Protein Metabolism Ruminants
Subjects to be covered
• Digestion and metabolism in the
rumen
• Protein requirements of ruminants
Models
Define requirements
Describe feeds
Optimize production
• Environmental issues
Prevent overfeeding nitrogen
Protein
• Analysis: Determine total N by Kjeldahl
– All N
NH4+
– Determine as NH3
– Total N x 6.25 = crude protein
• Peptide bond:
NH2
R1-C-C-NH
O C-C=O
R2 N-C-COOH
H R3
Nitrogenous Compounds in Feeds
• True proteins
 Polymers of amino acids (18 to 20 different
amino acids) linked by peptide bonds
• Essential amino acids (nondispensable)
– Have to be present in the diet (absorbed)
– Arg Lys Trp Leu Ile Val Met Thr Phy His
• Nonessential amino acids (dispensable)
– Synthesized in body tissues
– Glu Gly Asp Pro Ala Ser Cys Tyr
 Proteins
Peptides
Amino acids
Nitrogenous Compounds in Feeds
• Nonprotein nitrogen
– Nitrogen not associated with protein
• Free amino acids, nucleic acids, amines,
ammonia, nitrates, nitrites, urea
• Crude protein
– Total nitrogen x 6.25
– Proteins on average contain 16% nitrogen
Protein Degradation in the Rumen
Feed proteins
Peptides
Amino acids
Undegraded feed proteins
Escaped feed proteins
“Bypass proteins”
Enzymes from protozoa and bacteria
Many species of bacteria involved
Bacterial enzymes are extracellular
Enzymes not in cell free rumen fluid
Both exopeptidase and endopeptidase activity
Assumption in CNCPS: Enzymes (microorganisms)
in excess – substrate limited
Factors Affecting Ruminal Protein Degradation
Chemical Nature of the proteins
• Solubility – More soluble proteins degraded faster
Some soluble proteins not extensively degraded
Egg ovalbumin, serum proteins
• 3-dimensional structure – Affects solubility & availability
• Chemical bonding
Disulfide bonds – Reduces degradation
Physical barriers
• Cell walls of plants
• Cross linking of peptide chains – Reduces degradation
Aldehydes, Tannins
Feed intake
Rate of passage – Time proteins remain in the rumen
Feed processing
• Rate of passage
• Heat damage – Complexes with carbohydrates
Estimating Degradation of
Dietary Proteins in the Rumen
1. In situ digestion
Feed placed in Dacron bags suspended
in the rumen
Measure protein lost over time
2. Cannulated animals (rumen & duodenum)
Measure protein flowing through duodenum
Need to differentiate feed from microbes
3. In vitro incubation with rumen microbes
Relative differences among proteins
4. In vitro digestion with fungal enzymes
Log, % N remaining
Protein Degradation In situ
A - All degraded
B - Partly degraded
Slope = degradation rate
C - Not degraded
Digestion time, hr
Protein Degradation
DIP (RDP) = A + B[Kd/(Kd+Kp)]
DIP = Degraded intake protein
Kd = degradation rate, %/h
Kp = passage rate, %/h
UIP (RUP) = B[Kp/(Kd+Kp)] + C
UIP = Undegraded intake protein
Feed Protein Fractions (CNCPS & NRC)
NPN
Soluble
Feed
Insoluble
-
A
Sol Proteins - B1
Insoluble -
B2
Insoluble -
B3
Indigestible - C
Protein Fractions In Feeds
Laboratory Analysis
A - Soluble in buffer (borate-phosphate) and not
precipitated by tungstic acid
B1 - Soluble in buffer and precipitated by tungstic acid
B2 - Insoluble in buffer
= (Insol protein) - (protein insol in neutral detergent)
B3 - Insoluble in buffer
= (Insol in neutral detergent) - (Insol in acid detergent)
C - Insoluble in buffer and acid detergent
Kd Values for Feed Proteins
Fraction
A
B1
B2
B3
C
Kd, %/h
Infinity
120 to 400
3 to 16
0.06 to 0.55
Not degraded
Kp Values
Wet forages
Kp = 3.054 + 0.614X1
Dry forages
Kp = 3.362 + 0.479X1 – 0.007X2 – 0.017X3
Concentrates
Kp = 2.904 + 1.375X1 – 0.020X2
X1 = DMI, % Body Wt
X2 = Concentrate, % of ration DM
X3 = NDF of feedstuff, % DM
Feed Protein Acronyms
NRC Publications
Crude protein
Total N x 6.25
DIP (RDP)
Degraded intake protein
UIP (RUP)
Undegraded intake protein
SolP, % CP
Soluble protein
NPN, % CP
Nonprotein nitrogen
NDFIP, % CPNeutral detergent fiber insoluble
protein
ADFIP, % CPAcid detergent fiber insoluble
protein
B1, B2, B3, % hr
Rate constants for degradable
fractions
“Bypass proteins”
Proteins that are not extensively degraded in the rumen
1. Natural
Corn proteins, blood proteins, feather meal
