1. Application of the ideal protein concept in pigs
Jaap van Milgen

2. Outline Structure and roles of amino acids and proteins
Ideal protein :
Concept
Expressing requirements
Estimating amino acid requirements:
Experimental methods
Combining results: meta-analyses
Model-derived methods
How far can we go in reducing the CP content?
Conclusions

3. Outline Structure and roles of amino acids and proteins
Ideal protein :
Concept
Expressing requirements
Estimating amino acid requirements:
Experimental methods
Combining results: meta-analyses
Model-derived methods
How far can we go in reducing the CP content?
Conclusions

4. Structure of amino acids
Lys
Gly
Thr
Met

5. Structure of amino acids
“Some elements in proteins are essential constituents of the diet” (William Rose, 1932)
Essential
Semi-essential
Non-essential
Lys
Cys (from Met)
Arg
Met
Tyr (from Phe)
Ala
Thr
Ser
Trp
Gly
Val
Pro
Ile
Glu
Leu
Gln
Phe
Asp
His
Asn

6. Amino acids and proteins are required and involved in many processes
Structural proteins (e.g., myosin and actin in muscle)
Milk proteins (e.g., casein)
Functional proteins (e.g., enzymes, hormones)
Defense and protective proteins (e.g., glutathione, mucins)
Cell signaling
Nitrogen and energy transport between tissues

7. Amino acid composition of proteins

8. Amino acid composition of muscle proteins
Pearson & Young (1989)

9. Outline Structure and roles of amino acids and proteins
Ideal protein :
Concept
Expressing requirements
Estimating amino acid requirements:
Experimental methods
Combining results: meta-analyses
Model-derived methods
How far can we go in reducing the CP content?
Conclusions

10. Ideal protein (Mitchell et al., 1964)
Law of the minimum
(von Liebig, 1850)
All essential amino acids are equally limiting for performance:
no deficiency
no excess
Usually expressed relative to Lys:
Lys is typically the first-limiting amino acid in the diet
The Lys requirement (g/kg diet) changes during growth, but the requirements of other amino acids change proportionally to Lys (assumption)
Simple to use: only 1 value for each amino acid to remember (e.g., Thr:Lys = 65%)

11. Expressing amino acid values and requirements
nutrient
intake
nutrient
output
endogenous
secretions
nutrient
absorption

12. Expressing amino acid values and requirements
ileal indigestible
specific endogenous losses
diet
basal endogenous losses
apparent ileal digestible (AID)
standardized ileal digestible
(SID)
Basal endogenous losses are:
part of the feed value in an AID system
part of the requirement in an SID system

13. Expressing amino acid values and requirements
Lys
Thr
Content, g/kg
AID, %
SID, %
Soybean meal
27.8 87 90
17.7 82
Corn
2.4 70 80
3.0 74 83
Wheat
3.1 81
3.2 75
SID is the preferred mode of expression

14. Outline Structure and roles of amino acids and proteins
Ideal protein :
Concept
Expressing requirements
Estimating amino acid requirements:
Experimental methods
Combining results: meta-analyses
Model-derived methods
How far can we go in reducing the CP content?
Conclusions

15. Knowledge of the limiting factors in a dose-response study
test AA is limiting 
 some other factor is limiting

16. The requirement estimate depends on the statistical model used

17. A single study does not provide an answer:
studies on branched-chain amino acids
Ile
Val
Leu
Publications: 22 20 1
Peer-reviewed 12 9
Other 10 11
Dose response experiments: 46 28 2 24 15 13
van Milgen et al. (2012). Animal 6:

18. Metabolism of branched-chain amino acids
isoleucine
valine
leucine
a-keto-b-methylvalerate
(KMV)
a-ketoisovalerate
(KIV)
a-ketoisocaproate
(KIC)
BCAA
amino transferase
a-methylbutyryl CoA
(glucogenic + ketogenic)
isobutyryl CoA
isovaleryl CoA
(ketogenic)
BCKA
dehydrogenase

