Livestock producers
are continuously faced with the issue of
providing high quality animal protein products to
a growing population with limited resources. Ensuring livestock
are provided with feed and nutrients in
sufficient amounts is key to efficient growth
and proper health, which provides safe high quality
products for the consumer. Understanding the
nutrients livestock require and what ingredients can be
used to best meet these needs is important, as animals
convert these key energy sources into suitable
products for human use and help meet the
growing demands. Feed or feedstuff can be
defined as any material given to livestock to meet
nutritional requirements. Feed is a substance
given to livestock, while food is a substance
livestock find for themselves. Nutrients are components
found in feed, which provide the
necessary elements for physiological and
metabolic processes. These nutrients include water,
carbohydrates, lipids, protein, vitamins, and minerals. Ration balancing
and feed delivery are key in managing the quantity
and quality of nutrients fed to livestock. A ration is defined as
a mixture of feedstuffs supplied to an animal
in a 24-hour period. Providing the proper amount
of nutrients to an animal is crucial for the development
and growth of an animal as well as the success
of an operation. When nutrient requirements
are not met by the ration, livestock performance
will be compromised. But when excess nutrients are
supplied, they are excreted and resources are wasted. Therefore, ensuring
livestock receive correct levels of a nutrient
is important for both the wellbeing of the animal and
the productivity of a producer. When creating a
ration for livestock, there are two major
categories of feed-- roughages and concentrates. Roughages are generally
high in fiber, and concentrates are generally
high in energy and or protein. Understanding how rough edges
and concentrates are fed to and digested by livestock
help guide decisions for choosing ingredients to
provide required nutrients. The first category of feedstuff
used in livestock rations is roughages. Roughages are plant
based feedstuffs which are high in fiber, which
is a type of carbohydrate. The cell walls of
plants are made up of cellulose and hemicellulose. Cellulose and hemicellulose
are rigid molecules and are used by plants as
structural carbohydrates. Plants would wilt without
these structural carbohydrates and would not be
able to grow tall. For example, trees are
very high in cellulose. In contrast to the cell
walls, the cellular organelles and cytoplasm contained
within the cell hold sugars and starches. A roughage is a feed that's
fairly low in nutrients but very high in fiber. Examples of roughages are hay,
or a silage, or a corn stover, or cotton burrs,
anything fairly low in nutrients but high in fiber. Now, don't think that because
roughages are low in nutrients, they're not important. Several animals
such as ruminants require fiber to
keep the microbes in the rumen,
producing and happy. So roughage is, even though
they're low in nutrients, very important to animals. While roughages are fed to
both monogastric and ruminants with the same intended purpose,
the breakdown and absorption between these two animals vary. Ruminants are unique as their
digestive tract contains microbes which can break down
cellulose and hemicellulose. Roughages must be
fed to ruminants to keep microbes alive and
functioning in the rumen. Ruminants begin
roughage digestion by harvesting or
ingesting the roughage, where enzymes in the
saliva of the mouth begin to digest
sugars and starches. Ruminants do not spend a lot of
time chewing their feed as they are designed to consume
large amounts of feed in the morning and evening. The roughage enters
the rumen first, where microbes attach
to the feed particles and begin their
digestion process. The microbes convert cellulose,
hemicellulose, sugars, and starches into
volatile fatty acids, which are absorbed through
papillae on the rumen wall. The large particles of
roughages in the rumen, which are not
quickly digested, are moved into the
reticulum, where they are compressed into a bolus. The bolus is regurgitated
up through the esophagus back into the mouth, where
more mastication or chewing is done on the bolus. Rumination is the process
where forages and other feed are forced back to the
mouth for further chewing and then swallowed again. As ruminant contents
are digested and become small enough, they pass through
the omasum for absorption and then into the abomasum
for further digestion. Monogastrics have
a simple stomach, which is very similar to
the abomasum in ruminants. Since monogastrics have no
rumen, they have no microbes. Therefore, they cannot
break down cellulose and hemicellulose. However, they are
able to break down sugars and starches,
lipids, proteins, vitamins, and minerals. Monogastrics start
