Selection for antibody response against sheep red blood cells and layer age affect egg quality

1. After 22 generations of divergent selection for antibody response against sheep red blood cells (SRBC), hatchability differed between the selected lines. Whether there is a relationship between hatchability and egg traits in these lines is not clear. 2. The aim of the present study was to investigate whether eggs of selected lines differed in shell and albumen characteristics. 3. Fresh eggs were collected at layer ages of 25, 29, 33, 37, 41, 45, 49, 55 and 59 weeks. In total 776 eggs from three lines (high antibody response (H), control (C) and low antibody response (L) against SRBC) were examined. 4. Albumen height decreased with layer age, but this decrease differed between lines. 5. Eggs of the C line were heaviest, followed by the L line and finally the H line (59.44 vs 55.50 vs 54.15 g, respectively). Eggshell thickness, eggshell percentage, albumen height and albumen pH were lowest in the L line, and highest in the H line, whereas the C line was intermediate. 6. From this study, we concluded that selection on antibody response to SRBC affected egg characteristics (external and internal). This may have consequences for hatchability and furthermore for chick quality. When chick quality partly underlies the immune status of an animal, differences in immune responses among selected lines may be due to differences in egg characteristics. This implies inadvertent selection for chick health at an early stage of life. Whether this is the case needs to be investigated.