2. Modification of feed proteins to make them less
degradable
Heat - Browning or Maillard reaction
Expeller SBM, Dried DGS, Blood meal
Chemical
Formaldehyde
Polyphenols
Tannins
Alcohol + heat
Usually some loss in availability of amino acids - lysine
Average Ruminal
Degradation of Several Proteins
Used in Level 1
Soybean meal (Solvent processed)
Soybean meal ( Expeller processed)
Alfalfa
Corn proteins
Corn gluten meal
Corn gluten feed
Dried distillers grains
Blood meal
Feather meal
Urea
75%
50%
80%
62%
42%
80%
55%
20%
30%
100%
Degradation of NPN Compounds
Activity associated with microorganisms
• Urea
CO2 + 2 NH3
High concentrations of urease activity
in the rumen
Low concentrations of urea in the rumen
• Biuret
2 CO2 + 3 NH3
Low activity in the rumen
• NO3
NH3
Fate of Free Amino Acids in the Rumen
1. Amino acids not absorbed from the rumen
• Concentrations of free AA in the rumen very low
2. Amino acids and small peptides (up to 5 AA)
transported into bacterial cells
• Na pumped out of cells – Uses ATP
• Na gradient facilitates transport of AA by a carrier
3. Utilized for synthesis of microbial proteins
4. Amino acids metabolized to provide energy
Amino Acid Degradation in the Rumen
NH3
Amino acids
CO2
Keto acids
VFA
• Enzymes from microorganisms
Intracellular enzymes
• Peptides probably hydrolyzed to amino acids
and then degraded
• NH3, VFA and CO2 absorbed from rumen
Amino Acid Fermentation
Valine
Leucine
Isoleucine
Isobutyrate
Isovalerate
2-methybutyrate
Alanine, glutamate, histidine, aspartate, glycine,
serine, cystein and tryptophan
pyruvate
Threonine, homoserine, homocyseine and
methionine
Ketones
Control of Amino Acid Fermentation
When CHOH is ample for growth, incorporation
of amino acids into protein is favored
• Majority of transported amino acids and
peptides do not go through ammonia pool
When CHOH supply is limiting growth, amino
acids are fermented for energy
• There is an increase in amino acids going
through the ammonia pool
Does Source of Carbohydrate Affect
Amino Acid Fermentation?
CHOH slowly fermented or with a significant lag time
• CHOH fermentation for growth might
lag behind fermentation of AA
Rapidly fermented CHOH
• AA fermentation and CHOH might be more
closely matched
Recycling of N into the rumen might offset
disruptions in CHOH and AA fermentations
Amino Acid Fermenters in the Rumen
High numbers
Low activity
Low numbers
High activity
Butrivibrio fibrisolvens
Measphaera elsdenii
Selenomonas ruminantium
Clostridium aminophilum
Clostridium sticklandii
Peptostreptococuss anaerobius
109 per ml
10 to 20 NMol NH3
per min per mg protein
Monensin resistant
Involved in CHOH
fermentation
107 per ml
300 NMol NH3 per min
per mg protein
Monensin sensitive
Ferment CHOH slowly or
not at all
Fate of Rumen Ammonia
1. Bacterial protein synthesis
2. Absorbed from reticulorumen and omasum
NH3 passes from rumen by diffusion into portal
blood. (High concentration to low)
Form of ammonia dependent on pH of rumen
NH3 + H+
NH4+
Less absorption at more acid pH
3. At pH of rumen, no NH3 lost as gas
Fate of Absorbed Ammonia
1. Transported to liver by portal vein
2. Converted to urea via urea cycle in liver
NH3
Urea
Urea
cycle
3. Urea released into blood
4. If capacity of urea cycle in liver is exceeded
Ammonia toxicity
Over consumption of urea
Fate of Blood Urea
1. Excreted into urine
2. Recycled to digestive tract, g N/d
• Saliva – Related to concentration of
urea in blood
Sheep: 0.5 to 1.0
Cattle: 1.0 to 7.6
• Diffusion into GIT
Sheep: 2 to 5
Cattle: 25 to 40
Adjustments to Low Protein Intake
Kidney
Blood urea
Urea
Urine urea
Urea is predominant form of N in urine
Reabsorption of urea by kidney increased
when ruminants fed low N diets
• Conserves nitrogen in the body
• Greater portion recycled to digestive tract
• Sheep fed the same diet tend to
reabsorb more urea than cattle
N, g/d
Nitrogen Recycling - Cattle
45
40
35
30
25
20
15
10
5
0
GIT
Saliva
Wall
87.6
110.4
147.5
178.7
N intake, g/d
Marini et al. JAS 2003
203.5
Urea Diffusion into Rumen
Rumen wall
Blood
urea
Urea
NH3
1. Total N transferred is
greater when high N
diets are fed.