digestion in the mouth by mechanically breaking
down feed through mastication and chemically breaking down
feed with salivary enzymes. The bolus is the resulting
partially broken down feet. It then travels through the
esophagus to the stomach, where chemical and enzymatic
digestion takes place. Once the bolus
enters the stomach, enzymes are released which
activate hydrochloric acid in the stomach, which is
essential for breaking down the peptide bonds in proteins. The feed continues to
the small intestine where enzymes continue
digestion and absorption occurs. Due to a limited ability
to digest the cellulose and hemicellulose,
monogastrics are typically not fed large
amounts of roughages. When fed roughages,
monogastrics are able to digest the sugars and
starches contained in roughages but unable to digest cellulose
and hemicellulose, which are the predominant
components of roughages. For this reason,
monogastrics are not fed rations high in roughages. There are three general
types of roughages available for livestock rations. These different
types of roughages vary in palatability,
digestibility, and nutrient content. The three types are green
or grazed roughages, preserved ravages, and
crop residue or byproducts roughages. There are several individual
roughage feedstuffs in each category available
for livestock rations. Knowing specific
attributes of each stuff allow producers
to balance rations for optimal performance
and lowest cost. The first category is
green or grazed roughages, which encompasses
pasture or range forage, plant materials found
in the environment with no processing or
preserving applied. There are two subgroups within
this category, which include legumes and non-legumes. Plants which fall
into the legume group include alfalfa,
variations of clover, and any other bean
producing forage plant. Non-legume plants
include all grasses. Some examples are orchard grass,
tall fescue, smooth bromegrass, perennial ryegrass,
Timothy, Kentucky bluegrass, bermuda grass, and
native range grasses. There are several benefits
for the producer, environment, and livestock when livestock
are allowed to graze forages. Grazing forages are usually
a lower cost roughage, as the livestock harvest the
roughage instead of added labor and cost to
mechanically harvest. Additionally, land not suitable
for crop production benefits from grazing animals
through nutrient cycling and increased soil health. As for benefits of grazing
to the animal itself, pasture roughages provide
required nutrients while allowing a low-stress
natural environment. However, there can
also be challenges with grazing livestock. Pasture forages are often not as
nutrient dense as a fed ration. Thus, animals grazing
pasture forages will produce less
product per unit input. Additionally, when
overgrazing occurs, soil health can be compromised. Finally,
supplementation is often required when grazing
forages which will increase the cost of production. The second category of roughages
are preserved roughages which includes hay and silage. These forages are
plant materials mechanically harvested
and stored in a way to preserve the nutrient
content of the roughage. Hay is grown and
carefully monitored for the optimal harvest time. When harvest is optimal,
a swatter cuts the hay and leaves the hay in
rows called wind rows. Freshly cut hay is not
suitable for baling as the moisture content of
the hay can cause it to mold. The wind rows must be
left in the field to cure. While curing, moisture
content is constantly monitored as baling will not be
successful if the hay is either too wet or too dry. Once optimal moisture is met, a
rake compiles several wind rows into a larger wind draw. A baler then gathers the
hay from the wind rows and compresses the hay into
either round or square bales while binding the bales
with either wire or twine. Producing silage
involves harvesting a crop high in moisture,
which has not yet produced mature seeds. A silage chopper
harvests the crop and cuts the plant
into smaller pieces. The chop length
is very important, as the longer the chop
length, the less surface area for fermentation. The harvested crop is
hauled to a pit or stack. And large tractors are driven
over the silage several times to pack the silage
into the pit or stack. The goal of packing the
silage is to remove oxygen from the silage. Silage in the presence
of oxygen will spoil, but silage in an
anaerobic environment will ferment due to
anaerobic bacteria. The fermentation process
preserves the nutritional content of the silage
and makes the silage more palatable to livestock. After packing, the silage
should be covered with plastic and weighted down
to prevent oxygen from entering the silage. The process of
preserving forages can pose multiple benefits. As for the producer,
preserving forages allows for regular
availability of high quality roughages year-round,
regardless of the climate or growing season. Furthermore, cutting
