A review of embryonic mortality in cattle

Introduction Embryonic mortality, strictly interpreted, should refer to fertility losses during the embryonic period, i.e. the period extending from conception to completion of the stage of differentiation which, in the cow, occurs at approximately 45 days (Committee on Reproductive Nomenclature, 1972). However, many authors have included under this term, fertilization failure, as well as death after fertilization. Since the present review was written for presentation within the framework of a symposium on reproductive efficiency in domestic animals, it was considered necessary to include data on fertilization rates, for a more complete picture of fertility losses.