MAKIm AND USIh SILAGE
D. W. Beardsley
This report was presented orally be.
fore the Southwest Florida Cattlemen's
Short Course in Fort Myers, on May 21,
EVERGLAIES STATION 1ITIEO REPORT 56-15
Belle Glade, Florida
May 21, 1956
MAKING AND USING SILAGE
D.W. Beardsley 1/
Ensilage, or silage as commonly used, is a term used to denote moist material'
which has been preserved in the absence of air for feed. Originally it meant mater
al placed in a pit and stored for later use. The idea probably developed from the
use of pits for grain storage in Biblical times. "Today, however, it'includes mater-".
al preserved in all kinds of structures, --towers, trenches, bunkers, stacks, as wel:.
The primary aim in making silage is to preserve material grown at one season
or time for feeding at another season when forage is in short supply. In cold cl.-
mates with relatively short growing seasons enough forage has to be produced in sun-
mer to last the rest of the year. The same is true in areas of varied rainfall
which leads to long dry spells. In Florida the cold weather usually coincides with
or overlaps the dry season making a three to five months season when pasture is often
Because of tremendous fluctuations in carrying capacity from a low in winter
to a high in summer, it is almost impossible to stock a pasture so that its produc-
tion is utilized efficiently. At the Everglades Station the carrying capacity often
varies from less than one yearling per acre in winter to as many as five during the
early summer. Some means of leveling off these peaks and valleys of forage produc-
tion woald permit a more efficient ranch operation. The making of silage certainly
deserves consideration under these conditions,
In addition to the potential of summer grass production, the making of silage
from planted crops offers considerable promise in this area. Field corn, sorghum,
and similar crops can be planted in the spring following vegetables and harvested for
silage before the land needs to be plowed again for vegetables in the fall. A combi-
nation vegetable-ranch operation with silage produced in the summer offers many ad-
vantages to both sides of the enterprise.
In order to understand better the how and why of silage making, let us con-
sider just what changes occur in the ensiling process. It might be well to keep in
mind that in this process'the fresh material used for silage making goes through
about the same kind of a pickling process that cabbage does when making sauerkraut.
In material well ensiled, prepared without additives, the changes are as follows:
Phase 1. The continued respiration of the plant cells results in the production of
carbon dioxide, the utilization of simple carbohydrate and a flow of water from
the mass due to these biochemical happenings and the mechanical compression of
the crop. These events are accompanied by the evolution of heat.
Phase 2. The production of acetic acid in small amounts by organisms of the coliform
group and others. This phase is of short duration and merges into Phase 3.
I/ Assistant Animal Husbandman, Everglades Station, Belle Glade.
Phase 3. The initiation of a lactic acid fermentation dependent upon the activity
of lactic acid organisms, lactobacilli and streptococci supported by adequate
Phase 4. This is a stage of quiescence in the mass during which the lactic acid pro-
duction passes its peak and remains constant at 1-1.5% of the fresh materials,
the material remaining at a constant pH of less than 4.2.
These four stages take place in about three weeks with the first three com-
pleted in about three days. If the material has been properly ensiled, adequate
production of lactic acid has been obtained and air is excluded, the silage should
remain relatively stable and in good condition for a considerable length of time-
ten years or more. If, however, the conditions within the silage are unsatisfactory
and incomplete production of lactic acid is obtained, a fifth stage may set in.
Phase 5. The attack by butyric acid-producing organisms on both the residual solu-
ble carbohydrate and the lactic acid which has already formed. This is accom-
panied by, in extreme cases, a deamination of amino acids with the formation of
higher volatile fatty acids and ammonia as well, possibly, as a decarboxylation
leading to the formation of amines and carbon dioxide.
The discussion of the fermentation process boils down to this: the practical
aim in the ensiling process is the production of enough lactic acid by certain mi-
croorganisms to inhibit further breakdown of the ensiled material by other types of
From a chemical standpoint good quality silage has certain characteristics:
1. A pH of 4.5 or less (the nearer 4.0 the better).
2. Low volatile base content (0.5 % or less, expressed as ammonia).
3. Lactic acid content of 3 to 5% or more.
46 Butryric acid content of 2% or less.
All these characteristics except pH are expressed on the dry basis; pH is the
same, wet or dry. Silage which possesses these characteristics will have a mild,
pleasing odor, a light to dark green color, is readily accepted by cows and has a
higher feeding value than silage that does not approach these standards. It might be
added that husbands handling silage of good quality are more acceptable to their
wives than those handling foul smelling, poor quality silage.