forages allows for regrowth during the growing season. For example, most hay crops
can be harvested and baled several times during
the same growing season, making the crop
much more efficient. However, preserving
forages increases labor and requires
specialized machinery to harvest, process, store,
and manage these ingredients. The final category of roughages
are crop residues and byproduct forages. Crop residues are roughages
remaining after harvesting, including husks, grain,
straw, and stover. After a corn crop is
harvested, husks and stalks are left in the
field as a roughage, which can either be
grazed in the field or harvested and baled. Wheat after harvest
leaves straw residue, which is not very
nutrient dense at all. Wheat straw can be harvested to
include as a filler in a ration or can be used as
livestock bedding. A byproduct of
cotton harvest would be cottonseed hulls,
a roughage which can be used as a roughage source
in several different rations. Several other crops also
leave roughage residue, which can be used by
livestock producers as an inexpensive
roughage source. Crop residues provide
many benefits. Roughages are needed in
most ruminant rations, and crop residue can provide
those roughages at a lower cost to the producer. Furthermore, the farmer
is allowed added income from the crop when livestock
producers graze or harvest crop residue. When utilizing crop
residue, nutrient analysis must be taken on the
residue to ensure a proper nutrient balance
is achieved in the ration. Livestock receiving
these refuges are able to intake a
variety of nutrients. Finally, crop residue
forages improve soil health by increasing the
organic matter present, reducing evaporation
and keeping the topsoil from being blown away. Opposinngly, crop
byproduct forages have a lower
nutritional value, which may result in a lower overall
production of livestock. While there are a
variety of roughages available for
livestock consumption, there are also numerous ways
in which they can be fed. The first way is fresh. A fresh roughage is when plant
material is given to the animal as it would be found
in the environment. No preserving processes have
been applied to the material. An example of this
is having sheep graze fresh pasture forages. Additionally, roughages
can be fed dry. Dry roughages include
plant material which contain approximately
90% dry matter. Dry matter is a term to
describe the material which remains after all water has
been evaporated out of the feed. An example of this
is providing cattle with hay or other
dehydrated forages. Finally, silage is another
way refuges can be fed. These forages contain a range
of 20% to 50% dry matter. Grass, alfalfa,
or corn preserved are examples of plant
material preserved in a pit through fermentation. There are a wide range
of plant ingredients used to provide balanced
nutrients to livestock as well as numerous ways of
providing them in the ration. Understanding the
materials which can be used as
rough edges ensures livestock's nutritional
requirements are met while maintaining
quality performance. The second category of
feed for livestock diets is concentrates. A concentrate feed
is a feed that is very rich or
dense in nutrients. Now, those nutrients could be
different, such as an energy nutrient, such as a
carbohydrate, or a protein nutrient, such as
high in amino acids or certain types of proteins. A concentrate feed--
example of that would be corn, which is
very high in energy, a milo. For a protein feed, it
would be a soybean meal, a cottonseed meal,
anything high in protein. The main role of
concentrates in the diet is to provide highly digestible
energy and protein sources. Additionally,
concentrates are used to help meet an animal's
nutritional requirements in the ration. For example, concentrates
can be added to a ration to make up for energy and
protein requirements not met by roughages. Generally, monogastrics
have a ration with a higher percentage
of concentrates and ruminants have a ration
with a higher percentage of roughages. The breakdown and
absorption of this feedstuff varies among species and
is important to understand as concentrates are a
key nutrient source. In the ruminant,
concentrate digestion starts in the mouth
with salivary enzymes and mechanical digestion
by mastication. When concentrates
enter the rumen, some are digested
by the microbes. Microbes are able to digest
concentrates very quickly as compared to roughages. The result of microbial
digestion of carbohydrates in the rumen is
volatile fatty acids, which are absorbed
through rumen papillae and used by the
animal for energy. There are three
volatile fatty acids produced in the rumen-- acetate,
butyrate, and propionate. Microbial fermentation
of roughages tends to produce more acetate,
while microbial fermentation of concentrates tends to produce
more butyrate and propionate. Propionate is the most energy
