Making and Storing Quality Hay
The most important factors affecting the quality of hay are
- Moisture content at baling and time of storage
- Stage of maturity at baling
- Storage conditions
- The forage species
This guide has information on the first three factors as well
as on hay preservatives. It does not deal with forage species.
Some forages, such as alfalfa, orchardgrass, red clover and
so forth, have higher feeding values than some other forages. If
you have questions on forage species, call your local MU
When forage plants are cut, the plant continues to breathe
until the moisture content of the plants falls below 40 percent.
Dry matter is lost during this process, and in some cases the
loss may be as high as 15 percent. Respiration losses, however,
are usually about 5 or 6 percent of the total dry matter. In
normal hay curing, you cannot eliminate these losses.
When the moisture content of hay drying in the field reaches
about 40 percent, further dry matter losses are due to raking
and baling. Losses from these operations range from 10 to 25
percent, with most losses averaging about 15 percent. Dry matter
losses from raking and baling are especially severe because most
of these losses come from the most valuable part of the hay —
Using hay crimpers and crushers can greatly reduce dry matter
loss. Their use reduces curing time in the swath, exposure to
the weather, leaf shattering and respiration losses. All serious
hay producers use crimpers and/or crushers.
The key to keeping dry matter losses of hay to a minimum are:
- bale at a moisture level low enough to prevent excessive
- Prevent infiltration of moisture into the hay after it
has been baled.
When hay is baled, it should not be higher than 18 to 22
percent moisture. At higher levels of moisture, bales lose large
amounts of dry matter (Figure 1) caused by excessive heating and
molding (Figure 2). In severe cases, spontaneous combustion is
Effect of percent moisture at baling time on heat
retention in big bales.
Spoilage loss in bales made from alfalfa-grass at
different moisture levels.
Although there is no danger of burned buildings when you
store large bales outside, excessive heating and molding can
occur, resulting in large dry matter losses. Therefore, don't
bale hay to be stored in the field until the moisture level
reaches 18 to 22 percent. See Table 1.
Dry matter losses of alfalfa-grass in big bales under different
storage conditions. (Howard David Currence, MU.)
First cutting hay
- Moisture at baling
- Dry matter loss
Second cutting hay
- Moisture at baling
- Dry matter loss
Heating occurs to some extent in all forage material unless
it contains less than 15 percent moisture.
The extent of temperature rise and duration of heat
production in hay depends on moisture content. A relative
humidity of 90 to 100 percent, which favors mold development,
can develop in 20 percent moisture hay that is stored inside.
The heat generated by the metabolic activity of the
microorganisms and plant respiration increase the temperature of
hay (Figure 3). Heat resistant fungi are active when the
temperature is between 113 and 150 degrees Fahrenheit.
Causative agents in the heating of hay.
A large variety and number of microorganisms are associated
with plant material in the field, but fungi are the microbes
primarily responsible for breakdown of complex carbohydrates.
Heating above 175 degrees Fahrenheit results in thermal death of
microbes; then heat-producing chemical reactions serve to
further increase temperatures. A subsequent rapid oxidation of
reactive compounds may cause a further temperature rise to an
ignition point of 448 to 527 degrees Fahrenheit. If enough
oxygen is present, flames will erupt. The time required for
heating to combustion may vary from four to 10 weeks, depending
on storage and climatic conditions and on the moisture content
of the forage.
The obvious consequence of spontaneous heating of forages is
combustion, which has resulted in numerous barn and silo fires.
But molding of forages and heating to temperatures below
ignition also result in serious losses of forage quality and
quantity. Available carbohydrate and protein portions of forages
are reduced. Carbohydrates are used in microbial metabolism and
subsequent chemical oxidation. Protein is bound in an
unavailable form (sugar-protein polymer) through browning or the
Moisture levels for safe storage of hay vary with size and
density of the bale and type of hay. In general, hay in small
rectangular bales should be baled at less than 22 percent
moisture to keep molding and heating to a minimum. Large round
bales retain internal heat much longer than conventional bales.
