Feed Processing, and Increasing Forage
Utilization Through Protein Supplementation
Francis L. Fluharty, Ph.D.
Department of Animal Sciences
The Ohio State University
Wooster, Ohio
Ruminant Nutrition Basics
• Rumen bacteria are responsible for digesting feed.
• Rumen bacteria digest feed by attaching to the
feed particles and releasing enzymes.
• Increasing the surface area of feed increases the
rate of digestion by allowing more bacteria to
attach.
• With a forage-based diet, there are approximately
1 to 3 billion bacteria per ml of rumen contents.
• With a grain-based diet, there are approximately 8
to 10 billion bacteria per ml of rumen contents.
Rumen Contents Average 88% Water
“Healthy” Papillae
Reticulum and Omasum
Omasum and Abomasum
Understanding How Nutrients are
Used
Hierarchy of Nutrient Use
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Maintenance
Development
Growth
Lactation
Reproduction
Fattening
Forage Particle Size Affects a Ruminant’s
Maintenance Energy Requirements
• Visceral organs increase in weight as total feed
intake, diet forage content, or particle size of the
forage increases.
• Maintaining visceral organs requires 40 to 50%
of an animal’s daily energy intake, and 30 to 40%
of an animal’s daily protein intake with a forage
based diet.
• Decreasing organ weight results in improved
feed efficiency and reduces nutrient
requirements.
Effect of Temperature on DMI, Maintenance Energy and Intake
59 - 77°F
Rate of Passage Through the Rumen
• Liquid
4 – 10% / hour (1 to 1.7 times per day)
• Solids
Concentrate (grain) particles
2 – 7% / hour (.5 to 1.7 times per day)
• Roughage (forage) particles
1 – 6% / hour (.25 to 1.5 times per day)
Rate of Passage Through the Rumen is
Affected by:
1. Level of feed intake
Higher feed intake increases rate of passage.
2. Feed particle size
Smaller feed particles have a faster rate of passage.
3. Forage:Concentrate Ratio
Liquid rate of passage is faster with a higher
percentage of dietary fiber due to increased remastication and re-swallowing (ruminating).
Why Do We Process Forage?
• Ruminant animals in grazing situations need to
maximize forage digestion in order to meet their
energy and protein requirements.
• Factors that limit the animal’s ability to meet their
requirements include: forage species, maturity, lignin
concentration, and the ruminal ammonia requirements
of cellulose digesting bacterial species.
• Unlike grain-based diets, there is a time period,
referred to as the lag phase, required for cellulose
digesting bacteria to attach to forage particles, and the
energy available is directly related to surface area.
Why Do We Process Forage?
• More complete digestion by rumen bacteria
due to more surface area for attachment.
• More surface area for enzymatic digestion
in the small intestine.
• Higher levels of feed intake with forage
based diets.
• Better fermentation with ensiled feeds due
to less air space between particles.
Why Do We Process Forage?
• Better flow of materials through feed
conveyors.
• Better mixing of the diet that results in less
separation in the feed bunk.
Problems Associated with Processing
Forages
• Increased production costs.
• Dust and loss of leaf protein.
Forage Processing
• Digestibility is qualitative, referring to the
susceptibility to degradation. In contrast,
digestion refers to the extent of degradation.”
• Ruminal fiber digestion is a function of the
rate of digestion of the forage and the rate of
passage of the forage particles from the
rumen.
• From a practical standpoint with unprocessed
forages, the large particle size of mature
forage reduces the energy available to the
animal.
Forage Processing
• For digestion to occur, the microorganisms
in the rumen must first be associated with
the forage, and then attach to the forage.
• Digestion normally occurs from the inside
of the forage to the outer layers.
• Limitations to the speed at which this
occurs include the physical and chemical
properties of the forage, the moisture level
of the forage, time for penetration of the
waxes and cuticle layer, and the extent of
lignification (Varga and Kolver, 1997).
Forage Processing
• Undigested feed is broken down through the process of
rumination and re-chewing until it is either digested, or
small enough to pass from the reticulo-omasal orifice.
• Most particles leaving the rumen are smaller than 1mm,
although particles as large as 5 cm may leave the rumen
(Welch, 1986).
• It is, therefore, not hard to understand how reducing the
large particle size of many mature forages to 1mm to 5
cm can increase maintenance energy expenditures due to
an increase in visceral organ mass and the energy
expenditure of rumination and re-chewing.
Forage Processing
• The conversion of fibrous forages to meat and milk is
not efficient, with only 10 to 35% of the energy intake
being captured as net energy to the animal, because 20
to 70% of the cellulose may not be digested (Varga and
Kolver, 1997).
