Protein Metabolism III
Protein requirements and B agonists
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 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
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
and microbes
Need to feed higher concentrations of
protein or less degradable protein
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
Bacterial Protein
Synthesis in the Rumen
Microbial protein synthesis related to:
1. Available NH3 and amino acids (DIP)
2. Fermentation of CHOH - Energy
NH3
VFA
CHOH
Amino acids & Peptides
Amino acids
Fermentation
VFA
Microbial
proteins
BCP
Microbial protein synthesis
• BCP (gm) = .13 TDN (gm)
– Assumes
• TDN is corrected for fat
• RDP is adequate
RDP requirement
• RDP = 1.18 BCP (gm) - .2 diet CP (gm)
• If RDP < 1.18 BCP – .2 diet CP, then
– actual BCP (gm) = .85 (RDP+.2(CP)) (gm)
• BCP is assumed to be 80% protein which has a
digestibility of 80% in the small intestine
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
DDG
40
85
30
Brome pasture
80
74
21
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
DDG
120
110
-5
Brome pasture
161
91
-25
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
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
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
Protein Requirements of Dairy Cows
Body weight
Maintenance
Body weight change
Pregnancy
Milk yield
Composition of milk
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
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
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
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
Limiting AA for Dairy Cattle
• Lysine and methionine
• Based on corn silage or alfalfa based diets
• NRC (2001) suggests 7.3% of metabolizable
protein as Lys, 2.5% as Met
• Amino acid composition varies by protein
source
• Rumen protected (bypass) lysine and/or
methionine can be supplemented
Vyas and Erdman, 2009