Many different factors are involved in making silage. Some of the important
ones are the kind of crop used, moisture content, stage of harvesting, harvesting
equipment, preservatives, storage structures. One thing should be kept in mind at
all times, or consideration of these factors means nothing, and that is air must be
excluded from the material being ensiled by proper packing,
Any crop which is suitable for feeding to livestock green or fresh can be
used for making silage. It should be kept in mind, though,that the silage produced
will be no better than the material put in.
The most widely used crop for silage, at least in this country, is corn. In
the Midwest when the word "silage" is used in discussing livestock feeding, corn si-
lage is automatically understood. Grain sorghums are probably next in importance of
the grain crops used. An estimated 4,600,000 acres of corn and 900,000 acres of sor-
ghums are grown annually in this country for silage.
The use of legumes and grasses for ailage has grown tremendously in the last
twenty years, (The term "grass silage" is somewhat misleading because it has gener-
ally been used to denote silage made from legumes or legume-grass mixtures, but for
this discussion I prefer to call silage made from legumes, "legume silage", and that
made from grass, "grass silage".) One of the principal advantages of most of these
forages is their permanency and the fact that several cuttings can be made in one
harvesting season. Alfalfa, clovers, soybeans, cowpeas, hairy indigo are a few of
the legumes which will make good silage with proper handling. Most all the common
grasses in Florida, including pangola, St. Augustine, Bermuda, carib, para, and
napier have been used successfully. In addition, oats and millet have been used with
A few miscellaneous materials which can be mentioned that have been used for
silage are citrus pulp, sugar cane, potatoes, sunflower, beet pulp, sweet corn can-
nery waste and sweet corn stover.
One of the important factors which help to determine quality and the need for
preservatives and conditioners is the moisture content of the material ensiled. Most
silage-making authorities agree that the optimum moisture content is about 65 to 70%.
Good silage can be made with moisture ranging from 60 to 75%. Beyond these limits
more precautions must be taken to insure good quality. If the material is dry, water
should be added. If the material is wet, strong smelling silage will be produced un-
less absorbents or extra preservatives are added. Wilting a lush crop for a few
hours may serve the purpose when this is practical. Proper drainage is essential
even though runoff may carry away some of the nutrients.
Stage for Harvesting
Another factor which must be considered is the stage of harvesting the crop
for silage. In order to get the highest yield of good quality feed, most crops
should be harvested before they are completely mature. Some compensation has to be
made between total yield and highest quality. Corn and sorghums should be harvested
when the grain is in the dough stage. Most of the leaves are still green at this
time. Legumes such as alfalfa should be harvested in early bloom stage, before the
stems get too woody. With perennial grasses it is difficult to say at what stage
they should be harvested, but certainly before the stems get tough and the lower
leaves begin turning brown.
Preservatives and Conditioners
The need for preservatives in making silage depends upon the kind and condi-
tion of the material being ensiled. Any ensilable material which contains readily
available carbohydrates, such as sugars or starches, needs no preservative added.
Corn, sorghums, sugar cane, potatoes and some grasses are examples of this. All le-
gumes and many of the grasses need a preservative to insure good silage.
Two general types of additives have been used to insure proper preservation
of the ensiled material:
1. Carbohydrate sources--nolasses, ground grains, whey.
2. Mild antiseptics
(a) Acids--phosphoric, phosphoric-sulfuric, formic.
(b) Sulfur dioxide, sodium metasulfite.
The molasses and grains provide sugar and starches which can be used by mi-
croorganisms to produce acids. The mild antiseptics help prevent undesirable fer-
mentation. In the first case desirable bacterial action is promoted and in the sec-
ond undesirable bacterial action is prevented.
In many instances the addition of conditioners to the fresh material being
ensiled will improve the quality of the silage produced. This is especially true
with high moisture content materials. These conditioners are dry materials that act
by absorbing excess water from the mass; for example, corn cobs, dried beet pulp,
dried citrus pulp, citrus meal, chopped hay or straw. An excellent means of insuring
a high quality legume silage would be to add ground snapped corn or dried citrus pulp
with citrus molasses to provide both a carbohydrate source and an absorbent,
Molasses should be added when needed at about 60-100 pounds per ton of green
material. When ground snapped corn or dried citrus pulp is used 150-250 pounds
should be adequate. Sodium metabisulfite should be applied at the rate of 8-10
pounds per ton of green material.
