Reproductive wastage is a major inefficiency in all livestock production with embryonic mortality accounting for a major portion of this loss. Accordingly the Commission of the European Communities encouraged the organisation of a seminar on embryonic mortality in farm animals which was held in Brussels on the 11th and 12th of December 1984. This book contains the text of the papers, discussions and final summary presented at that Seminar. As a background to the Seminar, the extent and timing of embryonic loss was described for farm animals. Particular consideration was then given to the various mechanisms and signals, both embryonic and uterine in origin, that are so far known to be involved in the establishment of pregnancy. Possible causes of embryonic death including physiological, endocrinological, genetic and immunological components were outlined and discussed. The final summary contains general conclusions from the Seminar and recommendations for future research work on this topic. J.M. Sreenan M.G. Diskin July 1985. ******************** THE EXTENT AND TIMING OF EMBRYONIC MORTALITY IN THE COW J. M. Sreenan & M. G. Diskin, The Agricultural Institute, Belclare, Tuam, Galway, Ireland ABSTRACT The extent and timing of embryonic mortality in heifers, normal cows and repeat breeder cows has been reviewed.

In 1964, the Fertilization and Gamete Physiology Research Training Program (FERGAP) was established at the Marine Biological Laboratories, Woods Hole, Massachusetts. Over the course of the next 12 years, under the directorship of Dr. Charles B. Metz, FERGAP brought together, trained, and inspired a generation of students in reproductive biology from all over the world. As students of C. B. Metz and as FERGAP trainees, we would like to dedicate this collected work on comparative mammalian fertilization to our teacher and mentor, Dr. Charles B. Metz. Like a number of authors contributing to this volume, we have been struck by the significant impact that C. B. Metz and FERGAP had on the development of students of reproductive biology. Applying both the classical and molecular techniques of cell biology and immunology to problems of gamete biology, Dr. Metz emphasized a comparative and analytical approach that was reflected in his own research on fertilization in Paramecia, sea urchins, frogs, and mammals. It is hoped that this volume will serve to stimulate students to discover the myriad of fascinating research problems in gamete and reproductive biology. Bonnie S. Dunbar Michael G. O'Rand Houston, Texas Chapel Hill, North Carolina ix Contents Part I COMPARATIVE OVERVIEW OF MAMMALIAN GAMETES The Coevolution of Mammalian Gametes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 J. Michael Bedford I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Gamete Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Monotremes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . 2.2. Marsupials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . 2.3. Eutherians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Gamete Maturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 . . . . . . . . . . . . . . . 3 .1. Oocyte Maturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 . . . . . . . . . . . . . 3.2. Sperm Maturation in the Male . . . . . . . . . . . . . . . . . . . . . . . 15 . . . . . . . . . .