An examination of fertility, hatchability, embryo mortality, and chick weight in double versus single-yolked broiler breeder eggs

The objective of this study was to document the fertility and embryonic mortality problems that result in the poor hatchability of double yolk (DY) versus (single yolk) SY broiler breeder eggs. Both SY (n = 64) and DY (n = 141) eggs were collected from a commercial Hubbard Hi-Y flock and the eggs incubated for 21 d. All eggs were candled and weighed at 7, 14 and 18 d, and any non-viable eggs were removed and broken open to assess fertility, and if fertile, stage of embryonic death. Any unhatched eggs remaining after 21 d of incubation were broken open so that fertility, hatchability and embryo mortality could be calculated. Because there is the potential for two chicks to hatch from a DY egg, fertility, hatchability, and embryo mortality were calculated on a per yolk basis rather than an egg basis. Fertility, hatchability, and hatchability of fertile eggs were significantly lower (P < 0.05) in DY compared to SY eggs. Early- (≤7 d of incubation), mid (8–14 d of incubation), and late (≥15 d of incubation) embryonic mortality was significantly higher in DY vs. SY eggs. Chick body weights were significantly greater in solitary chicks hatching from DY eggs versus chicks hatching from SY eggs. Key words: Double yolk, embryo mortality, broiler breeders, chick weight, hatchability, fertility