Relationships among age of dam, egg components, embryo lipid transfer, and hatchability of broiler breeder eggs.

Fertility, hatchability, and their relationships to age of dam, egg components, embryo growth, and embryo lipid transfer were studied in a broiler breeder line segregating at the sex-linked feathering locus. Early-season increases in hatchability of eggs were due to a reduction in embryo deaths between Day 1 and 7 of incubation. No late seasonal declines in either fertility or hatchability were observed. Although less proficient in young dams, embryo lipid transfer was not directly associated with the lower hatchability of their eggs. Egg weight, weights of 18-day embryos, and embryo:egg ratios increased with parental age. Also with age, there were increases in shell, albumen, and yolk weights. Heavier albumen weight was due to increased moisture content, and those for shell and yolk were due to dry matter accumulation. Changes in yolk:albumen ratios reflected large increases in relative yolk weight, on a wet and dry weight basis, that were associated with age of dam. Eggs from late-feathering dams were heavier than those from early-feathering ones. Heavier embryos by 18 days of incubation were attributed to the transfer of albumen from the egg to the embryo.