workable. Under much circumstance and in many areas, custom harvesters are available to do the cutting, chopping, hauling and packing. This saves the need to invest in a chopper and silage wagon. Use of custom harvesters make timing of harvest more difficult since to produce the best quality silage the timing has to be right. If your silage cutter is down the highway at your neighbor's the day you need him at your place, a problem can present itself.
Preservation of forages through ensiling can provide us with another option in our overall forage program. By improving nutrient density and digestibility performance can be enhanced. However, it is imperative that producers understand the investments they will be required to make not only in terms of dollars but in the time they must take to learn to do it right.
Dr. Steve Blezinger is a nutrition and management consultant with an office in Sulphur Springs, TX. He can be reached at P. O. Box 653 Sulphur Springs, TX 75483, by phone at (903) 885-7992 or by e-mail at firstname.lastname@example.org.