Some of the best quality silage ever made has come from round bales
sealed in plastic. On the other hand, some of the worst silage that I have
ever seen likewise came from round bales in plastic. These extremes in
quality are related to procedural techniques for putting up round bale
silage and problems that can occur during storage. If proper techniques
are followed, excellent quality silage can be produced, especially from
late summer and fall cuttings. But if bales are not managed properly, it
can be a disaster resulting in total loss of the silage.
It may be easier to preserve hay crop silage in upright, trench and
bunker silos than in large bales sealed in plastic. Plastic is much more
susceptible to air leaks and oxygen infiltration than concrete or steel,
so the ease of maintaining an oxygen-free storage environment is much less
for bales surrounded by plastic than for conventional silos.
The round bale silage system, sometimes referred to as `balage', has
a number of advantages over hay and conventional
silage systems:
1. Substantially reduces the risk of weather damage
to the forage compared with a hay system.
2. Provides flexibility as the baler can be used
for both hay and silage. Main attraction of large round bales is the ease
and
simplicity with which they
can be mechanically handled.
3. Lower overall fixed and operating costs than other
forage systems--requires less specialized equipment and no storage
structures.
4. Baling requires less energy than chopping.
5. Lower field losses than round or square baled hay.
6. The system is easily expandable without a large investment.
7. Can store at a higher moisture content with less seepage loss.
8. Natural green color more likely to be maintained than in conventional structures.
9. Bales can be self-fed, eliminating the chore of
daily feeding usually required with chopped silage.
Round bale silage may be a solution for small dairy operations because
it can be a one man system that helps beat weather and leaf loss and does
not require investment in a large tractor, chopper and special wagons which
an under 40-cow dairy can hardly afford.
There are some disadvantages that need
to be considered as well:
1. Maintaining airtight storage can be a problem.
2. There may be less or incomplete fermentation, resulting in higher pH, unstable silage.
3. Potentially greater storage losses than conventional silos or hay if an airtight seal is not maintained.
4. Cost of plastic bags or wrap.
5. Increases labor requirement compared to round baled hay.
6. Disposal of considerable amounts of plastic is
a nuisance at best and may become a problem as environmental regulations
evolve.
A higher level of management is required for round bale silage-making.
While the manager must pay more attention to details for this system to
be successful, it isn't complicated. As with any other forage conservation
system, keep in mind that the final product will not be any higher in quality
than what is put into the bales. Harvesting the forage at the proper stage
of maturity is critical. A forage crop that is over mature and low in quality
may lack sufficient sugar content for good fermentation, especially if
moisture content is not greatly reduced.
PROCEDURES
Wilting. Baling at the proper moisture
content is more critical with balage than in conventional systems and is
probably the single most important factor in round bale silage-making.
Excess moisture results in improper fermentation (butyric rather than lactic
acid formation) and reduces the amount of dry matter stored per bale, which
greatly increases storage costs (more bags or plastic wrap per ton of dry
matter). Inadequate moisture reduces the extent of fermentation and heat
damage is common due to less compaction and greater entrapment of air if
the crop is too dry.
Low moisture silages (40-60% moisture) have limited bacterial growth
and fermentation (Noller and Thomas, 1985). Since less acid is produced,
the important factor with low moisture silages is the establishment and
maintenance of air-free conditions. That is why low moisture silage storage
is generally confined to sealed upright silos and fine chopping and rapid
filling are critical. Stacks, bunker and trench silos are seldom used because
of the difficulty of obtaining sufficient compaction and maintaining air-free
conditions.