2. Percentage of diet N
transferred is greater
when low N diet are fed
Bacterial population
Urea Diffusion into Rumen
Update
Rumen wall
Urea transporter
Blood
urea
Urea
High [NH3]
inhibits
NH3
Bacterial population
Sources of Nitrogen Recycled to GIT
1. Urea flowing back into digestive tract
 Rumen
• Saliva
• Diffusion from blood
 Lower digestive tract (large intestine, colon,
cecum)
• Diffusion from blood
• Endogenous protein secretions into GIT
 Mucins
 Enzymes
 Sloughing of tissue
2. Turnover of microbial cells in rumen & reticulum
Significance of Recycled Nitrogen
Source of N for microbes when protein consumption
is limited
• Wild species
Protein intake during winter is very low
Rumen deficient of nitrogen for microbial activity
• Slowly degraded feed proteins
Recycling provides nitrogen for microbial growth
• Infrequent feeding of supplemental protein
• Programs to reduce supplemental nitrogen
Difficult to make ruminants severely protein deficient
Urea Nitrogen - Cattle
N, % Diet DM
Marini et al. JAS 2003
N, % Diet DM
3.4
3.4
2.97
2.5
Urine, Urea N
2.5
1.45
140
120
100
80
60
40
20
0
1.45
14
12
10
8
6
4
2
0
Urine N
1.89
Saliva urea
N, g/d
mM
Plasm urea
Microbial Protein Synthesis
End product of protein degradation is mostly NH3
Protein synthesis
Fixation of N in organic form
Synthesis of amino acids
Synthesis of protein(s)
Bacterial Protein
Synthesis in the Rumen
NH3
VFA
CHOH
Amino acids & Peptides
Amino acids
Fermentation
Microbial
proteins
VFA
Microbial protein synthesis related to:
1. Available NH3 and amino acids (DIP)
2. Fermentation of CHOH - Energy
Microbial Requirements
Bacteria
Nitrogen
• Mixed cultures
NH3 satisfies the N requirement
Cross feeding can supply amino acids
• Pure cultures
Fiber digesters require NH3
Starch digesters require NH3 and amino acids
Peptides can be taken up by cells
Branched-chain fatty acids
• Required by major rumen cellulolytic bacteria
Energy from fermentation
• Need energy for synthesis of macromolecules
Amino Acid Synthesis
Ammonia Fixation
1. Glutamine synthetase/glutamate synthase
• Glutamine synthetase
Glu + NH3 + ATP
Gln
• Glutmate synthase
-ketoglutarate + glutamine + NADPH2
2 Glu
High affinity for NH3 - Concentrates NH3 in
cells – Uses ATP
Because of N recycling this reaction may not
be that important
Amino Acid Synthesis
Ammonia Fixation
2. Glutamic dehydrogenase
• -ketoglutarate + NH3 + NADH
Glu
Low affinity for NH3 – High concentration of
enzyme in rumen bacteria – Does not use ATP
Probably predominant pathway
3. Other AA can be synthesized by transamination
reactions with glutamic acid
Estimates of NH3 requirements range from 5 (culture)
to 20 mg/100 ml (in situ digestion)
Role of Protozoa
Do not use NH3 directly
Engulf feed particles and bacteria
• Digest proteins
• Release amino acids and peptides into rumen
• Use amino acids for protein synthesis
• Protozoa engulf bacteria
• Protozoa lyse easily – May contribute little
microbial protein to the animal
Efficiency of Microbial Growth
Grams microbial N/100 g organic matter digested
Ranges from 1.1 to 5.0
1. Kind of diet
Forages > Grain
2. Level of feeding High > Low
3. Rate of passage Fast > Slow
4. Turnover of microbial cells
Younger cells turnover less than aging cells
5. Maintenance requirement of cells
Microbes use energy to maintain cellular integrity
6. Energy spilling
Dissipation of energy different from maintenance
Most apparent when energy is in excess
Efficiency of Microbial Growth
Slow
passage
Low rumen
pH
Low quality
forages slow
passage
Bacteria
use energy to
pump protons
TDN, % feed DM
Microbial Growth in The Rumen
Nutrients available to microbes
1. DIP - NH3, peptides, amino acids
•
CNCPS adjusts for inadequate available N
2. Energy from the fermentation
•
•
Growth rate related to Kd of CHOH
Quantity of cells related to CHOH digested
CNCPS assumes microbes digesting
non-fiber and fiber CHOH both have
