Selection for Egg Mass in Different Social Environments

Changes in agonistic activity levels and in social dominance potential were studied in 6 strains of chickens derived from the Kentville Randombred Control. Two of the 6 were selected for increased part-year egg mass when kept in intermingled-family flocks, 2 strains were selected on the same criterion when kept in separated-family flocks, and 2 consisted of unselected controls, maintained in an essentially asocial environment (individual cages). Behavior was compared in generations, 2, 4, 6, and 7. Random genetic drift is the most likely cause for differences in frequency of agonistic acts found between strains within systems of selection. Increased social dominance ability occurred under both selection schemes as shown by peck-order ranks when selected strains were intermingled with unselected controls. We hypothesize that this result is in some way associated with the earlier sexual maturity of the selected strains. Housing environment influenced frequency of threat-avoidances; fewer were observed in colony cages as compared with floor pens. Agonistic acts were more frequent during adolescence than during the young adult stage.