Application of the ideal protein concept in pigs Jaap van Milgen

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

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

Structure of amino acids Lys Gly Thr Met

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

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

Amino acid composition of proteins

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

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

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%)

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

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

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

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

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

The requirement estimate depends on the statistical model used

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 6:1601-608

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

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

Meta-design of Ile dose-response studies

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

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

Protein sources used to study the Ile requirement

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

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

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

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

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

Model-derived Lys requirements for growing pigs

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

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

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

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. 92:637-644

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

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 www.feed-a-gene.eu The Feed-a-Gene Project has received funding from the European Union’s H2020 Program under grant agreement no 633531

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