a maximum yield of 50g cells/100g
CHOH fermented
3. Other - branched-chain acids, minerals
Microbial Growth
Computer Models
1996 Beef NRC
BCP (g/d) = 0.13 (TDN, g/d)
Can vary the 0.13
Lower when poor quality forages fed
1989 Dairy NRC
Cattle consuming more than 40% of
intake as forage:
BCP g/d) = 6.25 (-31.86 + 26.12 TDN, kg/d)
Microbial Growth
Computer Models
2001 Dairy NRC and Level 1 CNCPS
BCP (g/d) = 0.13 (TDN, g/d)
Correct TDN for fat added to the ration
Fat does not provide energy to the bacteria
Requirement for RDP (DIP) is 1.18*BCP
Microbes capture 85% of available N
If RDP < 1.18*BCP:
BCP (g/d) = 0.85* RDP
Composition of Rumen
Microorganisms
N fraction, % total
Bacteria Protozoa
Amino acids
82.5
86.5
RNA
10.0
8.7
DNA
5.0
2.5
True digestibility, %
80.0
Nutritional Value of Microbial Proteins
1996 NRC for Beef
Microbial protein 80% digestible in the intestine
UIP 80% digestible in the intestine
2001 NRC for Dairy and Level 1 CNCPS
Microbial protein 80% digestible in the intestine
Digestibility of RUP (UIP) is variable in Dairy NRC
UIP 80% digestible in Level 1 CNCPS
Amino Acid Composition
% Crude Protein or G/100g CP
Tissue Milk
----------Bact ----------
Corn
Soy
Cell wall Non wall Mean
Methionine
1.97
2.71
2.40
2.68
2.60
2.28
1.46
Lysine
6.37
7.62
5.60
8.20
7.90
3.03
6.32
Histidine
2.47
2.74
1.74
2.69
2.00
3.16
2.72
Phenylalanine
3.53
4.75
4.20
5.16
5.10
5.32
5.65
Tryptophan
0.49
1.51
NA
1.63
-
0.89
1.46
Threonine
3.90
3.72
3.30
5.59
5.80
3.67
4.18
Leucine
6.70
9.18
5.90
7.51
8.10
12.66 7.95
Isoleucine
2.84
5.79
4.00
5.88
5.70
3.67
5.44
Valine
4.03
5.89
4.70
6.16
6.20
5.32
5.65
Arginine
3.30
3.40
3.82
6.96
5.10
5.06
7.53
Amino Acids in
Undegraded Feed Proteins
Fish meal
Fish meal residue
His
3.4
2.9
Isl
4.2
4.9
Lys
6.6
6.0
Met
3.1
2.9
Meat & bone meal
Meat & bone meal residue
1.5
1.4
2.1
2.3
4.2
4.3
1.0
1.0
Sources of Amino Acids for Host Animal
1. Microbial proteins
Quantity determined by:
a) Fermentability of the feed
b) Quantity of feed consumed
c) Nitrogen available to microorganisms
2. Undegraded feed proteins (UIP)
Quantity will vary in relation to:
a) Degradability of feed proteins
b) Quantity of feed proteins consumed
History of Protein Systems for Ruminants
• ISU Metabolizable protein system
• Wisconsin system – When urea could be used
• Several European systems – Mostly MP systems
• 1985 NRC system – Summarized systems &
Proposed a MP system
Used in 1989 Dairy NRC
• Cornell CNCPS
• 1996 Beef NRC system – Mostly CNCPS system
Used in ISU Brands system
• 2001 Dairy NRC system
Metabolizable Protein Model
Tissue proteins
NH3
Blood urea
Urine
Amino acid
pools
Energy
A
B
NH3
Microbial
protein
Protein
Metabolizable
protein
C
Protein
from diet
Rumen
Intestine
Feces
Protein Metabolism of Ruminants
Concept of Metabolizable Protein
Metabolizable protein (MP)
= Absorbed amino acids or
= Digestible fraction of microbial
proteins + digestible fraction of
undegraded feed proteins
Digestible protein (amino acids) available
for metabolism
Concept is similar to Metabolizable energy
Protein Metabolism in the Rumen
Less Extensively Degraded Protein
Feed
Rumen
Intestine
Microbes
Digestion
Metabolizable protein
Undegraded feed
Protein Metabolism in the Rumen
Extensively Degraded Protein
Feed
Rumen
Intestine
Microbes
NH3
Digestion
Metabolizable protein
Undegraded feed
Metabolizable Protein
Supply to Host Animal
Metabolizable protein (MP):
Microorganisms – Digestible proteins
Undegraded feed proteins – Digestible proteins
Microorganisms
g/d = 0.13 (TDN intake, g/d) (0.8) (0.8)
Microbes 80% true protein that is 80% digested
Feed
g/d = (Feed protein) (Portion undegraded) (0.8)
Feed proteins 80% digested
Absorption of Amino Acids
Amino acids and small peptides absorbed
by active transport (specific for groups of AA)
From intestines
Portal blood
Transport of amino acids into cells is
similar process
From blood
Cells
Active transport, requires energy