dense of the three fatty acids. As for protein concentrate
digestion in the rumen, some proteins are considered
rumen-degradable proteins, and others are
rumen-undegradable proteins. Rumen-degradable proteins
are used by the microbes to satisfy their
protein requirements. These proteins,
when broken down, become part of the microbes. Microbe populations are
cyclic, with some microbes dying while new microbes
are being produced. The microbes which
die are passed through the rest of
the digestive tract and broken down by the
abomasum and small intestine to then provide protein
for the ruminant. Rumen-undegradable proteins
are proteins which cannot be fermented by the microbes and
pass to the abomasum and small intestine for digestion. Often, rumen-undegradable
proteins are higher in crude
protein percent. The ability for
ruminants to digest concentrates with ease raises
concern for digestive disorders to occur. There are two main
digestive issues which can occur from feeding too
much concentrate in the ration, which are bloat and acidosis. Bloat is a form of
indigestion marked by the excessive
accumulation of gas. Byproducts of
microbial fermentation are methane and carbon dioxide. When microbes
digest concentrates, methane and carbon dioxide
are produced more rapidly. Eructation, or burping,
is the ruminant's way to expel methane
and carbon dioxide. And under normal
circumstance, eructation can keep up with gas production. However, during times
of rapid gas production, the opening to the
esophagus can become blocked and excess gas builds
up in the rumen. This condition is
referred to as bloat and is diagnosed by a swollen
left abdomen on the animal. If not treated, bloat can
lead to death within hours. Bloat can be treated by
insertion of an esophageal tube or by a trocar,
which is a tool used to puncture the left
side of the animal to release the excess gas. Treatments for
bloat are effective, but the best way
to treat bloat is prevention by not feeding
an excess of concentrates too quickly. Acidosis is another
condition caused by the rapid fermentation
of carbohydrates. This condition occurs
when microbes in the rumen have an increased production
of volatile fatty acids, making the rumen
environment acidic and damaging the rumen
microbes and papillae. The acidic environment
may also lead to ulcers. Chronic acidosis
will lead to death, while acute acidosis will
lead to a decrease in animal performance due to lower
absorption by rumen papillae. To treat, neutralizing
the acidic environment in the rumen with a buffer such
as calcium carbonate can help, but prevention is the best
way to prevent acidosis. Overall, it is
important concentrates are fed to ruminants
at moderate levels and is important to slowly
introduce concentrates into the ration. Monogastric animals
do not have microbes and require concentrates
as their main source of energy and protein. Digestion begins
with the chemical and mechanical
breakdown in the mouth through salivary
enzymes and mastication. The material then moves
down through the esophagus into the stomach, where
chemical digestion breaks down the concentrates into
smaller molecules. The molecules then travel
to the small intestine, where digestion continues
and absorption takes place. The term "concentrate"
is a broad term to describe a feedstuff
with high energy or protein. However, this feedstuff
can be further broken down into subcategories based
on the nutrient provided. These categories include
energy and protein sources. Energy source concentrates
are the first category. Cereal grains are the main
feedstuff in this category. Cereal grains are the
seeds of the plant and contain high levels of
starch found in the endosperm, but also contain sugars and
fats, which all provide energy to livestock. Examples of these grains include
corn, wheat, oat, rice, barley, sorghum, millet, and rye. There are a variety
of benefits to adding energy source concentrates
into livestock diets. Regarding the producer,
these ingredients are easily accessible
as cereal grains are grown all over the world. This feedstuff not only
provides large amounts of energy but is highly palatable
to the animal as well. There can be challenges
which go along with using energy
source concentrates. For the producer,
these cereal grains may be higher priced,
as they are also used in the human food market. When these grains
are also needed for direct human
consumption, supply and price become a concern. Finally, there are a
variety of health issues which may arise in livestock
if these concentrates are not given at regulated amounts. The second category
of concentrates are protein-dense concentrates. As the name implies, this
category of feedstuff is fed to livestock to
balance protein requirements. Protein is made up
of amino acids, which are required by animals
for the development of body tissues and cell regeneration. These concentrates are typically
