Context There are pre-hatch factors that can influence performance during the growing phase, such as the egg size and breeder age. Aims Investigate the influence of egg weight and flock age separately on egg characteristics, hatching traits, hatchling weight, and initial offspring performance. Methods Treatments consisted of eggs laid by 28-week-old (Y), 42-week-old (M), or 61-week-old (O) broiler breeder hens and different egg-weight classes, light (L, 56.6–62.2 g), average (A, 62.3–67.9 g), or heavy (H, 68–73.6 g). Eggs of a similar weight from hens of different ages (treatments YA/ML, YH/MA/OL, and MA/OA) were selected, which allowed us to assess specifically the effect of maternal flock age on the following variables: egg characteristics (eggshell, yolk, and albumen), incubation traits (egg weight loss (EWL), and hatchability), hatchling weight, and live performance of the progeny (7, 14 and 21 days). When data satisfied homogeneity of variance, they were submitted to the one-way ANOVA, and means were compared by Tukey’s test at 5% probability level. Key results Eggshell thickness and albumen height were lower, but albumen weight, yolk weight, and percentage of yolk were higher in eggs produced by older flocks. When eggs of the same weight were evaluated, the variables were also affected by flock ages. EWL increased with the hen age. The age of the hen and egg weight significantly affect the hatchability and hatchling weight. The maximum hatchability was recorded in eggs from broiler breeders at the age of 42 weeks (90.53%). In the average egg-size group (62.3–67.9 g), the young hens produced the lightest chick, and the old flock had the worst hatchability. Broiler’s performance was influenced both by flock age and egg weight. Conclusions The eggshell thickness is mainly influenced by the egg size. However, other egg features are affected by flock age. EWL and chick weight are reduced in young flocks. The oldest flocks produced heavier chicks and the positive effect on feed intake and bodyweight remained until 14 days of age. Implications Egg size and broiler breeder age can influence the egg traits and performance of broilers.