Utilization of Absorbed Amino Acids
Via portal vein to liver
• Used for synthesis of proteins in liver
• Metabolized (deaminated) - Used for
energy – Carbon for glucose
• Escape the liver
Carried by blood to body tissues
• Used for synthesis of tissue proteins,
milk, fetal growth, wool
• Metabolized - Used for energy
Requirements for Absorbed Amino Acids
Metabolizable Protein (MP)
Protein (amino acid) requirements
1. Maintenance
2. Growth
3. Lactation
4. Pregnancy
5. Wool
Protein Metabolism
Concept of Net Protein
Net protein = protein gained in tissues,
milk, or fetal growth = NP
Metabolizable protein is used with less
than 100% efficiency
Net protein = (MP - Metabolic loss)
As a quantity, net protein is less than
metabolizable protein
Protein Metabolism
Metabolic Loss
Protein synthesis and metabolism of
amino acids draw from the same pool
Proteins
Amino
acids
Metabolism
• Metabolic loss results from continuous
catabolism from amino acid pools
• Continuous turnover of tissue proteins adds
to amino acid pools in tissues
Amino Acid (MP) Requirements
Maintenance (three fractions)
Protein required to support zero gain or production
1. Metabolism
Metabolized
Urine
Milk
Amino acids Feces
Wool
(Synthesis)
GIT
Scurf
(Degradation)
Pregnancy
Tissue proteins
= Endogenous urinary N
2. Proteins lost from body surface (hair, skin,
secretions) = Scurf proteins
3. Proteins lost from undigested digestive
secretions and fecal bacteria = Metabolic fecal N
Maintenance Requirements for
Metabolizable Protein
1. Maintenance (1996 Beef NRC)
3.8 g MP/kg BW.75
2. Maintenance (2001 Dairy NRC & CNCPS)
Endogenous urinary N
UPN = (2.75 x SBW0.50)/0.67
Scurf N
SPN = (0.2 x SBW0.60)/0.67
Metabolic fecal N
Dairy NRC: (DMI kg x 30) – 0.50 x ((bact
MP/0.80) – (bact MP)
CNCPS: 0.09 x (100 – digestible DM)
Maintenance Requirements for
Metabolizable Protein
BW, lbs
B NRC CNCPS NRC(85)
ISU
D NRC
MP
400
188
138
135
128
600
255
180
174
182
800
316
215
211
234
1000
374
250
244
284
1200
429
272
276
334
Relationship of Metabolizable Protein
Intake and Gain
700
MP, g/d
600
MP = 252.57 + 286.62 X Gain
3.8 g MP/kg BW.75
500
400
300
200
0
1
Gain, kg/d
Net Protein Required for Production
Amino Acids
Proteins
Milk
kg/d = (Milk yield, kg/d) (% protein in milk)
Growth
g/d = SWG (268 - (29.4 (RE/SWG)))
SWG = Shrunk weight gain, kg/d
RE = Retained energy, Mcal/d
RE obtained from net energy equations.
Efficiency of Utilization of
Metabolizable Protein for Deposition of Net Protein
1. Growth
Beef NRC
If EQEBW < 300 kg
0.834 – (0.00114 x EQEBW)
Otherwise 0.492
Dairy NRC
If EQEBW < 478 kg
0.834 – (0.00114 x EQEBW)
Otherwise 0.289
Efficiency of Utilization of
Metabolizable Protein for Deposition of Net Protein
2. Lactation
Protein in milk/0.65 (Beef NRC)
Protein in milk/0.67 (Dairy NRC)
3.Pregnancy
See equations in publications
Growth of Cattle – Change in Body Composition
70
60
Percent
50
40
Water
Protein
Fat
Ash
30
20
10
0
400
800
Empty Body Wt, lbs
ISU experiments
1200
Protein Requirements of Growing Cattle
Changes with Increase in Weight
Metabolizable
Protein Required,
g/d
Gain
Maintenance
Total
900
800
700
600
500
400
300
200
100
0
600
700
800
900 1000 1100 1200 1300
Weight, lbs
Example Calculation
Level 1
300 kg steer
Gaining 1.37 kg SBW/d
10.7% protein in gain
Consuming 6.8 kg feed DM
11.5% crude protein, 30% UIP
80% TDN
Is this steer being fed adequate protein?
300 kg Steer
MP requirement:
Maintenance (Beef NRC)
3.8 (300.75) = 273.9 g/d
Gain
(1.37 (.107)/.5) (1000) = 293.2 g/d
Total requirement
273.9 + 293.2 = 567.1 g/d
300 kg Steer
MP supplied:
UIP
(6.8 (.115) (.3) (.8)) 1000 = 187.7 g/d
Microbial
(6.8 (.80) (.13) (.8) (.8)) 1000 = 452.6 g/d
Total MP supplied
187.7 + 452.6 = 640.3 g/d
Requirement = 567.1 Supply = 640.3
Conclusion: Steer has adequate dietary protein
300 kg Steer
Was there enough protein degraded in
the rumen to furnish the nitrogen needs of
the microorganisms to produce BCP?