Forage harvesting equipment used in silage making ranges from a tractor with
a sickle-bar mower and a buck rake to a self-propelled forage harvester capable of
cutting a 7-foot swath-across a field of sorghum. The kind of crops harvested, the
amount of use it gets, the convenience of operation, the maintenance needed and cost
of operation all should be considered in trying to determine which type of machine is
best suited to your operation. If both corn and grass are to be harvested, a forage
harvester with a row-crop attachment night be most desirable. In instances where the
crop should be wilted to reduce moisture before ensiling, a pick-up attachment would
Two or more wagons or dump-trucks will be required for hauling the cut forage
to the silo. Self-unloading wagons operated from the power-take-off of the tractor
have proved very satisfactory for our work at the Everglades Station. For filling
upright silos a blower or elevator is needed in addition.
For adding straight molasses to the green-cut material at the harvester, a
gear or vane type pump with a minimum 1" intake can be used if properly installed.
Molasses may be diluted with water and pumped onto the material as it is spread in
the trench or bunker or onto the feed table of the blower with ordinary low gallon-
age, low pressure type spray equipment. This dilution of the molasses with water is
generally not recommended in this area because the forages used are already high in
The sodium metabisulfite can be easily applied to the forage as it is har-
vested through an ordinary star-type fertilizer drill mounted over the feed roll of
the harvester. Ground snapped corn and dried citrus pulp can be added by hand or by
blowing into the wagon as a layer or onto the feed table.
The main types of storage structures used in this country are:
1. Upright--concrete, glass-lined.steel, wood.
2. Trench--lined with concrete or wood, unlined.
3. Bunker-above ground; concrete, frame, or wire sides.
U. Stack-no structure at all.
Probably the best structure from the standpoint of nutrient losses is the
airtight, upright silo, while the poorest is no doubt the stack. The cost of the
structure per ton of stored material ranges from about $30.00 for the best to nothing
for the poorest. The trench and bunker which have become very popular in this state
probably cost from $2 $10 per ton of stored material. In hilly areas particularly
with clay subsoil, trenches are usually most economical. In muck areas, or where
drainage is poor, bunker'type silos can be used to advantage. In flat sand country
such as in South Florida, above ground trenches have been used very successfully.
The cost of making silage would naturally depend on the many factors which
enter into the operation. The type and amount of equipment used, the yield of for-
age, the cost of structures, etc., enter into the overall efficiency of the operation,
I have heard from many different ranchers who have made silage figures which range
from $2-$10 per ton of material ensiled. At the Everglades Station in our grass si-
lage studies, operating costs have run about $2-$3 per ton of green material put into
the bunker. Adding depreciation on equipment and storage structure and ensiling
losses, we obtain a figure of about $$ per ton for silage fed out. Assuming 3 to 4
pounds of silage is equivalent to a pound of hay, this means hay would have to be
produced at $15 to $20 per ton to be competitive.
Silage as a Feed
There is no question but what silage properly made is excellent feed. Ac-
cording to many Midwestern cattle feeders, corn silage is the feed par excellence.
Good quality silage is very palatable to cattle and very little is re-used. It usu-
ally contains considerably more carotene and other vitamins, except vitamin D, than
does hay. Although silages properly supplemented with protein and minerals might be
satisfactory for a year-round feeding program, the most practical use in this area
would be as a supplement to pasture during winter or as a part of a drylot fattening
Chemical analyses of selected silages are given in Table 1 for comparison be-
tween the silage made from grass and legumes and that made from grain crops. Two
principal differences may be noted. Generally, silages made from grasses and legumes
are higher in protein and lower in total digestible nutrients (TDIT) than silage made
from corn or sorghum. In calculating rations, consideration should be given to the
fact that the shelled corn equivalent of good corn silage is about 15% of the silage
Table 1. Proximate analysis of silages.
