Incidence and classification of early embryonic mortality in broiler breeder chickens.

1. Unusually high early embryonic mortality (EEM) was observed in hatching eggs from broiler compared with white or brown table-egg breeders in Atlantic Canada. Broiler breeder EEM in Atlantic Canada was twice the EEM in broiler breeders from other areas of North America. 2. Comparisons of holding temperatures (18 and 30 degrees C) for 24 h after egg collection, in combination with a storage time of 0 or 7 d at 18 degrees C prior to incubation, were made using the criteria: embryo development (stage), and size at 0, 3, 6 and 9 d incubation, EEM, late embryonic mortality (LEM) and hatchability (HAT). 3. Stage of development of embryos, at 0 d incubation, was highest for eggs held for 24 h at 30 degrees C and stored for 7 d. Embryo stage, weight and length at 3, 6 and 9 d incubation were positively correlated. 4. Hatchability of fertile eggs was lowest (66.5%) for eggs held for 24 h at 30 degrees C and stored for 7 d and highest (87.2%) for eggs held for 24 h at 18 degrees C and stored for 0 d. Holding temperature and storage time significantly influenced EEM and LEM. 5. EEM classification differed for strain of breeder. In broiler breeders the majority of the EEM was at a relatively late stage of development (exhibiting an obvious blood ring with a visible embryo). In comparison, EEM from table egg breeders was distributed equally among three categories.