Aus dem Institut für Tierzucht und Haustiergenetik Professur für Tierhaltung und Haltungsbiologie der Justus-Liebig-Universität Gießen Horse’s laterality: methods of determination, genetic aspects, interaction with human handedness and the influence on horse-rider communication, horse’s muscle status, sport success and risk of injury Inaugural -Dissertation Zur Erlangung des Doktorgrades (Dr. Agr.) im Fachbereich Agrarwissenschaften, Ökotrophologie und Umweltmanagement der Justus- Liebig-Universität Gießen vorgelegt von Sandra Kuhnke aus Köln Gießen, 2019 Mit Genehmigung des Fachbereichs Agrarwissenschaften, Ökotrophologie und Umweltmanagement der Justus-Liebig-Universität Gießen Prüfungskommission: Vorsitzender: Prof. Joachim Aurbacher 1. Gutachterin: Prof. Uta König von Borstel 2. Gutachter: Prof. em. Holger Preuschoft 3. Gutachterin: Prof. Stephanie Krämer Prüferin: Prof. Gesine Lühken Prüfer: Prof. Michael Röcken Tag der Disputation: 15.1.2020 2 Meinen Lehrmeistern und Wegbegleitern Roxanne und Luna 3 Table of Contents 1. Introduction ................................................................................................................................... 6 2. Aim of the present study ............................................................................................................... 7 3. Literature ....................................................................................................................................... 8 3.1 Laterality in ancient and modern human populations ................................................................. 8 3.2 The development of handedness ................................................................................................ 8 3.3 Structural asymmetries related to laterality .............................................................................. 10 3.4 Differences between left and right-handed humans ................................................................. 12 3.5 Laterality in horses .................................................................................................................... 14 3.6 The effects of laterality on performance and health ................................................................. 17 3.7 The rider’s influence on the horse ............................................................................................. 19 3.8 The horse’s balance ................................................................................................................... 21 3.9 The horse’s muscles and „trigger points“ .................................................................................. 23 3.10 The rider’s posture in European riding .................................................................................... 25 3.11 Rein signals in European riding ............................................................................................... 29 3.12 The rider’s posture and signals in Western riding ................................................................... 30 3.13 The influence of bits and bridles on the horse ........................................................................ 32 3.14 Rein tension ............................................................................................................................. 35 3.15 Rein tension and its relation to handedness in riders.............................................................. 39 4. Laterality of horses and riders in equestrian sports and possible impacts on competition results and risk of injury ................................................................................................................................... 42 4.1 Aim ............................................................................................................................................. 42 4.2 Material & Methods ..................................................................................................................... 42 4.3 Results ......................................................................................................................................... 42 4.4 Discussion .................................................................................................................................... 50 4.4 Conclusion ................................................................................................................................... 55 5. A comparison of different methods to determine horse’s motor laterality and its relation to rein tension ................................................................................................................................................. 56 5.1 Aim ............................................................................................................................................. 56 5.2 Material & Methods ..................................................................................................................... 56 5.3 Results ......................................................................................................................................... 62 5.4 Discussion ................................................................................................................................... 86 5.5 Conclusion ................................................................................................................................... 96 6. Genetic parameters for motor laterality and sport success in warmbloods and Thoroughbreds 99 6.1 Aim ............................................................................................................................................. 99 6.2 Material & Method ...................................................................................................................... 99 6.3 Results ...................................................................................................................................... 101 6.4 Discussion ................................................................................................................................. 108 6.5 Conclusion ................................................................................................................................. 112 7. The magnitude and symmetry of rein tension in conventional European and Western riding in relation to laterality of horses and riders ........................................................................................... 113 7.1 Aim ........................................................................................................................................... 113 4 7.2 Materials and Methods: .............................................................................................................. 114 7.3 The influence of laterality of horses and their riders on rein tension in different riding styles and disciplines .............................................................................................................................................. 124 7.4 The influence of horse –rider-laterality on sport results, risk of injury and the horse’s muscular system .............................................................................................................................................................. 161 7.5 Other factors that might influence rein tension, symmetry and performance in horse-rider combinations .............................................................................................................................................................. 182 7.6 Rein tension parameters in relation to the type of equipment used for communication and different ways of rein handling ............................................................................................................................. 204 8. Main Discussion ......................................................................................................................... 237 9. Conclusion ................................................................................................................................. 276 10. Summary ............................................................................................................................... 282 11. Zusammenfassung ................................................................................................................. 284 12. References ............................................................................................................................. 286 13. Appendix ............................................................................................................................... 312 13.1 Questionnaires ................................................................................................................... 312 13.2 List of tables ....................................................................................................................... 323 13.3 List of figures ...................................................................................................................... 325 13.4 List of abbreviations ........................................................................................................... 337 Danksagung ........................................................................................................................................ 338 Eidesstatliche Erklärung ....................................................................................................................