(6.8 (0.80) (0.13)) 1000 = 707.2 g/d BCP
(6.8 (.115) (.7))1000 = 547.4 g/d DIP
So this diet is short of DIP by 159.8 g/d
Would appear as negative ruminal N balance in
CNCPS model
Consequences of Shortage of DIP
Synthesis of bacterial protein is limited
547.4 g rather than 707.2
547.4 (.8) (.8) = 350.3 g MP from microbes
350.3 + 187.7 = 538.0 g MP supplied to steer
567.1 (requirement) - 538.0 (supply) = 29.1 g/d
shortage
Steer would not gain 1.37 kg/d according to model
How Can Rumen Available
Nitrogen be Increased?
Feed more degradable protein
Usually expensive to do so unless more
MP is also needed
Feed nonprotein nitrogen such as urea
All is degraded to NH3.
Usually cost is least
Does more DIP have to be added?
Models indicate yes
Supplementing Ruminal Available Nitrogen
Urea ($300/ton)
159.8/2.8 = 57.1 g/d of urea could be added
Urea is 280% crude protein
Cost: 57.1 x 0.00033 = $0.0189/d
Soybean meal ($200/ton)
(159.8/0.75)/0.5 = 426.1/0.9 = 473.5 g/d
Cost: 473.5 x 0.00022 = $0.1043/d
Dry DGS ($80/ton)
(159.8/0.5)/0.3 = 1065.3 g/d
Cost: 1065.3 x 0.00009 = $0.0937/d
Should: Correct urea for additional corn fed
Correct DGS for corn replaced
Cost corn ($2.00/bu) = $0.04/lb DM
Supplementation of Diets with Urea
If inadequate DIP is available for synthesis
of BCP, need to add degradable N
Can add urea
Urea Fermentation Potential (g urea/kg diet DM)
UFP = (BCP, g/kg - DIP, g/kg)/2.8
kg = kg diet DM
2.8 = Urea is 280% crude protein
+ UFP: Inadequate DIP, urea will benefit
- UFP: There is surplus DIP, urea of no benefit
Feed Values Beef NRC
Soybean meal
Dry corn
Corn silage
Alfalfa hay
Fescue hay
Corn stalks
% DIP
65
45
75
82
67
68
% TDN
87
90
75
60
56
55
% CP
49
9.8
8.0
17
9.1
6.3
Protein Values for Feeds
Soybean meal
Corn
Corn silage
Alfalfa hay
Fescue hay
Corn stalks
DIP,
g/kg
318.5
44.1
60.0
139.4
61.0
42.8
BCP,
g/kg
113.1
117.0
97.5
78.0
72.8
71.5
UFP,
g/kg
-73.4
26.0
13.4
-21.9
4.2
10.2
What is The Requirement for DIP?
Finishing Cattle
Cooper et al. JAS 2002
Fed different concentrations of urea to finishing steers
Diets: Dry rolled, high moisture and steam flaked corn
Measured feed intake and gain
Estimated requirement for DIP (DIP as % of diet DM)
Dry rolled – 6.3
High moisture – 10.0
Steam flaked – 9.5
High moisture and steam flaked corns more digestible
in the rumen – Increased microbial protein production
Limitations:
Protein requirements change during the experiment
Programmed Feeding of Supplemental Protein
Feedlot Steers - ISU
Program
Source within period
Program I
SBM-SBM-SBM
Program II
Urea-Urea-Urea
Program III
SBM-Urea-Urea
Program IV
SBM-Urea-Lo Urea
Crude protein, % DM
(MP – DIP, Percent of requirement)
1 to 42 d
43 to 84 d
85 to 135 d
12.4
12.4
12.4
(104 -101)
(127 – 101)
(151 – 101)
11.7
11.7
11.7
(96 – 101)
(117 – 101)
(138 – 101)
12.4
11.7
11.7
(104 – 101)
(119 – 101)
(140 – 101)
12.4
11.7
10.0
(104 – 101)
(119 – 101)
(123 – 80)
Programmed Feeding of Supplemental Protein
740 lb Feedlot Steers
I
II
III
IV
3.95
3.56
4.13
4.03
15.7
15.6
15.7
15.6
4.32
4.38
4.16
4.44
Feed/d
21.6
21.3
21.1
21.3
85 – 135 d, ADG
3.21
3.14
2.99
3.17
Feed/d
22.5
22.2
22.3
22.8
3.79
3.66
3.71
3.85
20.1
20.0
19.9
20.1
0 – 42 d, ADG
Feed/d
43 – 84 d, ADG
0 – 135 d, ADG
Feed/d
What is The Requirement for DIP?
