ESCUELA TÉCNICA SUPERIOR DE INGENIEROS AGRÓNOMOS UNIVERSIDAD POLITÉCNICA DE MADRID EFFECT OF SHORT-TERM FASTING PRIOR TO SLAUGHTER ON WELFARE AND MEAT QUALITY OF RAINBOW TROUT (Oncorhynchus mykiss) TESIS DOCTORAL JAVIER LÓPEZ LUNA Ingeniero Agrónomo 2013 ESCUELA TÉCNICA SUPERIOR DE INGENIEROS AGRÓNOMOS UNIVERSIDAD POLITÉCNICA DE MADRID EFFECT OF SHORT-TERM FASTING PRIOR TO SLAUGHTER ON WELFARE AND MEAT QUALITY OF RAINBOW TROUT (Oncorhynchus mykiss) JAVIER LÓPEZ LUNA Ingeniero Agrónomo Director de la Tesis Morris Villarroel Robinson Dr. en Biología ACKNOWLEDGEMENTS First, I would like to express my sincere gratitude to my supervisor, Dr. Morris Villarroel Robinson for his support and guidance during the last four years, for generously sharing his knowledge and time and for being patient with my questions. I am really grateful to all those who helped me during my PhD study. Many people have made invaluable contributions, both directly and indirectly to my research. These include Francisco Berdejo and the colleagues who participated in the trials of this Thesis. Teachers and members of the Departamento Producción Animal (ETSI Agrónomos, UPM), Fernando Torrent and members of the Piscifactoría (ETSI Montes, UPM), Miguel Ángel Ibáñez (Departamento de Estadística y Métodos de Gestión en la Agricultura (ETSI Agrónomos, UPM), Jesús de la Fuente and members of the Departamento de Producción Animal (Facultad de Veterinaria, UCM) and Pilar Barreiro and Adolfo Moya (Departamento de Ingeniería Rural, ETSI Agrónomos, UPM). This Thesis was made possible with a grant from the Ministerio de Ciencia e Innovación, project AGL2010-19479. III AGRADECIMIENTOS En primer lugar quisiera agradecer a mi tutor Morris Villarroel Robinson todo el apoyo y la confianza prestados durante el periodo de doctorado en la UPM, por su ayuda personal y técnica. Gracias por ser tan buen consejero. Gracias también a Francisco Berdejo y a todos los compañeros que tomaron parte en la realización de las pruebas de esta Tesis, a los profesores y personal del Departamento de Producción Animal de la ETSI Agrónomos, a Fernando Torrent y personal de la Piscifactoría de la ETSI Montes, a Miguel Ángel Ibáñez del Departamento de Estadística y Métodos de Gestión en Agricultura de la ETSI Agrónomos, a Jesús de la Fuente y personal del Departamento de Producción Animal de la Facultad de Veterinaria (UCM) y a Pilar Barreiro y Adolfo Moya del Departamento de Ingeniería Rural de la ETSI Agrónomos. Las pruebas experimentales que componen esta Tesis Doctoral han sido realizadas gracias al proyecto AGL2010-19479 del Ministerio de Ciencia e Innovación. V TABLE OF CONTENTS ACKNOWLEDGEMENTS ...................................................................................................... III AGRADECIMIENTOS ............................................................................................................. V LIST OF FIGURES .................................................................................................................. XI LIST OF TABLES ............................................................................................................... XVII LIST OF ABBREVIATIONS ................................................................................................ XIX SUMMARY ............................................................................................................................ XXI RESUMEN ........................................................................................................................... XXIII INTRODUCTION 1. The importance of aquaculture .............................................................................................. 3 1.1. Aquaculture in Spain ...................................................................................................... 4 1.2. Trout ............................................................................................................................... 5 2. Stress and welfare ................................................................................................................. 6 2.1. Animal welfare ............................................................................................................... 6 2.2. Fish welfare .................................................................................................................... 8 3. Pre-slaughter handling ......................................................................................................... 10 3.1. Fasting .......................................................................................................................... 10 3.2. Hour of slaughter .......................................................................................................... 13 3.3. Water temperature ........................................................................................................ 14 4. How to measure welfare ...................................................................................................... 15 4.1. Biometric indicators ..................................................................................................... 15 4.2. Stress indicators............................................................................................................ 16 4.3. Haematological indicators ............................................................................................ 17 4.3.1. Plasma cortisol ...................................................................................................... 19 4.3.2. Plasma glucose ...................................................................................................... 20 4.3.3. Plasma lactate ........................................................................................................ 21 4.3.4. Haematocrit ........................................................................................................... 21 4.3.5. Leucocytes ............................................................................................................. 22 4.4. Metabolic indicators ..................................................................................................... 22 4.4.1. Liver and muscle glycogen ................................................................................... 22 4.4.2. R-value (IMP/ATP ratio) ...................................................................................... 23 5. Product quality .................................................................................................................... 24 5.1. Muscle pH .................................................................................................................... 26 5.2. Rigor mortis ................................................................................................................. 27 VII 5.3. Water holding capacity ................................................................................................. 30 5.4. Meat colour .................................................................................................................. 32 6. Objectives ............................................................................................................................ 34 MATERIAL AND METHODS 1. Installations and fish material ............................................................................................. 37 2. Experimental design ............................................................................................................ 38 3. Slaughtering and sampling procedures................................................................................ 39 3.1. Biometric indicators ..................................................................................................... 40 3.2. Haematological indicators ............................................................................................ 40 3.2.1. Plasma cortisol ...................................................................................................... 40 3.2.2. Plasma glucose ...................................................................................................... 41 3.2.3. Plasma lactate ........................................................................................................ 41 3.2.4. Red and white cells ............................................................................................... 42 3.3. Metabolic indicators ..................................................................................................... 43 3.3.1. Liver and muscle glycogen ................................................................................... 43 3.3.2. R-value (IMP/ATP ratio) ...................................................................................... 43 3.4. Product quality ............................................................................................................. 44 3.4.1. Muscle pH ............................................................................................................. 44 3.4.2. Rigor mortis .......................................................................................................... 44 3.4.3. Water holding capacity .......................................................................................... 45 3.4.4. Meat colour ........................................................................................................... 46 4. Statistics .............................................................................................................................