Effect of Oral Administration of Megasphaera elsdenii on Performance of Holstein Cows During Early Lactation THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Katilyn

.............................................................................................................................. ii Dedication .......................................................................................................................... iv Acknowledgements ..............................................................................................................v Vita .................................................................................................................................... vii List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii CHAPTER 1: INTRODUCTION ....................................................................................... 1 CHAPTER 2: LITERATURE REVIEW ............................................................................ 3 I. Transition Cows ........................................................................................................... 3 II. Feeding the Transition Cow ....................................................................................... 4 A. Rumen Microbial Population .............................................................................. 4 Effect of Changing to a High-Grain Diet ................................................................ 5 B. Rumen Fermentation ........................................................................................... 6 Fermentation Products ............................................................................................ 6 Rumen pH ............................................................................................................... 7 C. Ruminal Acidosis ................................................................................................ 8 Rumen Microorganism Changes Associated with Acidosis ................................... 9 D. Prevention of Acidosis ...................................................................................... 11 ix Buffers.................................................................................................................... 11 Feeding Management ............................................................................................ 12 Environmental Stress (Heat Stress and Grouping) ................................................ 14 Ionophores............................................................................................................. 15 Direct-Fed Microbials ........................................................................................... 17 III. Megasphaera elsdenii .............................................................................................. 18 A. Metabolism of Lactate by M. elsdenii .............................................................. 19 B. In vitro Trials .................................................................................................... 21 C. Establishment of M. elsdenii in vivo ................................................................ 23 D. Beef Cattle and Sheep ....................................................................................... 24 Beef Cattle ............................................................................................................ 24 Sheep ..................................................................................................................... 26 E. Dairy Cattle ....................................................................................................... 27 F. Summary ........................................................................................................... 31 G. Hypotheses ........................................................................................................ 33 CHAPTER 3: MATERIALS AND METHODS .............................................................. 34 Experimental Design, Treatments, and Diets ............................................................... 34 BCS and Weight ........................................................................................................... 35 Urine and Blood Metabolites ........................................................................................ 35 Health and Reproduction Events .................................................................................. 36 Feed Sampling and Analyses ........................................................................................ 36 Milk Collection and Analyses ....................................................................................... 37