Temperature rise in a tightly sealed silo is dependent upon silage
dry matter (DM) content and compaction (Pitt, 1990). When oxygen is present,
plant respiration occurs, breaking down plant sugars into carbon dioxide
and water and releasing heat. Aerobic and facultative anaerobic microorganisms,
such as yeast, molds, and certain bacteria, can be significant sources
of respiration as well. The heat produced by respiration raises the temperature
of the ensiled forage. Elevated temperatures increase the rate and amount
of protein breakdown (proteolysis) to soluble non-protein nitrogen (ammonia,
nitrates, nitrites, free amino acids, etc.). Heating is less in more compacted
forage, because compaction tends to exclude oxygen. And, since water is
a good absorber of heat, temperature rise is less as moisture content increases.
Silage temperatures below 90F indicate good compaction and proper DM content.
Optimum moisture content for good round bale
silage-making is 50 to 60%. At 40 to 50% moisture, heat damage
can be expected and at less than 40% moisture, burnt forage or even spontaneous
combustion may occur.
Baling.
Most large round balers can successfully bale wilted forage, but the variable
chamber balers seem to do a better job than those with fixed chambers.
Chain-type balers have sometimes had an advantage over belt-type since
excessive slippage of belts may occur with wet forage in some machines.
Roll the bales as tightly and evenly as possible. This helps to exclude
air, improves fermentation and reduces losses during feedout. If you are
using bags, be sure bales are the correct size to fit the bags. Bags should
fit bales snugly to minimize air space, but should be big enough to slip
over the bales without difficulty. Tight, dense, uniform size bales not
only provide a better fit of bags and wrap but enables stacking bales for
storage. Baling ground speed should be less than speeds used in making
field-cured hay. This results in tighter, more dense bales. Desired density
is 10 to 15 lbs DM per cubic foot.
Keep in mind that bales containing 50 to 60% moisture will weigh about
double that of dry hay bales of the same size. The typical diameter and
weight of round bale silage baled at 55% moisture are: 4 ft, 800 to 1,000
lb; 5 ft, 1200 to 1600 lb; and 6 ft., 2200 to 2700 lb (adapted from Harrison
and Fransen, 1991). Don't overload the strength of your baler, tractor
or loader. After you have made the first bale, try to lift it with your
bale handling equipment to see if the weight is acceptable. There is not
much that you can do after the field has been baled and then discover that
the bales are too big for the bags or too heavy for the loader or wrapper.
Net or plastic twine are recommended for tying bales -- the chemical preservative
in sisal twine may degrade the plastic bag or wrap.
Storage site selection. Choose storage locations as close to the planned feeding sites as possible. Conditions are much more favorable for moving bales in the summer than they are during the winter. Bales should be stored in a well-drained site clear of trash or sharp objects and free of as much vegetative growth as possible. Grassy areas should be mowed before bales are moved onto the site. A clean site reduces the potential for rodent damage to the bags.
Select a shady area, preferably on a north-facing slope or in the shadow of a tree line or wooded area. Solar heating of the material inside the plastic appears to be the cause of much of the deterioration of silage from early summer cuttings stored outside until winter. The farther south you go, the greater this problem. Diurnal variations in temperature cause a migration of moisture from the tops and south-facing sides of bales to the bottoms and north-facing sides. Direct solar radiation increases temperature within the plastic during the day and vaporizes water, which then condenses primarily on the cooler north sides and bottoms of the bales at night.
In a storage trial conducted in Maryland in 1990-91, bales from each
cutting were placed in bags and stored in three ways: in a barn out of
direct sunlight, outside in direct sunlight and outside under a sheet of
black plastic to exclude sunlight. First cutting was baled May 7, second
June 11, third July 9 and fourth August 13. Feeding of the bales began
in early December and continued through February.
The bales from the first three cuttings stored in the barn had considerable
surface mold but were subjectively rated from `good' to `excellent' --
first cutting bales good, second cutting very good and excellent and third
cutting excellent. First cutting bales had more surface mold than third.
In all cases the balage had a good silage smell, palatability was good
and the bales were totally consumed by dairy cows.