Therefore, hay should be less than 18 percent moisture before
baling in large bales. If you are storing or sheltering some of
your big bales, this long-term heat retention affects the proper
time to move big bales into storage. See Figure 2. Hay baled
with more than 22 percent moisture should probably not be put
into storage for at least 30 days. This is especially true if
bales are to be stacked several layers deep.
With the threat of barn fires removed by outside hay storage,
many operators of large round balers try to bale hay with too
much moisture. But excessive heating and molding can cause the
loss of as much as one-third of the feeding value of hay baled
at 28 percent moisture.
Stage of maturity
The stage of maturity at time of harvest is one of the most
important factors affecting forage quality.
Most forages will have a 20 percent loss in TDN (total
digestible nutrients) and a 40 percent loss in protein by a
delay of only 10 days past the most desirable stage of harvest.
For instance, alfalfa-grass mixtures cut when the alfalfa is in
the late bud to early bloom stage will often contain 65 percent
TDN and 18 percent protein. Contrast this to cutting at the
half-bloom stage or later, with 48 to 50 percent TDN and 12
percent protein. This is a 20 percent loss in the value of the
Grasses, which are somewhat lower in feed potential than
legumes to start with, follow the same decreasing pattern in
feeding value as they mature. Grasses such as fescue and
orchardgrass will often be as low as 6 percent crude protein
after blooming when the seeds are beginning to form.
Legume-grass mixtures should be harvested when the legume
reaches the desired stage of maturity regardless of the growth
stage of the grass.
If the plants are not under stress conditions, the
recommended stages of maturity for harvesting common forage
plants in Missouri are:
- Alfalfa: bud to 1/10 bloom.
- Red clover: 1/4 to 1/2 bloom.
- Timothy: late boot.
- Bromegrass: heads emerged.
- Orchardgrass: blooms emerged.
- Reed canarygrass: heads emerged.
- Tall fescue: boot stage.
Overall losses due to late hay making can reach staggering
proportions. Shattering and wilting losses are always
proportionately higher with late-cut than with early-cut
forages. Such as economic loss affects the profit of livestock
The four major contributors to feed value losses in hay are:
- Late cutting losses in digestibility: 20 percent.
- Wilting losses in the swath: 5 percent.
- Shattering of leaves: 20 percent.
- Too high moisture at time of baling: 15 to 25 percent.
If hay is baled with a moisture content of 20 to 22 percent,
loft or mow-stored hay should not lose more than 5 percent of
its original dry matter during the first year of storage. It
will lose very little of its digestible nutrients during that
time or in succeeding years. One exception: The hay will suffer
some loss of carotene, the precursor of vitamin A, following one
year of storage.
Large bales stored outside will suffer variable losses,
depending upon a combination of factors. These factors are:
moisture of the hay at baling time, amount of rain and snow
during the storage period, internal drainage of the soil on
which bales are stored, amount of space between the bales, type
of hay (grass or grass-legume), and the skill of the operator
making the bales.
There are two types of storage losses suffered during outside
storage. The easiest to see and the one that has been measured
in many experiments is the total dry matter loss. This
represents the weight loss between the beginning of storage and
the time the hay is fed. While this loss is quite variable
between experiments, it is usually in the range of 6 to 15
percent of the total hay stored, with the norm much closer to 15
percent than to 6 percent.
The second type of loss in outside storage is the loss in
digestibility of the weathered portion of the hay. Just because
the cattle eat most of this portion does not mean that it is as
high in feeding value as the unweathered part. In fact, the loss
of feeding value in the weathered portion of the hay usually is
a greater source of loss than that from total dry matter loss.
When these two types of losses are added together, the loss of
total feed during storage will usually approach 25 percent.