byproducts from plant or animal source. The original source
has been processed to extract a product for
either human or industrial use. The byproduct of this
production yields a feedstuff useful for livestock. An example is soybeans having
oil extracted, and what remains is soybean meal. Soybean meal is high in protein,
which is valuable to livestock. A byproduct which has emerged
with the ethanol industry are dried distillers' grains. In ethanol production,
grains are ground, and the starch in
those grains are fermented to produce
ethanol, leaving a feedstuff which is high in
protein, digestible fiber, and fat. Other examples of
byproduct feedstuffs are cottonseed meal
and canola meal. Animal protein byproducts
such as fishmeal, blood meal, and meat and bone meal
are very high in protein but are also regulated. Due to safety concerns,
animal-derived byproducts are not allowed to be
fed to all species. Using protein-dense concentrates
provides a variety of benefits to a livestock operation. Overall, these feed ingredients
decrease the total number of human-edible feedstuffs
used for livestock consumption. For the producer, this allows
for lower cost ingredients to be used as there is less
competition for the human food market. With the ability to
use a single product to feed humans and
livestock, less land is used. Livestock are still
able to receive sustainable and
palatable nutrients which meet their production needs. The downfall to this
concentrate type is increased processing
of the ingredient, which may take more time to
receive as usable product. Additionally, these
byproducts may not be readily available
for producers to obtain as the facilities to
complete these processes may not be in close proximity
to the producer's operation. Concentrates can be
fed in several ways. Many concentrates are fed with
no processing, like whole corn. Feeding concentrates
in their natural state reduces processing
costs, but processing allows for more nutrient
utilization by the animal. Concentrates can be
minimally processed, such as grinding
or cracking, which increases surface area for
microbial and enzymatic digestion. Some grains, like milo,
have a very hard seed coat and must be processed at
some level for livestock use. More involved forms
of processing, such as steam
flaking, can increase the efficiency of concentrate
digestion even more. When grains are
steam flaked, they are exposed to
high pressure steam and then rolled to
produce a flake. The flaking process gelatinizes
the starch in the grain, making it more
available to the animal. Concentrates can also be fed
in a high-moisture state where the increased moisture content
increases fermentation. Lastly, pelleting
a concentrate is a very popular and beneficial
way to feed concentrates. Pelleting allows
moisture control, which allows feeds to last
much longer without spoilage. Pelleting can also
allow the addition of trace minerals
and other feedstuffs to provide a consistent
mix of feedstuffs. Concentrates are a
valuable energy source used in livestock rations to
provide required nutrients. Producers understanding the
needs of their livestock is important to
ensure livestock are receiving the proper quantity
and quality of ingredients. This, in turn, promotes
maximum growth and performance while maintaining
overall health. Feed processing is
the action of altering the physical and/or chemical
nature of feed commodities to optimize the
utilization by animals. The objectives for
feed processing include increasing palatability,
detoxifying or removing unwanted ingredients, increasing
storage time and capacity, increasing nutrient
content and availability, and reducing the particle size
or density of the ingredient. Feed processing allows
for better utilization of feedstuffs by
animals and depending on the situation
of the producer, it can be much more economical. Feed processing
is a process used to enhance the digestibility,
palatability, or just overall, utilization of a
feed by animals. Feed processing
for certain species is absolutely necessary. For instance swine. milo is fed to swine in
a high amount in rations and the milo kernel has a
very, very, very hard seed coat and without some
sort of a processing, either cracking,
grinding, or flaking, the swine you're not
going to be able to gather the nutrients out of that milo. So it must be processed
in order to be fed. In the case of cattle, steam
flake corn is often fed. The steam flake corn, when it
is rolled and steam flaked, the starch is gelatinous
and that gelatinous portion of the starch highly increases
the starch availability for the animal thus making
them much more efficient. In horses, pelican
feeds are often used because micronutrients
and nutrients needed in small amounts can
be added to the pellet and feed while still preserving
shelf-life of that feed. Pelleting adds quite