The highest rating for bales from the first three cuttings stored outside
in direct sunlight was 'fair' and many were a total loss. The top and south-facing
side of the bales were generally dry with considerable mold and very musty/moldy
odor. The north-facing side and bottom of the bales were wet and slimy
on the surface but had a reasonably good odor and cows would generally
consume that portion of the bale. When silage refused by the cows was combined
with bales that were unfeedable, total losses for each of the first three
cuttings were estimated to be 60 to 65%.
The intent of placing a black plastic sheet over bales stored
outside was to exclude sunlight, thereby reducing possible deterioration
of the bags and detrimental effects of sunlight on the silage. What seemed
like a good idea in theory was definitely not a good idea in reality --
all bales from the first three cuttings stored this way were a total loss.
These bales had very objectionable, foul odors and often the entire surfaces
of the bales were slimy. The black plastic turned out to be a superb solar
heat collector. The elevated temperature levels created under the black
plastic were not conducive for high quality silage. We were not able to
determine whether fermentation was inhibited or if the breakdown occurred
later in storage due to overheating.
The fourth cutting results were much better. All bales, whether stored
inside or outside, were rated as excellent. In this case, surface mold
was less of a problem on bales stored inside and moisture transfer was
much less of problem in bales stored outside in direct sunlight.
Our experiences on the research farm as well as some farmer experiences
indicate that under Maryland conditions, bags are not a satisfactory method
of storing spring and early summer cuttings of forage for winter feeding.
Use of bags or tubes in the more southern climates should probably be limited
to late summer and fall cuttings or where spring and early summer cuttings
will be fed within a relatively short storage period (within 1 to 2 months).
Side-by side comparisons of bagged and wrapped balage in Maryland in
1993-94 showed wrapping to be superior to bagging but moisture migration
and heat damage on the top and south-facing surfaces were still significant
problems with first, second and third cuttings stored outside. Tight wrapping
would be expected to exclude more air initially and to maintain a tighter
seal. And the tighter fit may minimize the pumping action of the wind as
compared to a loose fitting bag.
Again, shady areas on north-facing slopes are preferred storage areas,
especially in the more southern climates.
Bale handling equipment. Bale
handling equipment ranges from spear-type devices to fork lifts and trailer-mounted
sleds. Spears can be mounted on front-end loaders as well as three-point
hitches. If using a tractor with a front-end loader to move bales from
the field to the storage site, carrying another bale on the hitch not only
increases efficiency but provides better stability of the tractor. Spears
are the preferred implement for lifting bales when bagging. To move or
stack bales after wrapping, moveable forks with rollers to slide under
and cradle the bale or clamps which squeeze the bale while lifting are
needed to avoid puncturing the plastic. Trailer- mounted sleds can be used
to pick up and move several bales at a time from the field to storage site.
Bagging. Bag the bales at the storage
site. After positioning the bales for storage, slip the bags over the bales
before they are set on the ground or on top of other bales. Bagging is
easiest and most efficient with two people -- one on each side of the bale.
Excess air should be pushed out of the bag before sealing but it is not
necessary to completely evacuate the bag. In fact, removing air with a
vacuum cleaner or pump may result in punctures of the bag by plant stems
and cause more harm than good.
Sealing is also easiest with two people. One person pulls and twists
the end of the bag while the other ties it with a good quality twine. The
twisted end should then be bent back onto itself and tied again to ensure
air tightness. If bags swell up with gases for a few days after ensiling,
that is a sign of a good seal. However, polyethylene plastic film used
for these bags is not totally airtight, allowing the carbon dioxide formed
as the fermentation process begins to be vented. Thus the bags then shrink
back to bale size. If you see any bags that do not swell, check for leaks
or holes and repair them.
Use good quality polyethylene bags having an ultraviolet light inhibitor.
They are more expensive but allow less oxygen to infiltrate and will better
withstand storage in direct sunlight. Black bags tend to weather better
than white bags, but high temperatures can be a problem with black plastic.
Suppliers should be willing to guarantee bags for one year.