Conclusions
All of calculated DIP does not have to be satisfied
when MP is being fed in excess
• Enough nitrogen is recycling
• Reduces quantity of nitrogen fed
11.7
10
9
11.7
10
10
9
Apparent digestibility, %
Urea, mg/100 ml
80
9
8
7
6
70
60
50
40
30
20
10
0
5
DM
-1
1
3
5
Hours
7
9
OM
CP
NDF
If Diet Needs More Metabolizable Protein
First consideration
Can microbial protein be increased?
If short of ruminal available N
Add urea
Provide ammonia to microorganisms
If surplus of rumen available N
Add fermentable feed (TDN)
Provide energy to microorganisms
Second consideration
Supplement diet with less degradable protein
Application of Metabolizable Protein System to
Feedlot Cattle
Supplement protein in relation to requirement
Optimize performance
• High performing cattle
Phase feed supplemental protein
• Change supplement in relation to rate and
composition of gain
• Use computer programs
• Supplement to minimize environmental impact
Protein Requirements of Growing Cattle
Relation to Rate of Gain
Metabolizable protein,
g/d
740
720
700
680
660
640
620
600
1.75
1.87
1.97
Rate of gain, kg/d
2.07
Increased Protein Requirements
Ruminants
Situation
Consequences
1. Young animals
Leaner gain
Fast rate of gain
More total protein
Leaner gain
in tissues
2. Compensatory gain
Greater muscle growth
3. High levels of lactation
More milk protein
4. Hormone implants and bGH More protein synthesis
5. Low feed intakes
Less MP from diet
High energy diets
and microbes
Need to feed higher concentrations of
protein or less degradable protein
Effects of Feeding Soybean Meal
Feedlot Steers
Supplement
Urea
SBM
% CP in diet
11.5
14.0
ADG, lb/d
3.71
4.10
Feed DM, lb/d
21.5
22.9
Feed/gain
5.86
5.66
Yearling steers, Revalor implants
At high rates of gain, cattle respond to bypass protein.
Effects of Feeding More Urea
% Crude protein
11.5
14.0
ADG, lb/d
3.63
3.57
Feed DM, lb/d
21.2
21.6
Feed/gain
6.02
6.04
Yearling steers, Revalor implant
If DIP requirement is met, no response to feeding
more urea.
Effects of Level of Soybean Meal
Fed to Feedlot Steers
% SBM
Urea
5
10
14
14
14
ADG, lb
3.58
3.83
3.94
Feed DM, lb/d
22.4
22.1
22.4
Feed/gain
6.28
5.80
5.70
% CP in diet
Yearling steers, Revalor implants
Greatest response to first addition of bypass protein.
Changing SBM Supplement to Urea
Phase Feeding
Diet
Urea
SBM
SBM-U
% CP in diet
11.5
14
14-11.5
ADG, lb/d
3.89
4.25
4.14
Feed DM, lb/d
22.5
22.8
22.2
Feed/gain
5.86
5.40
5.40
Yearling steers, Revalor implant
Cattle require less protein as they approach mature finished weights
Industry standard is 13.5 to 14% crude protein for finishing cattle
Nitrogen Balance - Feedlot Steers
680 to 1377 lbs
Implanted and fed 14% crude protein
Lbs body N
N fed, lbs
N excreted, lbs
N excreted, %
Start
18.7
End
31.6
Gain
12.9
96.5
83.6
86.6
N excreted from 10,000 steers = 418 tons
Cattle retain 10 to 15% of dietary N during finishing.
