Advantages and Disadvantages
Round bale silage, like any storage method, has its strengths and weaknesses.
Making round bale silage consists of wilting a forage to 50 to 60 percent moisture content, baling it in a round baler, and ensiling it within a plastic cover. This silage-making technique can be used as a feed option by any farmer who produces forage, and it does not require a large silo or haylage harvesting equipment.
Round bale silage, like any storage method, has its strengths and weaknesses. As a low-cost storage unit for long-stem grasses or legumes, it benefits the small or part-time farmer in particular. The bales can be placed in convenient locations around the farm to provide small feeding units for planned consumption time. If silo capacity is lacking during times of forage surplus, round bale silage can supply needed storage capacity. In addition, large round bale silage can provide more precise allocation of forages, based on quality, to different classes of animals than either upright or bunk type silos. However, the storage cost per ton of forage is greater than for a permanent storage structure that will be filled twice each year. Disposal of the used plastic wrap or bag is also an environmental concern.
Another advantage is shortened harvesting time, since the cut crop needs to wilt only a few hours before baling. Anticipated rainstorms or high-humidity conditions are a constant risk when working with hay in Pennsylvania, but are less of a problem with silage. The 50 to 60 percent moisture content at baling reduces leaf loss during harvest, which results in a higher quality protein source than field-cured hay. Ensiling does not, however, improve forage quality. The general adage of "garbage in--garbage out" is certainly true with ensiled forage regardless of the storage structure.
Making and feeding the silage bales are labor efficient. One person can complete the steps involved in making round bale silage if adequate equipment is available. Without a well-designed feeder, feeding and trampling losses are comparable to or greater than hay losses. Assuring tight bale seals is of utmost importance since uncontrollable air leaks can result in varied feed value, mold, and excessive spoilage losses.
Steps in Making Large Round Bale Silage
Mowing with a mower-conditioner is best. Leave the mowed forage in the swath long enough for it to wilt to 55-65 percent moisture. Drying periods usually range from two to three hours, or overnight if mowing is done late in the day.
Baling with a fixed-chamber baler is easiest since it makes uniform size bales which fit easily into bags or stack neatly when wrapped. Some balers will require modifications, such as scrapers to prevent gum buildup on belt rollers, or shields to prevent wrapping of the crop. A slow forward speed helps make tight bales which are less likely to spoil. Net tying or plastic twine are recommended; sisal twine should be avoided since the chemical twine preservatives often degrade the plastic wrapping. Inoculants can be added, but usually are not necessary. Hauling the bales to a bagging or wrapping site immediately helps insure feed quality as well as bale roundness, which is mainly important when wrapping.
Wrapping bales is quicker than bagging, but it requires a bale wrapping machine, which means a capital expenditure which you don't have with bagging. Wrapping machines cost around $6000 to $12,000 depending upon the level of sophistication desired. In order to justify the machine cost, one should wrap a minimum of 100 bales per year. A recent study revealed that two workers can wrap 25 - 30 bales per hour.
Plastic for wrapping usually is one mil (0.001 inch) thick and comes in rolls which are 5000 or 6000 feet in length. Each roll will cover 25-30 bales. The plastic costs $3 to $4 per bale and can be used one time only. Each bale requires from 1.5 to 2 pounds of plastic, so ask your supplier about a recycling or rebate option for the used plastic.
Quality plastic has a tackiness agent which is crucial to proper sealing. The plastic is typically stretched 50 to 55 percent in order to get the correct tension. Several years ago, instructions were to wrap each bale rotation with a 25 percent overlap of the plastic, therefore providing each bale with four layers of plastic. Today, four layers are still recommended, but in order to create a better seal, the bale should be wrapped with a 50 percent overlap and then wrapped twice. Like bagging, the wrap is NOT airtight but it does restrict enough air exchange that fermentation can take place. Best results are achieved when 100 percent virgin plastic is used, which is warranted for a minimum of one year.
Bagging is trickier than wrapping. After a few bales are made, check the bag fit. Bag at the storage site only, since this area already should be cleared of obstacles and nuisances that puncture the bags. Once the bag is over the bale, push out excess air before sealing. To seal the bag, a strong hand is needed to twist and stretch the bag end while a second hand or a second person ties a knot with rope. Twist tightly and tie once, then bend the twisted plastic back onto itself and tie the two twists together. Polyethylene (PE) plastic film used for these bags is not airtight. As a matter of fact, low density PE is four times more permeable to carbon dioxide gas than it is to oxygen gas, allowing the bags to vent excess carbon dioxide gas as fermentation begins.
If you find holes in the bagged bales, patch them as soon as possible, since wind causes loose plastic to bellow out providing an air exchange which usually spoils most of the outer layer of the bale. Duct tape and masking tape last about three weeks before they fall off, but bag suppliers have a PE tape which adheres for bag life. Bags are rarely reusable because of minor pinholes.
No research has revealed that any bag color is better than another as far as silage quality is concerned. Black plastic bags have an ultraviolet inhibitor called carbon black, which limits bag degradation under sunlight. White and green bags will degrade quicker. If a bag is made from quality materials, your supplier should be willing to guarantee it for one year.
Bags cost from $6 to $8 each in 1991 prices. For comparison, it would cost about $52 and $30 per ton to ensile similar amounts of forage to 150 and 300 bales, respectively, in long tube type bags. The cost to ensile the equivalent of 300 bales in a concrete stave silo is over $42 per ton if the silo is filled only once and $21 per ton if the silo is filled twice each year.
There are numerous bale handling devices to move or transport the bagged or wrapped bales, with new ones being introduced regularly from other countries.
Most seem to fall into the following categories:
- Spears, either mounted on a front-end loader or on a three-point hitch
- Twin moveable forks with rollers which slide under and cradle the bale
- Disks which clamp and squeeze the bale while lifting
- Grapples with overhead arms
- Trailer mounted sleds which slide under bales
Regardless of the design, each requires at least a 50 hp. tractor in order to safely move the bales.
The storage site will give best results if stubble and sharp objects are cleared. Some people lay an old piece of plastic on the ground prior to placing the bales. Spray the perimeter of the stack to kill weeds which harbor insects and rodents.
Do not cover the bales with an extra layer of plastic because it makes an ideal nesting site for rodents. Rodents can chew through the plastic wrap or bag which will greatly increase storage losses. Find a shady area, preferably on a north facing slope, to avoid temperature fluctuations which can degrade both the silage as well as the plastic.
To increase bale density in storage, consider stacking the bales as follows:
- Above 75% moisture content, use a single layer stack
- Between 65% and 75% moisture, use a double layer stack, pyramid fashion
- Below 65% moisture content, stack up to three layers high, pyramid fashion
Feeding round bale silage is similar to feeding large-round bales of hay in that conventional bale feeding rings can be used. With the high investment in wrapping bales, it is essential to control feeding losses.
Some studies have shown there can be up to 50% loss when large round silage bales are simply unrolled on the ground. This loss can be reduced to less than 10% by using a simple ring feeder. Mobile feed carts, especially designed for unrolling or grinding large bales within narrow barn alleys are now available in the United States. In addition, tub grinders can work but plugging on the large bales of silage may be a concern.
The feed quality of large round bale silage, especially those bales with a high proportion of legumes, may cause overfeeding to some classes of animals. Consider using the the high legume bales for classes of animals that require high quality forage or restrict the amount of bales available at any time.