Reuse of bags is generally not recommended. Even with good quality
plastic, minor pinholes that may go undetected when examining bags can
result in loss of the silage, a loss much greater than the cost of new
bags. If bags are being considered for reuse, a good way to inspect them
is to inflate them with a fan in a brightly lit area (outside on a bright
sunny day is ideal). Then from inside with the bag over your head, look
for light shining through holes. Used bags should be rolled on a bar or
rod, stored in dry place protected from sun and excessive heat and kept
off the floor or ground to discourage rodent damage.
Some round bale silage makers report improved results with double bagging
utilizing used bags. A second bag gives added protection and further return
on the investment.
Wrapping. Wrapping is sometimes
quicker than bagging and requires less labor (Table 1), but it means a
capital expenditure for another piece of equipment. According to Garthe
and Hall, a minimum of 100 bales a year should be wrapped to justify the
machine cost ($6,000 to $12,000, depending upon level of sophistication).
Plastic for wrapping is usually one mil (0.001 inch) thick and should
have a tackiness agent to provide proper sealing. A roll will typically
cover 25 to 30 bales. Each bale requires 1.5 to 2 lb of plastic. Cost of
plastic per bale is about half that for bags (Table 1). A 50 percent overlap
of the plastic and wrapping twice (four layers) provides a better seal
than 25 percent overlap providing four layers. As with bags, the wrap is
not totally airtight and again the plastic should be guaranteed for at
least one year.
Inspect bales weekly. Inspect the
plastic weekly and patch holes as soon as they are found. With bags, wind
causes loose plastic to bellow and provide an air exchange if there are
holes, which usually results in spoilage of the outer layers and sometimes
the entire bale in a matter of a few days. Duct tape, masking tape, etc.
are not suitable for patching holes -- they usually do not adhere longer
than a couple of weeks. Appropriate polyethylene tape is available from
the bag or plastic wrap supplier.
Feeding. Livestock access to bale
silage should be restricted with feeding rings or other devices to control
feeding losses. If bales are simply placed on the ground with unrestricted
animal access, feeding losses can be up to 50 percent. Use of a feeder
ring can reduce loss to 10 percent or less. Mobile feed carts designed
for unrolling or grinding bales are available, but it means a capital investment
for another piece of equipment.
COMPARATIVE COSTS TO OTHER SILAGE
SYSTEMS
Garthe and Hall compared the costs of wrapping and bagging in Pennsylvania
(Table 1) to other systems. In their analysis it would cost about $52 and
$30 per ton to ensile similar amounts (150 and 300 bales, respectively)
of chopped forage 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 a year and $21 per ton if it is filled twice a year. Based
on these figures the 300-bale wrapped round bale silage system is competitive
in costs to the concrete stave silo system filled twice a year and considerably
cheaper than the stave silo only filled once a year. This is a particular
advantage for smaller dairy or livestock producers who can not justify
the large capital expenditures for new or expanded facilities.
POSSIBLE ANIMAL HEALTH CONCERNS
One of the advantages of balage listed at the beginning of the paper
is that forage can be stored at a higher moisture content without seepage
loss than in tower silos. This advantage led to a deadly problem in at
least one case that I am aware of.
During a period of extremely wet weather, an oats/alfalfa mixture (alfalfa
underseeded in a spring oats companion crop) was apparently baled too wet
for fermentation to occur. Since the crop was not wilted, it appears that
starch and sugar levels were not sufficient to enable fermentation and
thus the pH did not decrease. Three weeks after baling, a bale was fed
to 30 Jersey cows. The bale was not apparently moldy nor did it have any
other appearance to indicate that there might be a problem with this bale.
However, that one bale resulted in the death of 15 of the 30 cows.
Veterinary diagnosis determined that the cause of death was ochratoxin.
Ochratoxin is a mycotoxin produced by molds. It can be found on barley
and oats in Scandinavia, however, its occurrence in North America is not
as well documented as that of aflatoxin and several of the other mycotoxins
(Buchanan-Smith and Young, 1991). The toxin destroyed the cow's kidneys.