19. Meta-analyses to quantify the response to the Ile supply
Dose-response studies reported since the 1950s
Criteria for selection:
Supplementation with ≥ 4 levels of l-Ile (or d-Ile)
Diet composition
Intake and growth response

20. Meta-design of Ile dose-response studies

21. Response to the Ile supply
Standardization of the responses:
Within-study response (Y-axis)
Relative to the NRC (1998) requirement (X-axis)

22. Response to the Ile supply Is there a response (P < 0.25)?
33
 13

23. Protein sources used to study the Ile requirement

24. Response to the Ile supply
Relative daily gain, % 1
 9
32
 4
Ile supply, % of NRC requirement

25. Factorial calculation of amino acid requirements for growing pigs
ileal indigestible
specific endogenous losses
diet
basal endogenous losses
maintenance
standardized ileal digestible
available
minimum catabolism (=100% - maximum efficiency)
excess
deposition

26. Factorial calculation of amino acid requirements for growing pigs
SID Lys requirement, g/d
Item
Value
Body weight, kg 50
DM intake, kg/d 2
Protein deposition, g/d
150
Lys content in body protein, %
6.96
Minimum catabolism of Lys, % 28
Maintenance Lys requirement, mg/(kg BW0.75)/d
28.4
Basal endogenous losses, mg/kg DM intake
313

27. Body weight gain and protein deposition change in a similar way during growth …

28. … but protein deposition and feed intake vary differently
Amino acid requirement ~
protein deposition
feed intake
The bottom line:
We have to construct these curves!

30. Model-derived Lys requirements for growing pigs

31. Dealing with variation among pigs: which pig in the population do you want to feed?

32. Average ideal amino acid profile for growing pigs
InraPorc
NRC
Met 30 29
Met + Cys 60 58
Thr
65 (64-65)
64 (61-68)
Trp 18
Val 70
66 (65-68)
Ile 55 53
Leu
100
101
Phe 50 61
Phe + Tyr 95
His 32 34
Arg 42 46

33. Outline Structure and roles of amino acids and proteins
Ideal protein :
Concept
Expressing requirements
Estimating amino acid requirements:
Experimental methods
Combining results: meta-analyses
Model-derived methods
How far can we go in reducing the CP content?
Conclusions

34. How far can we go in reducing the CP in diets?
Cereals – soybean meal - AA
Cereals - AA
CP, %
17.6
15.6
13.5
11.8
13.0
14.0 P
l-Lys HCl
0.28
0.46
0.72
0.92
1.00
dl-Met, l-Thr, l-Trp + ++
+++
++++
l-Val
l-His, l-Ile, l-Leu, l-Phe
l-Glu
l-Arg, l-Gly, l-Pro
Feed intake, g/d
766
775
779
734
810
782
0.60
Weight gain, g/d
450b
454b
442b
358a
420b
451b
0.55
Gain:Feed
0.59b
0.57b
0.49a
0.52a
0.58b
<0.01
Diet were formulated with 1.0% SID Lys (10-20 kg piglets)
No deficiency in other amino acids (in theory)
Gloaguen et al. (2014). J. Anim. Sci. 92:

35. Conclusions
The response of the animal to the amino acid supply changes during the different production stages
Think “response” rather than “requirement”
There is variation among pigs in the response to the amino acid supply
There is (still) a potential to reduce the CP content in pig diets

36. EU funded Research project
€10 M
Budget
EU funded Research project
2015
2020
8 Academic 15
Industry + Extension
23 Partners
EU + China
Adapting the feed, the animal and the feeding techniques to improve the efficiency and sustainability of monogastric livestock production systems
The Feed-a-Gene Project has received funding from the European Union’s H2020 Program under grant agreement no

37. 1INRA-Agrocampus Ouest
Acknowledgements:
Roberto Barea1
Ludovic Brossard1
Alberto Conde1
Kees De Lange2
Serge Dubois1
Michel Étienne1
Mathieu Gloaguen1
Nathalie Le Floc’h1
Jean Noblet1
Bernard Sève1
Alain Valancogne1
1INRA-Agrocampus Ouest
2University of Guelph