Fertilization and embryonic mortality rates in beef heifers after artificial insemination

A total of 256 beef heifers, in 2 experiments, was used to establish fertilization rate and subsequent embryo survival rates. Fertilization rate following a single artificial insemination was 90%. Pooled estimates of embryo survival showed high survival rates up to Day 8 (93%) but markedly reduced (P < 0.001) survival at Days 12 (56%), 16 (66%) and 42 (58%). It is suggested that most embryonic mortality occurs between Days 8 and 16.