A loss of 20.2 percent of the original feeding value of the
hay was lost during storage, but the original dry matter loss
was only 7 percent. If the original dry matter loss during
storage had been 15 percent (an average loss that occurred in
several recent experiments), then the total feed nutrient loss
would have been 27 percent. This is a high price to pay for
outside storage, especially if hay is high quality.
Select your storage area carefully. Store bales on well
drained areas. Some farmers place them on poles or crushed rock
to minimize losses on the bottom of bales. Some research has
shown that these techniques reduce storage losses by 15 percent.
Always place bale rows in the same direction as the prevailing
There does not seem to be much difference in storage losses
of bales set side-by-side versus those set end-to-end. One note
of caution: Bales placed end-to-end should be the same size.
Cone-shaped bales or bales of different diameters placed
end-to-end often cause excessive spoilage on the ends of bales.
Some general guidelines can help reduce outside storage
- Always store bales on a well drained area.
- Use a minimum of 3 feet between bale rows for air
circulation. The more space, the better.
- If bales are stored side by side, leave at least 24
inches between bales.
- Avoid storing bales under trees and in the shade of
- If space is available, store some of the bales inside,
especially the higher quality hays that should be used near
the end of the feeding period.
Farmers in the past often applied salt to hay as it was
stored in the barn to prevent mold and heating. This practice
had some merit, but the amount of salt needed for hay of very
high moisture content would be so great that the salt would be
extremely expensive. In many cases, the salt would lower the
palatability of the hay.
Recent research to prevent storage losses of moist hay
involved organic acids. The ones receiving the most attention
have been propionic-acetic acid mixtures and pure propionic acid
products. They have been successful in reducing molding and
heating and in preserving the original feed value if applied at
correct levels. The major drawbacks have been cost and
application problems. The organic acids probably operate as
fungicides to prevent molds from forming in the hay.
Application rate is dependent on bale moisture. (Table 3).
Moisture content is best measured by taking a sample from the
windrow and drying it using a microwave oven or small commercial
convection ovens. Wet and dry weights can be taken with a gram
scale. For more information about drying hay using a microwave
oven. Stab-type capacitance moisture testers are less accurate
and give higher-than-actual moisture values, especially in dense
Effect of bale moisture on application rates of
propionic and propionic-acetic acid preservatives
- 20 to 24 percent of bale moisture
10 pounds of acid per ton
- 25 to 29 percent of bale moisture
20 pounds of acid per ton
- 30 to 35 percent of bale moisture
30 pounds of acid per ton
Acid preservatives are best applied at the baler. Propionic
and acetic acids are volatile and will be lost if applied long
before baling. Acids remove paint, allowing metal parts to rust.
To reduce rusting, avoid spilling acids on equipment, run
untreated hay through the baler after baling, and coat bare
metal with light oil.
Lactic-acid-forming bacteria and other biological products
are sold as hay preservatives. Research in Wisconsin shows these
products are less effective than propionic acid preservatives.
These products are restricted for use on hay of less than 25
percent moisture, but hay can be safely made at 20 percent
moisture with no preservative. This narrow moisture range limits
the usefulness of these products under Missouri conditions.
Bales treated with preservatives are extremely heavy and, in
most instances, they need to be handled mechanically. When the
bales dry, the strings and wires become loose, making them
difficult to handle. Re-baling may be necessary if hay needs to
be rehandled and transported.
Should you use preservatives? There is no firm yes or no
answer. First, consider the value of the final product. Adding
$5 to $10 per ton in preservatives' cost to a ton of
high-quality alfalfa hay worth $65 on the market is more
economically feasible than adding the same amount to fescue hay
worth about $25 to $30 per ton on the market.
Preservatives reduce the time needed for hay to cure in the
field and, thus, reduce the risk of rain damage to the hay. If
properly used, preservatives substantially reduce storage losses
of high-moisture hay.
Weigh these benefits against the original cost of the
preservative, the extra labor required to apply it, the extra
labor required to handle the heavier hay, and the value of the
end product. Then decide whether to use a hay preservative.