Silage DM CP EE CF Ash NFE TDN
Grass & Legumes % % % % % %
Alfalfa 25.0 4.2 0.9 8.1 2.3 9.5 13.7
Grass 26.5 2.9 1.0 9.2 2.5 10.9 16.2
Millet 31.1 2.7 1.0 9.6 2.9 14.9 17.5
Napier Grass 27.1 1.1 0.6 11.8 1.6 12.0 11.9
Sugarcane 21.9 0.9 0.6 8.6 0.9 10.9 13.3
St. Augustine (E.E.S.) 25.0 2.9 0.9 8.1 1.9 11.2 -
Pangola (E.E.S.) 25.0 3.3 1.0 8.5 1.8 10.3 -
Pangola (R.C.S.) 28.4 1.4 0.5 8.5 1.8 16.2 15
Corn 27.4 2.2 0.8 6.7 1.6 16.1 18.1
Hegari 33.4 1.9 0.7 6.8 3.0 21.0 18.7
Sweet corn stover 24.0 2.3 0.5 5.6 1,8 13.8 13.0
(Taken from Morrison's Feeds and Feeding except as indicated.)
In a wintering program the protein content of the silage and pasture would
determine whether or not extra protein supplement should be supplied. A mature cow
given all the grass silage she needed could be maintained on silage containing as
much as 9% crude protein on a dry matter basis. When corn silage, or silage made
from grass low in protein, is used as the major portion of a wintering ration, from
0.5 to 2 pounds of protein supplement may be needed. Certainly no protein supplement
would be required when good quality legume silage is used.
Cows nursing calves have been wintered on pasture and self-fed grass silage
at the Everglades Station for the past two years. Even when stocked at the rate of
1i cows per acre, the cows have maintained excellent condition. This past winter 64
yearling steers made gains of about 0.5 pound daily per animal when self-fed pangola
silage and blackstrap molasses on a 16-acre pangola pasture interplanted with rye-
grass, oats and alfalfa. The major portion of the wintering ration for both cows and
yearlings during the months of January and February waw grass silage. Equivalent re-
sults could be obtained with silages produced on sand land if protein needs are sat-
Hundreds of feeding studies in the Midwest have proved the value of corn si-
lage in a fattening ration. At Purdue, as much as 2.5 pounds per day gain has been
obtained on older steers fed corn silage and 3.5 pounds of a special protein supple-
ment. Probably the biggest drawback to using corn silage in this area for fattening
is the problem of consistently growing a high yielding crop of corn.
At the present time grass and legume silages show considerable promise as
part of a fattening ration. Studies at the various Experiment Stations in the State
have shown that steers fed silage made from St. Augustine or pangola grass will make
good gains and fatten readily when full feed of concentrates is given in addition.
The grass silages do not contain enough TDN to be used as the principal source of nu-
trients in a fattening ration as is sometimes done with corn or sorghum silage. For
best results, no more than one-third of the total dry matter intake of fattening
steers should come from grass silage.
Sweet Corn Silage
Since so much sweet corn is grown in this area, the question naturally arises
"What about using picked-over sweet corn for silage?" The answer is, "It will make
excellent silage, but--". The chemical analysis of sweet corn stover given in the
table indicates it would compare favorably with other silages. A very serious draw-
back from using silage made from the stalks, leaves and immature ears after the crop
has been picked is the insecticide residue. In the process of controlling budworms
and earworms, the leaves are practically coated with DDT or other toxic material.
Even after ensiling this sweet corn silage contains much more than the 1 ppm. maximum
considered safe to feed. Although the cattle fed silage containing more than 1 ppm.
DDT may show no visible effect, the insecticide is deposited in the fat and also se-
creted in the milk. It is the danger to human health that should be considered in
this instance. If a program can be worked'out using insecticides with low residual
action for controlling worms on sweet corn, an excellent feed source can then be
Silage is a term used to refer to moist material preserved in the absence of
air. The primary aim in making silage is to preserve feed material grown at one sea-
son or time for feeding at another season when forage is in short supply.
The ensiling process which takes place is a type of controlled fermentation
in which the production of lactic acid by microorganisms is encouraged. This lactic
acid prevents further breakdown of the nutrients in the mass as long as air is ex-
Good quality silage possesses certain characteristics, such as a mild, pleas-
ing odor, a light to dark green color, and is highly palatable and nutritious.
Among the many different factors which must be considered in making silage
are the kind of crops used, moisture content of the fresh material, stage of maturity,
use of preservatives, harvesting equipment and storage structures. Of primary con-
cern in a silage making operation is the exclusion of air from the mass by careful
Silage properly made is an excellent feed. It can be used as the major por-
tion of a wintering ration for cattle and as a part of a fattening ration. Consid-
eration should be taken of the differences in protein and total digestible nutrient
content when figuring rations based on silages made from grain, grasses and legumes.
The rapid expansion of silage making in this area in the last couple of yearF
testifies to the value of silage in the cattle operations.