• Research conducted at The Ohio State University found
that steers fed a chopped hay based diet gained 2.5
lbs/day while those fed round baled hay (same hay
source) in a rack gained less than 1.5 lbs/day.”
(Source: http://beef.osu.edu/library/AltFeedSuplong.pdf).
Forage Processing
• Williams et al. (1995) harvested wheat
forage with a mower conditioner, at an early
head stage of maturity, and allowed it to
wilt for either 0, 6 or 20 hours prior to being
cut with a forage chopper and ensiled.
• They reported that wilting for 20 hours
resulted in lower fermentation acids, a
higher concentration of water-soluble
carbohydrates, and improved fiber
digestibility compared with either direct-cut
or wilting for 6 hours.
Forage Processing
• Hintz et al. (1999) reported that maceration, an
intensive forage conditioning process that shreds
forage thus reducing rigidity and increases field
drying rates by as much as 300% by disrupting the
waxy cuticle layer of the plant and breaking open
the stem, resulted in an increase in surface area
available for microbial attachment in the rumen.
• Results were: a decreased lag time associated with
NDF digestion, an increase in NDF digestion, and
a decrease in the acetate:propionate ratio, which
would be positive for growing and finishing
animals.
Forage Processing
• If corn is $5.04 per bushel, it is $.09 per pound.
Likewise, if dried corn gluten feed or distillers dried
grains are $180 per ton, they are $.09 per pound. If hay
is $180 per ton, it is $.09 per pound.
• Normally, the digestibility of corn, corn gluten feed,
and distillers dried grains are all much higher than even
the highest quality hay.
• Therefore, in order for forages to be economically
competitive, they must be managed, harvested, and
potentially processed to their optimum digestibility.
Think in Terms of “OPTIONS”
Ground Corn Stalks
Distillers Grains
Think in Terms of “OPTIONS”
As Fed / Mixed Basis: 68% WDG, 24% wheat flour, and
8% wheat straw. Final moisture is around 52%.
On a DMB it is about 45% DDG, 41% flour, 14% straw
Ruminal Protein Degradation:
The Basics
Proteins are made from:
Amino Acids
Protein Functions in the Body
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Cell membranes in muscle, nerves, hair, skin
Blood serum protein
Enzymes
Hormones
Antibodies
Muscle
Protein Is Needed For:
• Nitrogen for microbial fermentation in the
rumen.
– Protein degraded in the rumen provides NH3
that the bacteria use to grow.
– Microbial protein typically provides about half
of the amino acids needed by the animal.
• Post-ruminal amino acids supplied to the
small intestine and absorbed for use by the
animal.
All Feed Proteins Degraded in the
Rumen Become Ammonia
• Ammonia = NH3
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• Urea = H2N – C – NH2
Ruminal Protein and Fiber Degradation
• Ruminant animals in grazing situations need
to maximize forage digestion in order to
increase performance parameters such as
average daily gain or milk production.
• Degradable intake protein (DIP) has been
reported to be the first-limiting nutrient for
beef cattle grazing low-quality forages
(Köster et al., 1996; Olson et al., 1999;
Bandyk et al., 2001).
Ruminal Protein and Fiber Degradation
• Cellulolytic bacteria prefer ammonia (NH3) as
their N source (Russell et al., 1992), so
substituting NPN for a portion of the degradable
true protein in supplements for range cows should
be a viable option (Köster et al., 2002).
• However, when DIP sources of protein are fed, the
profile of amino acids entering the small intestine
closely resembles microbial protein, and amino
acids that are limiting in bacterial protein will
probably be limiting to the ruminant's production
capability (Willms et al., 1991).
Ruminal Protein and Fiber Degradation
• In production situations where energy is limiting, either
because of relatively low-quality forage or in
production situations where there is reduced dry matter
intake, microbial protein reaching the small intestine
may be insufficient to maximize animal growth, and
ruminally undegradable intake proteins (UIP, or bypass
protein) may be warranted, (Firkins and Fluharty,
2000).
• This is because if energy and protein are limiting, there
is a reduction in both the number of bacteria and the
growth rate of bacteria, which results in a reduction in
the amount of ruminal NH3N that can be used for
protein synthesis (Satter and Roffler, 1975).
Ruminal Protein and Fiber Degradation
• Feeding combinations of ruminally
available (DIP) protein sources such as urea
or soybean meal (SBM) are commonly used
in combination with UIP sources that
mostly bypass rumen degradation but are
available for enzymatic degradation in the
small intestine if not over-heated during
drying. Common sources of UIP include
corn gluten meal (CGM), distillers grains
(DG), feather meal (Fth), or fish meal (FM).