Phase Feeding of Protein
830 lb Steers
0 to 61 days
ADG
11.0
F/G
14.0
ADG
14.0
6
5.5
5.5
5
5
Lbs
Lbs
6
0 to 130 days
4.5
4
3.5
3.5
3
3
SBM
SBM-U
Source of protein
11.0
Urea
SBM
SBM-U
4.5
4
Urea
11.0
F/G
14.0
Source of protein
Diets to Feed in a Phase Program
Theoretical Feeding Program
Diet
I
II
Corn
71.5
78.4
Corn silage
10.0
10.0
Alfalfa hay
5.0
5.0
Expeller SBM
11.0
3.5
Urea
0.33
0.83
Supplement
2.17
2.27
Crude protein, %
13.8
12.3
Crude protein: Corn 9.0%, Hay 16.0%
III
81.6
10.0
5.0
1.09
2.31
11.6
Rumen Degradable and Metabolizable Protein
Theoretical Phase-Fed Diets
Percent of
requirement
Metabolizable protein
150
140
130
120
110
100
90
80
70
60
50
Rumen available protein
Diet:
I
II
III
600
800
900
III
1000
III
1200
Body wt, lbs
Nitrogen excreted from 10,000 head feedyard: 312.9 tons
Develop Diets with Low Protein Ingredients
Reduce Nitrogen Excretion
Diet
Corn
Corn silage
Alfalfa hay
Expeller SBM
Urea
Supplement
Crude protein, %
I
68.2
10.0
5.0
14.0
0.52
2.28
13.5
II
74.2
10.0
5.0
7.6
0.99
2.21
12.2
III
78.4
10.0
5.0
3.0
1.32
2.28
11.2
Crude protein: Corn 6.0%, Hay 10.0%
IV
81.2
10.0
5.0
1.54
2.26
10.5
Rumen Degradable and Metabolizable Protein
in Phase-Fed Diets
Percent of
requirement
Metabolizable protein
150
140
130
120
110
100
90
80
70
60
50
Diet:
I
600
Rumen available protein
II
III
IV
800
900
1000
IV
1200
Body wt, lbs
Nitrogen excreted from 10,000 head feedyard: 283 tons
Response to Feeding Urea
KSU Study
Metabolizable protein
Rumen available protein
Percent of
requirement
120
100
80
60
40
20
0
0
0.5
% Urea
1
Response to Feeding Urea
Finishing Steers
% Urea
0
0.50
1.00
Feed DM, lb/d
24.4
23.1
24.0
ADG, lbs
3.34
3.52
3.63
Gain/feed
0.137
0.153
0.152
KSU, 1997 - 730 lb steers fed 154 days.
Diet: Dry rolled corn and 10% prairie hay.
Response to Implants and Protein
700 lb Steers
0 to 85 days
ADG
ADG
F/G
--No Implant-- --------Implant-------
8
7
5
6
4.5
5
Lbs
5.5
4
0
14
2
12.5
1
11
2.5
9.5
2
12.5
3
11
3
Dietary crude protein, %
No Implant
F/G
-----Implant-----
4
3.5
9.5
Lbs
6
86 to 186 days
11
11
14
Dietary crude protein, %
Effect of Implants on Nitrogen Retention
N Retained
Percent of N consumed
Feedlot Steers
20
19
18
17
16
15
14
13
12
11
10
C - 11%
C - 12.5%
I - 9.5%
I - 14%
Protein Requirements of Lactating Cows
Metabolizable protein, g/d
3000
2500
2000
1500
Maintenance
Lactation
Total
1000
500
0
20
30
Milk, kg/d
40
Protein Requirements of Dairy Cows
Milk yield
Composition of milk
Body weight
Maintenance
Body weight change
Pregnancy
Meeting Dairy Cow’s Protein Requirement
• Feed intake
Nature of feed ingredients
Fermentable energy
Microbial protein synthesis in the rumen
Proportion of feed protein(s) degraded
• Digestibility of proteins in the intestine
• Amino acids available for absorption
Amino acid balance
Recommendations for Feeding High RUP
Byproducts to Dairy Cows
CP
RUP
%
%
Recom ByProd
ByProd
intake CP intake CP intake
lb/d
lb/d
% total
Blood meal
Feather meal
Meat & bone
Fishmeal
Corn gluten meal
Corn distill. grain
87
92
54
67
67
30
82
71
70
60
55
47
.75-1.0
.5-1.0
2.0-2.5
1.0-2.0
2.0-3.0
4.0-6.0
Soybean meal
52
33
Extruded SBM
Extruded soybeans
Roasted soybeans
49
43
43
61
54
62
.87
.92
1.35
1.34
2.01
1.80
9.7
10.2
15.0
14.9
22.3
20.0
Feed as needed
Oil intake might limit
Digestibility of RUP
Dairy NRC
Grass/legume hay
Corn silage
Soy hulls
Corn, dry cracked
Soybean meal
Dry distillers grains
Corn gluten meal
Fish meal
Hydrolyzed feathers
CP, %
19.1
8.8
13.9
9.4
53.8
29.7
65.0
68.5
92.0
RUP, % dig
70
70
70
90
93
80
92
88
65
Why Limit High RUP Proteins?
Lactating Cows
• Animal byproducts tend to reduce feed intake
Palatability
Fat content (Fish meal decreases milk fat)
Decreased feed intake reduces
microbial protein synthesis
• Plant byproducts may have poor amino acid
balance
Corn proteins deficient in lysine and tryptophan
Digestibility of RUP (UIP)
• Might create a deficiency of RDP (DIP)
• Quality of RUP proteins can be variable
Why a Variable Response to RUP?
Lactating Cows
• Protein requirements may have been met
Protein might not be first limiting
Cows mobilizing body proteins
• First limiting amino acid might not be increased
Amino acid ratios of metabolizable protein
Digestibility of RUP
• Use of RUP might cause a shortage of RDP
• Overestimation of degradation of other
supplemental proteins