a bit of shelf-life and makes that feed accessible
for a longer period of time. Similar to swine,
chicken rations also must be processed
either ground, or cracked, or processed in some
way where the poultry can get the nutrients that it needs. There are typically two
categories of feed processing in livestock nutrition,
including dry processing and wet processing. Common dry processing methods
include grinding, rolling, cracking, and crimping. Wet feed processing techniques
include pelleting, steam rolling, or steam flaking. These feed processing
methods increase the nutrient availability
of feedstuffs to livestock. The first dry processing
technique is grinding. Grinding is a type of processing
found in both roughage and concentrates by changing
the physical properties of these ingredients. When grinding roughage, a bale
processor or a tub grinder is used to deconstruct a bale to
make the roughage fit in either a feed bunk mixer or
run through a feed mill. If necessary, different types
and qualities of roughage can be mixed in a hay grinder. For example, some sorghum
haze can be high in nitrates and dangerous when fed alone. But mixing them with
another roughage source can dilute the nitrate toxins. As for concentrates,
hammer mills are used to grind the grain
into very small particle sizes. Grain is typically fed into
a hammer mill from the top and gravity allows grain to
fall into the grinding chamber. The material encounters a series
of rotating hammers breaking the grain into smaller pieces. The end product of this
process is finely ground grains of uniform particle sizes. The purpose of grinding
is to increase the surface area exposed to enzymes
and rumen microbes during the digestion process. Other dry processing methods
include rolling, cracking, and crimping. These processing techniques
are seen most in concentrates to change the physical property. This process is completed
by passing the grain through a set of rollers
which break the seed coat. Roller mills use compression
to break or flatten the grain by having the grain travel
through two rollers turning in opposite directions. Overall, the purpose for
rolling, cracking, and crimping is to expose more
area of the grain to increase the digestibility
of the ingredient. Wet feed processing is when
moisture and/or heat, as well as pressure are added
to the ingredients. The first method used
in livestock production is pelleting and is seen
most in concentrates to change the physical
and chemical properties of the product. This process can be defined as
the conversion of finely ground feed into dense pellets
or capsules which involve steam injection
and mechanical pressure. There are multiple steps
in the pelleting process. The first being grinding
of the concentrates by sending it through a mill. After grinding, the different
ground raw materials are mixed. The third step is
conditioning or cooking the mixture with steam for
a certain period of time. Gelatinous occurs
during this step, a technique used to cause
the particles to swell. Next is the pelleting process
where the conditioned material is pushed through small
holes to form a pellet. Lastly, the pellets are left
to cool before distribution. Feed additives,
vitamins, and minerals can be added to pellets to
help balance the ration. Pelleting is a process
used by producers to increase the storage and
handling ability of feed ingredients, as well
as provide livestock an ingredient, which has a
balanced nutritional makeup. The second technique used
in wet feed processing is steamrolling or flaking. This is a common method used
for concentrates such as grains to provide higher
quality ingredients to a variety of
livestock species by altering both the chemical
and physical property of the feed. The process starts by putting
grain into a large chamber and introducing hot moisture
or steam for a period to allow the grain to
absorb this moisture. The combination
of heat and water causes the grain to swell. When the grain is rolled using
counter-rotating rollers, it ruptures the starch
granules increasing the starch availability. The heat causes bonds to
break within the grain, changing the
chemical composition and allows for the concentrate
to break more easily. The grain finally is left
to dry before distribution. The only difference between
steam flaking and steam rolling is the grain is held in the
steam cabinet for a longer period during flaking to
achieve higher moisture content. This allows the granules
in the grain to soften. Feed processing is
an important step in the delivery of
feed ingredients to fulfill livestock
nutritional requirements. Understanding
ingredient processes and the changes
which take place is key for proper selection of
feed to increase performance while maintaining
good animal health. Decreasing the total
ingredient input and increasing the quality
and quantity output allows producers to meet the
growing demand of consumers.