Bypass Protein
• Protein that escapes degradation in the
rumen, which is then digested in the
abomasum and small intestine and absorbed
as amino acids in the small intestine.
• The two sources of bypass protein are
undigested intake protein (UIP) and rumen
microbial protein from bacteria, protozoa,
and fungi.
Low Bypass Proteins
(Under 40% Bypass)
• Soybean meal, 20 – 30% on forage diet
• Peanut meal
• Urea, 0% bypass
Medium Bypass Proteins
(40 – 60% Bypass)
• Soybean meal, ~ 40% bypass with highconcentrate diets.
• Cottonseed meal
• Dehydrated alfalfa meal
• Corn grain
• Brewer’s dried grains
• Distillers Grains
High Bypass Proteins
(Greater than 60% Bypass)
• Corn gluten meal, 85% bypass
• Blood meal, 82 – 92% bypass
• Fish meal, 68% bypass
Non-enzymatic Browning
(Maillard Reaction)
HEAT DAMAGED PROTEINS
• In the presence of heat and water (such as occurs
in the processing of all the plant and animal
products from which we get protein supplements),
the carboxyl group (COOH) of a sugar is bound to
the free amino end of lysine.
• If the heat is not excessive, this bond is broken in
the acidic conditions of the abomasum, and the
amino acids are available in the small intestine
(bypass protein).
• If the heat is excessive, an artificial, indigestible
polymer is formed (heat damaged protein).
Heat Damage Varies With Time and
Temperature
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
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Urea = H2N – C – NH2
• Urea has a protein equivalent of 287% protein
equivalents on a dry matter basis (NRC, 1996).
• Low rumen pH reduces absorption of ammonia to
the blood, and reduces the incidence of ammonia
toxicity.
• When urea is fed, Sulfur (S), Potassium (K), and
Phosphorus (P) must be supplemented.
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• Urea is used to:
1. Increase diet organic matter digestion
(Classic example is urea treatment of straw.)
2. Increase microbial protein synthesis
• Two Possible Problems with urea at high intakes:
1. Ammonia Toxicity
2. Reduced Feed Intake
• Never Exceed Either of These Levels with Urea:
1. 1% of the diet dry matter
2. 1/3 of the total dietary protein
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• Williams et al. (1969) and Rush et al. (1976)
reported reduced performance in cattle receiving
NPN-based supplements compared with cattle
receiving true-protein supplements. However, in
those studies, NPN was a high proportion of the
total supplemental N.
• The basal diets that Williams et al. (1969) used
contained 4% or 12.1% urea.
• Rush et al. (1976) fed 30% protein supplements,
based on molasses, with half of the CP coming
from NPN.
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• However, not all studies with NPN give the same
results. In another series of studies, urea or biuret
provided 50% of the nitrogen in 30% CP dry
supplements, or urea provided 94% of the nitrogen
in 30% CP liquid supplements with molasses. In
these studies, cow winter weight loss, cow
summer weight gain, and calf performance were
not different (P > .50) for cows fed natural protein
or liquid supplements (Rush and Totusek, 1976).
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• Hersom (2007) suggested that the improvement in
performance which occurs with the addition of
protein to diets of ruminants being fed low-quality
forage occurs due to a correcting of a protein/N
deficiency in the diet, resulting in a better
synchronization of the supply of energy and
protein in the rumen, and in many cases occurs
regardless of the source of protein, although
increasing the proportion of natural protein often
improves animal performance.
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• Currier et al. (2004) used cows in the last third of
gestation to compare the difference between urea at 5.2%
of supplement DM or biuret at 6.1% of supplement DM in
diets where NPN provided 90% of the estimated DIP
requirement.
• Supplements were fed at .04% of the cows’ body weight
per day, or roughly .5 lb/d for a 1250 pound cow.
• Both NPN sources resulted in greater positive weight and
body condition score (BCS) changes compared with the
control group, and calf birth weight was not affected by
NPN supplementation. The authors concluded that
ruminants consuming low-quality forage can effectively
use supplemental NPN to maintain nitrogen status and
performance in both hand-fed and self-fed situations.
Urea or Non-Protein Nitrogen (NPN):
The Most Misunderstood Protein Supplement
• Köster et al. (2002) suggests that urea could
replace between 20 and 40% of the DIP in
high-protein supplements, containing 30%
protein, without significantly altering
supplement palatability or cow and calf
performance.
In Summary:
• Increasing the surface area for bacterial
attachment increases both the rate and efficiency
of microbial degradation of forages.
• Supplying combinations of DIP and UIP could
best meet the animal's amino acid requirement
through maximizing microbial growth and
cellulose digestion, as well as providing amino
acids from both microbial and feed origin to the
small intestine.