Mycotoxins are more frequently associated with moist grains and near
the surface of trench, bunker and non-sealed tower silos. While the toxins
seem to be everywhere in the environment, they are usually not a problem
in silage because the acids in silage prevent their development or destroy
them. But in this case the pH remained at 7 after three weeks. The pH should
have been 3.4 or 3.5 and the silage safe if the crop had been adequately
wilted and proper fermentation taken place.
This situation is presented to illustrate possible animal health problems
that can occur if proper management procedures are not followed and the
forage either does not ferment or fermentation is incomplete. The balage
system is not any more prone to these problems than other systems IF
proper bale silage management procedures are followed.
SUMMARY
Balage can be the best or worst of systems. More attention to details
is necessary but the system is not complicated. It is a flexible, lower
capital cost method of preserving forage. Its use is increasing, especially
on smaller farms that cannot justify investments in specialized equipment
and storage structures.
If you are not presently using this system and you want to try it,
go slowly at first. You may find it to be a valuable additional or alternative
way to handle forage, or you may find that it will not fit in your operation
at all. Trying it on a small scale is the best way to find out.
The assistance of Ivan Glick, Ag Journalist, Lancaster,
PA is gratefully acknowledged in the authorship of this paper.
REFERENCES
Buchanan-Smith, J. G., and L. G. Young. 1991. Storing and feeding of
high moisture grains. p. 93-103. In K. K. Bolsen, J. E. Baylor and M. E.
McCullough (ed.) Field Guide for Hay and Silage Management in North America.
National Feed Ingredients Assoc., West Des Moines, IA.
Garthe, J. W., and M. H. Hall. 1992. Large round bale silage. Penn
State Coop. Ext. Agronomy Facts 9.
Harrison, J. H., and S. Fransen. 1991. Silage management in North America.
p. 33-67. In K. K. Bolsen, J. E. Baylor and M. E. McCullough (ed.)
Field Guide for Hay and Silage Management in North America. National Feed
Ingredients Assoc., West Des Moines, IA.
Noller, C. H. and J. W. Thomas. 1985. Hay-crop silage. p. 517-527.
In M. E. Heath, R. F. Barnes and D. S. Metcalfe (ed.) Forages: The
Science of Grassland Agriculture. 4th ed. Iowa State Univ. Press, Ames,
IA.
Pitt, R. E. 1990. Silage and hay preservation. NRAES-5. Northeast Regional
Agric. Engineering Service, Ithaca, NY.
Table 1. Comparative costs of
wrapping versus bagging for two typical circumstances.
- 300 bales/year -
- 150 bales/years -
Inputs
Wrap Bag
Wrap
Bag
Plastic Price $/bale 3.50 7.00 3.50 7.00
Labor
No. workers
2 3
2
3
Bales/hour
25 20
20
16
Wage $/hour
6.00 6.00
6.00
6.00
Machine
Price $
6,000 5,000
6,000 2,000
Interest %/year
10 10
10
10
Life Bales
4,000 5,000
4,000 5,000
Salvage value %
20 20
20
20
Size
Bale weight lb DM
600 600
600
600
Results
Plastic cost
$/bale 3.50
7.00
3.50
7.00
$/ton 11.67 23.33
11.67 23.33
Labor cost
$/bale 0.48
0.90
0.60
1.13
$/ton 1.60
3.00
2.00
3.75
Machine cost
$/year 787.23 602.66
641.03 206.96
$/bale 2.62
2.01
4.27
1.38
$/ton 8.75
6.70 14.25
4.60
Total cost
$/bale
6.60
9.91
8.37
9.50
$/ton DM 22.01 33.03
27.91 31.68
Source: Garthe and Hall,
1992.
*This paper was published in the Proceedings of the 25th National Alfalfa Symposium, Feb. 27-28, 1995, Liverpool,NY