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Effects of immunocastration on feedlot performance in bulls of different breed-types implanted with estradiol 17-ß

by Erichsen, Christine Margaret

Abstract (Summary)
nie effects of anti-GnRH imrnunization on reproductive physiology, behavior, production and carcass traits of feedlot bulls were studied and compared with the effects on intact and surg icdly castrated bulis. Ninety-six bu11 calves were randornly allocated to 24 pens of four caîtle each in a 3x2 factoral design, replicated. Half the calves were implanted with Estradiol- 1 7P. The anti-GnRH vaccine elicited an imediate and high immune response. A significant reduction in serurn testosterone concentration followed and in tum, inhibited sexual development and behavior in irnrnunocastrates, but had little effect on growth, feed eficiency and carcass traits. Implanting appeared to complement some effects of imrnunization. There was a high degree of variation among individual cattle in their response to imrnunization. Anti-GnRH immunization may be a usefùl alternative to mrgical castration, but not in an environment requiring a 90 &y withdrawal period between vaccination and marketing, as was required for this experirnent. First, 1would like to acknowledge the Alberta Agricultural Research Institute and the Ecpartment of Agriculture, Food and Nutritionai Science for their financial support. Financial support received through the Hany J. Hargrave Memorial Graduate Scholarship in Animal Science and the Keith Gilmore Memorial Scholarship was aiso appreciated. The work of Gary Minchau, Jack Welch and the rest of the staff at the University of Alberta Kinsella ranch is gratefully acknowledged. 1am also grateful to Dr. Mark Redmond and Dr. Andrew Van Kessel of the Department of Animai and Poultry Science at the University of Saskatchewan, and Brian Turner frorn the Department of Agricultural, Food and Nutritional Science, for providing the blood analysis for this project. Dr. John Kastelic and Byme Cook of Agriculture and Agi-Food Canada deserve a huge thank you for helping me examine the technical aspects of bu11 reproduction. 1 very much appreciate the many hours they spent helping me collect data and sharing their expertise. 1would also like to thank Elanco Animai Health for providing Cornpudose@ for the second experiment. For suggestions and time spent editing my thesis, I want to thank rny supervisor Dr. Mick Price and my cornmittee members Dr. Laki Goonewardene and Dr. Mak Makatechian. 1would iike to specially acknowledge Mick Price whose abilities I have always admired and who in part, inspired me to seek ihis degree. During my stay in the department he has ken both a teacher and a friend. 1 sincerely appreciate the guidance, support and patience he has provided me throughout this project 1am also thankhil to him for sharing with me his tremendous knowledge base, and for teaching me to hang ont0 rny pens tightly. I am extremely grateful to Laki Goonewardene who spent a lot of time explaining statistics to me and helping me analyze my data. I could always count on him when 1had a statistical crisis. During the course of this degree he provided me with a lot of help in many areas, and with many interesting and enjoyable conversations. For both 1 am grateful. 1would like to acknowledge my parents who instilled in me the importance of education, leaming and thinking. 1am appreciative of the support and encouragement that my parents, dong with my sisters, Cathie and Carolyn, have provided. They've helped me through many tough circumstances over the past two years and for that 1am tmly gratefd. TmLE OF CONTENTS
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Source Type:Master's Thesis

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Date of Publication:01/01/1999

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