COMPARISON OF LONG-TERM CIDR-BASED PROTOCOLS TO SYNCHRONIZE ESTRUS AND OVULATION PRIOR TO FIXED-TIME ARTIFICIAL INSEMINATION IN POSTPARTUM BEEF COWS A Thesis presented to the Faculty of the Graduate School at the University of Missouri In Partial Fulfillment of the Requirements for the Degree Master of Science by NEAL TIMOTHY MARTIN Dr. David J. Patterson, Thesis Advisor DECEMBER 2012 The undersigned, appointed by the Dean of the Graduate School, have examined the thesis entitled COMPARISON OF LONG-TERM CIDR-BASED PROTOCOLS TO SYNCHRONIZE ESTRUS AND OVULATION PRIOR TO FIXED-TIME ARTIFICIAL INSEMINATION IN POSTPARTUM BEEF COWS presented by Neal Timothy Martin, a candidate for the degree of Master of Science, and hereby certify that, in their opinion, it is worthy of acceptance. Dr. David J. Patterson Dr. Michael F. Smith Dr. Scott E. Poock Dr. Mark R. Ellersieck DEDICATION This thesis is dedicated to my parents, Nathan and Susan, who have always supported and believed in me, who have instilled the values of honesty, integrity, responsibility, and dedication in me, and who inspired my passion for agriculture, and to my siblings, Brian and Elaine, my girlfriend, Ali, and to my other family and friends for their continual love and support during my education and throughout life. ACKNOWLEDGEMENTS This project would not have been possible without the effort and support of several individuals. I would like to thank my advisor, Dr. David Patterson, for his guidance during my graduate career and other life endeavors. Thank you for your generosity in allowing me to travel to conferences and make connections with people around the country and around the world. Next, I would like to thank my undergraduate advisor, Dr. Michael Smith, for his advice during my experiments and throughout my academic career. Dr. Scott Poock, thank you for assistance during my experiments and for mentoring me in the study of veterinary medicine. I would also like to thank Dr. Mark Ellersieck for his knowledge and patience in helping me to interpret statistics. Furthermore, my research would not have been successful without the hard work and dedication of the crew at the University of Missouri Thompson Research Center: Jon Schreffler, Stoney Coffman, and Dennis Hamilton. Additionally, I would like to thank my colleagues and fellow graduate students, Daniel Mallory, Justin Nash, Ky Pohler, and Jordan Thomas, for their help and support during this project and throughout graduate school. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................ ii LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii LIST OF ABBREVIATIONS .......................................................................................... viii ABSTRACT .........................................................................................................................x CHAPTER 1. REVIEW OF LITERATURE ..........................................................................................1 INTRODUCTION ........................................................................................................1 A REVIEW OF THE BOVINE ESTROUS CYCLE ...................................................3 The estrous cycle........................................................................................................3 The follicular phase ....................................................................................................4 The luteal phase .........................................................................................................6 Folliculogenesis and follicular waves ........................................................................8 FACTORS AFFECTING ANESTRUS IN CATTLE ..................................................9 Anestrus .....................................................................................................................9 Endocrine changes ...................................................................................................10 Suckling ...................................................................................................................11 Body condition .........................................................................................................11 Parity ........................................................................................................................12 Dystocia ...................................................................................................................12 Minor factors ............................................................................................................13 iii A REVIEW OF PROGESTINS ..................................................................................13 Melengestrol acetate ................................................................................................14 Controlled Internal Drug Release ............................................................................15 DEVELOPMENT OF ESTROUS SYNCHRONIZATION PROTOCOLS...............16 Development of GnRH-PG ......................................................................................16 Development of the Select Synch protocol ..............................................................17 Development of the CO-Synch protocol..................................................................17 Development of the 7-d Select Synch and CO-Synch + CIDR protocols ...............18 Development of the 5-d Select Synch and CO-Synch + CIDR protocols ...............18 Development of CIDR Select ..................................................................................19 Development of 14-d CIDR-PG ..............................................................................20 SUMMARY ................................................................................................................22 2. COMPARISON OF LONG-TERM CIDR-BASED PROTOCOLS TO SYNCHRONIZE ESTRUS AND OVULATION PRIOR TO FIXED-TIME ARTIFICIAL INSEMINATION IN POSTPARTUM BEEF COWS .............................33 ABSTRACT ................................................................................................................33 INTRODUCTION ......................................................................................................35 MATERIALS AND METHODS ................................................................................37 Experimental design.................................................................................................37 Estrus detection and artificial insemination .............................................................37 Ultrasonagraphy of dominant follicles.....................................................................38 Pregnancy diagnosis.................................................................................................39 Blood collection and RIA ........................................................................................39 Statistical analyses ...................................................................................................39 iv RESULTS ...................................................................................................................41 Estrous response after CIDR removal ......................................................................41 Dominant follicle diameters .....................................................................................41 Serum steroid hormone concentrations ....................................................................42 Estrous response after PG and prior to FTAI ...........................................................43 Pregnancy rates ........................................................................................................43 DISCUSSION .............................................................................................................44 LITERATURE CITED ......................................................................................................63 VITA ..................................................................................................................................79 v LIST OF TABLES Table Page 2.1. Number, estrous cyclicity status, age, days postpartum, and body condition score of cows prior to treatment initiation ..........................................................51 2.2. Estrous response after CIDR removal....................................................................53 2.3. Dominant follicle diameters at PG and FTAI ........................................................55 2.4. Serum concentrations of progesterone at PG .........................................................56 2.5. Serum concentrations of estradiol-17β at PG and FTAI ........................................57 2.6. Estrous response after PG and prior to FTAI.........................................................59 2.7. FTAI pregnancy rate and final pregnancy rate ......................................................60 2.8. Effect of estrous response after PG on FTAI pregnancy rate ................................61 2.9. Estrous response after PG and FTAI pregnancy rate by age group .......................62 vi LIST OF FIGURES Figure Page 1.1. Chemical structures of progesterone and melengestrol