UNDERSTANDING THE EQUINE DISTAL LIMB A Dissertation Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Mattia Ann Gunkelman In Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Department: Animal Sciences April 2019 Fargo, North Dakota North Dakota State University Graduate School Title UNDERSTANDING THE EQUINE DISTAL LIMB By Mattia Ann Gunkelman The Supervisory Committee certifies that this disquisition complies with North Dakota State University’s regulations and meets the accepted standards for the degree of DOCTOR OF PHILOSOPHY SUPERVISORY COMMITTEE: Dr. Carolyn Hammer Chair Dr. Erika Berg Dr. Sarah Wagner Dr. Adam Marx Approved: 04/03/19 Dr. Marc Bauer Date Department Chair ABSTRACT Studies examining health of the distal limb and lameness conditions are important for education and future research. It is hypothesized that changes to the external hoof would result in alterations to blood flow throughout the distal limb and changes to digital cushion thickness. To investigate these things, the following experiments (exp) were conducted. Exp 1: MRI images of the equine distal limb. All images had identified abnormalities to internal structures, and a lameness score assigned. Digital cushion thickness was measured, however no relationship of thickness and lameness was observed (P≥0.12). Exp 2: Trimming and shoeing is a routine procedure for maintenance of proper hoof health; therefore two exp at separate locations (NDSU and UMC) were conducted to examine digital cushion thickness, carpal joint circumference, and blood flow during this time. Specifically, measurements were obtained 24h post trimming and shoeing and periodically throughout an 8 wk period. No significant differences were identified in carpal joint circumference or digital cushion thickness at either location. Thermographic images identified changes in hoof temperature in bare and shod horses at both locations. Week by treatment interaction was significant at NDSU (P=0.04), with hoof temperature decreased in both treatment groups one week post trimming and shoeing. Shod horses remained below baseline throughout the 8 week period, and were significantly colder ( P=0.02) than bare at 8 wk. Week by treatment interaction was also significant at UMC (P<0.0001), with decreased hoof temperature in both treatment groups 4 wks post trimming and shoeing , followed by shod horses increasing to baseline at 8 wk while bare remained colder. Exp 3: Transformative learning in undergraduate students. Undergraduate students enrolled in an Equine Science research course conducted four individual studies. Transformative learning was assessed throughout the course through reflection questions and discussions. It was determined that transformative learning was iii achieved, however it was dependent on the particular student and their previous experience and knowledge. Overall, the current experiments provide further understanding of the distal limb. Further research should continue to place focus on those structures and mechanisms within the hoof which play an overall role in its proper function. iv ACKNOWLEDGEMENTS This dissertation would not have been possible without the guidance and support of many people. My journey to where I am today has been a long process, but I have been abundantly fortunate to have the same people stick with me the whole way. Without them, this would not have been possible and they deserve all the acknowledgement. First and foremost, I need to acknowledge and thank my advisor, Dr. Carrie Hammer. She has mentored me for more years than I can count. Without her guidance, everything I have accomplished in my graduate career would not have been possible and I would not be the person I am today. She has provided me with opportunity, knowledge, support, and leadership. Thank you so much for all you have done for me. My committee members: Dr. Erika Berg, Dr. Sarah Wagner, and Dr. Adam Marx, deserve so much thanks. They have each given me unique tools to ultimately mold me into a well-rounded individual. I appreciate your willingness to work with me and always be available to guide me throughout this process. The equine department (Carrie, Erika, Tara Swanson, and Shannon and Tate Eck) – you have all become my family!! Thank you for always caring for me. You have given me so much and I will forever be grateful to you all. Finally, my family has been the biggest support system I could ask for. I have incredible parents, a caring husband, and an adoring son. They have always been there for me and have never doubted me. They are so proud of me and my work, and their love keeps me going every day. v DEDICATION To my son, Olly. This little guy is the reason for everything I do. His energetic spirit and kind heart bring me joy every day. His hugs and snuggles are the light of my day. Having him in the midst of my graduate career has only encouraged me to keep going and has given me the drive and focus to be successful. Thank you for being my all little Ollyman! To my husband, Lucas. He has given me so many words of encouragement and support and I cannot thank him enough for that. Through this whole process he has never lacked in providing me with whatever I need. I dedicate this to him because without his continuous love and support, I would not be where I am today. I appreciate you so much Lucas. vi TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................................ v DEDICATION ............................................................................................................................... vi LIST OF TABLES ........................................................................................................................ xii LIST OF FIGURES ..................................................................................................................... xiii LIST OF ABBREVIATIONS ....................................................................................................... xv LIST OF APPENDIX TABLES ................................................................................................. xvii LIST OF APPENDIX FIGURES............................................................................................... xviii CHAPTER 1. INTRODUCTION AND LITERATURE REVIEW ............................................... 1 Introduction ................................................................................................................................. 1 Distal Limb External Anatomy ................................................................................................... 3 Distal Limb Internal Anatomy and Associated Lameness Diseases ........................................... 9 History of Trimming and Shoeing ............................................................................................ 19 Influence of Hoof Trimming ..................................................................................................... 20 Influence of Shoeing ................................................................................................................. 22 Potential Assocation of Digital Cushion and Performance ....................................................... 25 Conclusion ................................................................................................................................. 28 Literature Cited ......................................................................................................................... 29 CHAPTER 2. ASSOCIATION OF THE EQUINE DIGITAL CUSHION WITH LAMENESS AND ANATOMICAL CHANGES OF THE DISTAL LIMB ............................... 38 Abstract ..................................................................................................................................... 38 Introduction ............................................................................................................................... 39 Materials and Methods .............................................................................................................. 42 Medical Records .................................................................................................................... 42 vii Image Analysis ...................................................................................................................... 42 Digital Cushion Measurement ............................................................................................... 45 Statistical Analysis ................................................................................................................ 46 Results ....................................................................................................................................... 46 Discussion ................................................................................................................................. 48 Literature Cited ......................................................................................................................... 49 CHAPTER 3. INFLUENCE OF SHOEING AND TRIMMING ON TEMPERATURE, DIGITAL CUSHION THICKNESS, AND CARPAL JOINT CIRCUMFERENCE IN MATURE HORSES ....................................................................................................................