Institute of Animal Science Department of Animal Nutrition Prof. Dr. Markus Rodehutscord Variability of amino acid digestibility of cereal grains in laying hens Dissertation submitted in fulfillment of the regulations to acquire the degree “Doktor der Agrarwissenschaften“ (Dr. sc. agr. /PhD in Agricultural Sciences) to the Faculty of Agricultural Science presented by Tobias Zuber born in Heidelberg, Germany 2017 Die vorliegende Arbeit wurde am 10.11.2016 von der Fakultät Agrarwissenschaften der Universität Hohenheim als „Dissertation zur Erlangung des Grades eines Doktors der Agrarwissenschaften“ angenommen. Tag der mündlichen Prüfung: 07.12.2016 Dekan der Fakultät Agrarwissenschaften: Prof. Dr. Ralf T. Vögele Leitung des Kolloquiums: Prof. Dr.-Ing. Stefan Böttinger Berichterstatter, 1. Prüfer: Prof. Dr. Markus Rodehutscord Berichterstatter: PD Dr. Holger Kluth 2. Prüfer: Prof. Dr. Dr. h.c. Rainer Mosenthin 3. Prüfer: apl. Prof. Dr. Michael A. Grashorn This work was supported by funds of the Federal Ministry of Food, Agriculture, and Consumer Protection (BMELV) based on a decision of the Parliament of the Federal Republic of Germany via the Federal Office for Agriculture and Food (BLE) under the innovation support programme. TABLE OF CONTENTS ABBREVIATIONS .................................................................................................................. III LIST OF TABLES .................................................................................................................... V LIST OF FIGURES ................................................................................................................. VII 1 General Introduction and Background ................................................................................ 1 2 Overview of Own Work ...................................................................................................... 5 3 General Discussion ............................................................................................................. 7 3.1 Possible sources of error .............................................................................................. 7 3.2 Factors affecting amino acid digestibility ................................................................... 8 3.2.1 Assay-based factors .............................................................................................. 8 3.2.2 Non-starch polysaccharides ................................................................................ 21 3.2.3 Protein fractions ................................................................................................. 27 3.3 Predictability of amino acid digestibility ................................................................... 28 3.4 Conclusions and perspectives for future research ..................................................... 29 References ................................................................................................................................ 33 4 Included Studies ................................................................................................................ 45 4.1 Manuscript I ............................................................................................................... 45 4.2 Manuscript II ............................................................................................................. 49 4.3 Manuscript III ............................................................................................................ 53 4.4 Manuscript IV ............................................................................................................ 57 5 Summary ........................................................................................................................... 61 6 Zusammenfassung ............................................................................................................. 65 I ABBREVIATIONS Beneath abbreviations for the units defined by the international system of units and the symbols for chemical elements of the periodic table of elements the following abbreviations were used: AA Amino acids ADF Acid detergent fibre Ala Alanine Arg Arginine Asp Aspartic acid AX Arabinoxylans BD Basal diet β-glucan Mixed-linkage (1→3;1→4)-β-glucans CP Crude protein Cys Cysteine DM Dry matter Glu Glutamic acid Gly Glycine HDP Highly digestible protein His Histidine Ile Isoleucine Leu Leucine Lys Lysine Met Methionine NDF Neutral detergent fibre NIRS Near infrared reflectance spectroscopy NSP Non-starch polysaccharides pc Prececal Phe Phenylalanine Pro Proline SAS Statistical Analysis System Ser Serine Thr Threonine Trp Tryptophan Tyr Tyrosine Val Valine III LIST OF TABLES Table 1. Selected results and principle assay characteristics of studies examining the amino acid digestibility of triticale and rye grain in poultry ............................................................... 10 Table 2. Selected results and principle assay characteristics of studies examining the amino acid digestibility of corn grain in poultry ................................................................................. 11 Table 3. Selected results and principle assay characteristics of studies examining the amino acid digestibility of wheat grain in poultry .............................................................................. 13 Table 4. Digestibility (%) of the four basal diets used in the digestibility trials with triticale, rye, corn, and wheat ................................................................................................................. 19 Table 5. Concentrations of selected NSP fractions (mean and range, in g/kg DM, unless otherwise stated) and respective coefficients of the variation of cereal grains grown under standardized environmental and agronomic conditions ........................................................... 22 V